Nutzpflanzenwissenschaften Diss. 1995-2006 ENG - CiteSeerX

Akmal, Mohammad (1997): Growth of forage grasses under different water regimes and nitrogen levels. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 120 pages. The vegetative growth of forage grass is highly dependent on water and nitrogen (N) avail-ability. The objectives of these experiments was to examine the effect of limited water and N supply on biomass production, leaf and tiller number, N accumulation and distribution (15N) as well as water use efficiency in a model crop stand of perennial ryegrass (Lolium perenne L.) [pot experiment 1 and mini plots experiment 2 in chapter II and chapter III]. These ex-periments were conducted under the subhumid climatic conditions of Bonn, Germany. In fur-ther experiments additional to growth parameters, the objective of the study was to observe the influence of drought stress and reduced N application on the seasonal change in forage quality under the subtropical conditions of Peshawr, Pakistan [Experiments 3 and 4 chapter IV]. In these field experiments, barley (Hordeum vulgare L.) and oats (Avena sativa L.) were planted in addition to ryegrass. Irrespective of N supply, drought stress always reduced the amount of biomass production of both above and below ground plant organs in the first growth as well as in the regrowth of ryegrass (Experiment 1 and 2). A similar effect of drought was also observed on herbage regrowth during the field experiments conducted in Peshawar (Experiment 3 and 4). Consid-erable loss in biomass due to drought stress was observed in all the three graminacious crops. Regardless of drought stress, low N fertilizer application reduced the herbage biomass production in a similar pattern. In all experiments, drought stress effect was relatively stronger than the effect of reduced nitrogen. The reason to the comparatively low biomass yield was the reduced tiller mass and leaf area. However, the number of tillers and leaves per plant were not affected. In all experiments, the N concentration in different organs of the plants decreased with ad-vancement in age. At the beginning of the vegetative development of Lolium perenne L., drought stress showed lower N concentration in all organs, whereas, at the end of vegetative development of the plants drought stress increased N concentration in each plant organ. The N concentration in roots declined slower than the N concentration in shoots and within the shoots, N concentration declined faster in the side tillers than in the main tillers. After the onset of drought stress, 15N labelled nitrogen uptake was the lowest when water and N sup-ply was reduced (Experiment I). Nevertheless, this reduction of 15N was much lower at re-duced N supply than with sufficient N. When only the N fertilizer application was reduced, the effect of drought stress on N accumulation was significantly lower than did under the high N application. The effect of growth factors (i.e. water and N) on forage quality of the graminacious crops could not show any significant difference under field conditions in Peshawar. Though, protein and digestibility were declined by limiting both water and N regimes. The present results concerning growth and forage quality of the graminacious crops under drought stress and reduced N supply provided conclusions for the calculations of N supply in relation to limited rainfall or water availability to the crops under subtropical conditions. Re-sults obtained from both the pot as well as field experiments showed that quantity of the graminacious forage harvested under restricted water and N supply was low which was due to reduced number of leaves and tiller mass. The fact is that tiller number is mostly not af-

fected which can lead to conclusion that under subtropical conditions the above mentioned crops should be capable to form a constantly thick and close canopy but poor in growth. Finally, it has to be seen as a disadvantage of the limited water supply that canopy stand of the graminacious crops should be harvested less frequently and at late stage of the growth. This also yield in low quality herbage. However, on the other hand farmers can get benefit of the higher efficiency of the use of available water and the greater N concentration in dry mat-ter at final harvest under drought stress relative to normal irrigation. Alemayehu Damot, Getachew (2000): Measures to Counteract Alternate Bearing in Apple. Institute for Horticulture, Faculty of Agriculture, University of Bonn, 196 pages. In some apple growing regions ethylene releasing substances are sprayed shortly after fruit set to reduce alternate bearing in apple trees. This effect is supposed to be promoted by adding an inhibitor. The modes of action by such treatments and the reactions of the apple trees are hardly known. This applies specifically for flower formation, fruit set, shoot-, leaf- and root growth, CO2-assimilation, water consumption, nutrient uptake, accumulation of re-serve compounds, dry matter distribution and root/shoot ratios. On fruit bearing and non fruit bearing trees of ‘Golden Delicious’ on M9, therefore, the effect of ethephon sprays at 250ppm concentration on the above mentioned parameters were investigated either alone or in combination with succinic acid hydrazide. The experimental trees were cultivated up to the fourth planting year (1997) in lysimeters filled with quartz sand. The fruit load reduced the flower formation. This was less pronounced after ethylene treat-ment. Adding of an inhibitor to ethephon sprays didn’t promote flower formation. The effect of ethylene treatment on the fruit set was variable depending on the prevailing weather condi-tions. High temperatures and wind directly after treatments enhanced fruit drop. The fruit load resulted in an early termination of shoot growth, a reduction of total leaf area per tree, a decrease of specific leaf weight, and an increase of photosynthesis and transpira-tion rates, as well as, of leaf chlorophyll contents of apple trees. Ethephon promoted side shoot formation and, thereby, it increased the total leaf area of fruiting apple trees. Ethephon in combination with succinic hydrazide, however, inhibited the growth of shoots and the for-mation of total leaf area per tee. The fruit load increased the water consumption per unit leaf area and resulted in higher con-centrations of N, P, Ca and Mg of leaf blades. On the contrary, potassium concentrations of leaves were decreased by fruit load. As a consequence of strong inhibition of the vegetative growth by fruit load, the total amount of mineral elements in fruit bearing trees was lower than in the non bearing ones. Ethephon promoted the water consumption and nutrient uptake in fruit bearing trees, but not in non bearing ones. Ethephon combined with succinic hy-drazide reduced the water consumption and the nutrient uptake of apple trees. The fruit load reduced starch accumulation in all plant parts of apple trees. At the entire tree level, however, fruit bearing trees contained considerably higher amounts of sucrose, glu-cose and fructose than the non bearing ones. Neither the contents of starch and soluble sugars nor the production of dry matter was influenced by the treatments of ethephon alone. The treatments of ethephon combined with succinic hydrazide reduced the total accumula-

tion of starch, soluble sugars and dry matter. Ethylene treatments widened the root/shoot ratio of apple trees. Alemu, Tameru (2004): Characterisation of viruses of pepper (Capsicum spp.) and sweet potato (Ipomoea batatas) from Ethiopia. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 126 pages. High disease incidence of viruses in pepper and lack of research on viral diseases of sweet potato in Ethiopia led to initiatives to conduct this study. The investigations on pepper viruses had the objectives to determine field incidence of viral diseases, to identify the viruses and to map their distribution. Further, the most important virus had to be characterised biologically and serologically and its variability should be determined. The epidemiology as well as the sources of resistance against the virus had to be investigated. In sweet potato, this study was undertaken to identify and characterise the occurring viruses on biological, serological and molecular level. Diagnostic surveys were conducted in two cropping seasons in major pepper growing dis-tricts in the rift valley of Ethiopia. The highest (89%) and the lowest (15%) viral disease inci-dences were recorded at Awassa and Meki respectively. Of 503 pepper samples analysed, 88% were infected with one or more viruses. Ethiopian pepper mottle virus (EPMV, ~60%) followed by Potato virus Y (PVY, ~23%) were the prevailing viruses. Investigations on bio-logical variability revealed the presence of two EPMV pathotypes. The first pathotype in-duced severe symptoms on Nicotiana benthamiana in early stages of infec tion. It also in-fected tomato and produced severe symptoms on most pepper genotypes. The second pathotype produced only mild symptoms on N. benthamiana, did not infect tomato and caused mild and latent infections on some pepper genotypes. Cytopathological investigation of infected tissue by the severe pathotype showed massive development of pinwheels and scrolls as well as inclusions of virions. Isolates of EPMV were serologically indistinguishable. Aphids transmitted the severe EPMV isolate more efficiently than the mild isolate. Seed transmission of EPMV isolates was not found. Nicandra physalodes, Datura stramonium and Solanum nigrum were the main wild reservoirs of EPMV and other viruses Previously unde-scribed resistance sources against EPMV were found in pepper genotypes PBC 972, PBC 559, PBC 223 and Bakolocal. 318 collected sweet potato cuttings were indexed for virus infections. 62.8% of the cuttings revealed infections. Sweet potato feathery mottle virus (SPFMV) occurred commonly in all locations. The highest (86%) and lowest (32%) incidences were found in cuttings from the districts Humbo and Sodo Zuria respectively. Cuttings of the cultivar ‘Gadissa’ had a higher percentage of SPFMV infections than those of ‘Kogansengan’. Similarly, cuttings from farm-ers’ planting stocks revealed a higher percentage of SPFMV infections than those originated from the production fields. Among 13 cuttings examined with SPVG antiserum in DAS-ELISA, three cuttings were found to be positive. The host range of Ethiopian SPFMV and SPVG isolates was limited to Ipomoea species. Coat protein (CP) gene and untranslated region (3’UTR) sequences of two and the 3’UTR of another two Ethiopian SPFMV isolates were determined. Analysis of the sequences revealed the presence of the DAG- and other

conserved motifs, which are features of the coat protein gene of potyviruses. Sequences of deduced amino acid (aa) and nucleotide (nt) of CPs and 3’UTR were compared with se-quences of other SPFMV isolates in gene banks. The Ethiopian isolates humb1 and sodo19 had a similarity of >95% and ~83% with SPFMV-Russet Crack (SPFMV-RC) and SPFMV–Common (SPFMV-C) strains from America respectively. In a similar comparison, the isolates ark21 and bod24 showed sequence identities of ~82% and >94% with SPFMV-RC and SPFMV-C strains respectively. Phylogenetic analysis of the coat protein amino acid and 3’ UTR nucleotide sequences clustered the Ethiopian humb1 and sodo19 as SPFMV-RC and ark21 and bod24 as SPFMV-C strains accordingly. Furthermore, the Ethiopian SPFMV-RC isolates were genetically closer to other East African SPFMV-RC isolates than to isolates from other parts of the world. Sequence analysis of the CP gene fragments of the Ethiopian SPVG isolates ark15 and sodo20 showed features of the CP gene of potyviruses. Alignment of sequences revealed that SPVG isolates had longer CPs (355aa) and 3’UTR (221nt) com-pared to other potyviruses infecting sweet potato. Alignment of CP amino acid and 3’UTR nucleotide sequences showed >90% similarity among Ethiopian-, Egyptian- and Chinese SPVG isolates, demonstrating, that all are isolates of the same virus species. Furthermore, phylogenetic analysis grouped all SPVG isolates together. Both analyses showed that Ethio-pian- and other SPVG isolates had a closer relationship to Sweet potato virus II (SPVII) and SPFMV from Zimbabwe (SPFMV-Z) than to other potyviruses infecting sweet potato. Al Hafez, Mohamad-Samir (1997): Model experiments for to overcome lime induced iron chlorosis (Fe-deficiency chloro-ses) in maize (Zea maize) and sunflowers (Helianthus annuus) on calcareous soils by "active" sulphate according to the "CULTAN"-Cropping System. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 119 pages. Inspite of a large number of different procedures und recommendations are available, up to now there is no substantial basis for to overcome lime induced iron chlorosis on calcareous soils in arid/semiarid areas. It restricts to the application of iron as salts or chelates or on breeding as well, procedures which in a total are not convincing according to their efficacy. Under this point of view in present investigations in connection with the "CULTAN"-Cropping System new possibilities were tried for to overcome the lime induced iron chlorosis. After placement of ammonium into the soil a part of the roots of plants can be directed to very specific spots. In these spots calcareous soil was exchanged by compost acidified by sulphuric acid to pH 3,0 to 2,0 and protected by a cover against the surrounding calcareous soil. By these substrates behind sulphuric acid the plants were supplied with ammonium sul-phate, potassium sulphate and minorelements. The aim of this technique was, to cover the requirements of iron, manganese and zinc etc. of the plants; to prevent the reduction of nitrate within the plants and to neutralize calcium bi-carbonate within the plants by active sulphuric acid as H2SO4, (NH4)2SO4, K2SO4. Finally the aim of the treatments was, to get exoneration for carboxylation processes in plants and low-ering the pH-values within the plants in the range of a physiological optimum. As analytical proof the conventional procedures for the determination of active iron in plants in respect to the potential danger of lime induced iron chlorosis in plants did not assertion to

be convincing. More reliable informations were received by the procedure developed in the own laboratory, the negative balance between the concentrations of calcium and sulphate in plants, extractable by hot water. The results of the present investigations have shown that by the "CULTAN" Cropping System lime induced iron chlorosis in plants on calcareous soils can be prevented safe and without special costs. By the balance between calcium and sulphate, extractable by hot water, the potential danger, that lime induced iron chlorosis may arise or not, can be analyzed and con-firmed. Arendt, Bianca (2003): Effects of moderate consumption of native or dealcoholised red wine on antioxidant parameters in blood and DNA-strand-breaks in peripheral leukocytes in healthy men and women – results of an intervention trial. Institute for Agricultural Botany, Faculty of Agriculture, University of Bonn, 111 pages. Background and objective: Oxidative stress is probably involved in initiation and progression of cardiovascular disease, cancer, and chronic inflammatory processes. Red wine is rich in antioxidant polyphenols and thus might protect from oxidative stress in vivo. Aim of this study was to examine if a glass of red wine (RW) consumed once or regularly, respectively, shows antioxidant activity in humans. The effects of dealcoholised red wine (DRW) of the same batch were determined in comparison. Study: A) 27 healthy non-smokers received a single dose of 200 ml RW, 175 ml DRW or 200 ml water after an overnight fast. Blood samples were drawn before, 90, and 360 min after consumption. B) 49 subjects ingested 200 ml RW or 175 ml DRW daily over 6 weeks in addition to their normal diet. 25 controls did not receive any study drink. Blood samples were drawn before and after intervention. Methods: In both parts of the study antioxidant capacity (TEAC), total phenolic content (Fo-lin), vitamin C, albumin, urate, and bilirubin in plasma were determined. In B) α-tocopherol in serum was measured additionally. Endogenous and H2O2-induced (exogenous) DNA-strand-breaks (SB) in peripheral leukocytes were assessed by single cell gel electrophoresis (Comet Assay). Results: A) A transient increase of total phenolics in plasma was observed after consumption of RW or DRW indicating that bioavailability of polyphenols is comparable. Vitamin C de-creased 360 min after RW but increased after DRW, which might be due to pro-oxidant ef-fects of alcohol or antioxidant vitamin C-sparing effects of polyphenols, respectively. TEAC was not altered significantly. Changes of albumin, urate, and bilirubin occurring after RW, DRW, and in controls were all within the physiological range and did not affect plasma-TEAC. More endogenous SB were measured 360 min after RW or DRW compared to base-line, which cannot be ascribed to pro-oxidant effects, as exogenous SB were reduced in group DRW at the same time. B) After 6 weeks intervention RW, but not DRW lead to an increase of total phenolics in plasma, probably due to the lower polyphenol content of DRW. Concurrently endogenous SB

were reduced in group RW. Exogenous SB, TEAC, vitamin C, and α-tocopherol remained unchanged. TEAC was not influenced by changes of urate (control) or bilirubin (DRW). Conclusion: A) Polyphenols from RW and DRW are bioavailable and transiently increase total phenolics in plasma without affecting TEAC. Enhanced endogenous DNA-damage indi-cates genotoxic effects of RW-polyphenols but might also be due to activation of repair en-zymes. B) When RW is consumed regularly, polyphenols are accumulated in plasma without an in-crease of TEAC. In contrast to single ingestion endogenous SB are reduced. Thus, tumour-preventing effects of RW are possible. Discrepancies between short- and midterm effects of RW might be due to accumulation of different polyphenols in plasma and/or cells. To verify this, quantification of concentrations of the most important RW-polyphenols and their metabolites both intra- and extra-cellular would be necessary. Interactions of RW-polyphenols and DNA in vivo would be worth being further examined be-cause they show a protective as well as a genotoxic potential. Arnold, Christian (2003): Studies on the biological control of the Horse Chestnut Scale Insect Pulvinaria regalis Canard (Hom., Coccidae) on urban trees. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 97 pages. This study aimed to investigate biological control measures against the Horse Chestnut Scale Insect Pulvinaria regalis Canard (Hom., Coccidae), a pest of urban trees. Of particular interest were observations and investigations on biological and ecological aspects of P. regalis and four native enemies of the Horse Chestnut Scale Inscect, the coccinellid predator Exochomus quadripustulatus L. (Col., Coccinellidae) and the parasitic wasps Coc-cophagus semicircularis (Förster), C. lycimnia (Walker) (Hym., Aphelinidae) and Microterys flavus (Howard)(Hym., Encyrtidae). The main part of this study was the release of E. quadri-pustulatus and C. semicircularis in Bonn and Duisburg as well as M. flavus in Duisburg. The duration of larval development of E. quadripustulatus decreased with increasing tem-peratures as well as food consumption and weight of larva and pupa. Predation rates of adults were low within the first 30 days after the hibernation had ended but increased there-after. Freshly hatched adults consumed considerable amounts of food directly after hatching. The mean number of eggs laid at 9/19°C was 96,8 per female, which was less compared to 12/24°C with 139,1 eggs. Adult E. quadripustulatus preferred unparasitized P. regalis nymphs 12 days after parasitation. C. semicircularis and C. lycimnia parasitized P. regalis nymphs with a minimium body size of 0,98 mm and 0,92 mm, respectively. Higher numbers of C. semicircularis lead to an overall increase of parasitized P. regalis nymphs but to a de-crease of the individual parasitation rate. M. flavus could complete a full life cycle with instars (N2) and adult P. regalis as hosts. Field observations revelead that infestation levels of P. regalis varied between the cities as well as between the trees species within one city. Highest levels were observed in Duisburg on Chestnuts with 57406 nymphs/m2 leaf area. Lowest levels were found in Bonn on maple with 851 nymphs/m2. In the urban area of Bonn P. regalis has one generation per year. Eggs

are laid in spring. During the summer month P. regalis nymphs can be found on the leafs, during the winter on twigs and branches. Climatic variations were identified as reason for the postponement and prolongation of various developmental stages of P. regalis. Until now 65 plant species are known as host plants. P. regalis is distributed all over Germany but can be found mainly in the rhineland area. The appearance of all natural enemies observed coincided with the life cycle of P. regalis during the whole experimental period. The release of 20 and 30 E. quadripustulatus larva in Duisburg lead to a reduction of P. regalis numbers up to 47,7%. After the release of 20 and 30 C. semicircularis females an increased number of parasitized P. regalis of 12,9% was observed. The indigenous parasitoid C. lycimnia parasitized a maximum number of 21,8% nymphs. A combined release of 20 C. semicircularis (14,2%) and E. quadripustulatus (46,2%) decreased infestation levels up to 60,4%. M. flavus females parasitized 19,6% of adult P. regalis and layed up to seven eggs into one scale insect. The number of eggs de-posited by parasitized P. regalis was lower (217,9) compared to unparasitized P. regalis fe-males which layed a mean number of 1272,4 eggs. Aydogan, Ahmet (2003): Investigations on the penetration of selected foliar fertilizers into different crops. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 161 pages. Leaf application experiments with were carried out with wheat, raps, coffee and sugar beets under different environmental conditions. The plants were treated with sodium nitrate, urea, sucrose, boron-, potassium- or magne-sium-compounds. After a certain treatment time leaves were harvested, rinsed with distilled water, dried, weighed, ground and analysed The influence of the following parameters on uptake and translocation processes was stud-ied: point of deliquescence of the salts, molecular size, surface of the leaf (adaxial vs. abaxial), light, temperature, nutritional status of the plant, water content of the soil, addition of surfac-tants, additional chemicals, pH of the applied solution, droplet size and duration of treatment. The penetration increased with decreasing point of Deliquescence of the salt. Leaves of Coffee have stomata only on the abaxial leaf surface The penetration of nitrate, urea and sucrose was always higher on the abaxial leaf surface than on the adaxial leaf sur-face. The uptake of nitrate and sucrose into rape leaves in light was significantly higher than in the dark. Ambient temperature did not significantly affect penetration through leaf surfaces. Neither magnesium deficiency nor potassium deficiency showed any influence on the uptake rates of magnesium sulfate into wheat leaves. Additional salts such as NaNO3, Ca(NO3)2, NH4Cl and NH4NO3, did not affect wetting of leaf surfaces nor uptake rates of magnesium sulfate The addition of different surfactants significantly increased both the wetting of the leaf sur-faces and the penetration rates of magnesium sulfate and magnesium nitrate. Different soil

water contents influenced both the wetting of leaf sufaces and the penetration rates of so-dium nitrate, magnesium sulfate and magnesium nitrate. Penetration rates increased both with increasing concentration and with increasing duration of treatment. Uptake of nitrate into coffee leaves was higher with smaller droplet volumes than with larger droplet volumes. The pH solutions containing boron exhibited some influence on penetration rates. Bacher, Wolfgang (1997): Stickstoffversorgung bei Gemüse in Abhängigkeit von Stickstofform und Applikations-technik. Institute for Horticulture, Faculty of Agriculture, University of Bonn, 120 pages. This research was carried out in the field at Marhof experimental station of the Institut für Obstbau und Gemüsebau, Bonn university. Solid ammonium/urea fertiliser (ADK) was tested as deposit at vegetables in 1992-1994. ADK was applied to the soil in a depth of 10-12 cm as de-posits for every plant to provide nitrogen for the whole growing time. Three distances between placements of these ADK and plants were examined. The three deposit positions were either one deposit adjacent to the plant roots, one deposit between every plant in a row or one deposit with twice the amount of ammonium and urea between every other plants. Yield, diameter and nitrate contents of lettuce and kohlrabi were independent of positioning the ADK. Both positions within the plant rows improved yield of celery relative to the application of ADK close to the roots. The amount of nitrogen fertiliser was reduced by 20 to 30 % when using ADK relative to wide-spread nitrate fertiliser without effecting yield. Nitrate contents in harvest products were reduced by least 30%. Soil nitrate content at harvest was decreased by ADK compared with wide-spread control and nitrate leaching underneath ADK fertilised lettuce was delayed four weeks in the autumn. Min-eral concentrations in harvest products were unaffected by the different nitrogen fertilisers. 15N labelling showed 12 % higher nitrogen uptake of endive fertilised with ammonium compared with nitrate fertilisation. Ammonium fertilised endive produced significantly more dry matter. Ammonium-induced glaucousness was the result of a two-fold increase in the amount of epicu-ticular wax and a markedly altered fine structure. Leaves from ammonium fertilised kohlrabi plants also showed a 21 % increase in chlorophyll content together with a reduction in the chlo-rophyll a:b ratio and decreased ground state fluorescence compared to plants supplied with nitrate. Photosynthesis and stomatal transpiration were unaffected by the form of supplied nitro-gen. Bader, Simone (1996): The Potential of a Combined Application of Biological and Chemical Additives to Regulate the Fermentation Pattern in Silage. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 110 pages.

Over the last few years, various authors have achieved promising results with combinations of lactic acid bacteria (LAB) and formate used as ensiling additives. A first series of silage experiments was set up with the objective to extend the range of application of such com-bined biological-chemical additives and to limit the occurence of aerobically unstable silages. Various additive combinations were tested which contained, in addition to formate, one fur-ther chemical substance (acetate, propionate, benzoate or sorbate). The additive combina-tions were selected on the basis of a screening assessing the revival ability of lactic acid bac-teria in solutions of systematically combined chemicals substances. All tested ensiling additives reduced in-silo losses and the respective contents of butyric acid, ammonia nitrogen and clostridia spores. The combination of an inoculant with chemical solu-tions invariably amplified the effects in comparison to a sole inoculation. Combined chemical-biological additives were generally of greater effectiveness than the respective chemical sub-stances alone. The combined application of lactic acid bacteria with ammonia formate + so-dium benzoate or potassium sorbate resulted in both, distinct and reliable improvements of the fermentation quality. The substantially improved aerobic stability realized by the biological-chemical additive com-bination containing benzoate was only outranked in its effect by the combination of lactic acid bacteria with ammonia formate + potassium sorbate. In a second series of experiments, the amount of the chemical additive component (3,0 kg solid substance per t of fresh matter the previous year) was reduced. The results prove the applicability of reducing amounts of chemical preservatives, in combined chemical-biological solutions, without impairing the effect on decreasing fermentation losses. Except for the sor-bate containing additive, it was also possible to improve aerobic stability of silages when smaller doses of the chemical additive component were used (medium dose level). The combined application of 105 CFU of LAB/g FM and 2,4 kg of ammonium formate + 0,6 kg of potassium sorbate/t FM in liquid form is best suited to effectively improve the fermenta-tion quality in feed types difficult to ensile or under unfavourable ensiling conditions and to compensate, as far as possible, the negative effects that lactic acid bacteria have on aerobic stability. Badi, Marcela (2001): Importance of Basidiomycetes for the biological control of the root-knot nematode Meloidogyne incognita with emphasis on the mode-of-action of nematicidal active me-tabolites. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 111 pages. Ten Basidiomycete isolates out of forty tested in the present greenhouse screening on to-mato plants, achieved significant levels of biocontrol towards Meloidogyne incognita. The most successful isolates: Marasmius spp. 90019, Lycoperdon pyriforme 79131, Omphalotus olearius 90170 and Lentinus lepideus 82019 were shown to affect the penetration of M. in-cognita juveniles. Furthermore, the reduced penetration rate in case of Marasmius spp. 90019 and O. olearius 90170 could be correlated with the reduction in nematode activity in the potted soil. Nematode inactivation in the soil suggested the production of fungal metabo-lites with nematistatic reaction which reduce movement to the roots, penetration and further

nematode development resulting in a low infestation level. The isolate O. olearius 90170 was not found to produce the active compounds omphalotins in the wheat powder substrate used as carrier in the screening. Therefore, the high level of control achieved with this isolate was assumed to result from a high level of rhizosphere colonisation. Nine isolates increased sig-nificantly root and shoot weight of tomato plants promising success also in promoting plant growth. The possible practical use of those active isolates as biocontrol agents towards M. incognita justify further testing under field conditions. Among the four fungal compounds tested in the present study, omphalotin A (OMP A) iso-lated from O. olearius 90170 showed the highest nematicidal activity towards M. incognita juveniles. This was followed in effectiveness by 4methoxybenzene-1-ONN-azoxyformamide (MBONNAF) isolated from L. pyriforme 79131. Furthermore, OMP A showed a species spe-cific activity among plant parasitic and non-parasitic nematodes and both compounds, OMP A and MBONNAF had a stage specific activity towards Radopholus similis and Pratylenchus zeae where the second and third stage juveniles were most affected. Investigations to the mode-of-action of the two compounds OMP A and MBONNAF were conducted on the enzymatic activity in nematode nervous system (acetycholinesterase AChE), lipid, carbohydrate (pyruvate) and energy (adenosinthiphosphate ATP) metabolism. OMP A did not inhibit AChE activity in M. incognita extract and concluded no action similarity with the standard nematicide aldicarb. Lipase activity in OMP A treatment decreased parallel with the loss in juvenile mobility. The results obtained with OMP A on carbohydrate/energy assays showed significant reduction in pyruvate and ATP levels after longer exposure of ju-veniles and not shortly after the onset of nematicidal activity. The results with MBONNAF suggested that its action is more targeted toward energy metabolism (ATP) and this could correlate to the slower onset of its nematicidal activity. Different tests are still needed in order to obtain a comprehensive picture of the mechanism of action of OMP A and MBONNAF. Baget Pomés, Dolors (2003): A combination of Pesticides with the “CULTAN”-method. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 115 pages. In the integrated plant production pesticides are used according to the principle of the threshold of damage in repeated sprayings. A combination of systemic pesticides with the “CULTAN”-method is presented as an alternative to that practice, whereby some plant physiological and environmental advantages should be reached. In a first pot experiment (1996) some praxis relevant pesticides were selected according to their non-phytotoxicity. In a second pot experiment with spring wheat (1997), the crop protec-tion properties of the selected pesticides (the fungicide Matador and Amistar, the insecti-cide Confidor or their active ingredients) were quantified and valued through inoculation with mildew, trials with aphids and the analysis of the pesticides in the plant material. The plant protection of the fungicides tebuconazol and triadimenol (Matador) and azox-ystrobin (Amistar) were quantified by the help of an inoculation with cereal mildew (Erysiphe graminis). The plants treated with Amistar showed a statistically lower intensity of leaf infes-tation as compared to the plants treated with both tebuconazol and triadimenol.

The plant protection of the insecticide imidacloprid (Confidor) was quantified by the help of trials with aphids (Rhopalosiphum padi). At the growth stage EC-25 the “CULTAN” depots enriched with ammonium nitrate/urea fertiliser and different doses of Imidacloprid were placed in the pots containing the spring wheat. At the stage of growth EC-75 cages with aphids were attached to the flag leaves. All insecticide treatments showed a statistically higher mortality of aphids as compared to the controls. The mortality of aphids in the treat-ments “D1”, “D2” and “D3” reached 50, 60 and 90 % within three days of treatment. There was a linear regression (r2 = 0.996) between the applied doses and the concentrations of imidacloprid in the flag leaves. The uptake dynamics of Imidacloprid was identified by analysing different plant parts at dif-ferent growth stages of the summer wheat. The unchanged and the total residues of imida-cloprid in the grains of the spring wheat treated with Confidor were analysed. The spring wheat treated with the doses 1.01 and 2.04 mg Confidor/pot showed residue concentrations below the tolerance value. Bauer, Andrea Michaela (2006): Estimation of BLUP-breeding values of self-pollinating crop plants considering rela-tionship information and inbreeding. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 98 pages. In plant breeding often hundreds of crosses are carried out every year. Thereby the selection among the lines is mainly based on the phenotypic performance. However, especially if the regarded trait has a low heritability or the data set is unbalanced, the phenotypic perform-ance of a line does not give an appropriate estimate of the genotype. Additionally it is not possible till now to include the genetic relationship among the lines in the selection decision. The prediction of BLUP-breeding values is a widely used statistical method in animal breed-ing which could be able to manage these problems. Considering different environmental conditions and the relationship information among the lines, the BLUP-method leads to an estimation of the genetical disposition of the lines. The objective of this study was to adapt the BLUP-procedure to the conditions in self-fertilized crop plants. For that the coefficient of inbreeding of the parental lines was integrated in the relationship matrix. Furthermore, dominance effects were taken into account in the prediction of breeding values, since there could be a decrease in dominance variance due to the increasing coefficient of inbreeding. As the relationship information of the parental lines often is not known, the effect of considering genetic similarities among the parental lines in the prediction was examined. Then it was tested if the selection based on breeding values is more advantageous than the conventional approach in plant breeding. Therefore typical situations in plant breeding were generated by computer simulation. Compared to phenotypical selection, the application of the BLUP-method resulted in a sig-nificantly enhanced breeding success. Only if the trait has a high heritability or if in early generations progeny families, which arise from a specific single plant, are planted in a plot, the prediction of BLUP-breeding values was not significantly different from a phenotypic se-lection. Moreover, the consideration of all relationship information among the lines in the pre-

diction of breeding values is absolutely necessary to obtain an optimal result. This does not depend on the fact if the relationship information was calculated by coefficient of coancestry or by genetic similarities. In contrast, the inclusion of the dominance effects in the prediction of breeding values does not improve the breeding success further since the ratio of domi-nance variance to total genotypic variance of the simulated traits was too low. Beck, Christian Lukas (2004): Influence of fungicides on the yield physiologie of wheat. Institute of Plant Diseases, Faculty of Agriculture, University of Bonn, 120 pages For the group of strobilurine fungicides, is in addition to the effect on yield through inhibtion of the pathogen, also a effect on yield through direct effect on plant metabolism described. This is indicated by the maintainance of the green leaf area and the photosynthestic activity of the plant, which can be detected by the electron transport rate of the photosynthetic system and by the gas exchange of the plants. Despite the same mode of action the physical and chemical properties of the different strobilurins, differ for example, with regard to the uptake into the leaf, the distribution and mobility in the leaf as well as the redistribuition through the vapor phase. In this work the impact of newer strobilurin containing fungicides on the yield physiology of winter wheat were compared with products which have been on the market for a longer period of time. In field trials as well as under protected conditions the influence of the strobilurins (Azox-ystrobine, Fluoxastrobine, Kresoxim-methyle, Picoxystrobine, Pyraclostrobine and Triflox-ystrobine) on photosynthesis and the grain yield of wheat were compared with azole-treated plants. By repeated treatments all fungicide-treated variants were kept disease free to pre-vent effects of pathogens infestation on yield physiological relevant parameters. Already be-fore the beginning of senescence all strobilurins affected the metabolic activity of the plants (e.g. higher CO2 uptake) positivly – compared to azole treated plants –and finally also the yield. The influence of different fungicide treatments on the disease infestation, physiological pa-rameters of yield formation, as well as the acreage yield of winter wheat were evaluated through several vegetation periods in North-Rhine-Westfalia. Therefore wheat varities were chosen which differed in disease susceptibility, yield potential and grain quality. Neither yield potential nor disease susceptibility of the different varities correlated with higher yields due to strobilurins. Also, no correlation between the yield level of the location and the higher yields due to strobilurins were found. Furthermore the application amount and the timing of the application – in the range of recommended application amounts and the appli-cation time - showed no measurable influence on physiological parameters on yield forma-tion. Nevertheless, the environmental condition and the genotype modified the higher yields due to strobilurins. Varieties with geneticaly lower fixed thousand grain yields and a higher amount of grains per ear responded with significantly higher yields due to strobilurins. To a certain point, strobilurin treated plants could better compensate unfavorable environmental conditions.

With incipent drought stress the level of CO2-uptake decreased, but always had a higher level for the strobilurin treated plants compared to the azole treated plants. Measurements of the C12/C13-isotope signature confirmed the influence of drought stress and the fungicide treatment on the C-assimilation, which finally was reflected in the grain. Strobilurin containing fungicides provoke a permanent activation of the plant metabolism, which is not interrupted due to short term water deficiency. Beyenburg-Weidenfeld, Heinrich (1997): Influence of different insect net materials and polyethylene mulch on the quality of selected vegetable species. Institute for Horticulture, Faculty of Agriculture, University of Bonn, 143 pages. In the present study, the potential of a variety of insect nets (woven polyethylene and spun-bonded polypropylene) to reduce chemical sprays in vegetable production was evaluated. The influence of these protective covers on microclimate, yield and quality as well as on dis-ease development and pest infestation was assessed. The field experiments were conducted at the experimental station of the Institut für Obstbau und Gemüsebau of Bonn University. Five different cover materials, i.e. two dense-meshed, two wide-meshed woven polyethylene and one spun-bonded polypropylene, were tested in a three-year experiment (1993 - 1995). The results indicate that different crop covers have far reaching protective effects and were able to reduce or avoid chemical sprays. Market quality of the harvested products was com-parable to conventionally produced vegetables. The efficiency of these biotechnical plant protection methods could be further improved by changes in management techniques, e.g. choice of cultivar and planting technique. The cultivation of leek under wide-meshed covers did neither affect its biomass accumulation nor its yield in comparison to the uncovered control. On the other hand, the application of dense-meshed materials or spun-bonded polypropylene had negative influences on the growth and weight of the harvested products. The best protective effects against disease (Puccinia porri) and pest infestation (Thrips tabacci), however, were observed by using dense-meshed materials. Neither cover materials nor chemical sprays were able to guaran-tee complete protection against insect damage. The quality of harvested products was mainly reduced by thrips infestation and, consequently, leek covered with dense-meshed materials reached the highest quality levels. Wide-meshed insect nets did not have a significant influence on biomass accumulation and yield of butterhead lettuce compared to the uncovered control. However the use of dense-meshed nets or spun-bonded polypropylene reduced yields. Furthermore, under these latter two materials disease infestation with Botrytis cinerea increased. On the other hand, almost no infestation with Mycus persicae was observed. Quality of the harvested products was pre-dominantly affected by the occurrence of aphids. However, the good protection effects of the dense-meshed nets were outweighed by an increased percentage of plants with loose heads. The production of cauliflower, under different net materials in autumn 1994, resulted in lower yield compared to the uncovered control. The use of nets, irrespective of their meshsize, did

not affect any of the diseases. However, infestation with Delia radicum was completely pre-vented. The quality of harvested products reached the same level in all treatments. Binder, Andrea (2001): Mapping genes for the (1-3) (1-4)-ß-D-glucan content in barley. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 182 pages. The linear polysaccharid (1-3) (1-4)-ß-D-glucan is a major component of starchy endosperm and alleurone cell walls in barley and oat grains. Barley ß-glucans have properties of both technological and nutritional significance. On one hand a high ß-glucan level during the brewing process is responsible for retarding of malting, decreasing output during mashing, increasing of the viscosity of wort and beer and the formation of gelantinous precipitates during storage. On the other hand ß-glucans are desirable for human nutrition, because they are considered to have hypocholesterolemic effects. They lower the cholesterol level by reducing low density lipoproteins. Up to now no breeding program has been investigated that includes wild barley lines (H. spontaneum) as well as barley cultivars (H.vulgare). These wild barley lines distinguish themselves by a very high ß-glucan content, in some cases the ß-glucan content can reach up to 13 %. In the present investigation a wild barley line, that contains more than 8 % ß-glucan, has been used as a parent of a cross with a barley cultivar. The objective of this study was to achieve information on the genetic structure of the ß-glucan content. For this reason a QTL-analysis was carried out. Therefore, 282 F2 individuals originating from the cross of the German spring barley cultivar Lerche and the wild form BGR41936 were used for linkage mapping. By single point analysis 20 significant markers werde found. All in all five quantitative trait loci for barley ß-glucan could be detected by interval mapping procedures. Three of them were located on chromosome 1 H, the remaining two were located on chromosome 2 H. A part of the phenotypic variance (12,3 %) could be accounted for by the microsatellite HvALAAT on chromosome 1 H. It was possible to explain another 5.4 % of the phenotypic variance by the marker HvXYLISOG on chromosome 2 H. Seven selected significant markers explain allto-gether 31.4 % of the phenotypic variance. The three loci which were located on chromosome 1 H showed additive effects, just as one of the other two loci on chromosome 2 H. The second locus on chromosome 2 H showed a complete dominant effect. Beside these gene effects a further epistatic effect between the ß-glucan locus GMS003 and the (1-3) (1-4)-ß-D-glucanase-gene locus EI (HvBDG) could be detected. Binsfeld, Pedro Canisio (1999): Production and Characterization of interspecific transgenic plants in the genus Helian-thus using microprotoplast technique. Institute for Agricultural Botany, Faculty of Agriculture, University of Bonn, 161 pages.

Cultivated sunflower has narrow genetic variability with respect to important agronomic char-acters. The large variety and pronounced variability within wild Helianthus species offers op-portunities to increase genetic variability in the cultivated sunflower by interspecific hybridiza-tion. Symmetric somatic hybridization using protoplasts has often resulted in complex hybrids with many unwanted traits. Several researchers have attempted to reduce the number of undesired chromosomes by irradiation of the donor protoplast, but so far without much suc-cess. As an alternative, asymmetric somatic hybridization was used to transfer one or a few chromosomes using the micronuclei technique. Dividing cells of Helianthus giganteus and H. maximiliani were incubated with the anti-mitotic toxin amiprophos-methyl (APM) or oryzalin (ORY) for 24 h, and subsequently with cytochalasin-B. After 48 h the cell suspension was digested with an enzyme mixture for 4 hours in the presence of the anti-mitotic toxins to re-move the cell wall. The protoplasts (mono and micronucleated) obtained were fractionated on a continuous isoosmotic gradient of Percoll, using high speed centrifugation (120,000 g for 1.5 h). To separate the small sub-diploid microprotoplasts from the large microproto-plasts, sequential filtration through nylon sieves of decreasing pore size (30, 20, 15, 10, 5 and 3 µm) were used. Polyethylene glycol-induced mass fusion between donor wild sun-flower (H. giganteus and H. maximiliani) microprotoplasts, containing one or a few chromo-somes, and recipient diploid H. annuus L. protoplast, gave rise to 53 asymmetric somatic-hybrids after 14 months. Several regenerated plants exhibited H. annuus phenotype, but as could be shown by molecular analysis (RAPD), FCA and cytological analysis contained part of alien genome of the wild sunflower. Sexual transmissibility of the alien genome to the pro-geny could be also observed. Homoeologous chromosome pairing, observed in meiotic mul-tivalent pairing indicated that ASH can be used as a bridge for alien gene transfer. These results indicate that micronuclei induction and asymmetric somatic hybridization opens a way for selected partial genome transfer aiming in the increase of desirable variability in breeding programs. The unique advantages of the micronuclei fusion can be summarized as follows: it allows the transfer of traits which are polygenetically controlled or with unknown molecular background; it also allows the production of monosomic or dissomic addition lines for the transfer or introgression of economically important traits between sexually incompatible spe-cies. Blank, Birgit (2004): Integration of new molecular markers into the Tm-2a region of tomato. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 138 pages. Three known genes - Tm-1, Tm-2, and Tm-2a – confer resistance against TMV (tobacco mo-saic virus) and ToMV (tomato mosaic virus) in tomato. Of these genes, Tm-2a provides the most stable resistance against naturally occurring strains of TMV or ToMV. Tm-2a is local-ized near the centromere of chromosome 9 of tomato and originates from the wild species Lycopersicon peruvianum. In order to elucidate the molecular mechanisms of Tm-2a medi-ated resistance, it is intended to isolate the corresponding gene using a map based cloning strategy.

To follow this approach, the preexisting work done by Pillen et al. (1996a) was continued to generate an ultra high resolution map of the Tm-2a region. Using the strategy of a "bulked segregant"-analysis, the candidate region was enriched by 83 AFLP markers and one SSR marker. These markers were integrated to the existing high resolution map by analysis in the DNA of 77 recombinant individuals identified by Pillen et al. (1996a) and one recombinant plant identified in the present work. Ten AFLP markers cosegregating with the Tm-2a locus were converted to STS or RFLP markers to use them as anchors for the isolation of corre-sponding genomic DNA fragments. Four of these markers were polymorphic and their origi-nal chromosomal position could be verified. The sequences of two additional markers were frequently found in the tomato genome and display homology to retroviral DNA sequences. No polymorphisms were identified for three more markers, the conversion of another marker failed. One AFLP marker located on the short arm of chromosome 9 was converted to a SNP marker for its application in the subsequent screen for recombination events. This recombination screen was performed in a L. peruvianum population established by Pil-len et al. (1996a) to define the order of the new identified markers and to determine the ge-netic boundaries of the existing YAC contigs. A "miniscreen" of 1.395 plants revealed one recombinant individual. In a subsequent two level "high throughput"-screen a total number of 3.984 L. peruvianum plants were analyzed but no recombination event was found in direct neighborhood of the Tm-2a locus. The lack of recombination events prevented the genera-tion of an ultra high resolution map of the Tm-2a region. The observed low recombination frequency, despite the analysis of thousands of individuals, can be explained by a suppression of recombination frequently found in pericentromeric re-gions. The resulting ratio of low genetic distance to large physical distance complicates the isolation of genes by map based cloning. In this case the strategy of transposon tagging can offer an alternative approach. Block, Torsten (1997): Field and Laboratory Studies on Side-Effects of Plant Protection Products on Benefi-cial Arthropods in Apple Cultivation. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 97 pages. Apart from their effect on pathogens, plant protection products also have side-effects on non-target organisms such as beneficial arthropods. Especially in apple cultivation, efforts are made to maintain the natural control potential of beneficial arthropods by selecting prepara-tions, spray sequences or application dates that are compatible with beneficials. The objec-tive of the present thesis is to study the side-effects of broad-effect insecticides used at dif-ferent dates, in integrated and conventional spray sequences, and of different fungicide spray sequences on beneficials in apple cultivation. In laboratory trials, the side-effects of pesticide mixtures on three beneficial arthropod species relevant to fruit cultivation were compared with those of individual preparations. The application of the broad-effect insecticides ‘Decis’ (Deltamethrin) and ‘Bulldock’ (beta-Cyfluthrin) just before apple blossom was less harmful to predatory mite Typhlodromus pyri (Acari, Phytoseiidae), and the population recovered faster than with the application after blossom, with differences among varieties and a higher spider mite abundance observed in

the post-blossom variant. ‘Perfekthion’ (Dimethoate) strongly decimated predatory mites at both application times, with a somewhat faster re-population in the pre-blossom variant. Other beneficial arthropods were not damaged substantially. The apple trees treated with conventional spray sequences showed a markedly lower level of predatory mite and spider infestation than the trees treated by way of an integrated se-quence, whereas spider mite abundance was the other way round. The beneficials were not affected by the three spray sequences in which the fungicides ‘Om-nex + Delan/Polyram Combi’, ‘Rondo M’ or ‘Omnex plus’ were used alternatively. The preparation mixtures tested in T. pyri, i.e. ‘Dithane Ultra + Benocab’ and ‘Delan + Piri-mor’ showed an additive increase in mortality, ‘Systane 6W + Polyram WG’, ‘Omnex plus + Rubitox’ and ‘Systane 6W + Rubitox’ a synergistic increase in mortality. The combinations ‘Dithane Ultra + Benocap’, ‘Polyram Combi + Karathane’, ‘Omnex plus + Rubitox’, ‘Systane 6 W + Rubitox’ and ‘Insegar + Pirimor’ reduced the reproductiveness more markedly than the individual preparations. Related to the mortality of L2-larvae of Coccinella septempunctata- (Col., Coccinelidae), ‘De-lan + Pirimor’ showed synergistic side-effects. In mortality trials with Orius majusculus (Het., Anthacoridae) L2-larvae, ‘Bayfidan + Euparen’ and ‘Delan + Pirimor’ had synergistic effects, while ‘Polyram Combi + Karathane’ showed antagonistic effects. Bölling, Nina (2004) Phytopathological characterization of isolates of cucumber mosaic virus. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 149 pages. The biodiversity of 9 isolates of cucumber mosaic cucumovirus (CMV), including the well known isolates K-, Fny- and Q-CMV, were compared by RT-PCR, dsRNA electrophorese, host plant reaction, DAS- and TAS-ELISA under identical con-ditions. There-fore a purified virus suspension of defined concentration was used to inoculate Nicotiana rustica, N. gluti-nosa, N. clevelandii, N. tabacum “Samsun-NN”, Lycopersicon esculentum (Rheinlands Ruhm), Capsicum annum (Yolo Wonder B) and different varieties of Cucumis sativus and Valerianella locusta. RT-PCR with two sets of primers specific for subgroup I (S-I) and subgroup II (S-II), allowed the classification of the isolates within S-I and S-II. RT-PCR with primers specific for CMV RNA 3 followed by digestion with MspI substantiated the above re-sults. Distinct and different patterns were not found. Association of all isolates with satellites were detected by RT-PCR with primers specific for satellite-RNA and con-firmed by dsRNA analysis, indicating a high level of accumulation in infected plant cells. The isolates induced symptoms of different phenotype and severity, varying from complete systemic necrosis to no symptoms at all, but no correlation was found with sub-group type. In mixed infections, between two isolates within one subgroup or from sub-group S-I and S-II each, no synergistic or antagonistic effect was evident. Examinations of histological and cyto-logical changes in infected host plant tissue elucidated the extent of damage caused by the infection but neither isolate- nor CMV-specific effects were observed.

There was no general relationship between the severity of systemic symptoms and virus ac-cumulation. By ELISA high levels of virus accumulation were detected in plants with none or mild symptoms as well as in plants with severe symptoms. In all host species the sensitivity of both ELISA-variants was satisfactory. Virus was detected even in plants, which appeared to be not infected at all. The results of the present work confirm, that there is no correlation between symptom ex-pression, incidence and subgroup type of the CMV-isolates, and non of them are reliable guides to assess the actual amount of damage caused by infection. Bognonkpe, Jean Pierre Irénée (2004): Effect of land use on soil N dynamics at watershed scale in Africa. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 88 pages. With demographic growth, the use of inland valleys in the humid zone of West Africa has recently been intensified. The swampy bottomlands are opened for lowland rice cultivation while the adjacent upland slopes are increasingly being cleared from natural vegetation for the cultivation of upland food crops. The extent of slope use is likely to intensify water and nitrogen fluxes in the watersheds and thus to differentially impact on soil fertility and crop productivity on slopes and bottomlands as well as in upstream and downstream parts of the valleys. A quantitative understanding of the water and N dynamics with intensified land use is hypothesized to improve the spatial targeting of technical options aiming at conserving soil fertility and maximizing water use efficiency. The nitrogen supplying potential of soils from the ten major rice-based production systems of Côte d’Ivoire was determined by incubation experiments. Seasonal soil N dynamics were studied in-situ at two sites (forest and savanna) and three toposequence positions (upland, hydromorphic valley fringe, valley bottom). Additionally, a three-year study was conducted in a model watershed in the forest-savanna transition zone close to the city of Bouaké in Côte d’Ivoire (experimental farm of the West Africa Rice Development Association- WARDA). The land use of the valley slopes was gradually increased from all natural vegetation in 2000 to 4.5% (2001) and 9% (2002) of the slopes being converted into maize fields. Seasonal dy-namics of soil moisture and water discharge from the valley as well as of mineral soil >N con-tent and plant N uptake on the slopes and the valley bottomland were monitored all year round. Finally, several technical options to manage soil N on the slope and in the valley bot-tom were evaluated during the dry-to-wet season transition period. The net N mineralization potential (N supplying capacity during 6 weeks of anaerobic incuba-tion) from soils of the various rice-based systems of Côte d’Ivoire varied between 4 and 16 mg N kg-1 of soil. It was generally less in the savanna than in forest upland soils and intensi-fied land use reduced soil N supplying capacity more in savanna than in forest ecosystems. On-farm experiments showed that largest native soil N dynamics occurred during the dry-to-wet season transition period, when not only soil N supply but also the potential for N losses to occur were maximal. Cumulative N losses ranged from 9 to 18 kg N ha-1 during the wet season and reached up to 32 kg N ha-1 during the dry-to-wet season transition period. Valley slopes contributed substantial amounts of native soil N to the adjacent lowlands. The potential for this N influx was largest during the dry-to-wet season transition period. The rela-

tive N contribution from uplands to the lowland decreased with increasing slope length. Thus, with a length of slope of 50 meter, 8.3 kg N were translocated into the lowland, while with a slope length of 150 meter only 4.0 kg N were leached into the lowland from each hectare of valley slope. Extrapolated to the scale of the watershed, a calculated amount of about 120 kg N was translocated from about 33 ha of slopes into the 17 hectares of lowland in 2001. This Nmin was prone to further losses from the valley bottom by removal with the surface drain-age water. During the relatively dry year of 2001 (818 mm rainfall annum-1) only about 12.5 kg of N left the valley in the central drainage canal. This N loss increased to 103 kg N in the wet year 2002 (1230 mm rainfall annum-1). The change in land use from natural bush sa-vanna vegetation to maize had no apparent effect on N translocation or N losses at the study site in the derived savanna zone. Technical options to manage native soil N fluxes during the dry-to-wet season transition pe-riod involved the use of improved fallow (pigeon pea) to retain native soil N on the upland slopes, and of nitrate catch crops (Brachiaria and Sesbania green manures) to temporarily immobilize incoming N from the slope in the lowland. The presence of planted pigeon pea fallow on the upland slope conserved some 12 kg of soil nitrate-N ha-1 during the transition season. In the absence of pigeon pea (bare fallow), 47 kg N were translocated from the up-land into the lowland. Cultivation of pre-rice green manures in the lowland during the transi-tion season conserved some 20 kg N ha-1 in the biomass of these “nitrate catch crops”. The subsequent incorporation of this green manure biomass before the transplanting of lowland rice increased the grain yield of rice by up to 1.1 Mg ha-1 (p<0.04) compared to the bare fal-low lowland control plots. It may be concluded, that N fluxes from slopes into the valley bottom and potential N losses from inland valleys in West Africa can be large, irrespective of land use. Particularly in the humid forest zone, a high upland soil N supplying capacity, heavy rainfall events and the predominance of small and narrow valley (short and steep slopes) favor the occurrence of downslope N fluxes and downstream N losses. The use of soil N immobilizing green manure crops in the lowland before the cultivation of wetland rice can considerably reduce N losses and increase crop yields. Strategies to manage native soil should focus on the small and narrow valleys of the high-rainfall forest zone, where they are likely to show the largest im-pact. Final conclusions, the spatial targeting of technical options and a regional extrapolation of the findings must await both experimental confirmation from a wider range of inland val-leys and modeling approaches of N mineralization and N losses in inland valleys of West Africa. Bracht, Petra (1998): Change in quantity of carbohydrates and nitrogen in wheat (Triticum aestivum L.) as influenced by the nitrogen-fertilization. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 165 pages. In glasshouse and field experiments the change in quantity of carbohydrates and nitrogen in the culm, ears and leaves of winter wheat was examined with respect to a fertilization with urea, nitrate or ammonium. The main objective was to determine the influence of the applied form of nitrogen on source-sink-relation in the plant and to confirm the hypothesis of SOM-

MER (1996b), who emphasizes the „root- and shoot-dominance“ through different forms of nitrogen. The translocation of ammonium in the ears during the last phase of development was very intensive under an ammonium-fertilization, so that a higher content of nitrogen was observed in the ears at the time of harvesting in comparison to fertilization with nitrate or urea. It was due to an increased uptake of third and fourth split dose, which occured in ammonium treat-ments. During the first ten days after fertilization the uptake of urea and nitrate was higher as com-pared to ammonium. Nitrate was merely transported to the leaves, whereas ammonium was transported to the ears at a greater percent. The translocation of ammonium in the examined plant parts was influenced when combined with nitrate. Urea didn`t influence the uptake of ammonium. After a fertilization with ammonium-nitrate-urea-solution as placement the symptoms of a „grasslike wheat“ were observed as a reaction of a strong latent N-deficiency. It is supposed that the presence of all three N-forms namely ammonium, urea and nitrate in the ammonium-nitrate-urea-solution is responsible for these symptoms. The quantity of carbohydrates in the plant parts was lower under a fertilization with ammo-nium or rather ammonium-nitrate-urea-solution as compared to nitrate or urea. In contrast, the N-content was higher in the plant parts under ammonium-nitrate-urea-solution treatments as compared to nitrate. These differences had been observed mainly at anthesis. The present results confirm the earlier findings documenting intensive translocation of as-similates in the ears under ammonium fertilization as placement in comparison to nitrate or urea fertilization. The translocation pattern is defined through different source- and sink-relation-ships in the plant. This is in conformity with the hypothesis of SOMMER (1996b) to the root- and shoot-dominance of different N-forms. The culm as the place for carbohydrate storage has an important influence on the level and the duration of grain-filling and finally the yield. In further investigations to yield improvement it is suggested to take care of the role of the culm more seriously. Brenk, Christoph (1997): Estimation of the agricultural recycling potential of organic wastes (‘secondary raw materials’) in Northrhine-Westphalia using an integrated nutrient supply concept and its interpretation with regard to heavy metals. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 220 pages. Waste production of our society has continuously increased during the past decades. At the same time the growing concerns about limited resources and other environmental aspects have led to an increase in waste recycling. Stimulated by that development, a new decree in Germany now defines reusable wastes as ‘secondary raw materials’, which will probably lead to further increases in waste recycling. Agriculture may be affected by this process as it is a possible sink for organic wastes such as sewage sludge and municipal waste compost. Due to its very high population, a significant increase of agricultural waste recycling in Northrhine-Westphalia may be particularly difficult. Therefore, the main aim of this study is to

produce a spatially distinct estimation of the agricultural recycling potential for secondary raw materials in Northrhine-Westphalia. This is done by an integrated nutrient supply concept, which describes the nutrient flows in a certain region and interprets them with regard to the agricultural recycling potential of organic wastes. Based only on current nutrient balances, a recycling potential of about 50 % of the currently produced sewage sludge and organic waste compost was calculated, showing big variation between different regions of the country. These differences are mainly caused by variations in population density and the prevailing type of farming system. Of the factors that were looked at as possibly influencing the agricultural recycling potential of municipal waste, one especially is the high nutrient supply status of northrhine-westphalian soils, which could lead to a distinct reduction of recycling potential. The agricultural and economical conditions will probably in future lead to a decrease in live-stock density especially of pig and poultry production. This will reduce the amount of Phos-phate produced in farmyard manures and therefore cause a growth of the agricultural recy-cling potential of secondary raw materials. At the same time there will be a slight increase in sewage sludge production and a large expansion of organic waste composting, summing up to a more or less stabile rate of 50 % recycling potential. In a second step an evaluation of the heavy metal turnover that would occur if secondary raw materials were recycled in agriculture according to the nutrient demands was carried out. The absolute input as well as the input by secondary raw materials compared to other sources of heavy metals implicate no cause of concern. Nevertheless every possible meas-ure should be taken in future to further reduce the heavy metal content of sewage sludge and organic waste compost. Brinkmann, Olaf (2003): Effect of several resistance proteins on phytopathogenic fungi in vitro and the resis-tance effect of these proteins in transgenic potato and tobacco plants. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 107 pages. The development of plant transformation and cloning techniques has opened new possibili-ties in plant breeding research. With these new techniques now it is possible to transfer ge-nes from different organisms into plants. The objectives of molecular plant breeding are to optimise crop quality and to increase the disease resistance of plants to phytopathogenic fungi. Especially, the basic resistance of plants can be improved by the transfer of foreign genes coding for pathogenesis related proteins. In this paper transgenic potato and tobacco plants expressing the PR-proteins glucanase, chitinase, RIP, or a combination of two of the-se proteins, respectively, were studied for their resistance to several fungal plant diseases using a leaf disc assay. Tobacco lines expressing glucanase or chitinase, resp., showed significantly reduced infecti-on with the pathogens Botrytis cinerea and Phytophthora nicotianae. In comparison to these lines, the combination of the two PR-proteins led only to a slight further enhancement of re-sistance of tobacco plants. Furthermore, the co-expression of glucanase/chitinase, glucana-se/RIP or RIP/chitinase, resp., in the potato variety Désirée resulted in significantly reduced

disease symptoms after infection with Phytophthora infestans but not to a resistance increa-se higher than the resistance of lines expressing only one foreign protein. The lysozyme of the T4 bacteriophage is known to be bactericidal. Using in vitro assays, an inhibitory effect on germinating spores of phytopathogenic fungi was detected in this work. The same effect was shown for enzymatic inactive T4-lysozyme and for the synthesised pep-tides A4 and A23 of the C-terminus of T4-lysozyme. Thus, the fungistatic effect is likely asc-ribed to the membrane disturbing activity of amphipathic helices these peptides are coding for. Using a fluorescence test the membrane disturbing activity of T4-lysozyme on fungal spores could be proven. The expression of T4-lysozyme in potato plants (var. Désirée) under control of the 35S-promoter confers significantly increased resistance to Phytophthora infestans. Whereas pota-to plants expressing the T4-lysozyme gene under control of the mannopine-synthase promo-ter showed no significant Phytophthora resistance. Further resistance tests indicate that transgenic T4-lysozyme expressing potato lines of the varieties Panda and Secura, which have high or low natural resistance to Phytophthora leaf blight, resp., show significant en-hanced resistance, too. Cerboncini, Claudio (2003): Characterization of wild Helianthus species under natural conditions: biometrical, his-tological and biochemical investigations. Institute for Agricultural Botany, Faculty of Agriculture, University of Bonn, 180 pages. Sclerotinia sclerotiorum (Lib.) de Bary is one of the major fungal diseases of sunflower (Heli-anthus annuus L.) and causes great economic losses in sunflower production worldwide. The pathogen can attack all parts of the plant on every plant growth stage, predominantly the capitulum, the leaf and stem. Due to the narrow genetic variability no source of complete resistance to Sclerotinia is available in the cultivated Helianthus gene pool. However, wild species exhibit a great diversity and hence are promising sources of genes for disease resis-tance. In the present study, 21 perennial Helianthus species of diverse origin were evaluated in multiannual field trials and controlled environment studies on their resistance level to mid-stem and leaf infection using an artificial inoculation method. The evaluation revealed con-siderable and significant differences within the genotypes in all recorded resistance traits. The induced lesion length four days after infection was evaluated as a confident predictor of disease resistance level and was used as a reliable phenotypic trait for screening the wild Helianthus species against Sclerotinia stem and leaf rot. Three genotypes, two H. maximil-iani Accessions and H. salicifolius, showed enhanced partial resistance levels to mid-stem infection. H. divaricatus and H. maximiliani AC 7 exhibits resistances to leaf infection and additionally in H. maximiliani AC 7 partial resistances in both plant parts were discovered. Further histological investigations revealed a close interrelation between the genotypic lignifi-cation patterns of the stems and their level of resistance to Sclerotinia mid stem rot. More-over in H. salicifolius a reinforced stem cuticle was identified as preformed partial resistance factor to stem infection. Postinfectional in situ detection of phenolic compounds in stem tis-sues performed by epi - fluorescence microscopy showed their strong accumulation in partial resistant genotypes and was characterized as dicaffeoyl ester by thin layer chromatography.

Pathogen induced changes of the initial phenolic metabolism were examined by determina-tion the pre and postinfectional phenylalanine-ammonia-lyase activity (PAL) and revealed a great variation among the genotypes. A 30 fold increase of PAL-activity in partial resistant H. salicifolius internodes shows a rapid and coordinated induction of the phenylpropanoid me-tabolism in response to Sclerotinia attack. In addition, the defence reaction of stems from partial resistant genotypes was accompanied by a significant increase in cell wall bound per-oxidase (POX) activity which can be used as biochemical marker for Sclerotinia resistance. To investigate the interrelationship between preformed phenolic compounds in wild sunflower leafs and their resistance to mycelial extension a new chromatographic method was devel-oped to determine complete phenolic patterns in the genus Helianthus. The subsequently applied multivariate analysis revealed a close quantitative and inverse association between putative flavonoid leaf phenolics and the mycelial extension in the leaf mesophyll. Cramer, Benedikt (2006): Review from evaluation models in order to identify and predict harmful soil compac-tions on arable land in North Rhine-Westphalia. Institute of Crop Science and Resource Conservation, Faculty of Agriculture, University of Bonn, 178 pages. In order to avoid damage to soil structure, evaluation models of soil prognosis (“Compaction Risk Classes”, “Pre-compression stress”, “Pressure quotient of divided by soil stability”) are available. Their aim is an agricultural conception for the protection of soil structure. The aim of the “Indication model” is to identify an affected soil structure, as outlined by the Federal Soil Protection Act. Because of the controversial discussion about soil compactions the soil structure of arable land in North Rhine-Westphalia was quantificated in this study. It was also an objective of the work presented to verify models for preventing and identification of harmful soil structure as well as the development of a valued measure to evaluate large-scale equipment used in ar-able cropping. During a period of three years, soil physical, soil mechanical and soil chemical measure-ments were performed on 46 agricultural field areas with various location and using condi-tions. The topsoil (about 15 cm), the area of the plow-pan layer (about 35 cm) and the sub-soil (about 50 cm) were analyzed. The results point out that the subsoil of the investigated field areas fulfilled the function of water regime and aeration at this time. However, the plow-plan layers and the loosened top-soil are more compacted. The field estimation of soil structure and the low values of the air capacity point out the damage of soil structure. The application of the “Indication model” allows the identification of harmful soil compactions. On sandy soils, the air capacity and the waving of water permeability might be a problem. The concept “Compaction Risk Classes” is not suited to prevention of compactions, because the bulk density does not describe soil functions. Correlations between bulk density and air capacity were established at most for soils with similar geological soil origin. This model was based on examination with disturbed samples without considering soil aggregation, as well.

The concept “Pre-compression stress” describes the mechanical strength of agricultural soils and might expect an effective contribution to protect soil structure. If loads are higher than the precompression load, degradation and reduction of soil functions might occur. The me-chanical compressibility, which is characterized by the value of precompression stress, can-not be calculated and assessed by multiple regressions. The concept “Pressure quotient of divided by soil stability” is not qualified to prevent compac-tions, because of the defined limit of air capacity (5 Vol.-%). This harmful value means a risk for irreversible soil compaction in contradiction to a general concept of preventing harmful soil compactions. The comparison between the mechanical strength and the load input allows estimating soil compactions. The calculated soil pressure distribution shows that especially heavy agricul-tural vehicles are causing problems due to compaction in the loosened subsoil. Depending on the tyres, high wheel loads (6-10 tons) used in arable cropping can lead to long term damage of wet and silty subsoil derived from loess material. Cramer, Hubert (1994): Investigations of the function of inositol 1,4,5-trisphosphate in plant signal transduc-tion. Institute for Agricultural Botany, Faculty of Agriculture, University of Bonn, 92 pages. In animal systems, signal transduction of diverse important biological stimuli induces via the phosphoinositide-system. In plant cells, this reaction chain is however only poorly character-ized. Besides flagellar excision in green algae Chlamydomonas reinhardtii and the motor cells of Samanea saman, stomatal guard cells are suitable for the investigation of signal transduction processes in higher plants. To examine stomatal movement at a biochemical level, a method was established for the preparation of large quantities of epidermal peel from the leaves of Vicia faba (L.) using the blender method. From this epidermal peel, it was possible to isolate physiologically intact guard cell protoplasts. These protoplasts show reactions such as shrinking towards applied abscisic acid, which provide unambiguous evidence of their viability and represent a basic requirement for the study of signal transduction reactions in stomatal guard cells. To investigate the role of inositol 1,4,5-trisphosphate (InsP3) in stomatal signal transduction, a method was established for measuring this second messenger. Inositolphosphates were separated by HPLC. The eluate was fractionated and the inositolphosphates of the individual fractions were dephosphorylated. After desalting the samples, mass spectrometry coupled to gas-chromatography was used to detect the inositol released with sensitivities up to 100 fmol. Initial experiments with plant material revealed higher InsP3 contents in guard cell pro-toplasts than in mesophyll cell protoplasts. Furthermore, an abscisic acid induced InsP3 in-crease seems to be guard cell specific. Moreover, an InsP3-receptor was detected in plant membranes by western immunoblot. In microsomes prepared from leaves of Vicia faba and Zea mays, the antibody detected pro-teins with molecular mass of 260 kDa and 252 kDa respectively, which is in the range of the mammalian counterpart. Isolated vacuoles from V. faba revealed the same band pattern as microsomes, while no cross-reaction was observed with purified plasma membranes. These

results support the concept the the vacuoles function as an intracellular Ca2+ store in higher plants. Dagbenonbakin, Gustave (2005): Crop productivity and water use efficiency of important crops in the Upper Oueme Catchment: influence of nutrient limitations, nutrient balances and soil fertility. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 212 pages. The Upper Oueme catchment in the West African subhumid zone is a region in Northern Be-nin, which actually experiences major changes in land use, water availability, and population density. In the context of the IMPETUS project, the present work aimed to i) identify nutrients which are limiting productivity on the basis of soil and plant analysis, ii) compare effects of fertilizer application nutrition to current farmer’s practice, iii) determine the water consumption per unit of biomass (maize) and per unit of area, and iv) assess (simplified) nutrient balances to predict long-term trends of nutrient availability and soil productivity. Field experiments were carried out in 2001 and 2002 using a randomized complete block design with four treatments, 2001: n = 80, 2002: n = 109) at three sites: Beterou, Dogue, and Wewe. Soils of the sites had low fertility and were PLENTOSOL and Ferric-Profondic LUVI-SOL in Beterou, PLENTOSOL and LIXISOL in Dogue and ACRISOL or Plenthic-LIXISOL in Wewe. Treatments were: T0: farmer’s practice or plots without mineral or organic fertilizer applied with exception of cotton, where farmers applied fertilizers as usual; T1M: 10 t ha-

1crop residues; T1F: 10 t ha-1 of farmyard manure in 2001; T2: mineral fertilizer at the rates recommended; T3M: mineral fertilizer as applied in T2 + 10 t ha-1 of crop residues for mulch in 2001 and 2002, while for T3F mineral fertilizer was applied as in T2 + 10 t ha-1 of farmyard manure. Residual effects of manure application were evaluated without further OM applica-tion. Soil samples were taken before and at the end of the experiment to appreciate the nutritional status of plots. Leaves were sampled at critical stages for plant for nutrient assessment through critical Value Method CVM and Diagnosis and Recommendation Integrated System (DRIS). Yield (DM) of all the crops, their total biomass and harvest index were evaluated at harvest. A partial nutrient balance was calculated on the basis of tissue and product analysis for a high and a low – yielding sub-groups. Actual evapotranspiration was estimated by gra-vimetry, humidimetry and tensiometry for water use efficiency (WUE) of maize in Dogue in 2002. Rainfall during the crop growth was used to calculate rainfall use efficiency (RUE). Water or rainfall use efficiency was determined as the ratio between above ground biomass and rainfall for RUE or actual evapotranspiration for WUE. Crop productivities were significantly affected by farmer’s practice and the type of organic matter applied. Organic or mineral fertilizer or the combination of both increased crop pro-ductivities, RUE and WUE of maize although a relatively high variability was observed be-tween individual plots and farmers. Nitrogen was the most limiting nutrient followed by potassium and phosphorous according to DRIS-Evaluation while the CVM method revealed most of the macronutrients as low or close to the critical level. However, only the nutritional imbalance index of maize decreased from 2001 to 2002. Standard nutrient levels and reasonable DRIS norms were established for N,

P, K, Ca, Mg, S, Zn, Mn of maize, sorghum, cotton, yam and groundnut. They can be used to evaluate crop nutritional status, to correct nutritional imbalances and to improve crop produc-tivities. They can also be used as a basis for calibrating the fertilization programs for these crops. Negative nutrient balances were observed, as inputs of nutrients were insufficient to com-pensate outputs. The strategies to compensate the nutrient gap are to increase the recycling of residues, to increase the application of manure, or introduce fertilizers or a combination of all three. Actual farmers' practices in maize, sorghum, groundnut and yam cropping systems lead to depletion in soil nutrient levels, as there is actually almost no return of nutrients to the fields and mineral fertilizer are only rarely applied. When calculating the balance for a typical yam-cotton-maize-groundnut-sorghum rotation, the nutrient balances are negative by 177 kg ha-1 N, 33 kg ha-1 P and 163 kg ha-1 K. This leads to nutrient depletion (as actually found in the project area) and not sustains adequate yields. The only desirable scenario could be the practice of integrated soil fertility management where mineral and organic fertilizers are combined. Here, one should as well take into ac-count crop rotations with legumes to optimize nitrogen fixation, mineral fertilizer, and efficient management of crop residues. Management methods that limit nutrient losses and increase water use efficiency are some of the approaches that will be used to improve and sustain soil fertility and conversely to enhance crop production and in Upper Oueme Catchment. Diab El-Arab, Hanan (2001): Rhizosphere specific microbial communities in wheat: characterization using fatty acid extraction methods and possible role in maintenance of root health status. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 139 pages. The results obtained in the research on the determination of the rhizosphere specific micro-bial communities and their possible role in maintaining proper root health of wheat are pre-sented in three chapters. In the first chapter, the disease reaction of six wheat genotypes having different geographical origins to specific soil-borne pathogens was studied. In addi-tion, the degree of genetic relatedness of those wheat genotypes was determined using RAPD-PCR. Results of pathogenicity tests conducted in growth chambers showed that: German wheat genotypes were tolerant to most root-rotting fungi, Middle East genotypes were moderately susceptible while the South Asian genotypes were susceptible. On the other hand, results of the UPGMA cluster analysis of the genetic relatedness among wheat genotypes showed separate clustering of the Middle East genotypes from each other and from the other genotypes which had no distinct clustering. In the second chapter, the role of plant genotype on the composition of the rhizosphere specific microbial communities (RSMC) of wheat was elucidated. Different approaches were used to determine RSMC under con-trolled environmental conditions: the traditional culturing technique, colony forming units and the advanced fatty acid methyl ester extraction methods. Multivariate analyzes, including principal component analysis and cluster analysis combined with different fatty acids tech-niques revealed distinct RSMC of the Middle East wheat genotypes versus closely related

microbial communities of the other four genotypes. Targeted characterization of the microbial communities was accomplished using select fatty acid biomarkers for specific microorgan-isms. The third chapter describes the influence of an introduced biocontrol agent Pseudomo-nas fluorescens 2-79 in controlling the take-all pathogen Gaeumannomyces graminis var. tritici and on the composition of the RSMC of wheat. Results showed suppression of the take-all pathogen with the rhizobacterium. Furthermore, phospholipid fatty acids and fatty acids profiles of the microbial communities revealed distinct treatment effects on the struc-ture of the microbial communities. Distinct clustering of fatty acid biomarkers was observed between microbial communities in the presence of the pathogen versus the control treat-ments. The results indicated that the distinct composition of the rhizosphere specific micro-bial community was not only influenced by the introduced biocontrol agent, but also by the plant genotype of the wheat cultivar. This study showed that a number of interrelated factors influence overall plant resistance to fungal root-rot pathogens. Future research into the role of plant genes involved in hosting beneficial plant-associated microbes will provide greater insight into the interaction between genotype and rhizosphere specific microbial communities and provide new tools to improve root health management. Dicke, Dominik (2005): Directing site -specific weed control methods with respect to weed population dyna-mics using computer based models. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 152 pages. In this dissertation, site-specific weed control was studied in a crop rotation and in continuous maize from 1997 until 2003. Site-specific weed control resulted in high herbicide savings. The efficacy of site-specific weed control in most cases was similar to weed control methods with uniform herbicide applications. Spatial and temporal dynamics of weed populations were evaluated in all fields. Weed seedling distributions were heterogeneous in all years and most of the high density patches remained stable in density and location. In the crop rotation, the averaged weed density was very stable over all years of the study. However, in continuous maize weed density increased. A new dGPS controlled multiple patch sprayer was devel-oped and tested for site-specific weed control in malt barley on a farm near Nideggen. The sprayer allowed varying the herbicide mixture on the go. Additionally, two different weed thresholds were tested for site-specific weed control in malt barley. The GIS-based analysis of weed distribution maps, soil map and grain yield map revealed that weed competition had no significant effect on the average grain yield. However, competition of Cirsium arvense and Avena fatua reduced the fraction of larger grains (>2.5 mm calibration) and the protein con-tent in the grain at locations where more than 5 plants/m² of Cirsium arvense and more than 15 plants/m² of Avena fatua occurred. Another field experiment was established to study the influence of reduced herbicide doses and the competition effects of spring wheat and spring barley on density and seed production of selected weed species and to quantify weed seed predation after harvest in tilled and untilled plots.The efficacy of reduced herbicide doses against Galium aparine was similar to herbicide applications with the full herbicide doses. Competition of spring grain reduced density and seed production of Eschscholzia californica.

However, density and seed production of Galium aparine increased in spring grain. Weed seed predation in untilled plots varied between the years of study. Data of all experiments were taken to predict the spatial and temporal dynamics of weed populations using a weed population dynamic model. The objective was to simulate the distribution of Chenopodium album within two experimental fields, starting with weed infestation in the first year of the study. The results of a new model, which was developed at the Institute of Agronomy and Crop Science, could be validated using Pearsons coefficient of correlation. The model im-proves our understanding of spatial and temporal dynamics of weed populations and thus can be included in decision algorithms for patch spraying. Dickmann, Michael (2002): Einfluss des Kultursubstrats auf vegetatives und generatives Wachstum von Erd-beeren der Sorte ELSANTA im geschützten Anbau. Institute for Horticulture, Faculty of Agriculture, University of Bonn, 116 pages. The effects of a) source or type of planting material, b) planting substrate, c) composition of nutrient solution and d) type of overwintering were investigated to extent the strawberry sea-son under glass when both market price and demand rise. Strawberry plants cv. 'Elsanta' were used throughout this study. Neither vegetative nor reproductive growth were affected by the planting substrate. Frigo plants showed the least vegetative and reproductive growth of the three types or sources of strawberry plants employed, waiting bed, tray and frigo plants irrespective of planting sub-strate. Frigo plants also used the smallest amount of water. Strawberry plants overwintered in the open field showed improved reproductive growth rela-tive to plants kept in a greenhouse and affected vegetative growth in terms of leaf areas. This was attributed to respiratory losses. This hypothesis was confirmed by respiration measurements. Respiration of frigo plants in-creased with temperature from 1°C to 22°C, but decreased during subsequent plant devel-opment with a trough at flowering and peaked at fruiting. Potassium concentration in the nutrient solution was raised in order to improve the quality of strawberry fruit. Increasing the potassium concentration in the nutrient solution from 5 to 15 mmol K/l, however, did not affect the fruit quality. Further increases in potassium concentra-tion above 20 mmol K/L diminished the fruit quality. Diédhiou, Papa Madiallacké (2001): Investigations on the occurrence of arbuscular mycorrhizal fungi and importance for plant health and vitality. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 97 pages. The importance of arbuscular mycorrhizae for plant growth and vitality as well as for plant health was studied under field and greenhouse conditions. AM-fungi were isolated from soil samples taken in fields at different locations in Northrhine-Westphalia, Germany. Seven of

them were used after propagation on maize for further studies. The identification of the iso-lates was based on morphological features of the spores. The taxonomical methods were combined with results from DNA sequence analysis of the ITS and the 5.8S rDNA of ribo-somal genes. Comparison of the DNA sequences of the isolates with those from data banks gave evidence for AM identification, which could be confirmed or completed by the morpho-logical methods. The ability of the AM-fungi to improve plant growth depends on many factors among which the genotype of both partners plays an important role. Not only the plant species, but also the cultivar and the AM-isolate were essential for the efficiency of the symbiosis on plant growth. Experiments were carried out to study the effect of a co-inoculation of AM-fungi with other beneficial rhizosphere micro-organisms on plant growth. The combination between AM-fungi and Bacillus subtilis or a non-pathogenic isolate of Fusarium oxysporum gave neither a syn-ergistic nor an additive effect on plant growth. Nevertheless, root colonization with the AM-fungi was improved by the presence of F. oxysporum . Glomus coronatum proved to be an-tagonistic to Meloidogyne incognita on tomato and reduced the nematode damage. F. ox-ysporum also reduced disease severity and nematode damage. The combination between G. coronatum and F. oxysporum showed, however, neither an additive nor a synergistic effect against the disease due to M. incognita. Under field conditions mycorrhization of wheat roots was very low indicating a lack of impor-tance of this symbiosis in intensive wheat production. Fungicides, mainly strobilurins, and growth regulators, when applied at growth stages as usually, are not implicated in the reduc-tion of the AM-fungi in these biotopes. Wheat mycorrhization was significantly higher under organic farming conditions. Complementary greenhouse studies showed that spray applica-tion of strobilurins negatively influenced root mycorrhization only in early stages of estab-lishment. Later applications did not affect mycorrhization. In contrast, herbicide applications led to different results: Metsulfuron-methyl was very toxic to mycorrhizae, whereas prosulfo-carb and fluroxypyr had a weak negative effect on mycorrhiza. Dietrich, Stephan (1998): Investigations on the development of a preparation of the entomopathogenic fungi Metarhizium anisopliae and M. flavoviride for control of the African Locust Locusta migratoria and the Desert Locust Schistocerca gregaria. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn,172 pages. The fungi Metarhizium anisopliae and M. flavoviride are well documented pathogens of lo-custs and promising candidates for biocontrol of these pest insects. However, the commer-cial utilisation of the fungus as a mycoinsecticide necessitates the development of practical production, formulation and application techniques. A liquid fermentation technique was developed in order to produce high concentrations of submerged spores (Ss) of Metarhizium spp. using extremely cheap media. For M. flavoviride, isolate Mfl 5, the best medium was 4% sugar-beet syrup and 8% Naturpur® (composted chicken droppings) resulting in a maximum yield of 6,3 x 108 Ss/ml. Within a laboratory batch-fermenter a maximum yield of 1x109 Ss/ml was obtained. The production in fermenters with a capacity of up to 350 l was possible.

Light- and scanning electron microscope investigations were conducted to study the forma-tion of Ss. A spray-drying technique was developed which allowed drying of submerged spores of M. anisopliae and M. flavoviride without a significant loss of viability. The best protective agents for Ss were skim milk powder (20%) + sugar-beet syrup (2,5%). Finally, the virulence of spray-dried submerged spores of M. anisopliae (Ma 97) and M. flavoviride (Mfl 5) was tested in bioassays using L3-4 of Locusta migratoria. Results showed that there was no significant difference in the mortality curve between spray-dried and undried submerged spores of M. anisopliae but of M. flavoviride. For long-term storage, spray-dried submerged spores were incubated at different constant temperatures between 5° and 50° C under dry and oxigen reduced conditions. After 52 weeks of storage at 5°, 20° and 30° C, the germination rate of Mfl 5 was 73.1, 68.0 and 38.3%, respectively. Storage at 40° and 50° C for about eight and two weeks, respectively, resulted in a loss of viability of 50%. In semi-field trials in Mauritania three different formulations of Mfl 5 were tested against Schistocerca gregaria using ULV-application. Spray-dried submerged spores were highly infective in a water-based formulation, an oil/water emulsion and an oil formulation. In con-trast to laboratory trials, the highest mortality of nearly 100% after 15 days was observed with the water-based formulation (20% sugar-beet syrup in water). This formulation was also ef-fective against adults using concentrations of 1.2 x 1012 Ss/ha. Ditzer, Silke (2001): Factors affecting the rainfastness of selected protective fungicides in ´Golden Deli-cious`. Institute for Horticulture, Faculty of Agriculture, University of Bonn, 114 pages. The objective of this thesis was to obtain basic information on the rainfastness of the se-lected fungicides tolylfluanid, dithianon and mancozeb in ´Golden Delicious` apple trees. The fungicide residues, which were quantified by gas chromatography and spectrophotometric after the rain events, were used to determine the rainfastness. For a detailed study of the selected parameters and factors affecting the rainfastness it was necessary to generate rain events with a high reproducability and close agreement with natural conditions. For this pur-pose two rain simulators were developed, of which rainfall intensity, droplet spectra and rain quantity have been calibrated and verified. A modified rainfall simulator (B-LRS-2) and a newly designed device based on a rotary disk were used for this studies. The results of the studies are summarized as follows: In the first part of this thesis basic information on the rainfastness of dithianon and tolylfluanid was collected under field conditions and natural rain events. The studies were carried out under practice related conditions at the Fruit Experimental Station OVA Klein-Altendorf and under greenhouse conditions at the Institute for Horticulture of Bonn University. These refer-ence data were used for comparisons and validation of the following studies under rainfall simulation which showed wash-off losses of the active ingredients between 73 and 96 %. In order to determine the influence of intensity and/or amount of precipitation on the rainfast-ness of tolylfluanid, three rainfall-intensities were simulated, such as a light rainshower, a

continuous and a heavy rain event. The studies revealed a negative correlation between the rainfastness of tolylfluanid and rainfall intensity. The experiments on the impact of simulated continuous rain showed results which were very close to those obtained under natural rainfall. Comparative studies employing ´Golden Deli-cious` seedlings and grafted trees revealed that ´Golden Delicious`/M9 trees were more suit-able for these studies because the results under simulated conditions were closer to those under field conditions. The studies about the rainfastness of the protective fungicides allow the following gradual sequence: Mancozeb showed the best rainfastness, followed by tolylfluanid and dithianon. The impact of relative humidity was studied in the period (8 hours) between application and beginning of the rain event and tow was included in studies on the rainfastness of dithianon. No influence on the rainfastness of dithianon was observed when relative humidity was main-tained at 50, 70 and 90 %, respectively. The rainfastness of dithianon was reduced on seed-lings from growing conditions under dew in comparison to seedlings without dew. The rain-fastness of dithianon and tolylfluanid in apple trees grown in the field was higher than in ap-ple trees raised in the greenhouse. Field grown plants showed an increased amount of wax, reduced leaf area and shoot length, as compared to plants from the greenhouse. Different fomulations (WG/SC) of the foliage applied pesticides were tested in studies on the rainfastness of dithianon. Use of the SC formulation resulted in a higher rainfastness and retention of spray application than the WG formulation. When adjuvants were added to di-thianon as a tank-mix rainfastness of dithianon was mostly negative affected. Also, all adju-vants reduced retention of dithianon spray solution. By using a rotary disk and simulating continuous rain similar results as those of the rainfall simulator B-LRS were observed, al-though droplets diameters were different. Domeyer, Kay (2005): Accumulation and depletion of heavy metals in the rhizosphere and their removal by agricultural crops with particular regard to the aspects of phytoremediation. Institute of Crop Science and Resource Conversation, Faculty of Agriculture, University of Bonn, 370 pages. In growth chamber and greenhouse experiments the attitude of Cd, Cu, Pb and Zn in the rhizosphere of lettuce, spinach, wheat, sunflower and Indian mustard was explored using different techniques to collect rhizosphere soil. The aim of the study was to conceive accu-mulation and depletion processes of heavy metals in the rhizosphere and to decide an expli-cation for the wide variability of rhizosphere profiles. It was shown, that commonly the H2O- and citric acid-extractable fractions of Cd, Pb and Zn were depleted in the rhizosphere, whe-reas for Cu typically accumulations were observed. The results of the NH4NO3-extraction, characterizing the mobile heavy metal-fraction, were reciprocally. Except for Zn, which was depleted in the rhizosphere of wheat for all other tested heavy metals an accumulation in the soil close to the roots was observed. This seems to be linked with the varying nutrient acqui-sition strategy of monocotyledonous and dicotyledonous plants. The extraction with H2O and citric acid, respectively, often underestimate the plant removal, whilst the NH4NO3-extraction commonly overestimates the removal of heavy metals. After

depletion of the H2O-extractable fraction of Cd, Cu and Pb there seems to be an additional delivery from the mobile fraction. There is evidence that the organic bound fractions of Cu and Pb were also involved in the additional delivery. The soluble and mobile fraction of Zn do often not cover the demand of the plant. The additional delivery appears to be derived either from the fraction occluded in Mn-Oxides or also from the organic bound fraction. Soluble Zn-organic complexes seem to be not available to dicotyledonous plants. The fertilization strategy is notably applicable to influence the bioavailability of heavy metals in soils. As compared with an unfertilized treatment the impairment of the soluble and mobile heavy metal content - except for Cu - in soils is presumably influenced by phosphate. The application of 6 mM EDTA resulted in a hyperaccumulation of Cd by lettuce. Drescher, Karsten Erich (2005): Studies on the possibilities of biological control of Thrips tabaci Lind. (Thys., Thripi-dae) using different, predatory arthropod species in the production of vegetables. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 67 pages. The common vegetable pest Thrips tabaci Lind. (Thys., Thripidae) can hardly be controlled by using large amounts of chemical insectizides. Therfore, it was the aim of the present study to investigate the possibilities of ecologically safer biological control methods by releasing different predatory arthropod species. For this purpose, beneficial arthropods were tested for use in biological control under stan-dard laboratory conditions. During this evaluation special interest was put on developmental times, predation rates and reproduction. Suitable beneficial organisms were then mass re-leased under a standard crop production setting. Their efficacy measured in reduction of crop pests found per plant was evaluated in the field. The beneficial arthopods were released as single species, combined with plant protection netting, as well as in combination of different species. Of the beneficial arthropods studied in the laboratory predatory bugs (Heteroptera, Antho-coridae), predatory Thrips (Thysanoptera, Thripidae und Aeolothripidae), as well as preda-tory mites (Acari, Phytoseiidae und Hypoaspidae) were, in general, able to be used in the biological control of T. tabaci. Orius majusculus REUTER, Franklinothrips vespiformis CRAWFORD, Amblyseius cucumeris OUDEMANS, Amblyseius degenerans BERLESE, Amblyseius umbraticus CHANT, Amblyseius andersoni CHANT , Amblyseius limonicus GARMAN und MCGREGOR were evaluated. The predatory mites A. cucumeris , A. degenerans, A. andersoni, A. limonicus were used in the field studies. The reduction of T. tabaci caused by the mass release of the different bene-ficials varied in respect to the beneficial used, the year of the study, as well as through addi-tional use of the plant protection netting. An increase in efficacy of the mass release could not be observed by varying the dates for the mass release or a combination of used species. In conclusion, A. cucumeris and A. andersoni were able to reduce the number of pest per plant.

Durmusoglu, Enver (1997): The evaluation of the dislodgeable foliar residues and exposure of workers in pesti-cide-treated apple and rose cultures. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn,110 pages. The most common way that operators and workers can be exposed to pesticides is during the application or afterwards by contact to residues remaining on the foliage. Particularly for workers in treated crops, these residues are the main source of exposure to pesticides dur-ing their manual work activities. In this study, firstly the dislodgeable foliar residues and ex-posure of workers after application of Triflumuron and Bitertanol in apple culture as well as after application of Methiocarb and Bitertanol in rose culture were measured. The level of exposure of the workers during thinning and harvesting in an apple orchard and during break of shoot cutting in a greenhouse roses production was determined. Following a transfer coef-ficient was calculated representing the relationship between determined residues and the level of exposure of the workers. The amounts of the dislodgeable foliar residues of each pesticide measured in the two differ-ent crops varied greatly. The residues of Triflumuron and Bitertanol detected on the leaves in the apple orchard amounted to 0,06 to 0,24 µg/cm2 and 0,06 to 0,65 µg/cm2 respectively. The amounts of Methiocarb and Bitertanol found on the leaves of the roses could be determined to range from 0,21 to 2,6 and 0,24 to 1,54 µg/cm2. The level of exposure of the workers varied depending on the pesticide used, the kind of work conducted and the time after the application of the pesticides at which it was conducted as well as the characteristics of protective clothing worn. The range of the determined levels of exposures varied between 0,1 to 12,4 mg/h. The measured rates of exposure to both pes-ticides during the thinning of the apple orchard were clearly higher than during harvest, whereas in the rose greenhouses the measured exposure rates for the harvest were higher than during breaking of twigs. A transfer coefficient for the thinning out in apple orchard which is the activity that results in the most contact with pesticide treated material was calculated to amount from 1000 to 10000 cm2/h. The transfer coefficient for the harvesting of the roses was determined to be between 200 and 10000 cm2/h. The results of this study clearly show that the values of the level of exposure of the worker to all examined pesticides were distinctly below the values considered to be tolerable without danger to the health of the worker. It was also shown that use of gloves and wearing suitable clothing greatly reduces the level of exposure. Ellinger, Sabine (2003): Intervention study to investigate the effect of moderate red wine consumption on se-lected redoxsensitive immune functions from T-lymphocytes and phagocyte popula-tions. Institute for Agricultural Botany, Faculty of Agriculture, University of Bonn, 91 pages. Background: Polyphenols are secondary plant products occurring in plant foods, in especially high concentrations in red wine. They have many biological properties, among them immu-

nomodulatory and antiinflammatory effects. These effects have almost exclusively been ob-served in vitro. Hence the aim of this study was to investigate if single or repeated dietary polyphenol intake by means of red wine (RW) affects redox sensitive immune functions ex vivo, and if dealcoholized red wine (DRW) induces similar effects. Methods: A) 27 healthy non-smokers consumed a single dose of 200 mL RW, 175 mL DRW or 200 mL water (controls). The percentage of apoptotic T-lymphocytes was determined with annexin V labelling and phagocytosis and burst of granulocytes and monocytes with testkits (Phago-, Bursttest) before, 90 and 360 min after intervention. All investigations were done by flow cytometry. B) 49 healthy non-smokers ingested either 200 mL RW or 175 mL DRW daily for 6 weeks in addition to their usual diet. A control group including 25 participants did not receive any study drink. Blood samples were taken after an overnight fast before and after 6 weeks of intervention and the same parameters were investigated as in A). Results: A) Immunomodulatory effects related to intervention could only be observed after single, but not after repeated ingestion of either RW or DRW. The percentage of phagocytic monocytes increased 90 min after consumption of RW, but not after consumption of DRW, probably due to the alcohol or the higher polyphenol intake with RW in comparison to DRW. The percentage of burstpositive granulocytes decreased 360 min after consumption of DRW and increased progressively in monocytes compared to baseline values. As these effects occurred only after consumption of DRW, but not after consumption of RW, the alcohol seems to compensate the polyphenols’ effects, probably by prooxidative effects or by in-creased polyphenol elimination. Further parameter did not change in any group. Conclusion: Immunomodulating effects occurred only after a single ingestion of RW or DRW within the unspecific defense. It is not clear why immunomodulatory effects did not occur after repeated consumption of RW or DRW. As immunomodulatory effects of polyphenols are concentration-dependent in vitro, the polyphenol concentration in blood after an overnight fast might have been too low after 6 weeks of intervention to modulate phagocytosis. Another explanation might concern compensatory mechanisms which might have been activated to maintain homeostasis. Regarding the potential protection against chronic-degenerative, in-flammatory diseases, it should be investigated in further intervention studies whether an in-creased nutritional intake of other flavonoids, e.g. flavonols, may induce similar effects as polyphenols from red wine. Engel, Adrian (2005): Influence of long-term fertilization on soil, yield and fruit quality of apples on M9 as affected by replant problems and nutrient transfer in the grass mulch from the grass alleys into the tree rows. Institute for Horticulture, Faculty for Agriculturel, University of Bonn, 133 pages. A long-term fertilizer experiment with apple trees was initiated in 1968 at Klein-Altendorf Ex-perimental Station of the Institute of Horticulture, University of Bonn. The on-going field trial included three generations of apple trees. It’s one of the long-standing fertilization trials world-wide and was registered in 2003 with the German National Science Foundation DFG (Deutsche Forschungsgemeinschaft). The planting with a spacing of 4m x 1.8m, presently

with apple cv. ‘Gloster’ and 3.6m x 1.5m with cv. ‘Jonagold’ and ’Elstar’ all on M9 rootstock was subjected to the following annual treatments: 1. Control without treatment 2. 1 t of lime per ha 3. 1 t of lime + 10 t manure per ha 4. 1 t of lime + 3 x 20 kg N per ha 5. 1 t of lime + 60 kg P2O5 + 90 kg K2O+ 3 x 20 kg N per ha 6. 1 t of lime + 60 kg P2O5 + 90 kg K2O per ha 7. 1 t of lime + 60 kg P2O5 + 90 kg K2O + 20 kg N + 5 x 10 kg urea (46 % N) per ha 8. 1 t of lime + 60 kg P2O5 + 90 kg K2O + 5 x 10 kg urea (46 % N) per ha The soil of the experimental site is a loess loam with high nutrient contents (class C) and large water-holding capacity. Weed control in the tree rows was by herbicides. Grass alleys were mulched 3-5times a year. Long-term treatments significantly changed only the nutrient contents in plots without fertilization and manure treatments. Manuring increased both phos-phorus and potassium content in the soil up to 140-150 mg/100 g (DM) soil with a concomi-tant increase in humus content, which doubled in the upper 25 cm top soil layer. Soil pH changed from 6.8 to 5.0 in the control plots receiving no fertilizer. Of the cut grass, 25-50 % was transferred from the grass alleys to the tree rows as part of the mulching process, which added to the nutrient supply of the apple trees. This was equivalent to an annual nutrient translocation from the grass alleys to the tree rows of 10-25 kg N /ha, 2-4 kg P /ha, 15-25 kg K /ha, 3-5 kg Ca /ha and 1-2 kg Mg /ha. The nitrogen concentration in leaves of apple trees without nitrogen fertilization remained below 2 % DM. Nitrogen fertilization hardly influenced fruit yield. However, as far as yield is concerned, ‘Jonagold’ and ‘Gloster’ showed very little response to different levels of nutrient supply. ‘Elstar’ responded positively to 23 kg N, applied in foliar sprays (5 times per 10 kg of urea). Apple trees treated long-term with manure became more vigorous and grew fruit with less colour and higher incidence of bitter pit, e.g. up to 30 % in cv. ’Jonagold’ after a five months cold storage. Largest marketable fruit yields were obtained from the plot fertilized only with 1t lime every year, resulting in leaf nitrogen concentrations between 2.0-2.2 % N DM. The experiments have shown that minimum fertilization was necessary under the conditions of Klein-Altendorf in terms of climate and a fertile soil. An annual dose of up to 1 t lime per hectare and less than 30 kg N per hectare was sufficient for optimum apple yields with good fruit quality. Everding, Christoph (1998): Characterization of dynamics and susceptibility of erosion on cultivated soils with different textures in North Rhine-Westphalia (Germany) using rainfall simulation. Institute for Soil Science, Faculty of Agriculture, University of Bonn, 195 pages. Field experiments with a rainfall simulator were carried out on 28 cultivated sites to estimate the risk of soil erosion by water. On each site a single artificial rain at an intensity of 40 mm/h was applied for 90 min on two clean-tilled dry fallow plots of 10 m length. The particle size distributions of the Ap-horizons reflected a wide range of soil textures from silty sands (max. 80 % sand) to loamy silts (max. 82 % silt) and loamy clays (max. 47 % clay). The evaluation

of erosion behavior is based on changes in surface runoff, sediment concentration and soil loss with time. In addition to soil texture other topsoil properties like structure and moisture of the seedbed, stone cover and chemical soil parameters were considered. Empirical K-factors (KF-factors with index F for field) were determined as a measure for the erodibility of the ex-amined soils. The K-factors were derived from the Universal Soil Loss Equation (USLE) adapted by SCHWERTMANN et al. (1987). They were compared with calculated K-factors according to equations given by SCHWERTMANN et al. (1987) and MARTIN (1988a), which were estimated from several soil properties (KS respectively KM). For discussion the 28 sites were grouped into three soil textural classes (I-III) with differing soil erosion dynamics and soil erodibilities: The ten experimental field plots in texture class I (sandy loam silts and loamy silts) showed a relatively early runoff generation, a fast infiltration decrease, a high amount of runoff water and soil content of the surface flow as well as high to very high erosion rates. With KF-factors up to 0,48 the majority of these soils reacted very unstable with respect to the erosive forces. On two silty sites small furrows were formed that caused the highest loss of soil. Two other sites, however, were comparatively stable so that also some low KF-factors from 0,04 re-spectively 0,05 were determined in texture class I. Five out of nine plots of silty sands, loamy sands, sandy loams or sandy clay loams (texture class II) showed erosion susceptibilities comparable to the loamy silts. Only three very sandy soils and the only sandy clay loam in this class were characterized by a higher erosion resis-tance. Compared to texture class I, the water infiltration rate was slightly higher and the run-off rate therefore lower due to the higher permeability of the more sandy surface seal. Be-cause of the modest soil aggregate stability steady state conditions in overland flow and soil loss quickly occured. The sediment concentration in the runoff remained on an average level because heavy primary sand particles had to be transported by the water. The sandy loams proved to be more erodible than the loamy sands because their raindrop-detached soil parti-cles arranged themselves in a denser surface crust. As a result the KF-factors were up to 0,32. All at all the nine plots of texture class III (silty loam, silty clay loam, clayey loam or loamy clay) showed a high aggregate stability, therefore a low soil detachability and only a moder-ate to very low soil loss rates. The low erosion susceptibility was expressed by KF-factors of 0,12 maximum. An increase of the clay and organic matter content, the stone cover or the aggregate size obviously reduces erodibility. On four of the nine sites higher surface flow occured due to backwater in the subsoil leading to saturation of the Ap-horizon and exfiltra-tion of free water. Therefore a higher soil erosion risk has to be expected under these condi-tions. Because of a mostly low soil depth of the epipedon the tolerable erosion has to be es-timated lower on these soils rich in clay. The erodibility (KF) of the examined plots was mostly below the calculated K-factors (KS, KM). The ranking of the KF-factors of the three texture classes is in accordance with the cal-culated K-factors predicted by MARTIN's equation whereas calculations according to SCHWERTMANN et al. (1987) lead to an underestimation of the erosion hazard of soils with a high sand content. Faber, Thomas (1998):

Studies on biology and ecology of the newly imported horse chestnut scale Pulvinaria regalis Canard (Hom., Coccidae) and on its native natural enemies on urban trees in Germany. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn,77 pages. In this study the biology, ecology and spreading of the newly imported horse chestnut scale Pulvinaria regalis Canard (Homoptera, Coccidae) a pest of urban trees was examined in the open land and in the laboratory. Of particular interest were observations and examinations on the biological and ecological aspects of two native natural enemies of the horse chestnut scale, the coccinellid predator Exochomus quadripustulatus L. (Coleoptera, Coccinellidae) and the parasitic wesp Coccophagus scutellaris Dalm. (Hymenoptera, Aphelinidae). It was the purpose of this work to record data for the development of a biological control strategy. In the urban area of Bonn P. regalis laid eggs on stems and branches from end of April to mid May. From mid May to end of June first instar crawlers hatched and established themsel-ves on leaves for the rest of summer. Until autumn males reached second and females third instar and migrate to twigs before leaf fall. In April they developed to adults. A suitable method for separation of different developmental stages was to measure the anal plate length of P. regalis individuals. The development of body length as well as the dispersion and density of P. regalis individuals on the leaves seemed to be influenced by the host plant spe-cies. In the year 1995 the German pest area extended in the North to Dortmund, and in the South as far as Frankfurt and Offenbach. In the West the pest extended to Aachen and in the East to Offenbach. Horse chestnut, lime and maple trees were observed as main hosts. In the laboratory the development of P. regalis was heavily affected by warm temperatures of 26°C. On P. regalis infested urban trees the eggs of E. quadripustulatus were found from end of April to mid June, the larvae from mid May to mid July, pupae from end of June to end of July and adults during the whole period of investigations. In the laboratory E. quadripustulatus larvae fed on an amount of about 7899 and 9424 P. regalis eggs. Decreasing temperatures caused a higher uptake of feed. Directly after their last moulting E. quadripustulatus adults started distinct feeding activity. On the 10th day at 20/14°C (16/8 h) the daily predation rate reached its maximum of an average number of 120 P. regalis settlers. From the 40th day onward, the daily predation rate decreased to about 3 to 6 scales. The parasitic wesp C. scutellaris passed winter in the larval stage in P. regalis third instar nymphs and had at least 2 generations per year. Fertilized eggs of C. scutellaris were laid in the alimentary canal of the exposed third instar nymphs. At a set temperature of 25°C C. scutellaris larvae hatched on the 3rd and 4th days. Prepupae were observed from 11th, pu-pae from 13th and adults from 14th day onward. Virgin C. scutellaris females laid their eggs only in C. scutellaris larvae before they had reached prepupal stage. Temperature conditions had distinct effects on the duration of development of both sexes and on the number of male progeny. Honey from bees and honey dew from P. regalis had similar positive effects on the longevity of C. scutellaris adults. At alternating temperatures of 16/12°C (12/12 h) females of C. scutellaris parasitized an average number of 63.7 third instar nymphs of P. regalis. Faßbender, Klaus (1998):

Strategies to reduce nitrate leaching on ecological farms in the first and second year after tillage of grass/clover mixed swards. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 211 pages. The present research project (funded by BML) had the aim to determine crop rotations and cropping methods which reduce nitrate leaching and increase nitrogen availability to crops following tillage of clover/grass mixtures. Soil nitrate dynamics after tillage of grass/clover swards was examined on 18 farms in six regions of Germany. In addition, on the experimen-tal farm Dikopshof, an experiment was conducted to study the effects of different crops and cropping systems used in the first two years after grass/clover mixtures on the nitrate dynam-ics in soil and soil leachate. Yield and quality of the crops were also recorded. On-farm investigations: Timing of tillage of the grass/clover swards had the biggest effect on mineralisation and leaching of nitrate. In the second year after grass/clover mixtures, nitrate leaching was still substantial. This was most evident after intensive tillage of crop residues when the first crop was harvested early. Rotation experiment Dikopshof: Moving the timing of tillage for the first crop after grass/clover mixtures greatly reduced nitrate losses compared to winterwheat. Early tillage of grass/clover swards can only be recommended for crops that have high N uptake before win-ter, such as winter canola or catch crops. Potatoes, fodder beets, maize, and oats achieved relatively high yields after tillage in spring. Late tillage of grass/clover swards in November before winter wheat reduced nitrate losses, but wheat yields decreased on the silty loam of Dikopshof compared with earlier-sown winter wheat. The first crop after grass/clover mixtures also influenced the nitrate dynamics under the sec-ond crop. This was due to different N uptake of the crops as well as to different management and harvest timing. Very low soil nitrate concentrations were measured after late-harvested crops such as fodder beets or maize. Under typical local crop management, nitrate losses under the second crop after grass/clover mixtures were higher than under the first crop. Treatments to reduce these nitrate losses and to conserve ground water quality included sowing catch crops after the harvest of the first crop. Tillage for and sowing of the second crop were delayed by five weeks in these treat-ments. When the first crop was harvested early, catch crops could conserve large amounts of nitrate. Removal of the catch crop biomass did not greatly affect soil nitrate dynamics. The late tillage after catch crops reduced nitrate losses under a following winter wheat crop, but the late sowing negatively affected wheat yield. Winter wheat grown as second crop after grass/clover mixtures achieved comparable yield and quality to wheat grown as first crop, but appropriate N-conserving management of the first crop was necessary for this. Comparison of methods: Nitrate concentrations in the soil solution, measured by the Nmin method and by the suction lysimeter method were closely correlated only at medium or high nitrate concentrations. When nitrate-N concentrations dropped below 10 mg/l, correlation coefficients were markedly lower. Fatondji, Dougbedji (2002):

Organic amendment decomposition, nutrient release and nutrient uptake by millet (Pennisetum glaucum (L.) R. Br.) in a traditional land rehabilitation technique (zai) in the Sahel. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 142 pages. The zai technique is used in Sahel of sub-Saharan Africa to rehabilitate degraded land. The technique combines water harvesting aspects as well as nutrient management practices. As locally available material is used in this technique, the zai has the potential to be adopted by small-scale farmers, who are the major food producers in the Sahel. To study the resource-use efficiency in the zai in the context of the Sahelian zone of Niger, studies were conducted both on-station with a controlled water supply and on-farm, during the dry and rainy seasons 1999 and 2000. Zai treatment, when used in combination with good quality amendment applied at the rate of 3 t ha-1 , significantly increased total dry matter (TDM) as well as grain yield. lt appeared that increasing the zai pit diameter from 25 to 50 cm was not necessary for improving the tech-nique. Experimentally induced dry spells induced yield loss in zai and traditionally flatplanted plots. However, even under dry spells, the zai secured substantial TDM. Therefore the tech-nique appeared as labor-intensive crop insurance. On soil with relatively high native fertility, TDM as well as grain yield in the control zai was 2 to 3-fold that produced in the control flat planting, reflecting the importance of the water harvesting in the zai pit here. Manure decomposition was slower in the zai compared to soil surface exposure. Nutrient release was in line with the rate of amendment decomposition except for K, which was released faster than the rate of amendment decomposition. Nutrient (N, P and K) uptake was high in the zai compared to traditional flat planting and in plants under continuous irrigation compared to those under imposed dry spell. This resulted possibly from drying of the most fertile topsoil layer in flat planting and under dry spell. Nutrient accumulation occurred in the grains of the plants in the traditional flat planting, which was not converted into subsequent yield due to haying-off, as the plants might have run out of water before the grain was able to develop. Plant available water (PAW) was higher in the zai compared to flat planting, but a strong negative correlation was observed between total dry matter and PAW. In conclusion, a good total dry matter and grain yield far above the average yield is possible when using the zai technique in the Sahel even in rather dry years. However, a good-quality organic amendment is essential on highly degraded soils. Faupel, Annekathrin (2003): Characterization of potato-associated bacteria and their potential for the biological control of the root-knot nematode Meloidogyne incognita (Kofoid & White) Chitwood. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 136 pages. Plant associated bacteria are able to improve plant growth and health but little is known about their diversity, abundance and antagonistic potential for the biological control of soil-borne pathogens. Samples of roots and leaves of potato plants var. 'CILENA' were taken at

three different growth stages (establishment, flowering, maturity) and 2716 bacteria were isolated from the microhabitats rhizosphere/endorhiza and phyllosphere/endosphere. The isolates were characterized using FAME gas chromatography. Data obtained were used for calculation of richness (R1) and diversity (N1, N2) and evenness (E5) to compare population spectra between habitats and growth stages of the potato plant. Composition and diversity of bacterial populations changed significantly over time in all habitats. In general Bacillus and Pseudomonas were the most dominant genera. Further dominant genera were Stenotro-phomonas in the rhizosphere and endorhiza, Arthrobacter in the phyllosphere and Agrobac-terium, Curtobacterium and Micrococcus in the endosphere. Bacterial isolates were then tested for their antagonistic potential against the soilborne pathogens Verticillium dahliae and Rhizoctonia solani in vitro. The highest antagonistic activ-ity with 14-15 % of all isolates occurred in the rhizosphere and endorhiza at flowering. Eighty eight percent of this antagonistic bacteria belonged to the genera Pseudomonas and Bacil-lus. A total of 156 antagonistic bacteria were screened against Meloidogyne incognita on potato in the greenhouse. Forty seven bacterial isolates reduced the number of galls and egg masses for more than 25 %. Bacterial isolates effective against M. incognita predominantly belonged to the genera Pseudomonas (47 %), Streptomyces (15 %) and Paenibacillus (12 %). The best isolates with multiple effects against all the three pathogens were Strepto-myces violaceusniger RR76 and Pseudomonas putida 3R2-12 originally isolated from the rhizosphere. Both isolates reduced the number of galls caused by M. incognita for more than 50 % and caused a strong growth inhibition of V. dahliae and R. solani and might be potential candidates for the development of new biocontrol agents against these soilborne pathogens. Fehér, Marianna (1996): Researches on the cultivation technology of shiitake mushroom (Lentinula edodes (Berk.) Pegler). Institute for Agricultural Botany, Faculty of Agriculture, University of Bonn, 134 pages. The present work deals with different aspects of shiitake culture carried out in vitro experi-ments and growing trials. The following important results have been achieved. The optimal temperature for mycelium growth of three shiitake strains was between 23-27oC. Under laboratory conditions, the desinfectant P3-oxonia-aktiv shows an inhibiting effect on Trichoderma viride only at concentrations of 2-3%. The analyses of the element content inside and on the surface of the substrate gave very different result. The concentration of some elements was much higher on the substrate sur-face than inside. The applied procedure for heat treatment of the substrate (pasteurization, fractionated pas-teurization, sterilization) had no significant influence on the yield. Neither the applied procedures of spawning nor the different spawn types caused any signifi-cant difference in the yield. All the five filter types used for the bags were suitable for shiitake production. The use of dif-ferent filters leads to higher or lower CO2-concentration during the vegetative phase of shii-take. At too high CO2-concentration (16-20%) one has to reckon with total crop defi-ciency.

On the basis of the results a lot of deformed fruitbodies appear at too low substrate tempera-ture (20oC) during the vegetative phase. The reason for this is the insufficient decomposition of the substrate at low temperature. Therefore the determination of the optimal time for re-moving the bag from the substrate log plays an important role. With beech sawdust-corncob substrate and shiitake strain LE-5 the 80th day after spawning was the optimal time for re-moving the bag. Every shiitake strain needs a specific composition of substrate for producing a good crop. They react to uniform substrate with very different yields. It was proved that the browing of the substrate surface takes place under the effect of light. Feldmann, Thomas (2005): Biological, chemical and physiological studies on epiphytic ascot- and deuteromycetes as causal organisms of sooty blotch and pink rot in apple fruit. Department of Crop Science and Resource Conservation, Faculty of Agriculture, University of Bonn 98 pages. Within the scope of this study in Germany isolated causal organisms of sooty blotch of apple could be characterised and classified employing classical mycological, statistical and DNA analytical methods. Furthermore, it was clarified by analyses on basis of HPLC/MS/MS, if cultures of these fungal pathogens, infested and inoculated apples as well as apple products are contaminated with mycotoxins belonging to the group of trichothecenes. In addition, it was verified in agar plate tests, in how far certain stressors may influence mycotoxin produc-tion and growth of Trichothecium roseum selected as model fungus. On the basis of the bio-logical characterisation with subsequent statistical character analysis it was differentiated between 11 taxa. Some of them could be definitely identified: Phialophora sessilis, Tripo-spermum camelopardus, Tripospermum myrti and Peltaster fructicola. Tripospermum camelopardus was described in our study for the first time on a plant surface. Due to DNA sequencing (rDNA ITS 1+2 and rDNA LSU) with subsequent phylogenetic analysis in Ger-many isolated causal organisms of sooty blotch could be assigned to the following 12 spe-cies: Peltaster fructicola, Peltaster spec. 1, Peltaster spec. 2, Phialophora sessilis typical forma, Phialophora sessilis second forma, Phialophora spec., Pseudocercosporella spec. 1, Pseudocercosporella spec. 2, Pseudocercospora spec. 1, Pseudocercospora spec. 2. The mycotoxins trichothecin and trichothecolone could be analytically detected in liquid culture of Trichothecium roseum , the reference fungal species for these metabolites. In liquid cultures of sooty blotch pathogens no toxins were found. As a result of the analyses of apples inocu-lated with sooty blotch fungi also none of the analytes occurred in these samples. Further-more, dried peels of fresh apples from Germany, which were colonised by these fungi, did not contain any of the analysed mycotoxins. No mycotoxins could be detected in apple juices, either, or in apple sauces independent of their origin from German integrated or or-ganic production. The physiological studies revealed that the strongest stimulation of growth and toxin synthesis could be proven for the combination compound tested, which was com-posed of cyprodinil and fludioxonil. Stimulation effects in trichothecin synthesis were ana-lyzed for fenhexamid. For the mesostemic fungicides kresoxim-methyl and trifloxystrobin the working hypothesis could not be confirmed, because the expected effects could not be ob-

served, neither for the mycotoxin synthesis nor for stimulation of fungal growth. An increased mycotoxin biosynthesis was to be proven for temperature treatment 30 °C. Treatments 10 to 15 °C were having a retarding effect. Studies on the impact of nutrient supply showed for PDA that increasing glucose concentration was paralleled by an increase of mycotoxin pro-duction. Following MEA treatment an almost steady reduction of trichothecin production oc-curred beginning at the high nutrient level 48 g / l to nutrient treatment 5.3 g / l. In the SNA treatment group it was noted that at almost absence of sugar strong retardation of trichothe-cene biosynthesis occurred. Fischer, Bärbel (1996): Contributions to environmentally safe plant protection systems in grapevine cultiva-tion. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 166 pages. Experiments were conducted under laboratory, greenhouse and field conditions to study the effects of watery compost extracts on the control of major fungal diseases of grapevine, such as Plasmopara viticola, Uncinula necator and Botrytis cinerea. Field experiments from 1992 to 1994 under practical production conditions in the vinegrowing region of Baden should al-low a definitive judgement of effects and potential of compost extracts in disease manage-ment. The application of reduced copper concentrations against Plasmopara viticola was also tested. Rapeseed oil was applied to study its use in environmentally safe plant protec-tion systems. Possible side effects on predatory mites were observed. Grape and vine moths (Lobesia botrana and Eupoecilia ambiguella) were controlled by Bacillus thuringiensis. Test plots sprayed with water or unsprayed were maintained in conventionally-produced and or-ganically-managed vineyards. Wines were produced from selected plots and tested analyti-cally and by winetasters. Uncinula necator was well controlled by compost extracts if the infection pressure was not extreme, reducing the disease severity by 96 to 98% on ripening berries (veraison; Eichhorn-Lorenz Stage 35). However compost extracts did not control Uncinula necator sufficiently under heavy infection pressure. Copper sprays cannot be replaced by compost extracts. The population of predatory mites (Typhlodromus pyri) was hardly influenced by compost extracts whereas eriophyid mites (Calepitrimerus vitis and Eriophyes vitis) were stimulated. Other substances used as sprays by organic growers, such as Natriumsilicate, Ulmasud® and My-cosin® (two clay mineral preparations) suppressed predatory mites. Rapeseed oil effectively reduced the incidence of Uncinula necator by 66 to 99% and the severity of disease by 96 to 99,9% on ripening berries. Against Plasmopara viticola however, rapeseed oil was only mar-ginally effective. Copper concentrations could be reduced significantly, but in the high Plas-mopara viticola infection pressure of 1994, control was not reliable. Compost extracts and rapeseed oil did not have any negative effects on wine quality. The experiments demonstrated that even under difficult conditions, practical alternative pro-duction strategies are available both for conventional and organic grapevine growers.

Fischer, Lorenz (1999): Investigations of the ad-/desorption and diffusion processes of heavy metals and alu-minium with goethites of different crystallinity - Experimental results and process modelling. Institute for Soil Science, Faculty of Agriculture, University of Bonn, 205 pages. Adsorption and desorption experiments were carried out with ten metals (Al, Cr, Mn, Co, Ni, Cu, Zn, Cd, Hg and Pb) and seven synthetic goethites of different crystallinity (spe-cific surface area 35.1 to 158.9 m2 g-1) for a metal concentration of 1 µM. With these investi-gations metal and goethite properties which influence the adsorption of the metals on the outer goethite surfaces and the subsequent diffusion into the interior of the goethite particles should be determined. To characterize these processes binding constants for the adsorption of the metals on the outer goethite surfaces and diffusion coefficients for the diffusion of the metals into the goethite particles were calculated with the extended Four-Layer-Model of BOWDEN (1977) and BARROW (1983, 1987). The adsorption of heavy metals on the outer surfaces of goethite is strongly influenced by their hydrolytic properties. Metals with a high affinity for hydroxyl ions in solution also have a high affinity for the hydroxyl groups of the goethite surfaces. Therefore, the calculated bind-ing constants of the different metals were closely related to their hydrolysis constants in solu-tion. A synthetic goethite with Si in the pores between its domains plus adsorbed Si on outer sur-faces (Si-goethite) showed only a marginal change of the binding constants of Pb and Mn in relation to the pure goethites, whereas the binding constants of Ni, Cu and Cd were relative low for this goethite. Probably Si occupies sites on the outer goethite surfaces to which Ni, Cu and Cd have a particularly high affinity. The diffusion into the interior of the goethite particles decreases with increasing ionic radius of the metals. This result shows, that it is easier for smaller ions to penetrate the micropores or the smaller point and line defects of goethite. In contrast to the other divalent ions, Co and Mn seemed to be oxidized on the outer goethite surfaces and diffuse in the trivalent form into the interior of goethite. With decreasing goethite crystallinity, diffusion of Mn, Cu, Cd and Pb into the goethite parti-cles increases markedly. It can be concluded that the total amount of Pb and high propor-tions of Mn, Cu and Cd diffuse into the micropores between the domains of the goethites; the proportion of these micropores increases with decreasing goethite crystallinity. For Ni and Cr, which diffuse mainly into point and line defects of the goethite crystals, no effect of the goethite crystallinity on their diffusion was observed. Probably the well crystalline goethites also contain many of these defects. The incorporation of Si in the pores between the domains markedly decreases the diffusion of Mn, Cd and Pb into the goethite particles. In contrast to these results Cu shows a relatively high diffusion coefficient for Si-goethite. Probably Cu diffuses mainly into the smaller defects of this goethite. For Ni and Cr, which also mainly diffuse into smaller defects of the goethite structure, no effect of the Si on the diffusion into the interior of the goethites was observed. Förschler, Annette (2004):

Oxidative stress in Malus domestica and Phaseolus vulgaris: Plant responses at the tissue level and potential of exogenously applied antioxidants for stress reduction. Institute for Horticulture, Faculty of Agriculture, University of Bonn, 92 pages. In this study the fungus V. inaequalis as a biotic stress factor and UV-B radiation represent-ing an abiotic stress factor were used to elucidate primary reactions of the plant response to the stressors. Examinations were made on leaves of M. domestica seedlings after an infec-tion with V. inaequalis and on P. vulgaris leaves and M. domestica fruits, respectively, after exposition to UV-B-radiation (1.8 kJ/m2/d). The antioxidant ? -tocopherol (0.3 % or 0.5 %), which was emulsified in lecithin (2.5 %), was tested to reduce plant damage caused by the fungus and the enhanced irradiation, respectively. Additionally, other sun protecting agents (ZnO, cinnamic acid and ?? -tocopherol combined with a cinnamic acid derivative (MOC)) were analyzed for their sunburn protecting capacities. 1. An application with ? -toc./lecithin (0.5 %/ 2.5 %) and lecithin alone (2.5 %) 48 h before inoculation with V. inaequalis to susceptible apple seedlings resulted in a decrease of dam-aged leaf area up to 70 % compared to the untreated, inoculated plants during the observa-tion period of 14 days. At all sampling dates endogenous ? -tocopherol content of leaves pre-treated with ? -toc./lecithin was higher compared to the other groups. Peroxidase and lipoxy-genase activity of the untreated, inoculated test group increased in comparison to the plants pre-treated with ? -toc./lecithin and lecithin alone 7 and 14 dpi. 2. Susceptible apple seedlings inoculated with V. inaequalis showed neither a generation of H2O2 nor of O2

- during the early stages of infection until at least 7 dpi, when the conidio-phores erupted the plant cuticle and first tissue damages appeared. Contrary, in resistant cvs. H2O2 was detected 24 hpi and 48 hpi, when the conidia had successfully penetrated the plant cuticle. The superoxide anion was not detected at this time. AOS were also generated in parts of the pathogen. High amounts of H2O2 and O2

- were detected at sites with high metabolic processes, as there are the tip of germtubes, penetration sites and conidiophores. 3. For rainfastness experiments of ? -toc./lecithin and lecithin alone the residues of the ap-plication solutions on the leaf surface after the rain events were quantified and evaluated for their fungicidal activity. Exposure to 5 and 25 mm of artificial rain revealed a higher decrease of lecithin residues after treatment with lecithin than of tocopherol residues of leaves treated with ? -toc./lecithin. The fungicidal activity of lecithin also decreased at a higher degree than the one of ? -toc./lecithin. 4. Investigations of the plant response to enhanced UV-B-radiation were conducted with P. vulgaris leaves and M. domestica fruits. White particle film-based ZnO (1 %), UV-absorbing cinnamic acid derivative (0.5 %) and an antioxidative solution (? -toc./ MOC; 0.5 %/1%) were used to reduce solar injuries. In both plant species application of ? -toc./MOC before expo-sure to UV-B-light, prevented a major decrease of Fv/Fm in comparison to the UV-B irradi-ated and non pre-treated plants. Treatment of P. vulgaris leaves with ZnO and cinnamic acid also resulted in a minor decrease of Fv/Fm compared to the unprotected plants, but both treatments were not as effective as ? -toc./MOC. Application of cinnamic acid on M. domes-tica fruits did not show any significant differences compared to the untreated fruits. The survey revealed that the stress-reducing effect of the tocopherol preparation is attributed to a) metabolic interferences in plant and pathogen and b) modifications of the leaf surface.

Francken-Welz, Herbert von (2003): Comparative evaluation of flax (Linum usitatissimum L.), hemp (Cannabis sativa L.) and fibre nettle (Urtica dioica L.) with regard to yield and fibre properties for the pro-duction of high-quality industrial fibre. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 157 pages. In Central Europe flax, hemp, and fibre nettle are generally available for the production of natural fibres for industrial use. However, cultivation of natural fibres is only competitive if growing methods are optimised and if the produced fibre is of high quality. Therefore, pro-ductivity and quality of the indigenous fibre crops were compared over a period of two years and the influences of genotypes and environment were examined. So as to gain information about yield and quality during maturation, various samples were taken within the vegetation period. For hemp, the influence of locational factors was scrutinised over a period of one year. Flax, as well as short fibre flax, achieves higher fibre yields than linseed. The seed yield of short fibre flax falls behind that of linseed, but surpasses the seed yield of flax. The fibre yield rises with an increase of seed density. Higher seed density leads to finer fibres and in-creases the specific tensile strength of fibres. Raising the N-fertilisation does not affect the fibre yield but furthers the risk of lodging, while mechanical properties decrease. The fibre yield rises until the end of flowering. The mechanical properties do not change after blossom, so that the crop can be harvested at the point of capsular maturity. Hemp trials showed no significant deviation in yield at different locations in spite of varying soil quality. Moreover, an increase in seed density and N-fertilisation did not result in higher yields. In contrast, the fibre quality was affected by soil properties, i.e. clay soils lead to a higher strength of fibres compared to sandy soil. Higher seed densities also improve the fibre strength, whereas high N-fertilisation diminishes the mechanical properties of fibres. Both factors have no effect on the yield. Late ripening hemp genotypes produced a higher fibre yield than early ripening varieties. This can be enhanced by a later date of harvest. Early flowering species do not achieve any increase in fibre yield after flowering. With respect to fibre nettles, clones obtain a higher fibre yield than seedlings. By an increase of plant density with up to 5 plants/m² fibre content as well as fibre yield can be considerably enhanced. The fibre yield goes up during the vegetation period. The fibres become finer and more durable, while the mechanical properties of seedlings exceed those of clones. Of all the species looked at, flax shows the highest variability of yield components depending on the year, whereas fibre nettle has the most constant parameters of yield. Fibre nettle, though, shows the highest variability in the parameters of quality. Generally, the cultivation of hemp achieves the highest fibre yield. However, the results of the highest-quality flax varie-ties can be compared to mediocre hemp species. Due to the low fibre content, the fibre yield of fibre nettle falls clearly behind the yield of flax, short fibre flax and even linseed. Taking into account that the fibres differ in their quality, flax, hemp and fibre nettle are suit-able for various use, whereby the production of each plant can be optimised for a best out-come.

Friedrich, Gerardo Antonio (2006): Influence of agricultural measures on the interflow over plowsoles. Institute of Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn. The goal of this research was the quantitative assessment of how the water run-off depends on certain soil loosening measures as well as intercropping. Thereby the emphasis was par-ticularly on the interflow which runs on plow pans. This question was also examined in a model trial which additionally enabled the considera-tion of infiltrated water. The use of a rain simulator in the trial made it possible to consider various controlled raining conditions. The second goal was to examine the spreading of anthropogenic caused plow soles in three different regions in Northrhine Westphalia. Thereby, we conducted penetrometer measure-ment on 85 farms as well as interviews with the respective managers. The results can be summarized as follows: The low degree of interflow in the loose versions of the soil layer in the first period of our ex-amination indicates a better infiltration of the precipitation water in lower soil layers. During the second part of the study we realized, however, that the loosening of the soil from the year before had no further consequences. In the model trials the loosening led to a lag in the beginning of the run-off via the intermedi-ate soil layer, respectively to a faster vertical run-off. Here the ratio of infiltrated water turned out to be higher than the run-off in the intermediate layer, independent from the amount of rain. The intermediate crop acting as mulch cover led to a time lag as well as a reduction in the surface run off. With respect to the interflow and the flow of the infiltrated water, no differ-ences between the different trial versions were found. The penetrometer measurement results show that a large part of the examined surfaces can be classified as partially or mostly densified. Plowsoles appeared more expressed in the re-gions of Mettmann and Köln-Bonn than in the region of Euskirchen-Düren. This can be ex-plained by the different conditions of the soil moisture at the time of treatment. The results of the survey indicate that there remains space for improvement with respect to the knowledge about the German law of soil protection, soil compaction and minimum culti-vation. The assessment of the farmers about the soil compaction on their soil did not match the result of the penetrometer measurements. Frost, Maren (2001): Significance of mycorrhiza fungus Glomus mosseae for the mobilization of non-exchangeable ammonium. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 119 pages. The influence of the infection with the mycorrhiza fungus Glomus mosseae on the mobiliza-tion of non-exchangeable ammonium was investigated. In pot experiments with soils, which differs in the clay mineral composition, infection of plants with the mycorrhiza fungus favored the mobilization of non-exchangeable ammonium. How-

ever, there was no relationship between mycorrhiza infection and the amount of ammonium released from the clay minerals, dry matter yield of the plants and soil type. 15N-analysis of plants grown in pots, where fungal hyphae were separated from the roots with a nylon net, revealed evidence that hyphae and infected plants, respectively, could require N-sources out of the sphere of influence of non-infected plants. 15N-labelled ammonium or nitrate taken up by the hyphae was transported to the shoots of the plants. The higher mobi-lization rate of non-exchangeable ammonium in the hyphal compartment could be due to a higher ammonium-uptake as well as to a better nutrition status of the infected plants resulting in a higher ammonium-uptake of the plants themselves. With mycorrhizal infection as well as without mycorrhiza infection no “typical” release pattern of non-exchangeable ammonium could be shown in the rhizosphere of different plants. Higher release of non-exchangeable ammonium in the non-rhizosphere soil of infected plants is assumed not to be due exclusively to ammonium-uptake of mycorrhizal hyphae. An influence of P fertilization on dry matter yield of plants and the mobilization of non-exchangeable ammonium could not be found. Gachomo, Emma Wanjiru (2004): Studies of the life cycle of Diplocarpon rosae Wolf on roses and the effectiveness of fungicides on pathogenesis. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 158 pages. The blackspot disease of roses caused by Diplocarpon rosae Wolf teleomorph (anamorph Marssonina rosae) is widespread and important disease on outdoor grown roses. The devel-opment of D. rosae in rose leaves is not clearly understood and no detailed well-documented photographs of the fungus development in the host are available. The control of this patho-gen heavily relies on fungicides. The objective of this study was to provide a detailed growth pattern the D. rosae inside the rose leaves and to test the effectiveness of fungicides, the strobilurins and azoles, on the various fungal structures formed by this fungus. The aggressiveness of various Kenyan and Germany isolates was investigated into. The life cycle of the fungus was studied using different staining techniques for the light microscopy and the convetional preparation for electron microscopy on a german isolate: A conidium germinated to form a germ tube, from which an appressorium was sometimes formed. A brown ring that was presumably melanized was formed at the point of penetration of the host cuticle. Upon penetration an infection vesicle was formed in the subcuticular region. The subcuticular, intercellular and intramural hyphae formed haustoria of varying shapes. The intercellular hyphae also formed haustoria in palisade mesophyll cells.Intracellular hyphae were formed just before the formation of the reproduction structures. Brown heavily orna-mented structures formed in the overwintering leaves, opened in spring of the following year to release small thin-walled structures. No ascospores were formed in the subepidermal apo-thecia-like structures. The strobilurins completely inhibited germination of the conidia of D. rosae but the azoles did not. The azoles were able to destroy the fungal structures in the host even when they were applied after the fungus was fully established in the host but the effectiveness of the strobilurins was limited.

The study showed that D. rosae is a hemibiotroph: The biotrophic phase is marked by the formation haustoria and the necrotrophic phase by the formation of the intracellular hyphae. The weather conditions in Germany may not be suitable for the development of the asco-spores in the subepidermal apothecia. The strobilurins were only effective when applied pro-tectively. The azoles were effective when applied pre and post inoculation. Gay, Alexandra G. (2005): Introgression of resistance genes against Drechslera teres (net blotch diseases on barley) from wildbarley H. vulgare ssp. spontaneum in cultivar barley H. vulgare ssp. vulgare. Institute of Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 128 pages. The net blotch pathogen of barley, Pyrenophora teres, gains more and more in economic importance among the fungoid foliar diseases of barley. One reason for it is the use of sys-tematic, pathogen specific fungicide applications having caused a gap in the combat of P. teres. Profit cuts of up to 40% on an average are reported (Brandl und Hoffmann 1991). This project uses a new source of resistance derived from a wild form of barley (Hor-deum vulgare ssp. spontaneum) against P. teres improving the resistance of cultured barley (Hordeum vulgare ssp. vulgare) in order to confirm the quantitative heredity as it has been partly assumed and described in literature, and to analyse potential epistatic effects and the use of “Bulked segregant analysis” (BSA) according to Michelmore et al. (1991). With a BC2F2 test population Arena x BGRC 41923 of 636 plants resistance tests were conducted with the isolate 67/1 (Sachs, BBA Braunschweig) derived from the pathogen. It was followed by an analysis for detection of QRL (Quantitative resistance loci) as to this resistance. As a first step of analysis the individual plants of the resistant and the susceptible extrema group of the test population were used which had been made by BSA and reflected 15% each of the population. In a second step the whole test population was genotyped by means of SSR markers which, based on the statistic allocation of the first stage, gave a reference to puta-tive QRL. For verification two BC2F2 verification populations, Berolina x BGRC 41923 with 174 plants and Golf x BGRC 41923 with 154 plants, and one F2 verification population, Pasadena x BGRC 41923 with 167 plants, were used. These plants were analysed by means of the test population’s putative SSR marker as to QRL. Analysis of individual gene loci showed QRL which reduced the mean degree of infestation with P. teres by about 50-75% to 3.7-8.3%. Additionally, epistatic effects as a result of inter-actions between some of the examined marker loci were noticed. These led to a reduction of infestation by up to 96% and thus to an infestation of less than 1%. All in all eight QRL were detected for a resistance against P. teres: Pt BIa (1H, GMS021), Pt BIb (1H, Bmag0347, HVALAAT), Pt BII (2H, HVM36), Pt BIIIa, Bmag0606), Pt BIIIb (3H, EBmac0708), Pt IVa (4H, EBmac0906, HVPDIA), Pt BIVb (4H, EBmac0679) und Pt BVI (6H, HVM74, Bmag0613). The SSR markers of these QRL could be used in resistance breeding for a marker assisted se-lection.

Gebbing, Thomas (1996): The contribution of pre-anthesis reserves to grain filling of wheat. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 75 pages. The contribution of pre-anthesis assimilate to grain filling was determined by long-term 13CO2/12CO2 steady-state labelling. In 1991 and 1992 single plants of two spring wheat culti-vars (Triticum aestivum L. cv Star and cv Kadett) were established outdoors with two levels of nitrogen supply. At anthesis sets of plants were transferred to a growth cabinet and all photosynthate of the post-anthesis period were labelled. The amount of non-labelled i.e. pre-anthesis C in mature grains was taken to reflect the contribution of pre-anthesis reserves to grain filling. In addition, vegetative plant parts of main tillers were sampled at anthesis and grain maturity and the contents of protein (Nx6.25) and watersoluble carbohydrates (WSC) were determined. The mean relative contribution of pre-anthesis reserves to grain C yield was 20%. Contributions of pre-anthesis reserves differed significantly between years (14% in 1991 and 24% in 1992) and nitrogen fertilizer treatments (16% at 'high N' and 23% at 'low N'). Growth analysis estimates of the contribution of pre-anthesis photosynthate to grain fill-ing were inaccurate. This was mainly because dry matter losses of above-ground vegetative plant parts between anthesis and grain maturity underestimated the mobilization of pre-anthesis reserves (protein plus WSC). There was a close linear relationship (r2=0.87) be-tween the mobilization of pre-anthesis reserves in above-ground vegetative plant parts and the amount of pre-anthesis C in mature grains. The mean apparent efficiency of mobilized reserve-C utilization for grain filling was 0.83 at 'low N' and 0.71 at 'high N'. Efficiency of pre-anthesis-C utilization in grain filling was closely related to the C to N ratio in mobilized pre-anthesis reserves. Efficiency increased with increasing C to N ratio. This suggested that pre-anthesis C in WSC was utilized more efficiently in grain filling than pre-anthesis C present in protein. C originating from pre-anthesis photosynthesis accounted for 29-46% of the C con-tained in grain proteins. Mobilization of nitrogen from vegetative plant parts was closely re-lated to the amount of pre-anthesis-C in grain proteins. However, it was estimated, that only about 46% of the original amount of pre-anthesis C in mobilized protein was recovered in mature grains. This low efficiency is discussed in terms of C-losses associated with protein turnover and construction of transport forms of amino acids. The amount of pre-anthesis C present in the carbohydrate fraction of the grain was closely related (r2 = 0.91) to the amount of pre-anthesis WSC-C in vegetative plant parts at anthesis. The estimated efficiency of WSC-C utilization in grain filling was 76%. Gichora, Mercy (2002): Towards Realization of Kenya's Full Beekeeping Potential: A Case Study of Baringo District. Institute for Agricultural Zoology and Bee Biology, Faculty of Agriculture, University of Bonn, 170 pages.

In the Tugen community of Baringo District, Kenya, beekeeping is culturally defined as a man’s job. Training is normally conducted by an experienced member of an apprentice’s family or by a fellow beekeeper. While boys receive instruction in all aspects of beekeeping, the training of girls is restricted to non-productive roles. Women who wish to engage in bee-keeping therefore lack most of the necessary skills and are required to hire men for hive con-struction, placement of hives in trees, pest management, honey harvesting and processing. Beekeeping is ranked second or third among the four most important income-generating ac-tivities with its relative economic importance increasing as potential for crop agriculture di-minishes with altitude. 91% of beekeepers rely on fixed comb, traditional, log hives, which beekeepers make individually, receive as gifts or inherit. Where necessary to buy equipment, beekeepers do not look for credit but depend on savings or income generated from other economic activities at farm level. Beekeepers follow traditional colony management, harvest-ing and processing methods to produce honey. They sell crushed honeycombs as a crude product to middlemen who follow simple procedures to produce semi-refined honey. The grade of combs containing most of the pollen and brood is sold to brewers of traditional beer and other alcoholic beverages. Wax does not have an established route for trading and is discarded as waste or put into domestic use. There have been attempts to introduce Kenya Top Bar Hives (KTBH) as transitional, movable comb hives in order to raise the yield and quality of hive products in Kenya. In Baringo District beekeepers have not adopted this tech-nology as they have no one reliable and close-by to help them when they encounter various difficulties in using such hives. Areas in which beekeepers would like to receive further train-ing in order to improve colony management and productivity include bee biology, principles of management based on KTBH and other movable comb hives, quality harvesting and processing procedures as well as marketing. These areas comprehensively sum up current problems faced in beekeeping. With regard to the performance of KTBH, top bars are the only parts that must be made to precision. Newly manufactured bars in workshops varied by only 1 mm from the specified width of 32 mm. In the field, this precision was lost as dimen-sions of unseasoned wood adjusted on exposure to natural elements. Beekeepers also com-plained that extreme temperatures arose in KTBH during the hot season to the extent of wax melting and combs dropping from bars. Two variants of the KTBH were therefore tested for temperature regulation and one that was fitted with a modified flat cover, insulated by a tim-ber ceiling and painted white, was found to attain significantly lower peak temperature than a normal KTBH. Placing hives in a thatched bee hut also kept them significantly cooler in all seasons compared to open and tree-shaded sites. A study of vegetation revealed that spe-cies composition varies widely from area to area with respect to plants that beekeepers con-sider as most important for beekeeping. Natural flowering gaps exist during the hot season at the beginning of each year causing bees to migrate elsewhere and not to return until condi-tions improve with the onset of rains. Since most beekeepers utilize land that is communally owned with several types of interests at times vested in the same plants, vegetation is re-ported to be declining and this calls for conservation measures to be put in place. Based on these findings, recommendations are made at the end of the study suggesting a way forward for beekeeping not only in Baringo District but also for other areas of Kenya. Gierth, Katherine (2004):

Morphological and physiological studies of tolerance in sugar beet to the cyst nema-tode Heterodera schachtii. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 114 pages. Tolerance is the ability of a host genotype to withstand or recover from the damaging effects of nematode attack and yield well. Resistance describes the effects of host genes to restrict or prevent nematode multiplication in a host species. To investigate the underlying mecha-nisms of tolerance three cultivars of sugar beet were chosen, 'Penta' (intolerant), 'Nematop' (tolerant) and Stru1915 (tolerant). Greenhouse experiments with increasing densities of Het-erodera schachtii were conducted and growth of roots was measured with a rootscanner. This method allows screening for tolerance on young plants within the first 6 - 8 weeks. Fol-lowing nematode attack, total root length and number of lateral and fine roots were much higher for the tolerant cultivars 'Nematop' and Stru1915 than for the intolerant cultivar 'Penta'. Furthermore tolerant sugar beets showed a better compensatory root growth, rooted deeper and had a more branched root system. Under nematode attack tolerant plants developed more lateral and fine roots allowing them to remove more water and nutrients from soil. His-tological studies showed severe damages of the root tissues of intolerant plants after nema-tode attack. The syncytia were extended reaching into the vascular system thus interfering with water and nutrient uptake The syncytia of tolerant and resistant sugar beets were re-stricted to the outer layer of the cortical cells far away from vascular system. Regarding physiological mechanisms, no correlation between tolerance and photosynthesis was found. All sugar beet cultivars showed high rates of photosynthesis independent from high or low initial nematode densities. Nematode infested intolerant plants showed alterations of the pri-mary metabolism. Glucose concentration increased compared to sucrose in intolerant sugar beets but remained unchanged in tolerant plants. Glutamic acid revealed to be unsuitable for assessing tolerance, i. e. tolerant sugar beets yielded well despite low contents of glutamic acid in leaves similar to those found in intolerant sugar beets. Girma, Adugna Senbeta (2004): Diversity in Pathogenicity and Genetics of Gibberella xylarioides (Fusarium xylarioides) Populations and Resistance of Coffea spp. in Ethiopia. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 81 pages. The coffee wilt disease (CWD) is a typical tracheomycosis caused by the fungal pathogen Gibberella xylarioides (Fusarium xylarioides). The disease in Ethiopia is endemic and wide-spread on Arabica coffee (Coffea arabica) and re-emerged as a major threat to Robusta cof-fee (Coffea canephora) in Congo, Uganda and Tanzania recently. The major objectives of the study were to assess and determine the occurrence and distribution of CWD, collect sex-ual and asexual forms of the pathogen and investigate the fungus population structure and biology. CWD was prevalent in semiforest, garden and plantation coffee production systems with sig-nificantly varying incidence. The disease is more important in plantation followed by the gar-den-based production. There were implications of variations in resistance levels of Arabica cultivars in the field. Agronomic practices such as close spacing, replanting and slashing or

hoeing were among the factors aggravating CWD. G. xylarioides was isolated from almost all fields being the main cause of wilting trees although other Fusarium spp., namely, F. ox-ysporum , F. solani, F. stilboides and F. lateritium var. longum were identified. The cultural appearances of G. xylarioides isolated from Arabica coffee on potato sucrose agar are gray-ish white to bluish black or dark purplish, which varied from those strains with orange pig-ments from Robusta and Excelsa coffee. In mating tests, some crosses produced fertile perithecia with extruded ascospores in culture. The pathogenic diversity of G. xylarioides was studied by inoculating 10 isolates colleted in 10 major Arabica growing districts in Ethiopia and one from Robusta coffee; in seedlings of 9 Arabica cultivars and one Robusta line in the greenhouse. All Arabica isolates were pathogenic only to seedlings of C. arabica with varying degrees of aggressiveness, but incompatible with seedlings of C. canephora. In contrast, the Robusta strain was specifically compatible with seedlings of C. canephora without showing any infection symptom in all C. arabica cultivars. This result is the first cross inoculation evi-dence proving host specialization of G. xylarioides populations to the two coffee species. There existed highly significant (P < 0.001) differences among cultivars, isolates and cultivar-isolate interactions. The cultivar-isolate interactions indicate vertical resistance and virulence combinations. Among cultivars, Catimor-J19 and Kurme were resistant to all isolates except one; while F-59, Caturra, Dega and Wolisho manifested susceptibility to all Arabica isolates. The isolate from garden coffee in Yirgacheffe (Gx11) was the most aggressive with being virulent to all cultivars. Jimma (Gx1), Gechi (Gx4) and Tepi (Gx7) isolates proved to be also aggressive, whereas Yayo (Gx5) and Mettu (Gx6) both from semiforest coffee were less ag-gressive. RAPD-PCR analysis showed that Ethiopian Arabica isolates formed a genetically homoge-neous population but distinctly polymorphic to strains from C. canephora and C. excelsa. The historic Arabica strain was slightly different from the recent collections illustrating little genetic change in the population over the last 3 decades. This in turn implies that the sexual teleo-morphic state of the fungus contributed only less to diversity of the pathogen populations instead serving as survival and disseminating structure. The RAPD fingerprinting revealed that the coffee wilt pathogen populations are genetically diverse related to Coffea spp. and geographic origin in Africa. The present investigations employing cultural comparisons, patho-genicity tests and RAPD-PCR markers corroborated existence of host specialization into at least two pathogenic forms within G. xylarioides populations. Thus two formae speciales , namely; Gibberella xylarioides f. sp. abyssiniae (anamorph: Fusarium xylarioides f. sp. abyssiniae) for the fungus strains attacking only C. arabica; and Gibberella xylarioides f. sp. canephorae (anamorph: Fusarium xylarioides f. sp. canephorae) pathogenic to C. canephora and C. ex-celsa were proposed. This subdivision enables to design effective CWD management strate-gies, develop resistant cultivars/lines and formulate further breeding programs towards each population group. Gnosa, Thomas (1997): Microwave remote sensing of agricultural used areas - scatterometer measurements over winter wheat and sugar beet canopies. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 107 pages.

Remote sensing is becoming increasingly important as an information source on agricultural over large areas. A typical application is the collection of agricultural statistics in the EU yield-ing standardised and comparable data sets. The use of optical sensors in remote sensing is already well established and has been inves-tigated over many years. However it is sensitive to atmospheric conditions. Due to the dy-namic nature of agricultural crops, the all-weather capabilities of radar offers considerable advantage in this respect, especially in humid regions. On the other hand radar backscatter from vegetation is still poorly understood. To determine the main relationships between the radar backscatter as a function of the bio-physical parameters of vegetation, scatterometer measurements over winter wheat and sugar beet canopies were carried out between 1991 and 1993, at the experimental farm Dikopshof belonging to the University of Bonn. A network analyzer based scatterometer sys-tem was used covering frequency ranges between 4.8 - 6.8 Ghz and 9.0 - 11.0 Ghz, inci-dence angles 10° - 70° subdivided into 10° steps and using all polarisations (HH, VV, HV, VH). In 1994 measurements were recorded only for winter wheat canopies. These meas-urements were carried out for frequency ranges 4.8 - 8.2 Ghz and 8.0 - 12.6 Ghz, incidence angles 10° - 60° subdivided into 5° steps and using full polarimetry. In all cases a detailed examination of the plants with regard to their material and morphological composition was carried out simultaneously to these measurements. For the differentiation of winter wheat and sugar beet canopies frequencies > 9 Ghz and inci-denc angles between 30° and 50° are best. The greatest difference was found after the clos-ing of the sugar beet canopy and during the development stage flowering or milk ripeness of the winter wheat canopy. The bio-physical condition of winter wheat and sugar beet crops are best determined using copolarized microwaves in the frequency range 4.8 - 6.8 Ghz and with incidence angles ranging from 30° - 50°. The greatest influence on microwave backscatter were related to changes in plant geometry and in the water content of the above-ground biomass; until the end of flowering for winter wheat and until 2 weeks after closed canopy for sugar beets. Since not all plant parameters are observable using microwave sensors it will be important to combine optical and microwave data in the future. Operational remote sensing in agriculture then has the potential to be a helpful tool in the collection of spatially reference data on agri-cultural vegetation. Graab, Martin (1997): Isolation and Characterization of Ubiquitinated Proteins from Chloroplasts of Vicia faba L. and their modulation. Institute for Agricultural Botany, Faculty of Agriculture, University of Bonn, 93 pages. Ubiquitin is a highly conserved 76-aminoacid protein. It appears to be present in all eukaryo-tes examined so far and has recently been detected in some prokaryotes. Ubiquitin becomes covalently ligated to target proteins via a three enzyme pathway (E1, E2 and E3). Several biological roles for ubiquitin have been proposed, the best characterized are the selective proteolysis of target proteins and the stress-response.

Via immunological studies the existence of ubiquitin or ubiquitin-protein conjugates within chloroplasts could be demonstrated. Experiments with thylakoidmembrane-preparations of Vicia faba L. showed a modulation in the appearance of ubiquitin-protein conjugates with molecular weights of 15, 18 and 19 kDa depending on age, heatstress and omnilateral grav-istimulation (horizontal clinostat rotation). The goal of this study was the isolation and characterization of these proteins. The first 12 aminoacids of a 18 kDa protein isolated from thylakoidmembrane-preparations were N-terminally sequenced. The result was a 100 % homology to histone H3. After improv-ing the method for isolating chloroplasts including an additional treatment of the chloroplasts with the protease thermolysin the examined proteins were no longer present in thylakoid-membrane-preparations. Thus the 15, 18 and 19 kDa proteins were identified as nucleic con-taminations which coinsides with the similarity of protein-patterns from cell nuclei and thyla-koidmembranes prepared by the original isolation method. A modulation of nucleic protein-patterns in response to leaf age and clinostat rotation could not be shown. The stroma of thermolysin treated chloroplasts, isolated from non-developed leaves of 9 day old Vicia faba L., contained ubiquitin-immunoreactive proteins with molecular weights of 15, 18, and 19 kDa. The same protein-pattern appeared in stroma-preparations of totally ex-panded primary leaves of 14 day old plants in the case of dehydration stress. Equivilent samples from non-stessed plants showed only one immunoreaktive protein of approximately 8 kDa, which may be free ubiquitin. Simulated weightlessness (fast rotating clinostat) and microgravity (TEXUS-flight) caused a modulation of free ubiquitin and ubiquitin-conjugates in isolated protoplasts, which were pre-pared from primary leaves of 14 day old Vicia faba L. It remains to be examined whether the ubiquitin-immunoreactive proteins in the chloroplast-stroma of 9 day old and stressed 14 day old plants are identical. Furthermore it has to be shown that the proteins responding to weightlessness which were isolated from protoplasts are the same as the stress- and age-dependent proteins in the chloroplast stroma. There are certain hints that the ubiquitin-conjugates in the chloroplast stroma could be E-enzymes or ubiquitin-extensionproteins. Griesbach, Matthias (2000): Occurrence of mutualistic fungal endophytes in bananas (Musa spp.) and their poten-tial as biocontrol agents of the banana weevil Cosmopolites sordidus (Germar) (Col-eoptera: Curculionidae) in Uganda. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 129 pages. The results are presented in five chapters. The first chapter gives a comprehensive literature review on banana production in East Africa and describes the major insect pest Cosmopo-lites sordidus as well as the occurrence and mode-of-action of fungal endophytes in different plant species. In the second chapter the oviposition behavior of the banana weevil is described in the con-text of integrated pest control. Oviposition rates, egg size and eclosion rates were all posi-

tively related to adult size. In addition, oviposition rates and larval development were influ-enced by the banana cultivar as well as by the adult population density. The subject of the third chapter is the isolation and screening of fungal endophytes for bio-logical control activity on banana weevil eggs and larvae. Two hundred isolates were ob-tained from healthy banana rhizomes of different cultivars in Uganda. Twelve of these iso-lates caused in-vitro mortality rates of 80-100% on weevil eggs and up to 48% on weevil lar-vae. The effective isolates were mostly Fusarium and Acremonium species. The mode-of-action of these isolates included both direct colonization and production of secondary me-tabolites. The fourth chapter describes the colonization of banana plants by fungal endophytes. In-vitro tests with excised banana roots showed that fast growing Fusarium isolates were the best colonizers. These observations were confirmed in-vivo with tissue cultured plants of different cultivars. The rhizome and older root parts were generally higher colonized than the root tips and the shoot of the plants. The results of container and field trials with different banana cultivars and fungal endophytes are presented in the fifth chapter. A significant reduction in damage of up to 64% was ob-served on endophyte-inoculated plants. The reduction in damage is attributed mainly to an-tifeedant effects in inoculated plants resulting in retarded development of weevil larvae. The results demonstrated the potential of fungal endophytes in the biological control of the ba-nana weevil. Gulati, Mukesh Kumar (2001): Studies on biocontrol of crown rot (Phytophthora cactorum ) and red stele (Phy-tophthora fragariae var. fragariae) disease of strawberry. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 134 pages. The present work is divided into four chapters. The first chapter gives a comprehensive in-troduction, its contents include a brief literature review on soil borne crown rot disease (Phy-tophthora cactorum) and red stele disease (Phytophthora fragariae var. fragariae) of straw-berry. In the second chapter dual culture and culture filtrate tests as well as greenhouse and field studies were conducted to evaluate the potential of pre-selected rhizobacteria against crown rot (Phytophthora cactorum ) and red stele disease (Phytophthora fragariae var. fragariae) of strawberry. Three antagonistic bacteria isolates: Erwinia herbicola isolate G-584, Paenibacil-lus macerans isolate G-V1 and Pseudomonas putida isolate I-112 proved to be potential bio-control agents in dual culture, culture filtrate and greenhouse studies. In greenhouse experi-ments following bacteria treatment the disease symptoms of crown rot and red stele disease of strawberry were significantly reduced after 72 days and significant increases in both root and shoot weights were also recorded. Field experiments revealed that root dip bacterization against crown rot and red stele disease of strawberry can be successfully combined with a foliar spray of Aliette. The third chapter describes the spread of bacteria in the rhizosphere of strawberry. The in-vestigations revealed that the applied rhizobacteria could successfully colonize strawberry roots. Alternative methods of characterizing microbial communities, including gas chromatog-

raphy and BIOLOG plating were conducted. In further observations using Low-Temperature-Scanning-Electron-Microscope it was shown that colonization patterns of applied rhizobacte-ria differed between strains. The fourth chapter deals with the mode of action of antagonistic bacteria used in this study. Results revealed that the production of antifungal metabolites depended directly on culture media and initial pH value. In the present study it was shown that King’s B Broth was the most suitable culture media for the production of secondary metabolites from P. putida I-112 and Tryptic Soy Broth for the production of secondary metabolites from E. herbicola G-584 and P. macerans G-V1. Amplification of genomic DNA from P. putida I-112 by PCR with the specific primers Phl2a and Phl2b yielded a 745-bp fragment indicating the presence of genes for the synthesis of phloroglucional compounds. In HPLC analysis the presence of 2,4- di-acetylphloroglucinol was confirmed. On TLC plates the antifungal bands produced from P. macerans G-V1 and reference isolate BSA85 had identical Rf values. In HPLC analysis re-sults showed that P. macerans G-V1 is capable of producing the antifungal peptide “Bacillo-mycin D”. To determine whether secondary metabolites of selected rhizobacteria play a role in biocontrol of soil borne Phytophthora diseases of strawberry, plant roots were treated with cell free extracts of bacteria. Following treatment with cell free extracts of isolate E. herbicola G-584 and P. macerans G-V1, P. putida I-112 and Aliette the disease level was significantly reduced compared to the untreated control. The results confirm a direct effect of the applied rhizobacteria on the soil borne Phytophthora diseases of strawberry. Gutberlet, Volker (2001): Studies on the suitability of the encapsulation of the nematophagous fungus Hir-sutella rhossiliensis for biological control of Heterodera schachtii and Meloi-dogyne incognita using renewable resources. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn. The suitability of the encapsulation of the nematophagous fungus Hirsutella rhossiliensis for biological control of plant-parasitic nematodes was studied in laboratory tests, bioassays, and greenhouse and field trials. The fungus was encapsulated in sulfoethylcellulose together with various additives. Fungal capsules with corn gluten and yeast extract as nutrient sources had nematicidal and phytotoxic effects in bioassays with Heterodera schachtii and sugar beet seedlings. It was not possible to re-isolate H. rhossiliensis from nematode juve-niles or from soil. Similar nematicidal and phytotoxic effects were observed with pure corn gluten meal, which was also nematicidal to Meloidogyne incognita on tomato in the green-house. The short-term increase of ammonia up to cytotoxic concentrations during the micro-bial decomposition of corn gluten is considered to cause the nematicidal and phytotoxic ef-fects. Therefore corn gluten was removed and yeast extract kept as the sole nutrient source. Capsules of this new formulation degraded much slower in soil than the former and caused no detectable ammonia production. Their application resulted in parasitism of nematode ju-veniles by H. rhossiliensis, reduced invasion of H. schachtii into beet roots, and improved root length of sugar beet seedlings. In a field trial with sugar beet in microplots containing soil naturally infested with H. rhossiliensis, the rate of parasitism of H. schachtii juveniles in the soil was enhanced when fungal capsules with H. rhossiliensis were applied. Sugar beet yield

was also improved, indicating a reduction in nematode early root invasion. The reproduction rate of H. schachtii, however, was not substantially influenced. The application of fungal cap-sules in the greenhouse showed no effect on M. incognita on tomato. In a bioassay the intro-duction of Aphelenchus avenae as an additional host for H. rhossiliensis did not increase the efficacy of the fungal capsules against H. schachtii. Fragmentation of the fungal mycelium during the fermentation process, as well as replacing yeast extract by autoclaved yeast cells improved the efficacy of the fungal capsules. The control of H. schachtii was positively corre-lated with increasing content of yeast in the capsules, thus demonstrating the importance of an organic nitrogen source. The encapsulation technique is considered to have significant potential for improving biological control of plant-parasitic nematodes with H. rhossiliensis or other nematophagous fungi. Haefs, Roland (2001): Rapeseed oil ethoxylate surfactants and their effects on retention, penetration, rain-fastness and biological efficacy of selected agrochemicals. Institute for Horticulture, Faculty of Agriculture, University of Bonn, 117 pages. In this study the effectiveness of a homologous series of rapeseed oil derivatives as formula-tion components or tank-mix adjuvants for selected foliar applied pesticides and leaf fertiliz-ers was evaluated. The surfactant effects on retention of spray solutions on leaf surfaces, on cuticular sorption and penetration of active ingredients, on rainfastness of spray deposits on plant surfaces and on biological efficacy of the active ingredients was investigated employing the plant growth regulator NAA, the herbicidal compound glyphosate, the fungicidal active ingredients prochloraz and tolylfluanid and the nutrients CaCl2, Mg(NO3)2 and MgSO4 as rep-resentatives. The results are summarized as follows: The surfactants were not phytotoxic at a concentration of 10 g litre-1, and they markedly af-fected physico-chemical properties of spray solutions at a concentration of 1 g litre-1. Glyphosate spray retention on Phaseolus vulgaris increased with increasing surfactant hy-drophilicity. Retention on Setaria viridis was higher for lipophilic surfactants. A positive rela-tionship was established between surfactant EO content and glyphosate penetration through isolated tomato fruit cuticles. The chlorophyll fluorescence emission from 10 various plant species after treatment with different glyphosate solutions depended markedly on the plant species and the surfactant EO chain length. Botrytis cinerea incidence of Lactuca sativa can be controlled by prochloraz application. Pro-tective prochloraz treatments were more effective than curative ones, and lipophilic surfac-tants enhanced biological efficacy more than hydrophilic ones. Prochloraz spray retention on Lactuca sativa was significantly improved, as the surfactant EO chain length inreased from 5 to 60 units. About 70 % of the applied non-formulated active ingredient tolylfluanid and less than 6 % of solely applied prochloraz were recovered on leaf surfaces after their exposure to 25 mm of artificial rain. The commercial formulations significantly reduced rainfastness to about 30 % (tolylfluanid) and to less than 1 % (prochloraz) of the applied doses. Calcium penetration through isolated fruit cuticles increased with decreasing surfactant EO content. The addition of the lipophilic surfactant with 5 EO units to CaCl2 resulted in increas-

ing calcium contents and decreasing K/Ca ratios in fruits of Malus domestica cv. Braeburn and in a reduction of bitter pit incidence. A negative relationship was established between surfactant EO content and magnesium penetration through isolated tomato fruit cuticles. MgSO4 and Mg(NO3)2 treatments enhanced magnesium content in leaves of Vitis vinifera whereas the magnesium level in clusters merely increased when formulated MgSO4 was applied. Haensel, Eva (2005): Control, competition and diversity of Abutilon theophrasti MED. (Velvetleaf) in sugar beet. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 152 pages. Field trials were conducted in 2003 and 2004 in Germany and the Czech Republic to study the influence of different control measures on the competition between the invasive neophyte A. theophrasti, the cultivated sugar beets, and the “indigenous” weeds in sugar beets. A. theophrasti proofed tolerance to the active ingredients Phenmedipham, Desmedipham, Etho-fumesat, Metamitron and Chloridazon (e.g. Betanal Expert + Goltix 700 SC), which are stan-dard herbicides used in sugar beets. Therefore, exclusive application of these active ingredi-ents was conductive to the development of A. theophrasti by eliminating competing weeds. Without the chemically induced competitive advantage over other weeds, the success of A. theophrasti was limited (untreated control). Additional applications of Triflusulfuron (Debut, Safari) led to varying effects, depending on the climate. High temperatures in 2003 reduced biomass and seed production of A. theophrasti by approximately 55 per cent. Cooler tem-peratures in 2004 reduced biomass and seed production by approximately 80 per cent. Gly-phosate (Roundup Ultra) controlled all treated plants of A. theophrasti (100 per cent). How-ever, due to the application with a wiper the sugar beets were damaged (Glyphosate dropped onto the sugar beet leaves). The combination of hoeing and cutting of all parts of the plants protruding beyond the sugar beet canopy (both treatments carried out two times in the season), as well as the combination of two times hoeing and the application of Triflusulfu-ron and Clopyralid (Safari + Lontrel) led to satisfactory effects. Both combinations signifi-cantly reduced the biomass production of A. theophrasti as well as the seed production and increased the sugar beet yield. None of these additional control methods affected the compe-tition between A. theophrasti and the other weeds. Furthermore, populations of A. theo-phrasti from Germany were compared to established populations of the Czech Republic, Hungary, China, Korea and the USA regarding their morphological, phenological, and ge-netic diversity. The objectives were to investigate the origin of the recently introduced Ger-man populations and to estimate the potential threat of invasion of A. theophrasti. For a self-fertilising species, the genetic similarity within the population was relatively high (GSDice = 0.71 - 0.75). Because of the high genetic diversity, an analysis of the origin of the German populations based on the “bottleneck effect” or the correlation between phenotypic and ge-netic similarity and the degree of kinship was not possible. The phenotypic similarity was very high both between and within populations (correlation coefficient of 0.96 - 0.99). It can be concluded, that A. theophrasti shows a high phenotypic plasticity, which has no or weak

genetic underpinnings. With its high genetic diversity and its high phenotypic plasticity A. theophrasti exhibits traits of a successful invader. Both characteristics increase the success to colonise new habitats and to adapt to changing environments and different methods of cultivation. With its strong invasive potential, A. theophrasti is currently difficult to control in sugar beets. As a consequence, the establishment of this species in sugar beet fields has to be avoided by all means. A. theophrasti is thought to be propagated with seeds of Fodder Radish and White Mustard. Immediate measures to reduce the risk of widespread invasion are the improvement of the seed cleaning process accompanied by the creation of aware-ness among farmers and extension workers. Hagner-Holler, Silke (2002): Occurence and biology of Septoria petroselini (Desm.) on parsley (Petroselinum cris-pum). Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 90 pages. Septoria petroselini causes Septoria leaf spot of parsley and is in Germany one of the major diseases in parsley. In rainy years the disease spreads epidemically and provokes serious losses of yield and quality. Until now control strategies were mainly based on general pre-ventive measures. No data were available on the biology and epidemiology of the pathogen which are essential to be able to fight the blight efficiently. S. petroselini exclusively infected P. crispum, whereas wild growing herbs, including celery, did not show any leaf-symptoms, a prove for the straight specialization on its host plant. In vitro the fungi showed optimal growth at 20-25°C. For the infection of parsley plants an incu-bation period at 100% humidity after inoculation was necessary. Under optimal conditions the sporulation of the pathogen started 14-21 days after inoculation. The isolates showed differ-ences in virulence, the investigated varieties of parsley showed differences in suspectibility for S. petroselini. No variety was completely resistant against the pathogen. On many seeds pyknidia with conidia were found, which were not capable to infect parsley plants. On dried plant residues infection structures of S. petroselini were found to be vital for 3 years, on dead leafs the pathogen stayed infectious for weeks. Spreading of pathogen on a parsley field took place from leaf tissue and remnants of harvest by irrigation water onto the under-surface of leafs from surrounding plants. S. petroselini infected the plants trough their cavity openings and grew intrecellular in the leaf tissue, before development of pycnidia and sporu-lation took place or the fungi grew out of the cavity openings onto the leaf surface and caused further infections. Plants on parsley fields were regulary strong infested with S. pet-roselini, mostly off middle of august. The increase of infestation correlated with the time of production of dew, caused by great differences between temperatures of day and night. The number of cuts did not influence the development of the pathogen on parsley fields, even measures like removing the cut and hoeing the parsley field were not sufficient for a signifi-cant reduction of infestation. Considerable reduction of infestation has been achieved by using an azol-containing fungicide. Initially the infestation took place through infected seeds, from this focus of infection the pathogen was spreaded all over the parsley field. For practice it should be strived to develop a model of prediction for the probability of infection out of the

acquired data, to facilitate a purposeful protection of plants. Moreover it has to be attached great importance to the hygienic status of fields and seeds. Hamacher, Maria (2000): Monitoring growth and development of winter cereals and sugar beet with the sate l-lites ERS-1 and ERS-2 using C-band radar. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 113 pages. The primary aim of remote sensing in agriculture is to determine landuse inventories of ar-able regions. Optical sensors have been successful in classification and monitoring the vital-ity of plants using the NDVI (Normalized Difference Vegetation Index). However they are sensitive to clouds, weather conditions and dependent on daylight. The main advantage of radar systems in comparisation to optical sensors is the capability to acquire images of the earth´s surface independent of daytime and cloud cover. Multitemporal radar backscatter characteristics of crops were analyzed for an agricultural area located in the western part of Germany using ERS-1 and ERS-2 SAR imagery from 1996 until 1998. From the calibrated data, SAR temporal backscatter profiles were generated for winter wheat, winter barley, winter rye and sugar beet. The SAR imageries have been ordered every 35 days, during the main vegetation period every 17,5 days. One of the main results is that each crop has its own distinctive backscatter profile. Therefor it is possible to identify different crops at optimum acquisition dates. The best time period to distinguish between winter barley, winter wheat and winter rye is from the end of may until the beginning of july. Sugar beet can be distinguished from winter cereal in may and august. C- band radar with VV-polarisation is suitable to monitor the growth of winter cereals. How-ever it is impossible for sugar beet. The backscatter profiles of winter cereals showed a clear decline during tillering and shooting and reached a minimum at the stages ear emergence and flowering respectivly. This mini-mum was followed by an increase at the time of grain filling and ripening. Until ear emergence the crop parameters plant height, fresh biomass, dry matter and water content were highly correlated with radar backscatter. Thereafter no correlations between these parameters and the backscatter could be found. Hamer, Martin (2000): Acid neutralizing capacity and mechanisms of proton buffering of defined minerals as well as selected rocks and soils from North Rhine-Westphalia. Institute for Soil Science, Faculty of Agriculture, University of Bonn, 282 pages. Laboratory experiments were carried out to measure the processes of H+-buffering of nine defined minerals (carbonates, silicates, oxides), three selected rocks (loess, greywacke, clay shale), and 21 soils (selection criteria: acidification state, parent material, cultivation). The buffer capacity and buffer kinetics were measured by the proton consumption and by the

cations released in equivalent amounts in batch- and pH-stat-experiments. The buffer mechanisms were characterized qualitatively using X-ray diffraction (XRD), light microscopy (LM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The extent of the acid neutralizing capacity (ANC) of the minerals determined by different methods depends mainly on the mineral structure, the chemical composition, and the specific surface of the minerals. The kinetics of the H+-buffering can be divided into three partial reac-tions with different rates. The initial fast (0-24 h) and medium (24-400 h) buffer reactions can be attributed to desorption of cations adsorbed with various strengths, a protonation of active surface functional groups, a beginning dissolution of unstable parts of the surface with lattice defects and a dissolution of impurities containing CaCO3, manganese and iron oxides and of extremely fine mineral fragments on the mineral surfaces. The slow H+-buffering between 400 h and 1000 h is characterized by a constant reaction speed, which allowed the estima-tion of typical buffer rates for the different minerals. In this period of slow buffering a H+-consumption by mineral destruction occurs. The buffer capacity of selected soil samples could be subdivided into a short-term, a me-dium-term and a long-term ANC. Depending on the pH-value, the buffer capacity of carbon-ates, exchangeable cations, pedogenic oxides and easily weatherable minerals of the soil samples were measured. The kinetics of the fast, medium and slow H+-buffer reactions of soils is mainly governed by the different reactivity of these buffer substances. The buffer ki-netics of soil samples could also be divided into three reactions with different reaction kinet-ics. The comparison of soil samples from sites under different use (arable land and forest) con-firmed the influence of vegetation and cultivation on soil acidification. At forest sites, the total buffer capacity of soils with the same parent material is lower than under agricultural use (alluvial sand: 28 %, loess: 18 % and greywacke/clay shale: 5 %). Furthermore, the parent material and the depth of sampling affected the buffer capacities of individual soil horizons. The long-term ANC of selected rocks increased in the following order: greywacke < loess < clay shale. Because of the high CaCO3 content of the loess the medium- and short-term ANC increased in the order greywacke < clay shale < loess. Hasky-Günther, Katja (1996): Investigation of the mode of action of antagonistic rhizosphere bacteria Agrobacte-rium radiobacter (isolate G12) and Bacillus sphaericus (isolate B43) against the potato cyst nematode Globodera pallida in potato. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn,138 pages. A number of rhizobacteria applied to seed or planting material have been shown to signifi-cantly reduce G. pallida early root infection of potato. To improve the effectiveness of that biological control system it is necessary to determine the mechanisms of action. Two bacte-ria strains, Agrobacterium radiobacter (isolate G12) and Bacillus sphaericus (isolate B43) were used representatively. Mechanisms that could be involved include bacterial production of specific metabolites or metabolism of root exudates which reduce hatch, mobility or disrupt host finding behaviour. The third main feature was the investigation of a bacterial induced systemic resistance. Bacteria treatment of the potato roots showed no reducing effect on the

attraction of larvae to the roots. A lot of rhizobacteria produce antibiotics, siderophores, HCN and other toxic compounds, which are discussed as one mode of action in biological control. Culture filtrates of B. sphaericus lead to a high percentage of larvae inactivation. The culture filtrate of A. radiobacter showed a minor effect. Bacteria fermented potato root exudates, which should simulate nutrient conditions in the soil lead to no significant inactivation of nematode larvae. Systemic effects of the bacteria strains were checked in a split root system by applying bacteria to one part of the root system. After one day nematodes were inoculated either to both parts of the roots or to the untreated part only. Both strains showed a signifi-cant systemic effect. Nematode penetration was reduced both on the bacteria treated part of the root and on the untreated one. This systemic effect could be induced not only by vivid bacteria but also by dead bacteria. Furthermore, culture filtrate of B. sphaericus showed the strongest systemic effect. The culture filtrate of A. radiobacter, however, had no systemic effect at all. Both bacteria strains not only had an influence on larvae penetration of nema-todes but also a systemic effect on the phytopathogenic fungus Phytophthora infestans. Bio-chemical investigations of the physiological reactions of potato plants to the bacteria showed a quantitative and qualitative difference in protein expression. These different proteins, how-ever, could not be identified as one of the common PR-proteins in potato. Endophytically growing cells could only be identified with A. radiobacter. For the first time it has been proven that rhizosphere bacteria are able to induce a systemic resistance against cyst nematodes. Henn, Hans-Joachim (1997): Production, regeneration and characterization of somatic hybrids of Helianthus an-nuus L. and Sclerotinia resistant wild Helianthus species. Institute for Agricultural Botany, Faculty of Agriculture, University of Bonn, 121 pages. Sunflower (Helianthus annuus L.) production in northern regions is limited by pathogens like Botrytis cinerea, Phomopsis helianthi und Sclerotinia sclerotiorum. Resistance against these fungi is lacking among sunflower cultivars due to their narrow genetic base. Wild Helianthus species show a high variability for important traits like salt tolerance, oil content, oil composi-tion and disease resistance. From eight wild Helianthus species screened for their reaction to S. sclerotiorum, H. maximiliani showed complete resistance, whereas H. nuttallii and H. gi-ganteus were partial resistant. Althought these wild species offer a source for resistance against S. sclerotiorum their use in classical breeding drafts is limited by sexual incompatibil-ity. Biotechnological methods such as somatic hybridization via protoplast fusion are re-garded as possible tools to overcome this barrier and to use wild Helianthus species in sun-flower breeding. However, this method requires the ability to regenerate plants from proto-plasts. Therefore a protocol for regeneration of fertile plants from H. annuus hypocotyl proto-plasts was developed and applied with slight modifications for regeneration of plants from mesophyll protoplasts of H. nuttallii and H. giganteus. Fusion of hypocotyl protoplasts from H. annuus with mesophyll protoplasts from Sclerotinia resistant wild species was carried out using PEG and DMSO. The average yield of fusion products was dependent of the wild Helianthus species used as donor of mesophyll proto-plasts. About 8 - 10% fusion products were recovered with H. giganteus and H. nuttallii whe-reas fusion rates of 5 - 6% were obtained with H. maximiliani. Regeneration of hybrid plants

plants from heterokaryons was achieved by a similar culture regime developed for regenera-tion of mesophyll protoplasts. The hybrid character of 125 H. annuus * H. maximiliani and 47 H. annuus * H. giganteus greenhouse plants was revealed by RAPD analysis. Hybrid plants were fertile and six weeks after reciprocal pollination seeds were harvested of which 70 - 80% could be germinated three months later. Hentschel, Armin (2001): Integration of agriculture and nature conservation in grassland regions of the West Eifel (North Rhine-Westphalia). Institute for Agricultural Botany, Faculty of Agriculture, University of Bonn, 293 pages. Possibilities and limits to integrate agriculture and nature conservation in hill country areas are illustrated in grassland regions in the North Rhine-Westphalian part of the „Eifel“. For this purpose changes of the agrarian structure, agricultural political supporting programmes and different instruments of nature conservation are investigated for their effects. First the frame conditions of the agricultural and nature conservation policy are described. For a better understanding of the present situation in the study area and of the main factors influencing the development a detailed analysis is given of the agriculture within the study area and in the region during the last 200 years. Concerning the present agricultural situation the study area belongs to a region with a relatively disadvantageous agrarian structure and a marked dependence on state transfer payments. The study area is not only of great up to very great importance to the biotic ressource protection as documented by a comprehensive regional inquiry, but also nearly complies with the requirements of the abiotic ressource pro-tection. On the basis of the results from these inquiries and analyses some aims for development are formulated, the aims concerning the nature conservation as well as agriculture being associ-ated with each other. With regard to the realization of these aims detailed model calculations are carried out. For this purpose a mathematical model was especially developed, the pre-sent as well as modified structural conditions being taken into account by it. This model veri-fies the effects of the actual agricultural political supporting programmes and different instru-ments of nature conservation, particularly their impact on the maintenance of the land use in the study area and on the realization of the formulated aims for nature conservation. At the end a strategy to integrate agriculture and nature conservation is given, the require-ments of a functional, temporal and socio-economical integration being taken into account. The acquired knowledge and the developed strategies can fundamentally be transferred to hill country areas with similar structures. Hoffmann, Christian Ludwig (1999): Nitrous oxide emissions from permanent meadow grassland at diverse field sites with different nitrogen fertilization. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 126 pages.

Nitrous oxide (N2O) emissions contribute to global warming and the destruction of the ozon layer. Agricultural production is supposed to be a main anthropogen emittent of N2O. In the temperate climate permanent grassland is regarded to be more conductive to N2O-formation than arable land. There is still considerable uncertainty in the amount of nitrous oxide emis-sions and their influencing parameters. From October 1995 to March 1998 measurements of N2O flux using the closed-chamber-method were conducted throughout the year. Experimental sites (true meadows) were lo-cated at a hill land site (Eifel), at a lowland site (Niederrhein) and on a moist meadow (west-ern Münsterland). The investigations took place at established experimental plots fertilized with calcium ammonium nitrate (CAN) and cattle slurry; the annual amounts of both fertilizers were 0, 120, 240, and 360 kg N ha-1a-1, respectively. N2O emissions were related to tempera-ture, waterfilled pore space, precipitation and the soil contents of nitrate (NO3

-), ammonium (NH4

+), and disolvable organic carbon (DOC). Overground nitrogen extraction by plants was also determined. Highest nitrous oxide emission rates (mg N2O-N ha-1h-1) were measured after fertilizer appli-cation or in winter during frost, depending on the field site. Marked differences between the N2O emission rates between both fertilizer forms were found only at the hill land site fertilized with 240 and 360 kg N ha-1a-1, respectively. Except of the water-filled pore space and the soil nitrate content none of the other parameters effeced on the N2O emissions. Annual N2O losses were dependend on field site and the amount and type of N-fertilizer. With the exception of the CAN-treatment with 360 kg N ha-1a-1, the avarage N2O losses were less than 1,5 kg N2O-N ha-1a-1 in this experiment; in literature commonly higher values are reported. At low fertilizer levels there was no correlation between the amount of N-fertilizer and N2O emissions. However, with high fertilizer rates the N2O emissions seem to increase gradually. Finally, N2O emissions were much more influenced by the location of the field site than by fertilizer amount. Holtschuize, Michael (2005): Tipburn in head lettuce - the role of calcium and strategies for preventing the disorder. Institute for Horticulture, Faculty of Agriculture, University of Bonn. In the present study the efficiency of preventive methods for the reduction of tipburn inci-dence was examined in head lettuce. Foliar applications of calcium chloride or short-term irrigation treatments were carried out in order to decrease tipburn incidence in the field. On the basis of root pressure measurements under controlled environment approaches should be made to explain the tipburn reducing effect of a reduction in VPD or the use of unsuscep-tible genotypes. 1. The efficiency of Ca-sprays depending on plant development and frequency of the applica-tion were examined in iceberg lettuce. Plants that were treated to the time of head formation showed a reduction in tipburn severity. An elevated foliar uptake due to the Ca- sprays could not be manifested by leaf mineral analysis. 2. Tipburn symptoms can be induced under controlled environmental conditions by a con-stant high VPD. Tipburn incidence could be reduced by a diurnal reduction of VPD. Contrary

to the expectation this could not be explained by an encouraged root pressure flow during night time. Rather the concentration of mineral constituents in the root pressure exudate (K/Ca) seemed to be related to reduced tipburn incidence. 3. Shortly after the onset of short-term irrigation VPD within the crop stand was decreased. Tipburn incidence was influenced by the irrigation treatment depending on temperature and daily intervals. This diurnal reduction of VPD lead to a recurrent tendency of the efficiency of the short-term irrigation treatments throughout the planting sets. Although tipburn incidence could be reduced about 20 % by the irrigation treatments, however, the differences could not be calculated by statistical analysis. 4. Head lettuce genotypes expressed symptoms under controlled environmental conditions according to their variation in tipburn susceptibility. Higher growth rates during during early stages of plant development, lower specific leaf weight and also smaller cells per area could be observed in tipburn sensitive cultivars. Differences between the genotypes regarding tip-burn incidence could not be explained by variations in the amount of root,pressure flow. However, there was an effect on the qualitative compounds in the root pressure exudate, in particular during night time. This was most probably revealed by an increase of the K/Ca ra-tio during night period for the sensitive cv. 'Herman'. Hornung, Joachim (1995): Possibilities and Limits of the Use of Multiple Regression-Equations between the For-mation of Yield and the Amount of Yield-Increasing and Yield-Securing Materials for the Cultivation of Winter Barley. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 248 pages. In the harvest years of 1984-1986, (non-orthogonal) field experiments were conducted at the trial farm of Dikopshof near Cologne on winter wheat regarding the factors of variety (2 stages), sowing rate (2 stages), nitrogenous fertilisation (9 stages, varied according to amount and time of distribution), and herbicide and plant protection risks (4 and 6 stages), in order to set the stage for experiments on the question complexes of "Cultivation of Winter Barley" and "Effect of Graded Risks in the Use of Plant Protection Products". On the area of "crop management", the behaviour of crop and yield characteristics (ears per square metre, seed per square meter, thousand seed mass, seed yield and lodging) with regard to varied plant density, amount of nitrogen and times of nitrogenous fertilisation was recorded separately according to variety. Only those (360 out of 780) parcels which showed "good practical conditions", especially regarding plant protection and herbicide use, were included in the results. The crop-describing regression equations, especially those of the multi-row winter wheat, were used on the one hand to make possible a graphically portrayed ("four-dimensional") critical discussion of the model-like background of the computer-assisted crop management system "Anbauverfahren Bonn"/"Abo" (~"Bonn Cultivation Procedure") which has been in use in agricultural practice since 1982. On the other hand, the complex regression equations were implemented as a compact basis of knowledge which is flexible with respect to various goals and parcels, in a suitable optimising mathematical model (e.g. a computer program)

which was thus enabled to calculate, in the sense of crop development, a favourable partition of nitrogenous fertilisation during tillering and shooting, depending on a given plant density and the nitrogen supply level required for the desired yield level. The optimisation process does not need to be limited to a single goal, e.g. yield, but can also be directed towards fur-ther goals, such as a low risk of lodging. The new recommendation model, which could be easily embedded into the "Abo", was verified with a positive result on the basis of data which was not involved in the model formation (different year, different variety). In the field of plant protection, regressions between mildew levels and the descriptive vari-ables of variety, sowing rate and nitrogenous fertilisation during tillering were calculated. Fur-thermore, the attempt was made to calculate multiple regressions between the crop and yield characteristics and the five plant protection stages classified and graded according to risk. The contradictory, unstable results and in-depth variance analyses of the data material led to the conclusion that due to the discontinuous behaviour of the crop and yield characteristics regarding risk-graded plant protection measures, the use of the continuous, descriptive vari-able "plant protection risk" is inadmissable. Afterwards, there was a discussion about the extent that the results from the field of plant protection limit the validity of the crop controlling models for healthy crops under ordinary practical conditions. In the field of herbicide use, on the basis of results following one year of trials, the extent that mistakes in herbicide use can be compensated for through nitrogenous fertilisation could be explained. Hövelmann, Lothar (1996): Modifications of crop rotation and soil conserveing tillage systems on recultivates loess soils in the north-west German brown coal area – Effects on crop development and soil properties with special regard to aggreate stability. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 118 pages. Open pit mining in the north-west German coal area is combined with the removal of valu-able arable soils, esp. cambisols. Therefore, after mining the company is obliged to restore arable soils into the former quality. However, these recultivated loess soils are characterized by high contents of silt, low levels of organic matter and reduced microbiological activity, leading to an increased tendency of compaction and surface sealing. In this thesis different means of tillage and crop management have been tested with special respect to soil im-provement after recultivation. To promote soil genesis and structure by means of crop rotation winter barley (Hordeum vul-gare) can be substituted by gras-legume mixtures like red clover (Trifolium pratense) and red fescue (Festuca rubra), or this mixture can be planted as a fourth crop following the typical north-west German rotation with sugar beets (Beta vulgaris), winter wheat (Triticum aesti-vum) and winter barley (Hordeum vulgare). These measure, characterized by long time inter-vals between tillages (up to 14 month), accumulation of organic matter and intense rooting of red clover in the top soil and subsoil layers, leads to an improvement of soil structure. Plant-ing gras-legume mixtures before sugar beets caused an increase in the microbiological activ-ity and aggregate stabiltiy of the soil under sugar beets and was even higher in the following

crop of winter wheat. However, plant development of sugar beets and winter wheat was not affected. Methods of soil conserving tillage were characterized by a reduced depth and intensity of tillage. Soil conserving tillage systems led to a significant increase of organic matter, a higher microbiological activity and an improved stability of aggregates in the top soil layer. Aggre-gate stabiltiy also increased throughout the rotation from sugar beets over winter wheat to winter barley. Negative effects on crop development, e.g. caused by increased soil density, have not been observed. Hüging, Hubert (1997): Effects of grazing intensity on N-contamination of the soil water, forage production and grazing efficiency in a drinking-water supply area in the highlands of Germany. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 90 pages. The effects of different grassland management practices on nitrate leaching were studied in a three-year trial on a pasture grazed with yearling heifers. The field sites, located next to Radevormwald-Borbeck in the highlands of Germany, are characterized by high annual pre-cipitation (1.300 mm/a). Two continuous grazing systems were compared: i) no N and 2,9 animal units per hectare and ii) 250 kg N per hectare and 4,7 animal units per hectare. Nitrate leaching was determined over three seasons of infiltrated water in short spatial and temporal intervals using the suction cup-method. In addition, residual nitrogen in the soil was examined. N-flow was estimated for both grazing systems by calculating N-utilization by the plants and life weight gain of the grazing animals. Several parameters were recorded to de-scribe the effects of the grazing systems on total productivity, i.e. botanical composition, dry matter yield, crude protein and energy content of the sward and weight gain of the yearling heifers. The achieved results can be summarized as follow: Different grazing systems didn´t cause significant changes in the botanical composition of the sward. Up to the third year of the trial extensification of grazing reduced plant biomass and energy yield as well as life weight gain per hectare. Crude protein concentration of the sward was usually higher with increased N fertilization. However, in the final year, crude protein and energy concentration were high although no N was applied and the pasture was grazed intensively. N-fertilizer on the intensive pasture associated with a higher plant mass production and higher stocking rate enhanced nitrate concentrations in the soil water leakage. Total N leak-age, calculated on climatic water balance and soil water analysis, was 87 kg NO3-N/ha at intensive grazing management (season 1993/94 and 1994/95), but only 27 kg and 12 kg NO3-N/ha at extensive grazing management in 1993/94 and 1994/95 respectively. Similar, residual N concentration in the soil was higher at intensive grazing management. In conclusion, no N fertilization in association with lower grazing intensity significantly re-duces nitrate losses. Financial losses due to extensive grazing management could be com-pensated by assigning a deficiency payment. This provides, even under grazing conditions, an efficient tool to guarantee high quality drinking water.

Huerkamp, Petra (2000): Ecological Development Concept of the Hellenbrucher Brook (District of Mettmann, NRW). Institute for Agricultural Zoology and Bee Biology, Faculty of Agriculture, University of Bonn, 167 pages. The thesis presents the Hellenbrucher brook in the district of Mettmann (NRW) as an exam-ple for an ecological development concept for a brook of a low mountain range. The drawing up of the concept is carried out on the basis of a general set up for ecological development concepts of the German Association of Water Supply and Cultural Landscape Building. The investigation and the assessment of the brook has been carried out after estab-lishing a model of the natural state of the brook, which is given through the hydrological and morphological situation of the Hellenbrucher brook. Between 1996 and 2000 limnological, botanical and zoological investigations have been carried out. In addition the use of the area in the watershed has been mapped out. The Hellenbrucher brook is been affected by human influences in its geomorphological struc-ture, its material balance and its diversity of species and fulfils the model of the natural state only in a few areas. As the brook valley shows in its natural structures worthful greenlands (wet and damp greenlands) and partly natural bank forests (Carici remotae-Fraxinetum) the Hellenbrucher brook indicates a high potential for ecological development. Furthermore the brook valley is an important integrated system for amphibians. Sewage and rain water discharges are mainly affecting the brook which results in hydraulical damages and a worsening of water quality and hydraulically damages (ground and bank ero-sion). Through the intensive agriculture in the watershed area the content of nitrate in the water is very high, and lies mostly in water quality class III. Through hydrological steps and pastural agriculture beside and in the brook the possibility for a free natural course develop-ment is strongly reduced. For the drawing up of the ecological development concept the demands for the biotope and species protection come first. Through the removal of ground and bank constructions the condition for a free natural course development will be created, which is to the fore. That for an area for free movement and development (5 – 10 m on both sides of the brook) must be provided and the entry of the pasture animals must be prevented. The ecological development concept of the Hellenbrucher brook comprises the whole water-shed area and takes into account an holistic approach. Hunsche, Mauricio (2006): Rainfastness of selected agrochemicals as affected by leaf surface characteristics and environmental factors. Institute of Crop Science and Resource Conservation, Faculty of Agriculture, University of Bonn, 99 pages.

In our studies the contact fungicide mancozeb and the systemic herbicide glyphosate were used as model substances to elucidate the influence of leaf surface characteristics and envi-ronmental factors on rainfastness of agrochemicals. The effect of drying time, rain intensity, rain amount, interruptions of rain showers, and seed oil ethoxylate adjuvants were studied in detail in apple seedlings. Furthermore, the involvement of surface roughness as well as amount and composition of epicuticular waxes on rainfastness of mancozeb with or without tank-mix adjuvants was examined in adaxial leaf surfaces of apple seedlings, bean seedlings and kohlrabi The interaction between rain intensity and type of linseed oil ethoxylate adjuvant on the wash-off and biological efficacy of glyphosate was investigated in C. album, A. theo-phrasti and S. viridis. Light, heavy and torrential rain events with intensities of 0.5, 5, and 48 mm h-1, respectively, were simulated using a laboratory rain simulator. The results can be summarized as follows: Mancozeb was washed-off easily from the leaf surface of apple seedlings due to impact of few millimeters rain, whereas a higher amount of rain caused only little additional a.i. removal. Regardless of drying time, fungicide removal from the leaves followed a hyperbolic curve. Intensity and amount of rain independently affected a.i. removal from the seedling leaves. Equations for mancozeb removal at light, heavy and torrential rain were determined for precipitation ranges between 0 and 30 mm, and between 0 and 5 mm, respectively. Interruptions of rain showers had only little influence on rainfastness at 2 mm rain, and no effect at 5 mm precipitation. All rapeseed, linseed and soybean oil ethoxylates, especially the more hydrophobic ones RSO 5, LSO 10, SBO 10 significantly reduced surface tension, contact angle, and drying time of water droplets. As a rule, mancozeb formulated with the more hydrophobic adjuvants had lower retention, but enhanced rainfastness after 5 mm heavy rain. SEM micrographs in not rain-exposed leaves revealed that fungicide deposit was mainly located along anticlinal cell walls, in form of crystals. In rain exposed leaves, greatest part of the a.i. was detected along anticlinal cell walls as well, but in the form of balls or annuli. Studies in adaxial leaf surface of apple seedlings, bean seedlings and kohlrabi revealed great differences in roughness, as well as in amount and composition of epicuticular waxes. A Pearson’s correlation analysis showed very strong correlations between roughness and total EW, amount of C29 alkanes, and total mass of alkanes. Retention and rainfastness of mancozeb differed among plant species; moreover, addition of adjuvants to spray solution caused differential responses. In general, retention was highly and negatively correlated with surface roughness, total epicuticular wax, amount of C29 alkane, and total of alkanes in the EW. Rainfastness was highly positively correlated with amount of C28 alcohol and C33 alkane in the EW. The weed species used in the glyphosate study presented significant differences in micro roughness and surface wettability, as a result of surface characteristics, such as cell size, presence of trichomes, glands or wax structures. No significant interactions between treatment solutions and rain intensity could be established when determining biological effi-cacy of glyphosate. In C. album, heavy and torrential rain events reduced, while light rain slightly raised biological efficacy. In A. theophrasti and S. viridis, all rain intensities reduced the efficacy of herbicidal treatments significantly. Biological efficacy of glyphosate as a func-tion of ethoxylation degree of the LSO adjuvants was species dependent. Ismail, Suha (2001):

Host-parasite interaction between the Mediterranean cereal cyst nematode (Heterod-era latipons) and barley (Hordeum vulgare) with emphasis on biological control. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn,118 pages. This work is divided into eight chapters. The first chapter is on introduction consisting of a brief literature review on the importance of cereal crops and cereal cyst nematodes in the Mediterranean regions, control strategies and the importance of antagonistic fungi in the con-trol of nematodes. The second chapter deals with general material and methods used throughout the research program. Studies on the hatching behaviour of H. latipons are covered in the third chapter. The results showed that dormancy of H. latipons eggs is broken by exposure to a pretreatment tempera-ture of 27°C but not by exposure to cold temperature. It was further shown that cysts were first pre-treated at 5°C, hatching with root exudates of both barley cultivars was significantly greater than in the water control. This suggested that root exudates also may play a role as an external signal, inducing hatch of H. latipons eggs at low temperature. In the fourth chapter, further studies were conducted to elucidate the life cycle of H. latipons. It was demonstrated that H. latipons required 350 degree-days to complete its various life stages from second stage juveniles to the appearance of female at 15°C. In the fifth chapter, the spectrum of H. latipons egg pathogenic fungi in semiarid and temper-ate soils was examined in two fields. Eighteen fungal strains present in either German or Syrian soils were isolated from uninfested eggs of a Syrian isolate of the barley cyst nema-tode H. latipons. Fusarium and Acremonium were the most common fungi isolated from both soils. A slightly higher level of antagonistic potential and a greater level of fungal egg patho-gen diversity were present in the semiarid soil from Syria. This is important for the natural control of the Mediterranean cereal cyst nematode H. latipons common in this climatic re-gion. Investigations on the biological control potential of fungal egg antagonists towards Heterod-era latipons and H. schachtii are presented in the sixth chapter. The fungal isolates from the barley cyst nematode H. latipons were re-tested on water agar for their pathogenicity towards eggs of both H. schachtii and H. latipons. Only in four isolates, from eighteen, was H. schachtii more susceptible to the egg pathogenic fungi than H. latipons, while H. latipons was more susceptible in eight isolates than H. schachtii. These isolates were screened in the greenhouse for their potential in reducing H. schachtii and H. latipons densities in soil and subsequent nematode infection of sugar beet and barley, respectively. Only two of the iso-lates significantly reduced H. schachtii density and caused an early root infection in compari-son to the untreated control. Conversely, all the isolates except Chaetomium (SHL-3) re-duced the densities of H. latipons. The seventh and eighth chapters deal with the mode-of-action of the antagonistic fungi. The results indicated that besides mechanical penetration, enzymatic processes also play a role in eggshell destruction. The negative effect of some fungal isolates on the penetration and/or on the hatching of nematode eggs and juveniles, implies the existence of toxic and/or lytic secondary metabolites acting before or during egg infection. Jacobi, Jan (2005):

Site-specific identification of fungal pathogens and nitrogen deficiency on wheat with optical remote sensing. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 141 pages. Remote sensing is a widely accepted tool to observe agricultural crops and land cover. The new generation of satellites, äs for instance QuickBird, provides optical sensors with im-proved repetition rates and high spatial resolution. Due to its technical improvements, Quick-Bird may have an enormous potential in Precision Farming applications, for example, to monitor vitality and yield variations across individual field plots and development stages of the crops. The objective of this study was to monitor and analyse the spectral properties of winter wheat under field conditions with remote sensing, particularly deficits in plant vitality äs caused by nitrogen deficiency and by fungal disease infestation. The results indicate that a precise detection of stress Symptoms induced by nitrogen defi-ciency and fungal diseases is possible based on an optical very high resolution satellite sen-sor. The four factorial combinations established in wheat plots with nitrogen and fungicide treatments showed significant differences in the reflectance of individually spectral channels of the QL//'c/cß/7'cy-image in 2002 and also in the caiculated Vegetationindices NDVI, NDVI(green), SAVI and WDVI (or = 0,05). The coefficient of determination (R2) between NDVI and percentage infested leaf area äs well äs between NDVI and kernel yield was 0.62 and 0.88, respectively. In the year 2002 - with high pathogen infection pressure - the plant stress was pre- domi-nantly caused by fungal disease and plot-precisely visible. The changes in spectral reflec-tance of a timeline of aerial images in 2003 were less obvious, but in tendency similar to the year before. During the study, the deficits of today's satellite Systems for operational applications in Pre-cision Farming become visible; especially the limited availability of satellite images, due to weather dependency during the growing season. In terms of applications of remote sensing in Precision Farming operational satellite Systems have to meet demands, mainly far better spatial coverage than today's QuickBird. Furthermore, daily repetition rates with similar spa-tial and spectral resolution should be realised. Jaeger, Bert (2002): Characterisation of disorders in the Fe-metabolism in sunflower (Helianthus annuus L.) and mais (Zea mais L.) on calcareous soils and their removal by physiological ac-tive sulphate according to the “CULTAN”-system. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 138 pages. On calcareous soils, plant growth is frequently limited by Fe-deficiency. The development of Fe-deficiency symptoms (lime induced iron chlorosis) is thereby attributed to the alkaline nu-tritional conditions prevailing on these sites. HCO3

- and NO3- have been identified as factors

inducing Fe-deficiency chlorosis, as both compounds cause alkaline conditions in the

apoplast of plants after their take-over into plant metabolism. Subsequently, the apoplastic pH rises and Fe is physiologically inactivated. Within the scope of the present work it was investigated, to what extend plant nutrition ac-cording to the CULTAN-system, coupled with a supply of so-called physiological active SO4

2- from the compounds (NH4)2SO4 and H2SO4, relieves carboxylation processes in plants, such that plants are capable of regulating their apoplastic pH. Essentially the following results were obtained: With the CULTAN-system alkaline surpluses caused by Ca2+ and Mg2+ in the shoot of sun-flower and maize can be balanced by physiologically active SO4

2-. The contents of Ca2+ and Mg2+ in the shoot are reduced after fertilisation according to the CULTAN-system. Analyti-cally, the balance of the hot-water extractable Ca2+ + Mg2+ – SO4

2--S functions as a measure for the stress or relief of carboxylation processes within plants. One has to distinguish between a Cl--free, pure SO4

2--system and a Cl--containing SO42-/Cl--

system. In the latter Cl- and Na+ have to be considered analytically. The pH-value of the apoplastic washing fluid after infiltration and centrifugation at 75 g is significantly lower after N-fertilisation performed with the CULTAN-system compared to N-fertilisation with NO3

-. Roots growing in a distance from the depot are supplied with active SO4

2- by translocation. Ca(HCO3)2-containing water promotes the translocation of SO4

2-. Roots growing in remoteness from the depot, which do not participate in the uptake of NH4

+, are able to lower the pH-value of the rhizosphere also against a carbonate-buffer consisting of 5 Vol. % calcareous soil and Ca(HCO3)2-containing water. The supply of plants with Fe was secured at any time by the N-fertilisation according to the CULTAN-system as well as by N-fertilisation with NO3

-. Jende, Gabriele (2001): The cell wall of the oomycete Phytophthora infestans as a target of fungicides. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn,114 pages. The influence of ‘Iprovalicarb‘ as a novel fungal compound from the new class of amino acid amidecarbamates, on the development of Phytophthora infestans, causing late blight of pota-toes and tomatoes, was characterised and compared to the activity of other fungicides. The infestation of Phytophthora infestans on tomato plants was effectively limited after a pro-tective or curative application of ‘Iprovalicarb‘ in concentrations of 5 ppm a.i. and the forma-tion of symptoms was prevented successfully. Microscopical investigations, which were carried out with a confocal laser scanning micro-scope, could demonstrate that early developmental stages of Phytophthora infestans on the surface of tomato plants were inhibited after a protective application of ‘Iprovalicarb‘. Morpho-logical changes of the germ tubes, especially the lysis of cell wall structures, indicated that the cell wall lost stability substantially. ‘Iprovalicarb‘ was found to affect mainly the infection structures of Phytophthora infestans in the tissue of tomato leaves. The spread of the patho-gen into deeper tissue layers was suppressed to a high extent. The swelling of fungal struc-tures and the lysis of hyphal cell walls indicated that ‘Iprovalicarb‘ influenced the fungal cell wall.

Compared to other oomycete-fungicides, with different modes of action, only ‘Azoxystrobin‘, an electron transport inhibitor, and ‘Dimethomorph‘ had an excellent effect in vitro like ‘Iprovalicarb‘. Both ‘Iprovalicarb‘ and ‘Dimethomorph‘ caused similar morphological changes in the hyphae of Phytophthora infestans like a ‘beaded morphology’ of the hyphae and swollen hyphal tips, but they interfered differently with the cell wall structure. ‘Iprovalicarb‘ showed an influence on the evidence of mono- and polysaccharides in the cell wall, which was not observed after an application of ‘Dimethomorph‘. Futhermore, ‘Iprovali-carb‘ caused structural changes of the cytoskeletal components, which probably influenced their regulation of the alignment of the cellulose microfibrills. Electron microscopical investigations showed that the cell walls became thicker and had a higher marking density for cellulose after an ‘Iprovalicarb‘-treatment. However the cell walls lost stability under the influence of ‘Iprovalicarb‘. This might be due to the fact that the state of crystallisation of cellulose had changed. After a ‘Dimethomorph‘-treatment abnormally thickened cell walls appeared as well, but in contrast to ‘Iprovalicarb‘ the structure of the cy-toskeletal elements was not affected. The present investigations indicated that ‘Iprovalicarb‘ is different from other oomycetes-fungicides concerning it’s effects despite similar changes in the fungal cell wall and by this ‘Iprovalicarb‘ broadens the instrumentarium of plant protection. Jennissen, Heinz-Peter (1998): Elements of a planning system for crop production to ensure the in time usage of ag-ronomic measures developed on the example of cultivation activities in spring. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 143 pages. A work diary, which was kept on a research farm in the form of an electronic record between the years 1975 and 1987, was used as a reference base for this study. In the work diary, every Friday the production manager scheduled all of the work that had to be done in the coming week. At the end of each workday, all of the jobs were entered along with information as to whether they had been carried out according to plan, or the reason why they had not been done as scheduled. The analysis of this work diary showed, that only about one third of the jobs could be carried out as planned. The most frequent cause for not being able to carry out the work as planned was an unfavourable weather condition. With the help of soil-moisture models and the short-term weather forecast it is possible to predict the soil conditions and the chance of being able to till or to drive on the ground, so that the available hours for working in the fields can be estimated. The traditional planning methods in crop production are too inaccurate and are too tight in respect to the planning period. The solution is to separate the scheduling into a long-term (strategy) and a short-term (tactics) plan. The short-term schedule is used to evaluate the nominal and the actual performance of management activities. With this approach the so far peaks of work in a model farm could largely be avoided under differnt weather situations. Thus the optimum timing for soil and plant cultivation could be maintained within the ana-

lysed crop rotations a) sugar-beets, winter-wheat, winter-barley, b) sugar-beets, summer-wheat, corn, winter-wheat and c) sugar-beets, oats, winter-wheat, winter-barley. Junge, Birte (2004): The soils in the Catchment of the Upper Ouémé in Benin/West Africa - Soil Genesis, Classification, Land Use and Degradation. Institute for Soil Science, Faculty of Agriculture, University of Bonn, 291 pages. In the work, the soils developed in the catchment of the Upper Ouémé are characterized and their degradation in the current low input land use system is pointed out. Furthermore, possi-bilities of a sustainable land use are discussed to achieve the conservation of the resource. The soils developed in the undulating pediplain in the centre of Benin are characterized by the layering of fine grained and gravely substrates over saprolite. Sols ferrugineux tropicaux lessivés or Acrisols dominate on the slopes, whereas Sols hydromorphes peu humifères or Gleysols are distributed in the valleys, the bas-fonds. The natural fertility of these soils is low according to LANDON (1984), the Fertility Capability Classification System (FCC) of SANCHEZ

et al. (1982) and the Framework for Land Evaluation (FAO 1976, 1981). Some reasons for the low suitability of the soils for plant production are the low field capacity, the low exchange capacity for nutrients, the limited rooting space and the water logging of the bas-fonds during the rainy season. Traditionally, cereals like maize or sorghum and yam are cultivated on the soils without any fertilizer for self-sufficiency. Because of intensified land use due to the increasing population and the shortening of the fallow period which is important for the rehabilitation of the soils, different kind of soil degradation take place. Soil erosion by run off has already led to the reduction of the top surface layer. Furthermore, land use has deteriorated the soil structure due to the low cover of the soil surface and the low density of the crops which favour soil erosion. Soil loss, bush fire, harvesting and the shortening of the fallow period lead to the decrease of organic matter and nutrients which means the chemical deterioration of the soils. The population density of earthworms and their activity are decreased on agricultural used fields which are also biologically deteriorated. To counteract soil degradation and to preserve the resource for further generations, the modification of the traditional land use system by different measures of plant cultivation and the use of fertilizer are necessary. Juroszek, Peter (1999): Photocontrol of weeds. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 132 pages. The objective of this research was to evaluate photocontrol of weed germination as a weed management option. Field studies were conducted to test the effect of light during soil tillage on the emergence of common weed species. Soil tillage was conducted at night, during day-

light and during the day with a light proof cover at the soil tillage implement. Another purpose of this research was to investigate the factors influencing the efficacy of this weed manage-ment method. In 20 out of total 23 field experiments, weed density after nighttime tillage was reduced com-pared to conventional daytime tillage. The average reduction of weed density due to photo-control was 28,4%. The results presented and those of other studies suggest that especially the emergence of Chenopodium album, Matricaria spec. and Stellaria media is reduced by nighttime tillage practices, but photocontrol had almost no effect on the emergence of Galium aparine. Covering tillage implements during daytime cultivation caused a reduction in the number of emerged weeds, similar to nighttime tillage, indicating that nighttime tillage can be replaced by machines with a light proof cover for practical application of this weed control method. The level of reduction of weed emergence after nighttime tillage was highly variable. Impor-tant factors effecting this variation were: (1) the heterogeneous distribution of seeds in natu-ral seed banks which sometimes overexpressed the effect of light during soil tillage, (2) the different light sensitivity of weed species, (3) the different light sensitivity of populations within one specie, (4) the dormancy status of the seeds in a natural seed bank. There was no evi-dence found that either soil moisture, soil temperature, soil nitrate content, weather condi-tions before or after cultivation, light conditions during daytime tillage, weak illumination dur-ing nighttime tillage nor the light penetration through soil had contributed to the variation. Keppler, Jürgen (1999): Model experiments and field investigations on the kinetics of heavy metal fixation as well as solubility, mobilization and movement of heavy metals in polluted soils. Institute for Soil Science, Faculty of Agriculture, University of Bonn, 252 pages. In a model experiment, soluble salts of Cd, Cr, Cu, Ni, Pb and Zn were added to 10 unpol-luted soil samples with different properties. The samples were incubated for 1008 days at a temperature of 20 °C, running a defined cycle of drying and wetting. Sequential extractions according to ZEIEN & BRÜMMER (1989) showed that during this incubation period, the mo-bility of all added heavy metals decreased in the soil samples. The extent and kinetics of the formation of more stable binding forms obviously depended on the chemical properties of the soil samples (particularly pH value and content of sorbents) and the chemical and physical properties of the heavy metals (especially affinity to form hydroxy complexes and ion radius). Most of the sorption of heavy metals by Mn oxides (mainly for Pb, Cd, Cu) as well as by or-ganic matter (mainly for Pb, Cu) took place during the first day after spiking the soil samples. The proportion of these binding forms was rather constant during the further incubation. In contrast, long-term diffusion processes to the inner surfaces of iron oxides were observed (mainly for Cr, Ni and Zn). A comparison with heavy metal binding forms in soils which had received high heavy metal inputs for many years confirmed most of the results of the model experiment with respect to heavy metal partitioning. Thus, it can be assumed, that the redistribution of heavy metals at the end of the model experiment has approached to an equilibrium. Nevertheless, the pro-portions of heavy metals occluded in well crystalline Fe oxides were lower in the field soils

than in the soil samples at the end of the model experiment. Obviously, processes like ad-sorption on outer surfaces and diffusion into well crystalline Fe oxides - which were observed in the model experiment – were of less importance in the field soils because of a lower heavy metal solubility for example in the applied sewage sludge. Based on the results of the sequential extractions and on investigations of the soil solutions (paste saturation extracts), computer simulations were conducted in order to predict the fu-ture movement of Cd and Zn in two soils which had been polluted by the amendment of in-dustrial sewage sludge. Assuming constant acidity and sorption conditions, the expected movement of Cd and Zn on these sites is insignificant during the next 300 years. In contrast, a scenario of increasing soil acidification led to an almost complete movement of Cd and Zn from the polluted surface horizons into the subsurface horizons. Keutgen, Anna (2000): Modification of Spinach quality by selected pre- and postharvest treatments. Institute for Horticulture, Faculty of Agriculture, University of Bonn, 137 pages. Chlorophyll fluorescence and colorimetry were investigated as non-destructive methods to determine the quality of spinach. They completed each other and adequately described the quality of spinach non-intrusive and in vivo with short time needed. Optimal quantum yield of chlorophyll fluorescence was closely related with the plant’s physiological state and reflected the extent of various stress factors, e.g. loss of fresh mass, pesticide treatment, and wilting. Colorimetry completed the latter results with quantitative information on the outward appear-ance of the leaves such as yellowing and indirectly the contents of soluble carbohydrates and starch. In field and storage experiments, it was investigated, whether selected pre- and postharvest treatments were able to improve the quality of spinach and to extend its shelf-life. The appli-cation of Basammon-nitrogen resulted in a more intense leaf colour, a higher chlorophyll con-tent and an in tendency higher yield when compared with Kalkammon-nitrogen. The standard application of 220 kg N/ha was proved to be optimal. A luxurious supply of 330 kg N/ha re-sulted in lower contents of carbohydrates, increased nitrate concentrations, and an impair-ment of taste. Costs were unnecessarily increased and the environment excessively polluted by washed-out nitrate. A preharvest treatment with CaCl2 or Previcur N, however, improved the quality and shelf-life of spinach. It increased yield, delayed senescence-processes, and reduced quality-losses during storage. Moreover, Previcur N protected spinach from downy mildew. An effective weed control was achieved with 0,5 kg/ha Venzar. The lower herbicide-dose reduced costs and minimised environmental pollution. In comparison, mechanical weed control increased labour costs and damaged the plant material, resulting in a lower retail price and a shorter shelf-life. For spinach, the experiments pointed to an optimal storage-temperature of about 2-4 °C in cold storage and an optimal relative humidity of about 98%. A reduction of the oxygen con-tent to 4% in CA-storage revealed a negative effect on spinach quality at a CO2 concentra-tion of 3%. It promoted carbohydrate-depletion and presumably fermentation processes, im-paired chloroplast functions and, last not least, increased costs considerably.

Khan, Imtiaz (2003): Biological and ecological studies on Typhlodromus pyri Scheuten (Acari, Phytoseii-dae) as an efficient biological control agent of the European red mite Panonychus ulmi (Koch) (Acari, Tetranychidae). Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 89 pages. The present research aimed to study in the laboratory biology and prey consumption by Ty-phlodromus pyri Scheuten (Acari, Phytoseeidae) with Panonychus ulmi (Koch) (Acari, Tetranychidae) nymphs as prey at different high temperatures. Preference and consumption on apple pest mite species and production of scars on apple leaves as well as fruits by T. pyri was determined. Toxicity of some pesticides to T. pyri was evaluated. Prey preference and consumption by Chrysoperla carnea (Stephens) (Neur., Chrysopidae) on apple pest mite species was recorded. Biology of P. ulmi at the different high temperatures and effectiveness of some pesticides against the pest mite was investigated. Finally, in the field experiments on T. pyri seasonal population dynamics; within tree- as well as on leaf distribution during vege-tation period; within-tree distribution as well as density/twigs during winter; fecundity during different generations and mortality during autumn was studied in apple orchards region Meckenheim. The results of the laboratory experiments showed that T. pyri was able to develop, consume prey and reproduce at both the higher temperatures, but, duration of all life stages, prey con-sumption and fecundity decreased significantly as the temperature was increased from 25∀2°C to 30∀2°C. T. pyri preferred all stages of Aculus schlechtendali Nalepa (Acari, Erio-phyidae) than P. ulmi or Tetranychus urticae Koch (Acari, Tetranychidae). The adult T. pyri females produced longitudinal irregular scars on the leaves and fruits of apple. Metasystox, ordoval and telmion were found harmful to T. pyri and the predatory mite showed 5.3-17.0-fold resistance against the different pesticides. C. carnea also showed preference for A. schlechtendali than P. ulmi or T. urticae. With the increasing temperature duration of different life stages and fecundity in P. ulmi were significantly reduced. Apollo, metasystox, masai and ordoval were found highly toxic to P. ulmi. The pest mite showed 1.7-23.3-fold resistance against the various pesticides. It was found in the field experiments that density of T. pyri peaked each year in mid-July. More than 50% of the predatory mite population congregatted in bottom layer of the trees. About 90% of the eggs, 75% nymphs, 60% females and 50% males were found in the inner area of apple leaves. About 50% of the T. pyri overwintering population was found in bottom layer of the trees in winter. Fecundity of T. pyri was significantly higher each year in June generation than August or winter. Falling on apple leaves of T. pyri in autumn results in about 10% mortality each year. Kirsch, Andreas (2002): Use of composted fermentation residues in agriculture. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 156 pages.

Effects of composted fermentation residue from municipal biowast on plants and soil were investigated in 1997-99 at the Institut für Pflanzenbau, University of Bonn, Germany. The investigations concentrated on the effects of the valuable compost constituents such as or-ganic matter, nitrogen, phosphate and potassium as well as alkaline constituents. Field experiments were carried out at three sites, two locations in the foothills of the ‚Ber-gisches Land‘(NE of Cologne) with sandy loam and loess-based cambisol and one at ‚Dikop-shof‘, the institut´s experimental station near Bonn. Composted fermentation residue from municipal biowaste was applied at a rate of 7-15 t dm ha-1 at the beginning of the vegetation period in the spring. In addition two pot trials aided interpretation of field data in terms of nu-trient availability. The results can be summarised as follow: 5-10 % of overall nitrogen content in the employed composted fermentation residue became available to the plants during the vegetation period in the year of the application. Most of the overall applied nitrogen increased the nitrogen pool of the soil. 35-45 % of the phosphate and 75-85 % of the potassium in the composted fermentation resi-due became available to the plants during the vegetation period in the year of the application which exceeded the amount of nitrogen. The employed 10 t dm ha-1 of composted fermentation residues compensated the humus degradation in the maize-maize-oat crop rotation. The composted fermentation residues improved the biological and physical soil properties. The strong alkaline compounds of the composted fermentation residue increased the soil pH to a larger extent than those of ordinary biowaste compost. Overall, the composted fermentation residue showed positive effects on the cultivated plants and soil. This work has shown that composted fermentation residue is a valuable and eco-nomic organic fertiliser, if the content of heavy metals and foreign substances do not exeed the legal threshold. Klein, Christine Ina (2004): Effects of vegetative filter strips on the losses of selected herbicides with surface runoff and interflow in cultivated soils of highlands. Institute for Soil Science, Faculty of Agriculture, University of Bonn, 224 pages. The losses of four herbicides in surface runoff were investigated at an arable site (ca. 10 % slope) situated in Velbert-Neviges, North Rhine-Westphalia, Germany. The selected herbi-cides are used in agricultural practice on a regular base. Additionally, effects of vegetative strips as a filter between field and receiving water course were examined. Furthermore, her-bicide losses in interflow were investigated as this pathway may become more important due to the increased infiltration in filter strips. During three growth seasons of corn (1997 to 1999) the herbicides Metolachlor, Terbuthylazin and Pendimethalin were applied in May. Addition-ally, Chlortoluron was applied in late autumn of 1997 on winter wheat. Field plots (40 * 3 m arable land) were used to examine surface runoff after natural precipitation; variants were: without filter strip, with a filter strip that was cultivated without herbicide application (cultivated strip, 12 m) and two grass filter strips of different width (6 m, 12 m). Additionally, rainfall simulations were carried out. Interflow was investigated in the variants without filter strip and

with 12 m grass filter strip. Soil samples from different positions along the hill slope were ex-amined several times. Transport of the single herbicides was strongly influenced by their solubility and sorption properties with relevant losses occurring either in solution or bound to the transported soil sediments. At the different runoff events, average concentrations in the aqueous phase reached 721 µg l-1 (Metolachlor); in the solids up to 4977 µg kg-1 (Pendimethalin) were measured. In particular, the extent of herbicide losses was determined by the interval be-tween application and runoff event, by the distribution of precipitation and by the runoff rate. Losses of Chlortoluron in winter wheat were negligible. High amounts of herbicide losses were observed in corn during single, heavy runoff events shortly after herbicide application. Accordingly, between 0.51 and 0.84 % of the applied herbicides were lost after a single rain-storm. Averaged over the study period of three years, losses in corn amounted to 0.22 and 0.38 % of the applied herbicides Metolachlor, Terbuthylazin, and Pendimethalin in the variant without filter strip. Surface runoff and soil losses were decidedly reduced in all variants with vegetative filter strips. Furthermore, herbicide concentrations in the runoff suspensions were mostly lower for the variants with filter strips than for the variant without filter strip. In all, losses after natural precipitation were reduced between 56 and 58 % in the cultivated strip variant; retention in the grass strip variants amounted to 87 to 94 % (6 m width) and 96 to 98 % (12 m width), respectively. These results were supported by the rainfall simulations. Regarding interflow, the findings did not indicate enhanced losses via this pathway. Furthermore, the herbicides that were transported into the filter strips were mostly degraded or bound there. In conclu-sion, vegetative filter strips can bring about a strong protection for surface waters even at losses of high amounts of herbicides. Effectiveness increased from the cultivated strips via the 6 m grass strip to the 12 m strip. Accordingly, the installation of vegetative filter strips near surface waters can be recommended. Klimsa, Kurt (1996): Sorption, degradation, and leaching of selected pesticides in different soils with and without addition of mulch - laboratory and field experiments. Institute for Soil Science, Faculty of Agriculture, University of Bonn, 226 pages. It was the main aim of this project to study the behaviour of pesticides in different soils with and without addition of mulch. In batch studies Freundlich-sorption-isotherms of the pesti-cides Atrazine, Simazine, Terbuthylazine, Methabenzthiazurone, Isoproturone, and Chlor-tolurone were established. Also column experiments were carried out to study the leaching behaviour of the pesticides Terbuthylazine, Methabenzthiazurone, and Isoproturone. For these purposes three soil samples with different pH-values and different contents of organic carbon were selected. Field experiments with the pesticides Terbuthylazine and Isoproturone were done at the Dikopshof (Cambisol) near Bonn. In the laboratory studies wheat straw and phacelia hay were used as mulch substrata whereas in the field trials wheat straw, paper, and cress were approached as mulch substrata. The results of the batch studies show increasing sorption of the pesticides in the following sequence:

Isoproturone < Atrazine< Simazine < Chlortolur. < Terbuthylazine < Methabenzthiaz. For all six pesticides sorption hysteresis could be recognized. The extent of this hysteresis falls with: Simazine > Atrazine > Isoproturone > Chlortolur. > Terbuthylazine > Methabenzthiaz. The influence of mulch substrata on the sorption of the pesticides depends on the properties of the chemicals, the soil constituents and the properties of the mulch substrata. Only six of 33 examined variants on mulch showed increased pesticide sorption and two showed in-creased solubility. The reason for the increased solubility was the higher concentration of soluble organic matter in the mulch variants compared to the variants without addition of mulch. The column experiments confirmed the data of the batch studies, showing an increasing sorption in the order Isoproturone < Terbuthylazin < Methabenzthiazurone. Distribution functions were fitted to describe the leaching behaviour and to calculate linear distribution coefficients. This distribution coefficients were slightly lower than those received from the batch studies. Furthermore, the column studies showed stronger effects when mulch substrata were added to the soils. 50% percent of the variants examined revealed an increased and 14% a slightly decreased pesticide sorption. Generally, for wheat straw there is a stronger tendency to increase pesticide sorption whereas phacelia hay is stronger to increase the pesticide solubility. But all in all these ef-fects were small. The field trials show no effect of added mulch substrata on the sorption of pesticides. But there was an increased degradation of Terbuthylazin in the variants with wheat straw and with cress compared to the variant without addition of mulch. Mulch effects on pesticide leaching were not detectable because of the dry weather conditions. Also there was no effect on the behaviour of Isoproturone, which was applied in the following vegetation period. The results of the field trials show, that there were no danger for leaching of Terbuthylazine and Isoproturone into groundwater. Klinkenberg, Hans-Josef (2002): Phytopathological characterization of oomycetes with different field resistance to fun-gicides. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn,151 pages. Oomycetes can spread rapidly within fields of cultivated plants. The fungal disease attack is associated with severe economic losses. Currently an effective control of the pathogen is only possible with few fungicides. The efficacy of these fungicides is often limited by the development of fungicide resistant isolates of the pathogens. The objectives of the following work were: 1. to describe the fungal stages affected by various fungicides, 2. to evaluate the occurrence of fungicide resistant fungal isolates in the field and 3. to develop a sensitive method for early detection of the pathogen in potato plants. The work was carried out on the economically important host-pathogen-systems: potato / tomato – Phytophthora infestans, grape – Plasmopara viticola and pickling cucumber – Pseudoperonospora cubensis. The inhibiting effect of the fungicides on different developmental stages of the pathogen such as

sporangia, zoospores and encysted zoospores was determined in laboratory assays. Addi-tionally, the fungicide effect on disease reduction was evaluated in situ. The non systemic active compounds mainly affected zoospores and encysted zoospores. The systemic active compounds primarily inhibited mycelial growth and to a lower extent zoospores and encysted zoospores. At lower concentrations the strobilurine azoxystrobin gave better control than all other compounds tested. Fungicide resistance was only shown for systemic active ingredients, i.e. metalaxyl and cymoxanil against Phytophthora infestans and Plasmopara viticola and to some extent for fosetyl-al against Pseudoperonospora cubensis. Fungicide resistant pathogen populations only cause a problem in agriculture if they outcom-pete sensitive fungal populations. Field populations of Phytophthora infestans were sampled and tested for vitality, aggressiveness and fungicide resistance. The following scenarios were considered: potatoes grown organically, potatoes grown following the IPM standards and potatoes collected from refuse piles. Fungicide resistant isolates with high vitality and ag-gressiveness could pass the winter on plant debris and represent an important inoculum source in next years spring. In organically grown potatoes, fungicide resistant pathogen populations developed despite any selection pressure due to fungicides indicating air-borne migration of fungicide resistant populations. Fungicide resistance was also commonly ob-served in IPM farmed fields and even enhanced by the repeated use of fungicides with simi-lar mechanisms. It is concluded, that the development of fungicide resistance in fungal field populations can be delayed or even inhibited by alternating use of fungicides with different mode of action. Prerequisite for an early and reliable detection of the fungus in the field is a sensitive and specific diagnosis. Therefore a serological test based on tissue printing was developed for pathogen detection within potato plants. Knauff, Udo (2000): Transformation of organic sulphur compounds in the rizosphere of different agricul-tural plants. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 101 pages. The transformation of sulphur in the rizosphere of two dicotyle plant species (rape, mustard) and two monokotyle plant species (winterwheat, ryegrass) was investigated. The following results were obtained: The mean arylsulfatase-activity in the rizosphere of the studied plants is to explain with the following sequence: rape = mustard >> winterwheat > ryegrass. The mean arylsulfatase-activity (mean of al treatments of one plant species) in dependence of the root distance differs between plant species. In the vicinity of raperoots activity was lower, while it in the rhizosphere of mustard and winterwheat, respectively, it was higher as compared with the activity in the soil from some distance away from root surface. To explain the results the pH in the rizosphere of the experimental plants was determined. After 14 days pH in the rezosphere of rape was lower as compared to winterwheat. However, the pH difference was more or less compensative after 21 days. pH changes were highly influenced by the former cultivation of the soil. From the relationship between arylsulfatase-

activity and pH of the soil it may be deduced, that two different arylsulfatases with different pH-optima are existing. To investigate the origin of arylsulfatase (plantroots, soil microbes) a method to cultivate steril roots was developed. Furthermore a method to determine the arylsulfatase-activity of roots was established. The determination of arylsulfatase-activity of sterile cultivated plants shows, that the roots of all plant species dispose arylsulfatase. The mean activity was 90 µU/g freshweight of roots. Plant cultivation in different nutrientsolutions resulted in an increase of the arylsulfatase-activity from 30 % (mustard) to more than 100 % (rape) when sulphate was missing. The characterisation of crudeextracts from roots shows that arylsulfatase of plants origin is a very stable enzyme. Arylsulfatase denaturation starts at temperatures between 57 °C and 60 °, while treatment at 100 °C will lead to a complete denaturation. Two pH-optima are existing, supposing the existence of two different arylsulfatases. The pH-optima of arylsulfatases are 6,2 (slightly acid) and 8,0 (alkaline). The optimum amount of proteinin an assay is up to 75 µg/ml testsubstance. The optimum substraconcentration (p-nitophenylsulfate) was deter-mined in a range between 2 – 5 mM. The half maximum reaktionspeed (Vmax) was deter-mined by 1,3 mM/assay. Whether the arylsulfatase of roots is derived from endphhytic bacteria could not be cleared in this investigation, because the characteriastion and cultivation from endophytic bacteria is very expendable. von Korff Schmising, Maria (2005): Detection of QTL for agronomic traits and disease resistance in two advanced back-cross populations derived from a wild barley accession (Hordeum vulgare ssp. spon-taneum). Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 130 pages. The objective of the present study was to identify favourable exotic QTL alleles for the im-provement of agronomic traits and pathogen resistance in two BC2DH populations derived from the crosses of two German spring barley varieties, Scarlett and Thuringia, with the wild barley accession ISR42-8 from Israel (Hordeum vulgare ssp. spontaneum). The two BC2DH populations, referred to as S42 and T42, were genotyped with 98 and 78 SSR markers, re-spectively. Agronomic performance and disease resistance of the two populations, counting 301 and 84 BC2DH lines, respectively, were recorded in a maximum of six different locations and in two consecutive years. QTL detection was carried out with a three-factorial ANOVA including the marker as fixed effect, the environment and lines nested in the marker geno-type as well as the respective interactions as random effects. The QTL analysis for the popu-lation S42 resulted in 111 putative QTL for ten agronomic traits and for three traits related to pathogen resistance. The exotic genotype improved performance at 33 (35.5 %) of 93 QTL detected for agronomic traits and increased resistance at eleven (61.0 %) of 18 QTL identi-fied for disease resistance. In the population T42, the QTL analysis yielded 69 putative QTL for nine agronomic traits and for two different leaf pathogens. The exotic genotype improved performance at 33 (52.3 %) of 63 putative QTL detected for agronomic traits and at four

(66.7 %) of six putative QTL discovered for disease resistance. The exotic allele increased yield, for example, by 7.1 % and 3.9 % at a QTL detected on chromosome 4H in S42 and T42, respectively. In addition, the favourable effect of exotic alleles on pathogen resistance was demonstrated, for instance, by the reduction of powdery mildew leaf symptoms at the QTL QPm.S42-1H.a and QPm.T42-1H.a by 51.5 % and 56.6 % in S42 and T42, respectively. When the 41 putative QTL with a marker main effect detected in T42 were verified by a cross-validation, 23 could be confirmed in S42 (56.1 %). An analysis for epistatic interactions yielded eleven, eleven and five highly significant digenic interactions for the traits heading, plant height and yield, respectively, demonstrating that epistatic interactions do play a major role for the expression of quantitative traits. A direct implication of epistasis is that selection for increased trait values may be more efficient when it is practised on specific allelic combi-nations at two or more loci. The verification of QTL effects in NILs (near-isogenic lines) selected from the populations S42 and T42 showed that half of the QTL effects tested could be confirmed in the NILs, in particular for the traits heading, height and powdery mildew resistance. The present study has demonstrated that exotic alleles do improve quantitative agronomic traits and that these effects could be verified in different environments, in two different genetic backgrounds and in near-isogenic lines. Korte, Anne-Marie (1997): The development of principles of regeneration and transformation systems for the induction of resistance to plum pox potyvirus in Prunus domestica L. Institute for Horticulture, Faculty of Agriculture, University of Bonn, 138 pages. The transfer of phytopathogen derived genes into plants for establishing resistance is attract-ing increasing interest for the control of various diseases affecting agronomically and hor-ticulturally important crops. Plum pox potyvirus is considered to be the most important pathogen in plums, prunes, apri-cots and peaches. Originally described in Bulgaria the sharka disease causes heavy yield losses. Fruits of susceptible cultivars are extremely damaged by severe 'pox' symptoms and drop down prematurely. An effective treatment to cure virus infected trees is not available. Because of lack of natural resistance genes and the long breeding procedures genetically engineered resistance offers advantages. For this purpose possibilities for the induction of resistance to plum pox potyvirus in Prunus domestica were investigated in the presented work. Plants have been transformed by Agro-bacterium-mediated gene transfer with PPV genes coding for the P1 protein, the cylindrical inclusion body (CI, helicase), the nuclear inclusion body (NIb, polymerase) and the coat pro-tein (CP) of a non aphid transmissible isolate. Aiming to get a stable transgenic plant of a chosen cultivar a reproducible regeneration pro-tocol was established to enable a reliable adventitious shoot regeneration of non meris-tematic plum tissue. The plant transformation was carried out by time schedule, the regener-ated shoots were tested and cultivated on selective media. Problems with the selection of transgenic Prunus domestica were detected and analysed.

During investigations of Nicotiana benthamiana model plants the suitability of specific genes used for the induction of resistance to plum pox potyvirus could be demonstrated. Kranz, Joachim (2002): Laboratory and field studies on the attractiveness of different wild and cultivated plant species to some polyphagous predators. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 94 pages. In the present study, laboratory and field experiments were conducted in order to investigate the attractiveness of different wild, ornamental and cultivated plants as well as of their al-lelochemical secretions to the adults of the polyphagous predators Coccinella septempunc-tata L., Adalia bipunctata (L.), Propylea quatuordecimpuctata (L.) (Col., Coccinellidae) and Chrysoperla carnea (Steph.) (Neur., Chrysopidae). A modified 4-armed olfactometer was used in the experiments on both laboratory and field strains of the predators. Results showed that the differences between the predatory individuals from laboratory and field strains re-mains low. Furthermore, no remarkable differences were found among the individuals from different sexes or age groups. In the laboratory experiments by the olfactometer, clear differ-ences were found in the attractiveness of the different plants to the four predatory species tested, where it ranged, for instance, from 6 % with Centaurea cyanus to 32 % with Artemisia vulgaris for the laboratory-individuals of C. septempunctata. Maximal attractiveness level of 38 % was achieved for C. septempunctata with Fagopyrum esculentum as an odour source, 42 % for A. bipunctata with Medicago sativa, 34 % for P. quatuordecimpunctata with M. sativa and 38 % for C. carnea with Urtica dioica. The field-individuals showed a relatively more readily attracted to the different plant species than those individuals obtained from the laboratory rearings. In the field experiments, the population density of the predators was studied on different cultivated plants in the presence of accompanying plants from these species. On the other hand, the population density of the aphids, which were most commonly encountered, was also determined. The presence of accompanying plants, which have a considerable olfactory attractiveness, had lead to a partially significant increase in the popu-lation density of the predators on neighbouring vegetable plants, while the differences among the different variants remained low. Some wild plants such as A. vulgaris, U. dioica and Tanacetum vulgare as well as F. esculentum, M. sativa and Phacelia tanacetifolia had re-markably enhanced the predatory population, which resulted in a partially significant reduc-tion in the population density of the vegetable specific aphid species in the variants with ac-companying plants. In conclusion, the results of present study showed a combination of labo-ratory and field experiments on the olfactory attractiveness of plants, and clarified the effect of olfactory attractive accompanying plants on the population density of predators and aphids on vegetable plants. The results are discussed with a special consideration of their imple-mentation possibilities for the conservation and augmentation of natural enemies. Krohmann, Peter (2003):

The efficacy of site-specific weed control and spatio-temporal dynamics of weed populations in a rotation and continuous crop. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 175 pages. In this study, the effects of site-specific weed control on the dynamics of weed populations in a rotation of maize, sugar-beet, winter wheat and winter barley over four years and in con-tinuous maize were evaluated. The results show, that an increase of the weeds over the study period due to site-specific weed control cannot be observed. However, the weeds varied in their density from year to year under the influence of the grown crop and the year. For eliminating weed patches with high population density, seed production of weeds within these patches should be prevented. In plot trials different weed control measures to reduce late weed infestation and subsequent seed production were carried out. The tested variations showed no distinct results: less intensive measures often led to a higher reduction of weed density. Furthermore a objective definition for a weed patch was specified. According to this, weed patches were weed infested field areas within the distribution maps, whose distance to each other not exceeded the maximum distance between two sampling points (in this study: 15m). All these weedy areas were combined to one weed patch. For the interpretation of the weed populations the dispersal patterns of the complete period of the study were considered. Field areas, that were defined as a weed patch in at least one year, were investigated for weed occurrence in the other years, too. Therefore, the boundaries of the resulting field area were determined bf the spatial expansion of weed infestation of all years. By statistics (“Pearsons correlation coefficient”, “Chi-squared test for two by two contingency tables”) the stability of weed populations was substantiated. Localisation of the changes within the weed populations by the use of statistical values was not possible. For these pur-poses the visual interpretation of weed distribution maps was necessary. Image analysis was a helpful tool for further investigation of the visual obtained information. With this method, marginal changes within the weed populations could be determined. However, exact decision models for the interpretation of the results of the image analysis have to be developed. The analysed weed populations were stable in their existence within the selected field areas throughout the period of the study. Still, the patches varied in their size within the selected field segments depending on the crop and year. Founded on the obtained results, a long-term prediction of the development of the weed populations under the influence of site-specific weed control is not possible. Kühnen, Volker (2003): Heavy metal fluxes and balances on selected farms with different production methods. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 201 pages. Investigations of the inputs and discharges of cadmium, chrome, copper, nickel, lead and zinc were performed on practical farms in North Rhine-Westphalia over a period of three years. Balances were made up for different crop rotations and animal production procedures.

Crop production was investigated by a total field balance, animal production was described by a total stable balance. Because of the influence of animal production systems onto crop production, the following classification system was choosen: Farms with cattle husbandry (dairy cows/fattening bulls), farms with pig husbandry (pig production/pig fattening), farm with poultry fattening, crop farm with varied use of organic fertiliser and a farm with field vegetable farming. As a result recommendations were derived which aim to reduce heavy metal input into agroecosystems. The effectiveness of some of these measures is tested at selected farms. For crop production and the aligned in- and outputs of heavy metals in/onto agricultural land (field balance) the following results were obtained. In the field of plant production on conventional farms with husbandry significant exesses of input were assessed for the ele-ments chromium copper, nickel, lead and zinc: Cr (21-1101), Cu (37-895), Ni (11–38), Pb (9-171) and Zn (221-1427) (all data [g ha-1 a-1]). The organic farm exhibited an overplus of entry only for chromium due to liming. The cadmium balances were balanced at pig holding farms (sometimes even with an overspill of discharge) and at the organic-farm with dairy cattle husbandry. The inputs of chromium, nickel, and lead were usually affected in the main by the choice of the mineral fertilizers: chromium (P-fertilizer and lime), nickel (lime) and lead (lime and N-fertilizer). If not influenced by trace element fertilization, copper and zinc entries were affected by the type of animal production procedure. Thereby for copper the following se-quence with decreasing input could be determined: Dairy farming, piglet production, pig fat-tening~poultry husbandry, bull fattening. For zinc this sequence read: piglet production, pig fattening, poultry husbandry~dairy cattle husbandry, bull fattening. The balance of animal production systems (stable balances) revealed relevant entry paths for heavy metals within different production systems. Here for example, the copper entry by claw baths in the dairy cattle husbandry as well as copper, zinc, and chromium input by min-eral feeds in pig husbandry are to be mentioned. Kuhl, Thomas (2004): Competitive sorption, diffusion processes, and transport of cations in soil: Measuring and modelling binary systems. Institute of Soil Science, Faculty of Agriculture, University of Bonn, 264 pages. Sorption and transport behaviour of cations in binary systems of Zn2+-Ca2+, Zn2+-Mg2+, and K+-Ca2+ were investigated by batch experiments with reaction times between 7 min and 512 hrs as well as column experiments under conditions of saturated water flow. Three soil samples from the Ap, Bv, and AhBt horizons of loess soils were collected from two locations near Bonn. For the numerical analysis of the measured data the new deterministic simulation model OOSDIT (Objekt Oriented Sorption, Diffusion and Transport Model) was developed in cooperation with the Department of Applied Mathematics of the Agricultural Faculty of the University of Bonn. The time-dependent and diffusion controlled sorption behaviour of sub-stances is described by a combination of various adsorption isotherms and cation-exchange equations with a diffusion term for solid-state diffusion. Refering to the Zn2+-Ca2+ system (batch experiments), the observed sorption behaviour of Zn2+ is characterised by a rapid and reversible adsorption on outer particle surfaces followed

by a diffusional transfer of Zn2+ along micropore walls and defects of the mineral structure to internal sorption sites. Experimental data of Zn2+ sorption in Mg 2+ background solution did not show substantial deviations from the Zn2+-Ca2+ system in the long-term sorption pattern. Considering cation exchange, specific sorption phenomena, and diffusion of Zn2+ into parti-cles, the model OOSDIT describes accurately the time-dependend sorption pattern of Zn2+, Ca2+, and Mg2+ in the soil material. The estimated apparent and effective diffusion coeffi-cients for the investigated period of time are in the range of 10-4 to 10-5 d -1 and 10-20 to 10-22 cm2·s-1, respectively. Diffusion rates are found to decrease with reaction time. Model results are validated by independent measurements. A sensitivity analysis has shown no improve-ment of transport description for reactive solutes by using the mobile-immobile approach. The long-term adsorption behaviour of K+ in Ca-saturated soil samples (batch experiments) is characterised by increasing adsorption and fixation of K + in interlattice positions with time. Subsequent desorption experiments have shown a significant decrease in extractability with increasing adsorption time, indicating a change in K+ binding forms. At sufficiently high K+ concentrations, the spontaneously bound K+ on external surface sites of clay minerals was transfered to the fraction of diffusion controlled interlattice bound K+. The experimental data were described adequately with OOSDIT. The type of the exchange isotherm did not signifi-cantly influence the goodness of fit. The estimated apparent and effective diffusion coeffi-cients for the investigated period of time are in the range of 10-5 to 10-6 d -1 and 10-19 to 10-20 cm2·s-1, respectively. The main features characterising sorption behaviour of Zn 2+, K+, and Ca2+, as recognised in the batch experiments, have been observed in column transport studies as well. Based on data of batch experiments, the model is able to predict the transport behaviour qualitatively well. Recalibration of sorption and diffusion parameters with data of column experiments also led to quantitatively satisfying descriptions of breakthrough curves. For K+ transport, recali-bration of parameters was necessary for forward and backward exchange considering struc-tural changes of the interlattice space. Considering cation exchange and solid state diffusion, complex sorption and transport pat-terns of Zn2+, K+, and Ca2+ in batch and column experiments were successfully described. Kuol, Betram Gordon (2004): Breeding for drought tolerance in Sesame (Sesamum indicum L.) in Sudan. Institute for Horticulture, Faculty of Agriculture, University of Bonn, 224 pages. Three phases of field investigations were carried out for two consecutive years (2000-2002) to assess the genetic variability among exotic and local sesame, study inheritance of drought tolerance and determine possibility of breeding sesame genotypes that combine drought tolerance with high yield potential. A wide range of genetic variability existing in the tested material was reflected in a broad range of heritability estimates obtained for characters. The genotypes C14F4, P10C15 and P6C7 maintained an impressive yield outlay across the four environments but in a different rank. Their yield superiority was not necessarily associated with high content of oil, protein and fatty acid components except P10C15, which exhibited high seed yield accompanied with relatively high oil, protein palmitic and oleic acid content at Wed-Romli location.

Four selected sesame genotypes were crossed among themselves in all possible pair wise combinations resulting in twenty-four progenies. Twenty-eight sesame genotypes represent-ing six generations, (P1, P2 parents), (F1, F2 hybrids) and (BC1, BC2 progenies) were tested for presence or absence of non-allelic interactions. Six-parameter model provided an exact fit to the generation means in the interacting crosses, while the three-parameter addi-tive-dominance model was judged adequate for describing the genetic variation in non-interacting crosses. Additive, dominance and three types of non-allelic gene interactions we-re observed for seed yield and yield components in most crosses. All types of gene action contributed to the control of oil, protein and components of fatty acid with dominance effects being more important in most crosses. On the other hand, estimates of interaction parame-ters in some crosses of arachidic acid were not significantly larger than their standard errors, thus the analysis of their genetic components was fitted to additive-dominance model of gene description. However, significant genetic contributions in these crosses were attributable to additive gene effect. Putative yield-based drought tolerance parameters were calculated and pattern of their corre-lations with yield was identified. Yield under normal irrigation (Yi) and yield under drought stress (Ys) were strongly correlated (r= 0.88**) in parental genotypes and moderately corre-lated (r = 0.36**) in progenies. STI was highly and positively correlated with Yi (r = 0.95**) and with Ys (r = 0.98**) in parental genotypes, whereas it revealed non-association with yield under both water treatments in progenies. A moderate negative association was detected between SSI and STI in parental genotypes (r = - 0. 39**) and (r = 0.30**) in progenies. Ge-netic variance for Yi and Ys was highly significant among parental genotypes as well as a-mong progenies with differences being markedly pronounced among progenies. Heritability estimates for Yi and Ys followed the same order of magnitude in both generations. Negligible reduction in heritability for Ys (h2 = 0.70) compared to Yi (h2 = 0.73) in parental genotypes did not imply a linear reduction in heritability of yield under drought stress conditions. SSI was moderately heritable (0.69 and 0.59) whereas STI was highly and moderately heritable (0.80 and 0.51) in parental genotypes and progenies, respectively. Genotypes C14F4, P10C15 and P6C7 had differentially high STI and relatively low SSI. F1 hybrids or advance generations produced from crossing the well-adapted C14F4 and P6C7 with exotic genotypes characterized by improved tolerance mechanism to drought like P10C15, can provide a source of germplasm that would be useful for improving drought tol-erance in sesame. Kyong Ran, Chang (1998): Long term supply of large vegetables with nitrogen by beaker-deposits, demonstrated by white cabbage (Brassica oleracea L.), cucumbers (Cucumis sativus L.) and toma-toes (Lycopersicon esculentum Mill.). Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 184 pages. Large vegetable crops like tomatoes, capsicum, cucumbers, melons etc. are cultivated in green houses and under special conditions in fields as well on a high level of productivity with intensive irrigation as so called long life cultures. These crops have high and continuous demands in nitrogen during their whole growing period.

These high and continuous demands of nitrogen for these vegetables can not be covered satisfactorily by splitted top dressings with commercial mineral fertilizers, slow release fertil-izers or by fertigation systems. A lot of nitrogen is easily lost by leaching or denitrification. For to overcome these problems in intensive crop rotations like those mentioned above the "CULTAN"-beaker deposit technique has been developed. In this case, nitrogen as a mixture of (NH4)2SO4 and CO(NH2)2 is put into beakers and placed into the root zone of large vege-table crops at planting time. The amount of nitrogen applied covers the total demands of the crops for the whole vegetation period. This nitrogen is taken up by the crops actively and for the reason of its phytotoxicity according to the intensity of growth of the plant itself. At present a mixture of nitrogen fertilizers of 1/3 N as (NH4)2SO4 and 2/3 N as CO(NH 2) 2 is used placed into PVC-beakers according to the demands of the crops planted. A buffer of loamy soil takes care for the build up of a diffusion gradient which is surrounded by plant roots by attracted growth of the root tips.These beakers upside down are placed into the root zone of the plants. Present observations are, that in comparison to common fertilization systems by the "CUL-TAN"system the vegetative growth of the plants is retarded but at the same time the fruit set is increased resulting in higher yields in those crops mentioned above. As final conclusion it can be mentioned, that the "CULTAN" system under economic and eco-logic aspects is a large improvement in comparison to common fertilisation systems. These differences will increase, when the supply of minorelements and the application of pesticides and growth regulators are connected to the "CULTAN" system. Labusch, Ute (1997): Usage and Distribution of Seed Reserves and Products of Photosynthesis during the Seedling Development of Wheat (Triticum aestivum L.). Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 120 pages. The contribution of seed-C and C derived from photosynthesis during the wheat seedling development up to the 4-leaf-stage were quantitatively described in this study. To distinguish the two C-sources and to quantify their contribution and their distribution towards different plant organs, the experiments were made under controlled environment in a long-term steady-state labelling growth chamber with a distinctly changed isotopic composition of the 13CO2/12CO2 applied. In this way seed-C and autotrophic-C could definitely be distinguished after massspectrometrical analysis of the plant material. Seed-C was the most important C source for the coleoptile and the first leaf. Approx. 24 h after the emergence of the first leaf the plant started to assimilate carbon. This marked the beginning of the young seedling´s transition towards autotrophy. The transition phase ended with the enrollment of the 3rd leaf. At this stage the fourth leaf grew within the sheath of the third. The fourth leaf was the first leaf to consist completely of C derived from photosynthesis. As the coleoptile was of no major importance in supplying the plant with C derived from pho-tosynthesis, the transition towards autotrophy and the distribution of C was studied in detail at the first leaf, especially with regard to growing and differentiating tissue.The extension zone of the first leaf was 12 mm long (10 % of final leaf length) and the differentiation zone,

the zone of secondary cell wall depositions, was located from 12 mm to 20 mm of the leaf base. The zone of maximum elongation ranged from 3 mm - 8 mm of the leaf base. This area contributed 70 % - 78 % to the total elongation of the leaf. Within the elongation zone, seed-C was the predominant C-source for local deposition rates into growing tissue till the leaf reached 62 % of its final length. Up to this time seed-C had always contributed more than 60 % to the total deposition of carbon. But the importance of C derived from photosynthesis rose constantly. Effects due to the diurnal cycle in elongated and extended regions of the first leaf almost completely comprised C derived from photosynthesis. The different seedborn roots (radicle, epiblastic and scutellar rootpairs) as well as their sec-ondary roots were analysed separately in this study. The radicle, the first seedborn root, was - because of its high mass of secondary roots - the most important root to make the soil ac-cessible for the plant. The total roots contained 55 % - 62 % of the total seed-C incorporated into the plant. Seed-C contributed decisively to the growth of the primary roots. 2 - 3 days after C derived from photosynthesis had been found in the shoot it was also measured in the root. Fluctuations in the supply with assimilates during the diurnal cycle could not be found within the root. During the observed time periods of the different experiments the root was continuously supplied with assimilates. Lamprecht, Sybille (2002): Effect of different ozone exposure patterns on the pathosystem wheat-Mycosphaerella graminicola. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 122 pages. The impact of ozone on the pathosystem wheat-Mycosphaerella graminicola was investi-gated by exposing wheat plants to various concentrations of the air pollutant in controlled growth chambers. Furthermore, two different ozone exposure patterns with the same total dose were compared; one with short-term peak concentrations representing urban areas and the other one representing rural areas containing a relatively constant ozone concentration. The effects of ozone during day/night cycles on leaf injury due to chlorosis and necrotization as well as on photosynthetic activity, biomas and yield were investigated. Results showed that exposure to both ozone patterns led to acute leaf injury and consider-able yield reduction. These effects were strongest after exposure to the pattern with short-term peak concentrations. Ozone exposure before inoculation influenced the disease rate of M. graminicola. The constant concentration pattern always induced significantly higher infec-tion rates in all cultivars tested. The effect of the short-term peak concentrations on infection rate was strongly related to the cultivar-specific susceptibility to ozone injury. The concentra-tion of antioxidants in wheat leaves led to the assumption that the cultivar-specific suscepti-bility to ozone damage depends on differences in the genetically based level of antioxidants in each cultivar. An additive effect of ozone and infection with M. graminicola could be dem-onstrated only for grain weight. In general, damage caused by ozone was more significant than that caused by M. graminicola infections. The results of these exposure models indicate that increased tropospheric ozone, which nowadays usually occurs in summer, can inhibit plant growth, reduce yield and alter the predisposition of wheat to M. graminicola. Therefore,

the exposure pattern seems to play a key role in the type and severity of ozone damage to plants. Lange, Annette (1998): Influence of sulphur nutrition on biological N2 fixation of different legumes. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 178 pages. The objective of our experiments was to prove the influence of the S nutrition on the biologi-cal N2 fixation (BNF). For this reason we investigated the effects of a different S nutrition on the nitrogen accumulation by the BNF, on the nodulation, on the nitrogenase activity and on the activity of some enzymes, involved in the C and N metabolism of nodules (PEP carboxy-lase, malate dehydrogenase, glutamate synthase, glutamate dehydrogenase). The cultiva-tion of plants fertilized with N besides the symbiotically fed legumes as well as the installation of a split root system should give some information if sulphur plays a direct role in the nitro-gen fixing process. With all legumes severe S deficiency resulted in a significant decrease of the S content in the above grown plant parts and of yield formation. In a similar way the BNF, the nodulation, the activity of the PEP carboxylase and the protein content of the nodules of the fixing legumes were reduced. No differences in the yield were visible by the response of legumes to sulphur deficiency in the absence as compared with the presence of added nitrogen and the in-creased N-concentration of N-fertilized legumes did not result in an increased dry matter yield. Moderate S deficiency diminished the nodule formation and the nitrogenase activity without affecting the yield. The influence of the S nutrition on the activity of enzymes of the N assimi-lation was more pronounced as compared with the enzymes of the C metabolism. The results of the split root experiment showed an important effect of the external S supply on nodule formation if the internal S supply was adequate. For this reason it can be stated that moderate S deficiency directly affected the microsymbiont without any implications to the host plant. Severe S deficiency seemed to act indirectly on the symbiosis by decreasing the host plant growth in a greater degree than the nodulation and the metabolic activities of the bacteroides. Furthermore a strong correlation between plant growth and the growth and ac-tivity of the nodules was determined. For nutrients like Co and Mo other investigations revealed a much greater requirement for symbiotic nitrogen fixation than for host plant growth. Deficiency conditions increased nodu-lation, decreased nitrogen concentrations in plant tops and Co and Mo showed a negative interaction with fertilizer nitrogen.. The authors resumed that these elements are probably specifically involved in nitrogen fixation. However severe sulphur deficiency reduced the nodule mass and/or the nodule number and affected the yield in a greater extend than the nodule metabolism. In most cases the content of nitrogen in the tops of the legumes did not change and the addition of combined nitrogen did not correct sulphur deficiency. These results suggest that under sulphur deficiency condition the BNF decreased to a great extent. Nevertheless the restricted growth of the legumes at low S levels was not due to inef-fective symbiotic nitrogen fixation, but to a deficiency of S in the host plant. Presumable an

inadequate assimilation of fixed N and the reduced building of proteins restricted the growth of the legumes. Lange, Katarzyna (1998): Dry matter production and Reserves accumulation in apple trees in relation to fruit load, water supply and pruning methods. Institute for Horticulture, Faculty of Agriculture, University of Bonn, 118 pages. Lysimeters experiments with Golden Delicious apple trees on M9 rootstock were conducted during 1995-1998 to investigate the influence of fruit load, water supply and pruning methods on dry matter production and distribution, as well as storage of nitrogen and carbohydrates in different parts the trees. The apple trees were separated in October into roots, stems, shoots, leaves and fruits and analysed for nitrogen, amino acids, glucose, fructose, sucrose, sorbitol and starch. The fruit load inhibited the growth of all vegetative parts of the trees, particulary the root growth in comparison to non-fruit producing trees. In addition the nitrogen and protein nitro-gen content were reduced in the perennial parts. However the nitrogen content in leaves was not affected. Fruit load also decreased the content of arginin nitrogen in the perennial parts, but increased the content of asparagin nitrogen in the perennial parts of these trees. Sucrose and sorbitol were the major translocated forms of carbon, while starch was the major storage form of carbohydrates particularly in the roots. Fruit load strongly reduced sorbitol and starch content in all vegetative parts of the trees in comparison with non-fruit producing trees. The sucrose content was reduced as well. Long term warter deficit treatments decreased the leaf and shoot growth, but contrary to ex-pectations had no influence on the root growth. Deficiency of water also decreased the nitro-gen content in all parts of the trees. In addition the content of sucrose and sorbitol in the shoots were lower as compared to the content in the trees well supplied with water. Further-more continous low water supply reduced the starch content in all above ground parts of the trees without influencing the starch content in the roots. Pruning methods also reduced the vegetative and generative growth in the first three years as compared to the unpruned trees. Pruning decreased the nitrogen content in the shoots, leaves and fruit, but not in the stems and roots. Pruning methods diminished the starch con-tent significantly only in the shoots. Le, Huong Thi Thu (2003): The role of Pythium aphanidermatum (Edson) Fitzp in tomato sudden death in the tropics with emphasis on integrated disease management. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 114 pages. Sudden death causes severe damage to tomato grown under field conditions following flood-ing at high soil temperatures. P. aphanidermatum plays a key role in sudden death. The fun-gus damages the root cortex, which causes wilting and plant death.

In a field experiment conducted in the hot growing season between June and September 2002 in Taiwan, 51, 72 and 93-day-old tomato plants were flooded and tested for susceptibil-ity to sudden death. Three isolates of Trichoderma harzianum, two of Trichoderma virens and one of Streptomy-ces saraceticus were evaluated for biological control of tomato sudden death due to P. aphanidermatum in the greenhouse and in the field. The results revealed that neither Tricho-derma spp. nor Streptomyces gave significant biocontrol of tomato sudden death. The per-centage of diseased tomato plants growing in soil treated with either Trichoderma isolates or Streptomyces after flooding was not significantly different when compared to the soil treated with P. aphanidermatum alone. The soil amendments, SFMC, FNB-5A and S-H Mixture tested in this study also showed little promise for controlling tomato sudden death due to P. aphanidermatum. In both greenhouse and field experiments conducted in the summer of 2001 in Taiwan, the number of wilted and dead tomato plants was not significantly reduced over the control. The Trichoderma aureo-viride added to the soil amendment treatments also gave no significant improvement in con-trol of P. aphanidermatum with respect to tomato sudden death. Similar poor results were observed in treatments with the fungicide Mefenoxam. Grafting tomato onto eggplant rootstocks successfully protected the plants against tomato sudden death. The eggplant roots were colonized by P. aphanidermatum, but no extensive damage was caused to the plant. The results of the present study indicate that, with exception of grafting with eggplant root-stocks on biocontrol or the use of organic amendments would not give adequate control in the field. More research on biocontrol and organic matter for control of tomato sudden death is thus required. Lenthe, Jan-Henrik (2005): Detection of yield relevant climatic factors in wheat by digital infrared-thermography. Institute for Plant Diseases, Faculty fo Agriculture, University of Bonn, 141 pages. Digital infrared thermography allows the geometricly resoluted measurement of surface tem-perature of large, planar objects such as plant canopies. The data can be fed into a geoin-formation system to evaluate the distribution of canopy temperature. The canopy tempera-ture is largely influenced by the cooling effect of transpiration, so that vital leaves appear can be expected to show another leaf temperature than stressed leaves.

A site specific plant protection management depends on the detection of local differences in the occurance of yield relevant factors such as fungal pathogens, canopy density through availability of water and nutrients or local conditions of microclimate, especially leaf wetness.

The intention of the conducted studies was the application of digital thermography as a sen-sor for yield relevant factors under greenhouse and field conditions. Biotic and abiotic factors expected to influence leaf temperature of wheat were monitored thermographically. A me-thod to determine the leaf temperature of fragmented leaf area such as wheat plants was developed. The thermal effect of a rust infection on wheat and bean leaves was studied.

Laboratory studies showed different canopy temperature compared to ambient temperature due to differences in supply of water and nitrogen of a wheat plants. The effect of biotic

stress factors, rust of wheat and beans, was small compared to abiotic stress. The patho-geneses resulted in changes of the thermal pattern of leaves rather than effecting the abso-lute leaf temperature. Wheat canopies were thermografically monitored as a whole through-out the growing season. The temperature distribution was compared with yield maps show-ing little correlation, however hinting at a local correspondence of low canopy temperature and high yield level. In contrast an abiotic factor on yield, canopy density, was readily detect-able. The evaluation of local differences in canopy temperature compared to levels of infec-tion by leaf pathogens between fungizide treated and untreated plots and different levels of infection within untreated plots showed little correlation. The signal leaf temperature was found to be very unspecific. Biotic and abiotic factors influenced the transpiration in the same manner. Therefore an identification of the cause of leaf temperature differences was not pos-sible. Even in a very homogenous canopy that was kept healthy by a conventional plant pro-tection management, a considerable heterogeneity of canopy temperature was found. The temperature span leveled with the span between plots with and without fungizide treatment. Local canopy temperatures were compared to micro-climatic parameters measured within the canopy. Of these, leaf wetness, a crucial parameter for the prognosis of important leaf pathogens was detectable by its decreasing effect on canopy temperature, both under greenhouse conditions and in the field. Therefore the method of digital thermography seems to have high potential for the temporal and spatial improvement of prognosis of leaf infections of brown rust and septoria leaf blotch.

Lellmann, Arno (2005): Nutrient cycling, grassland productivity and animal performance on a suckler farm system on extensively fertilised grassland in the Eifel mountains. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 269 pages. Since the introduction of the milk quota in 1984, the number of suckler cows has increased significantly. In general, suckler production on grassland is considered as ecologically advan-tageous. However, suckler production has hardly been investi-gated in regard to nutrient cycling. It is evident that suckler farms export less nutrients than dairy farms. Therefore, on these farms the major fraction of nutrient uptake is excreted, hence potentially increasing the risk of nutrient release to the environment. On Rengen Experimental Farm of the University of Bonn (Eifel mountains, Germany), the nutrient cycling of N, P, K and Mg, as well as grassland productivity and animal perform-ances were investigated between spring 1999 and autumn 2001. Two farming systems were compared: a more extensive one (O) without nutrient input, and a less extensive one (M) with nutrient input. Each system consisted of approximately 19 ha pasture with 20 Limousin suck-ler cows and their calves. The objective of this study was to gain a better understanding of external and internal nutri-ent flows among soil, grazed forage, excreta on pastures, silage, farmyard manure and the animal product, as influenced by the level of input. Particular focus was on nitrogen, due to its potentially high impact on the environment.

The annual gross yield from pastures (grass uptake and silage) varied between 6.0 to 7.3 (O) and 5.2 to 8.2 (M) tons of dry matter (DM) ha-1. The average daily forage intake per livestock unit was 7.4 kg (cowshed in winter) in both systems and 8.9 to 10.9 (O) and 8.4 to 12.1 (M) kg (pasture in summer). The mean live weight increase of the suckler calves per kg DM intake of cows and calves was 89 (O, both years) and 94 and 85 (M) g while kept in the cowshed, and 39 to 64 (O) and 47 to 71 (M) g on pastures during summer. The related nutrient excretions of N, P, K and Mg in kg ha-1 were 26, 5, 31 and 3 during winter, and 55, 6, 57 and 4 during summer, respectively. The nutrient excretion per cent was highest for K and Mg (99 and 98 %), followed by P (83-90 %) and N (90-96 %). The nitrogen use efficiency was 2.8 times higher in the cowshed than on pasture. The excretion of nitrogen on pasture contributed to over 50 % to the total N losses, which were 62 and 57 (O) and 108 and 66 (M) kg ha-1. White clover significantly contributed with 12 and 7 (O) and 22 and 9 (M) % to the nitrogen gross yield, representing an estimated N2 fixation of 40 and 23 (O) and 80 and 30 (M) kg N ha-1 yr-1. Considering losses, N-balances of all paddocks ranged from -78 to -13 (O) and from -34 to 84 (M) kg ha-1. This study indicated that the amounts of nutrients circulating internally within the system were 2.4 to 7.9 higher as compared to the amounts of nutrients imported. Some agro-environmental indicators and options to reduce N-losses were discussed. It was concluded that due to considerable nutrient losses on pasture, particularly in regards to nitrogen, extensive suckler cow production is not necessarily environ-mentally sustainable, even if there is no nutrient input through forage and fertilisers. The crucial point is rather the amount of nutrients that are cycling internally via pasture uptake and related excreta. Lennartz, Burkhard (2001): Biologische Bekämpfung von Septoria spp. an Weizen mit Chaetomium cochliodes und Ulocladium atrum durch Einschränkung der epidemischen Entwicklung des Erre-gers. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 140 pages. Although the biological control of plant diseases with fungal antagonists had been frequently described, there are only few details known about the application of biological agents in field cultures. In most cases strategies of biological control on aerial parts of plants are directed on the elimination of the pathogen. Another promising strategy is the retardation of the epi-demiological development by competition for nutrients and space. It was investigated if fungi that were isolated from wheat leaves are able to reduce colonization, reproduction, and epi-demic spread of the necrotic pathogens Septoria nodorum (Phaeosphaeria nodorum) and Septoria tritici (Mycosphaerella graminicola) on wheat. The aim was to control Septoria spp. by reduce of the epidemic development with antagonists and to find forms of application that are appropriate for agriculture. Chaetomium cochliodes and Ulocladium atrum proved to be proper of antagonists because of their efficiacy against different growth stages of Septoria spp., their apathological features, their high potential of spread, and their fast colonisation of necrotic tissue. The antagonists are able to colonize wheat leaves and reduce the development of Septoria nodorum or Sep-toria tritici. Competition for nutrients and space seems to be the antagonistic mechanism of

U. atrum because interactions like hyperparasitism or antibiosis could not be detected in microbiological studies. In contrast C. cochliodes produced antibiotic metabolisms and dis-placed the pathogen by competition and antibiosis. The efficiency of the biological control was proved in field trails. Both antagonists controlled the development of Septoria spp.. They reduced the necrotic leave tissue and the reproduction of the pathogen. The production of pycnidia and pycnospores was considerable lower. This was proved on different locations under different intensities of production. Applications of fungicides led to a reduction of yield losses between 10 and 25 % depending on location. Three to four treatments with C. cochliodes or U. atrum resulted in a yield increase up to 9 % and 17 %, respectively. A cheap medium was found with oat kernels, on which C. cochliodes and U. atrum produced a large amount of spores. The spores of the antagonists could be stored for more than one year without any greater loss of vigour. Different oils and oil products used as formulation improved the distribution and adherence of the spores at the plant. Both antagonists were relatively insensible against agrochemicals. Herbicides and insecticides had no or only small effects on sporulation and growth. Against fungicides C. cochliodes und U. atrum showed a lower sensitivity than S. nodorum and S. tritici. The application of a combination is possible after an interval of several days. Liebe, Frank (1999): Trace elements in soils and plants of North Rhine-Westphalia - Contents of different chemical soil fractions and their relationship to soil pH and contents in plants. Institute for Soil Science, Faculty of Agriculture, University of Bonn, 375 pages. In order to evaluate soils with very different contents of trace elements, 335 soil samples - spread over all of North Rhine-Westphalia - were taken. This project was sponsered by the ministery of environement and agriculture of North Rhine-Westphalia (MURL). The location of the soil samples are characterized by different soil uses (arable fields, grassland, forest, gardenland, and dump sites, locations in city areas, playgrounds) and different soil contami-nations (none or less polluted till extremly polluted locations). Furthermore the soil samples contain a wide spectrum of different parent materials, type of soils, and compositions. They are not representative for the area of North Rhine-Westphalia. For the determination of trans-fer of trace elements from soil to plant, different plant samples were taken from arable field locations 89 wheat grain samples - e.g. from gardenland 17 samples of green cabbage. The total contents of the elements in the soil and plant samples were extracted by aqua regia (Thallium: HNO3 extraktion). The mobilizable (potentially available) fraction was determined by a cocktail of 0,025 M EDTA, 1 M NH4OAc and 0,1 M NH2OH.HCl (pH 4,6). The extraction with an unbuffered salt solution (1 M NH4NO3, soil-solution ratio 1 : 2,5) was used to charac-terize the mobile fraction in soils. The concentrations of elements in the soil solutions were specified by analysing the soil saturation extracts. 18 elements (Al, As, Be, Bi, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sb, Sn, Tl, V, Zn) were analysed with different spectrometric meth-ods (AAS, ICP-OES) in the different extracts. The analysed elements vary widely in their total contents, in their extractable proportions of the total contents, and in their mobility and availability in soils. The proportion of the mobiliz-able fraction (EDTA-Cocktail) in percent of the total contents of Cd, Co, Cu, Mn and Pb are >

30 %. On the other hand the proportions of the NH4NO3 extractable contents in percent of the total contents of Al, As, Be, Bi, Co, Cr, Fe, Hg, Pb, Sb, Sn and V lie mostly below 0,1 %, except for Ni, Zn, Cu, Mn, Cd and Tl (max. 3,5%). The average proportions of the watersolu-ble fraction (saturation extraction) in percent of the total contents of all elements are below 0,1 %, except for Cd reaching up to 1,25 % in strongly acidic forest soils. The contents of the different trace elements from different plant samples have a relatively small variation. The data of this project can also be used to derive background contents for trace elements. Therefore, frequency distributions of element contents in soils were established with the Ker-nel Density Estimation. With this procedure background levels can be determined per ele-ment for corresponding groups of soil samples being characterized by common features (e.g. parent material, region of origin, specific source of pollution). Lienemann, Kerstin (2003): Incidence of Fusarium species in winter wheat in the Rhineland and possibilities of control with special reference to wheat cultivar. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 152 pages. In 1998 – 2000 incidence of Fusarium head blight (FHB) in integrated and organic farming considerably depended on year, weather conditions, location and wheat cultivar. In 1999 and 2000 infection rate of kernels by Fusarium spp. was three times higher (18 – 20%) than in 1998, the incidence of Microdochium nivale was significant only in 1998. Despite same tillage system and previous crop, kernel infection varied considerably with location, similar as the composition of Fusarium species. F. avenaceum and F culmorum prevailed on the kernels harvested, whereas infections with F. graminearum and F. poae occurred less frequently. Incidence of some Fusarium species was promoted by previous crops as winter wheat or sugar beet, but not by minimum tillage. Because of its ecological flexibility F. culmorum seems to be highly adapted to growth conditions in the Rhineland. Similar demands on grow-ing conditions can be obviously assumed for F. avenaceum and F. tricinctum while infection levels of F. avenaceum and F. culmorum indicated antagonistic interactions. Ear infection occurred by successive – and symptomless – infection of the leaf levels, which was impor-tant for all Fusarium species except F. graminearum and F. poae. In a three years trial under field conditions `Charger`, `Bandit`, `Rialto` and `Haven` showed high susceptibility to FHB, `Hybnos`, `Convent` and `Residence` were least susceptible. Low susceptibility of cultivar `Atlantis`, `Kanzler` and `Ludwig` was due to plant height, whereas kernels of `Atlantis` had a low infection rate additional when inoculation was done at anthe-sis. Genotypes `Bandit`, `FR 444/06` and `Hanseat` showed also high susceptibility to FHB but it was remarkable that the breeding line ‘FR 444/06’ gave high yields despite of high in-fection level. The morphological resistance mechanism was plant height (r = -0,66), in con-trast to spikelet density within the ear. A short distance between flag leaf and ear and an erectophile leaf position at the same time promoted ear infection. Fungicide treatment of wheat leaves resulted in a significant increase in kernel infection by Fusarium spp. in 40% of trials. In some cases also mycotoxin content of the kernels was in-creased. Ear treatment with the azoles metconazole or tebuconazole resulted only in 40% of the experiments in a significant decrease in the incidence of Fusarium infection of the kernels

harvested. There was a selective effectiveness of the tested azoles against the occurring Fusarium species. Lindenthal, Miriam (2005): Visualisation of downy mildew development of cucumber due to Pseudoperonospora cubensis using thermography. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 123 pages. The epidemic of downy mildew of cucumber, caused by the obligate biotrophic oomycete Pseudoperonospora cubensis, is strongly depending on environmental conditions. In this study, small-scale measurements of the microclimate in cucumber fields allowed estimation of intra-field variation referring to the risk of downy mildew infection. The development of downy mildew disease under field conditions was closely related to the heterogeneity of the calculated infection risk. Hence, the distribution of downy mildew within cucumber fields is predictable applying maps of the microclimate. Pathogenesis of P. cubensis resulted in various changes in the metabolic processes within cucumber leaves including changes in the transpiration rate of infested tissue. Due to the negative correlation between transpiration rate and leaf temperature, digital infrared thermo-graphy permitted a non-invasive monitoring and an indirect visualisation of downy mildew development on cucumber leaves. Depending on the stage of pathogenesis, the infection of P. cubensis resulted either in a decrease or in an increase in leaf temperature. Under con-trolled conditions these changes in leaf temperature of infected leaves allowed the discrimi-nation between healthy and infected leaves in thermograms, even before visible symptoms of downy mildew appeared. In contrast, first distinct changes in the temperature of the cu-cumber leaves infected with powdery mildew only occurred with the appearance of symp-toms on the upper leaf side. In addition, the environmental conditions during thermographic measurement in particular air temperature and humidity, as well as the water content and the age of the leaf influenced the temperature of its’ surface. In laboratory assays environmental conditions enhancing the transpiration rate of leaf tissue facilitated the detection of changes in leaf temperature of infected leaves at early stages of infection. Under field conditions differences in the incidence of downy mildew within a cucumber field caused deviations in the canopy temperature as visualised by digital infrared thermography. The application of thermography in the field in order to improve an objectivity and reliability of disease assessment is limited due to the influence of environmental conditions and the lack of specificity of the parameter canopy temperature, and thermograms have to be analysed thoroughly in order to avoid misinterpretations. Linscheid, Karl Peter (2002): Flow cytometric detection of adrenocorticotropic hormone in human leukocyte popu-lations under performance-physiological cell culture conditions. Institute for Agricultural Botany, Faculty of Agriculture, University of Bonn, 88 pages.

Modelling main aspects of the systemic stress reaction, cellular performance physiology de-scribes coping with environmental challenge in microscale. Pro-opiomelanocortin-derived neuropeptides, synthesized and recognized in lokal leukocyte networks, project the hypotha-lamo-pituitary-adrenal axis into cellular microenvironments. In the present study, commer-cially available monoclonal antibodies and secondary immunofluorescence were used to flow cytometrically detect adrenocorticotropic hormone (ACTH) in stimulated human leukocytes. The effects of inducers, previously described in scientific literature, on the amount of ACTH synthesized was assessed by calculating the mean fluorescence intensity. Flow cytometric characteristics of cellular micromorphology in combination with immunophenotyping proved that human lymphocytes and monocytes from peripheral blood are involved in adaptive physiological reactions. The results also helped to propose how to optimize blood sampling, cell culture and leuko-cyte stimulation. Direct fluorochrome labelling of antibodies may broaden this approach to-wards quantification. Thus, flow cytometry may further contribute substantially to understand-ing the interplay mediated by hormones, cytokines and other signal molecules in functional aspects, such as proliferation, apoptosis, cellular and humoral defense. In vitro and ex vivo studies on the health effects of food constituents, the beneficial and adverse potentials of bioactive compounds in food and supplements, or immunotoxicological investigations on contaminations and toxic residues are perspectives of application of the method. Lopotz, Harald-Wolfgang (1997): Biological N2 fixation of clover in pure stands and clover/grass-mixtures with particular consideration of the available soil nitrogen. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 145 pages. It was the aim of the pot and field experiments to anaylse the influence of soil nitrogen on the biological nitrogen fixation by red clover, red clover-italian ryegrass mixtures and other forage legumes. The relationships between the amount of symbiotically fixed nitrogen (NFix), the per-centage N from symbiosis (%NFix) and dry matter or total nitrogen yield were investigated. The N2 fixation was measured by the 15N isotope dilution procedure and the difference method. A comparison of NFix and %NFix found with the respective methods showed, that mineral nitro-gen supply from soil or fertilization, development of the plant and environmental plant growth conditions may influence the difference between the results of the two methods. The relation-ship between the results of the difference method and the 15N method for NFix and %NFix was inconsistent. In most experiments with red clover and red clover-italian ryegrass mixtures closer relationships were determined for the amount of fixed N (NFix) than for the percentage N from symbiosis (%NFix). Slight differences between the methods could be detected under conditions with low mineral nitrogen supply and high %NFix values (>80%). A negative relationship was found between the percentage from symbiosis (%NFix) of clover in pure stands and available soil nitrogen. In most experiments a decrease of %NFix was associ-ated with a reduction of the amount of fixed N (NFix). Under conditions of a steady mineral ni-trogen supply the amount of fixed N by pure red clover swards was equally reduced by the up-take of mineral N. A feedback control mechanism, which enables legumes to regulate the N2 fixation according to the N demand, can be assumed. The N-uptake of ryegrass in clover/grass

mixtures minimized the direct inhibitory effect on N2 fixation by lowering the concentration of available soil N. The percentage of clover-N from symbiosis usually exceeded 85%. On the other hand increased mineral nitrogen supply from soil or fertilization enhanced the competive-ness of the grass and reduced the legume production and the amount of fixed N. Strong correlations between the symbiotically fixed N (NFix) of pure clover stands and dry mat-ter or total N yield were only found under conditions of low mineral nitrogen supply and high %NFix values. The amount of fixed N from clover in clover/grass mixtures was determined by the dry matter yield of the clover/grass mixture and the percentage of clover in the mixed stand. Mahdi, Osman (2001): Rainfall and its Erosivity in Ethiopia with special consideration of the Central High-lands. Institute for Soil Science, Faculty of Agriculture, University of Bonn, 249 pages. In this research project the characteristics and the erosive potential of precipitation in Ethio-pia were examined, with particular emphasis on the central highlands of the country. Fur-thermore, the hydrologic implications of rainfall variability and socio-economic context of wa-ter erosion were studied. Long-term rainfall data spanning from 1898 to 1997 of 168 weather stations were statistically analysed. A detailed assessment of precipitation and its erosive potential in the central highlands was made using data of 44 selected weather stations. The erosivity of rainfall was estimated using the modified Fournier’s index. The consequence of rainfall variability on flow regime was examined based on hydrometric records ranging from 1982 to 1997 of 5 gauging stations. The socio-economic context of water erosion was as-sessed by examining previous project documents, supplemented by socio-economic and field survey. Generally, the summer is the major rainy season in most parts of Ethiopia. Two types of sea-sonal precipitation distribution patterns, namely single and double peaked were noted. The latter was further subdivided into two groups: One with a short gap between the two peaks and another with a long gap. The lowest rainfall variability in the country was noted in April and the highest in June. With regard to precipitation in the central highlands, the area has seen periods of extremely wet and drought events. On the whole, the region has experienced high positive deviations from the long-term average in the first half of the 20th century, but dominantly negative depar-tures have been evident since then. However, a general decline in precipitation was noted in the area. In the central highlands, highly erosive rainfalls were observed in the first half of the 20th century, compared with the succeeding periods. Concerning prediction tools, a linear regression model was found to be the best predictor of regional water erosion. In the central highlands of Ethiopia, long-term rainfall erosivity tended to increase from east to west and from south to north. Generally, the summer precipitation was found to be the major agent of water erosion in the study area. The erosive potential of rainfall varies temporally and spa-tially. Hence, various prediction models were developed for the weather stations in the study area for different seasons. Six standard classes of annual and summer rainfall erosivity, namely very low, low, moderate, high, very high and extremely high were established for the region.

Regarding the implications of rainfall variability on flow regime, it was noted that flow is af-fected by the variability in areal precipitation. However, further research is needed to deter-mine unexplained factors influencing the flow regime. Concerning the socio-economic context of water erosion, Ethiopian farmers have long-standing indigenous knowledge of land and water management techniques. These became less effective with intensification of land-use. The compensatory interventions were neither socially acceptable nor environmentally useful. Today, socio-economic and environmental sustainability are gaining attention in resource management policy design and implementa-tion. Social participation in land and water management should be encouraged, especially through defined and clear property rights. The database established by this study is a useful resource for environmental management planning. The models developed are appropriate to forecast water erosion under conditions of data scarcity and financial constraints. It is recommended that the database and its man-agement be regularly improved for appropriate land and water management planning. Future research should focus on testing and adaptation of modern water erosion prediction tech-nologies as well as models to devise the best predictive tools with maximum efficiency. Wa-tershed and river basin approach to curb rainfall erosion, sedimentation assessment, and promotion of indigenous knowledge should gain much focus in land and water management research in Ethiopia. Mahdy, Magdy (2002): Biological control of plant parasitic nematodes with antagonistic bacteria on different host plants. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 171 pages. Root-knot nematodes, Meloidogyne spp., are recognized as the most economically important genus of plant parasitic nematodes worldwide. The nematode causes severe damage and yield loss to a large number of cultivated plants and especially on vegetable crops in the trop-ics and subtropics. In the investigations conducted in this study, the potential control of plant parasitic nematodes using different antagonistic bacteria was studied with particular refer-ence to the control of species of Meloidogyne on tomato. The results obtained from the re-search are presented in four chapters. The first chapter gives a: comprehensive introduction to the problems associated with root-knot nematode attack, outlines the major control meth-ods being used and and gives an inside into integrated pest management now as well as the potential use of biological control in future integrated strategies for nematode management. In the second chapter the results of experiments on the biological control activity of the plant health promoting rhizobacterium Bacillus cereus strain S18 for biocontrol of the three major species of Meloidogyne are discussed. The results showed that B. cereus introduced either as a soil drench or as a root dip, reduced the number of galls and egg masses of M. incog-nita on tomato significantly. B. cereus applied 10 days before nematode inoculation caused significant reductions in root galling and number of galls. No differences, however, were de-tected between the different application times in the number of egg masses produced. It was also shown that B. cereus does not control all three major species of Meloidogyne to the same degree. B. cereus had little to no biological control activity toward M. arenaria, but gave

significant control of M. incognita and M. javanica. Furthermore, the results demonstrated that B. cereus is an effective biological control agent of M. incognita on a broad spectrum of host plants. In the third chapter the plant health promoting rhizobacterium Rhizobium etli strain G12 was tested for control of different genera of plant parasitic nematodes on a broad spectrum of crops. R. etli exhibited strong biocontrol activity towards M. incognita on different host plants. The reduction rates varied however between crops. Results showed that R. etli had the ability to control three economically important species of Meloidogyne. The highest reduction was against M. incognita and M. javanica, whereas it had little effect on M. arenaria. It was also demonstrated that increasing inoculum densities of R. etli caused in-creased reductions in nematode infection. Reduction in the number of galls occurred at 1010 cfu/ml whereas reductions in egg mass number were detected at 106 to 1010 cfu/ml. R. etli also caused significant reductions in sugar beet cyst nematode, Heterodera schachtii infec-tion. R. etli reduced significantly the number of cysts/plant and number of eggs and juve-niles/plant. The bacteria, however, did not affect the number of eggs and juveniles/cyst. The experimental data also showed that R. etli can reduce infection of the cyst nematode Glo-bodera pallida on potato, but had no activity towards the migratory endoparasitic root-lesion nematode Pratylenchus zeae on maize. In the fourth chapter the spore-forming endoparasitic bacterium Pasteuria penetrans (Pp3) was used as a biocontrol agent for the biological con-trol of M. javanica on tomato. The results revealed abiotic factors affect attachment. Culture filtrates of the two antagonistic rhizobacteria B. cereus S18 and R. etli G12 reduced attach-ment of Pp3 spores to the cuticle of M. javanica juveniles at 100 strength and dilutions of 10 percent of the original fermentation broth. The experiments also demonstrated that perco-lates of chicken manure compost treated soil had a strong negative effect on the attachment of Pp3 spores to M. javanica juveniles. In greenhouse tests P. penetrans multiplied quickly and within 6 months and gave good biological control of M. javanica when initially introduce into the planting soil during seedling production. The seedlings with P. penetrans in the pot-ting soil were then grown for two additional tomato cropping cycles in a sand substrate previ-ously infested with root-knot nematodes, at temperatures above 25 C. The overall results of these studies demonstrated the importance of three different bacterial antagonists for root-knot nematode control and supplied new information on how to improve activity of the bioloigcal control agents as well as ideas on their use in integrated management under field conditions Makhonpas, Chaiwat (2001): Water logging effects on dwarfed apple trees as dependent on fruit load. Institute for Horticulture, Faculty of Agriculture, University of Bonn, 152 pages. The effects of water logging for a few days in summer and of fruit load were investigated on young ´Golden Delicious` trees on M9. They were cultivated in sand filled lysimeters at the Institut für Obstbau und Gemüsebau, University Bonn. Of the 24 experimental trees, 12 were deblossomed in 1996 and 1997 respectively. Main attention was placed on the vegetative and reproductive growth of trees, yield, fruit quality, gas exchange of leaves, root respiration, water consumption, nutrient uptake and the carbo-

hydrate accumulation. It was shown, that the water logging had adverse effects on most of the above mentioned parameters when trees had no fruit load. Fruit bearing trees reacted more tolerant to the water logging treatments. This was mainly so in regard to flower formation, fruit set, growth of shoots and leaves, leaf shedding, photosyn-thesis and transpiration rates of leaves, ethylene evolvement from leaves, water consump-tion, dry matter production, nutrient uptake and carbohydrate accumulation in trees. On the other hand also the fruit load had inhibiting effects on the growth of the vegetative plant organs in particular of roots, Also the distribution of dry matter, nutrients and carbohy-drates was considerably affected by the fruit load. The amounts were determined of dry matter, mineral nutrients and carbohydrates, which were removed with the fruits from the trees during harvest. The amounts were hardly influ-enced by the water logging treatment. Makumbi-Kidza, Nakato (2002): Studies on the distribution, pathogenicity and control of the root-knot nematode (Meloidogyne incognita) on cassava (Manihot esculenta). Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 172 pages. The study is organized in seven chapters. Cassava is presented as a staple of the tropics with outstanding features that have made it the most important root crop in Africa. Major pests and diseases occurring on cassava are listed. Nematode damage is dealt with in more detail. Field surveys were made in major cassava growing regions of Uganda. Root-knot nematode incidence and damage on cassava was investigated in two regional surveys in northern and western Uganda, and in two local surveys in central and eastern Uganda. Al-though Meloidogyne spp. and susceptible cassava cultivars occurred at all locations the dif-ferences in nematode damage observed were considerable. The environmental causes for increased nematode damage were identified as: sandy soils, susceptible alternate host crops (particularly Nicotiana tabacum L. and Solanum aethiopicum), an alternate weed host (Ag-eratum conyzoides L.) and an annual rainfall regime that allowed for a permanent presence of vegetation on agricultural land. Pot experiments were conducted in which cassava was screened for resistance to M. incognita (race 2). The nematode infected and reproduced on all clones tested. The predisposition of second stage juveniles (J2) to hatch from nematode egg masses was dependent on the cassava clone on which the egg mass had been formed, significant differences occurred between clones. The total number of J2 hatching per egg mass was also cultivar dependent. There was a significant difference in reaction of the cas-sava clone tested to the different root-knot nematode species M. incognita and M. javanica. Experiments were carried out to examine the effect of M. incognita on yield and root cyano-genic potential (RCNp) of cassava. M. incognita reduced sprouting (shoot-emergence) of cassava (TMS 30572) significantly. Cassava was most vulnerable to nematode attack during and before the time of storage root initiation. Infection during this time greatly reduced the number of storage roots formed. RCNp was raised in most nematode infected plants, for some clones the increase was significant. A field experiment lasting 12 months showed that nematodes significantly reduced the number and the size of storage roots formed by some of the clones tested. The effect on yield of different nematode inoculum densities was investi-

gated at three, six and nine months after planting. Some clones were able to compensate early losses with later growth increases. Based on the results obtained an integrated pest management (IPM) strategy, TRAP, for the control of nematodes on cassava was developed. It focuses on pest, host and site as the three factors that need to be targeted by IPM in order to effectively reduce root-knot nematode damage to cassava. The control measures are lim-ited to specific ‘high risk areas’ that are identified with help of the Geographic Information System (GIS). Malcharek, Alexander (2000): Forage quality of extensive grassland stands and its utilisation in grassland farms. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 174 pages. The management of late-used species-rich grassland under nature conservation programs, like the „Mittelgebirgsprogramm (MGP)“ in North Rhine-Westphalia, includes several man-agement prescriptions. Especially the stipulated delayed harvest dates for hay and onset of grazing period have a far-reaching influence on the forage utilisation in grassland farms. The key issue of a profitable forage utilisation in grassland farms and for the acceptance of grass-land conservation programs by farmers is the quality of botanically different composed herb-ages and the proportion at which these forage can be integrated in the feeding plan of grass-land farms. At three different low mountain ranges of western germany 106 grassland sites were investi-gated over three years. All sites have been managed under the prescriptions of the MGP and were neither harvested nor grazed before 1st of July. The herbage quality was primarily ad-dressed by net energy lactation (MJ NEL kg-1DM). Additional estimations for the forage utili-sation in grassland farms are based on a survey of 59 individual farms. In consideration of losses due to harvest the fodder quality with 4,8 MJ NEL kg-1DM from late-used species-rich grasslands is low compared to fodder from intensively managed grasslands. Forage quality and its loss with delayed harvest date was mainly influenced by the prime population forming species and their stage of development. However this influence was partly overlapped by the varying climatic conditions of the different years. Harvest date had a significant influence on herbage quality of both extensively and intensively managed grassland. Swards mainly composed of herbs and low growing grasses maintained higher quality over time than top rich swards. The survey of grassland farms showed, that low quality forage was used mainly in cattle feeding. A comparision of actual and potential proportion of extensive used grassland of the farms showed, that especially dairy farms with followers can use more of this fodder than they do already. On the other hand suckler farms with a low stocking rate could often use only a small proportion of the extensive grassland. In dairy farms with followers it is possible to utilize about 0,5 ha of extensively managed grassland in the feeding plan of followers and dairy cows in dry period without decrease in performance. Over all the investigated dairy farms can manage about 12 percent of the total forage area as extensive meadows and 21 percent as extensive pastures under the prescriptions of a grassland conservation program.

Thus the preservation of dairy husbandary in low mountain ranges is important for the nature conservation in these regions. Meier, Anja (2003): Towards the impact of environmental conditions and plant cultivation measures on Fusarium infection and mycotoxin contamination of wheat. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 180 pages. The influence of plant cultivation measures on plant health of wheat in organic and conven-tional farming systems in the Rhineland was investigated in studies of several years. The effect of site, weather, cultivar choice, fungicides, soil preparation (tillage), crop rotation, pre-vious crop, intensity of cultivation and weed on infection of wheat ears with different Fusa-rium species and Microdochium nivale as well as on mycotoxin contamination was investi-gated. Valuation of ears was only partly suitable for the assessment of infection rate with Fusarium species, as distinct symptoms were only visible when infection was caused by a single Fusa-rium species. The major proportion of grain infection with all Fusarium species investigated occurred at the time of flowering. However, danger of infection before inflorescence (BBCH 49) and until wax-ripe stage respectively should not be underestimated when the weather is appropriate. The spectrum of Fusarium species isolated was the same for all sites, only the infection rate with each Fusarium species varied. The species F. avenaceum, F. culmorum , F. poae, F. graminearum, F. tricinctum , F. sporotrichioides as well as Microdochium nivale were identified. Soil preparation in interaction with the previous crop, such as G. aparine, had significant impact on infection potential of the soil. Some weed population was also infected and might thus be an alternate host; especially those weed varieties developing within the standing crop were partly showed heavier infection than the wheat. Comparing wheat varie-ties of different environmental conditions ‘Bold‘, ‘Zentos‘ and ‘Petrus‘ were least susceptible to Fusarium infection. Susceptibility to Fusarium infection of different varieties was not corre-lated with susceptibility to Microdochium nivale infection. Wheat from organic farming in comparison with wheat from integrated farming showed by 10% lower infection rates and with 100-350 µg/kg also lower DON contents which is probably mainly due to lower intensity of cultivation and different crop rotation. In conventional farming, Fusarium infection and my-cotoxin contamination could be reduced by up to 60% when azole fungicides were applied on schedule. Application of a strobulurin fungicide could lead to increased DON content. Fungi-cide treatment alone is not sufficient to assure quality of grains, so that further plant cultiva-tion measures have to be included. As a large variety of Fusarium species was identified, other mycotoxins than DON should be included in analysis. Mekuria, Tadesse (2003): Characterisation and Mode of Action of Natural Plant Products against Leaf Fungal Pathogens. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 144 pages.

The medicinal uses and chemical diversity of bryophytes, spices and herbs are long known, but their potential application in crop protection seems largely unexplored. The objectives of this study were to find crude extracts, new fungicide leads, and resistance inducers to meet the current uprising demands in the discovery of biopesticides. Research schemes were car-ried out to isolate and determine antifungal compounds from 20 bryophytes and from 23 spices and herbs. These were used as crude ethanolic extracts to investigate their bioactivity on globally important 16 different pathogens and 8 important host plants under in vitro and in vivo conditions. The screening of extracts for their antifungal effects exhibited that activity of products varied significantly according to their sources. Extracts of bryophytes, especially Bazzania trilobata, Diplophyllum albicans, Sphagnum quinquefarium, Dicranum denudatum and Hylocomium splendens showed higher antifungal efficacy against Botrytis cinerea, Alternaria solani, Phy-tophthora infestans, and Blumeria graminis. Similarly, extracts of Piper nigrum, Carum carvi, Cassia spp., Artemisia dracunculus, Urtica dioica, Foeniculum vulgare and Coriandrum sati-vum were found as the best antifungal products among spices and herbs. The extracts of B. trilobata and P. nigrum were investigated in more detail. The B. trilobata extract inhibited fungal stages like germination of conidia, germ-tube formation, elongation and mycelial growth. Plants received the product (1% m/v) at different time intervals before inoculations with pathogens. Application of the extract 2 days before fungal inoculation showed reduction of disease severity against diverse pathosystems up to 98%. Under such circumstances, the extract gave high efficacy in 9 of the 13 tested pathosystems, though the biotrophic pathosystems were more sensitive than the perthotrophic ones. The extract of P. nigrum showed both protective and curative mode of action, whereas the efficacy of the ex-tract from B. trilobata was reduced by 50 % for its curative application against Puccinia re-condita on wheat. Bioassays determining systemicity of the B. trilobata extract demonstrated that the product showed a translaminar and at distant effectivity against P. infestans, Podos-phaera leucotricha, Uncinula necator and Uromyces appendiculatus. The active guide component of P. nigrum extract had a similar molecular structure as piper-ine as detected by different chromatographic techniques. The extract of B. trilobata was composed of unidentified metabolites like flavonoids and procyanidins. But its major bioactiv-ity was linked to the hydrophilic fraction and lysosome like organelles (LLOs). Lysosome like organelles (LLOs) described as vesicles, vacuoles, lysosomes, spherosomes and melanosomes which were bounded with a single membrane. They had positive reactivity with acridin orange and showed lysosomal acidic hydrolase activity. There were positive re-actions with specific dyes staining nucleic acids. Incubation of LLOs with different substrates detected their phagolysosomal enzymatic activities. Chitinase endocytosis activity was rec-ognised by the formation of electron dense granules at the interface, vesicles and specific loci on the body of LLOs. Incubations were proceeded using LLOs with sporangia and zoospores of P. infestans, co-nidia and mycelia of A. solani, urediospores of U. appendiculatus and teliospores of Ustilago nuda. Unspecific degeneration of fungal cell walls and entire protoplasms were detected. Germination, basidia formation and sporidia differentiation of teliospores of Tilletia caries were delayed on a medium amended with the LLOs. The protective spraying of LLOs signifi-cantly impaired the infection structures of pathogens on the leaf surfaces and in tissues, lo-cally and systemically. Infection, disease development and propagation of leaf pathogens

were reduced irrespectively of variations in their taxonomy and host pathogen interactions. Thus, pretreatments of susceptible plants with LLO preparations of mosses provide a new perspective for an integrated disease management of fungal pathogens of different crop plant. Metz, Claudia (2003): Influence of pathogen genotype on the antagonistic efficacy of Ulocladium atrum in the control of Botrytis cinerea. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 131 pages. The necrotrophic fungus Botrytis cinerea (Pers.) is a pathogen with a wide host range caus-ing economical losses in many crops worldwide. Effective control of the pathogen using fun-gicides with the same mode of action is restricted by the fast development of resistant iso-lates. Biocontrol may offer a supplementary or alternative crop protection tool and also can be used for the management of fungicide resistance. The saprophytic hyphomycete Ulocla-dium atrum has been described for its antagonistic potential against gray mould in various crops. The efficacy of U. atrum depends on the saprophytical competition with B. cinerea during the colonization of necrotic plant tissue, affecting the epidemic spread of the multi-cyclic pathogen. In this work the efficacy of U. atrum in the biocontrol of various genotypes of B. cinerea was investigated. The strains were differentiated for their morphological and physiological charac-teristics, as well as on their sensitivity against common botryticides from different chemical groups. The antagonistic potential of U. atrum has been proven under controlled conditions on necrotic grapevine leaves, in greenhouse crops such as begonia, sweat pepper and grapevine plantlings as well as under field conditions in grapes on different cultivars and at several locations over several years. The aggressiveness of B. cinerea strains differed in various crops indicating specific interactions between pathogen and host species. The effi-cacy of the antagonist U. atrum was also influenced by the genotype of the pathogen strain to be controlled. The differences in vulnerability to the antagonistic activity of U. atrum were neither correlation to strain specific characteristics like spore size, growth or aggressiveness nor to fungicide sensitivity. Furthermore, efficacy of disease control depended on the rea-sonable coordination of application parameters like spore concentration applied, timing and number of U. atrum applications, as well as the growth media used for spore production of the antagonist. Neither the crop development nor the quality of the wine fermentation was negatively affected by the application of U. atrum. Alternate applications of U. atrum and the botryticide fenhexamid reduced the gray mould infection on berries significantly, whereby the number and dosage of fungicides decreased. However, at high disease pressure like in 2000, the efficacy of U. atrum was not able to re-duce significantly the rapid spread of B. cinerea on the grapes, because the incidence of U. atrum on berries decreased before harvest and the antagonistic activity depending on nutri-ent competition became insufficient. The antagonist showed low sensitivity against pesticides and may be integrated in existing crop protection strategies in viniculture.

Meyer, Gunter (2006): Grain infection by Fusarium species of winter wheat in Northrhine-Westphalia in the years 2001 – 2003 under special observance of moniliformin producing species. Institute for Plant Disease, Faculty of Agriculture, University of Bonn, 150 pages. Depending on year, weather, location and wheat cultivar, some partially high incidences of Fusarium head blight have been observed in Northrhine-Westphalia between 2001 and 2003. In all three years higher precipitation in Westphalia caused higher levels of grain infec-tion than in the Rhineland. In the Rhineland the level of infection in 2002 was higher than in 2001, while in Westphalia it was lower than the year before. Despite the hot summer, at all locations, except Kerpen-Buir, the highest levels of infection occurred in 2003. In average Fusarium avenaceum was the most frequent species in Northrhine-Westphalia, followed by F. graminearum, F. poae, F. culmorum and F. tricinctum. The moniliformin producing species F. avenaceum and F. tricinctum were as frequent as the DON-producing species F. graminearum and F. culmorum. Beside the weather conditions, the level of grain infection was determinated by cultivar prop-erties and cultivation method. Cultivars with higher FHB resistance classification und increas-ing plant length showed lower levels of grain infection, even though single cultivars, as Win-netou, showed deviation from their classification. Growth regulators and fungicides applied in the intensive cultivation method, resulted higher levels of infections in those cultivars with higher resistance or long straw. The Fusarium spectrum was based upon the location and the pre-crop. Even though maize promoted the proportion of F. graminearum, at no location this species was predominant. The high proportion of F. avenaceum and F. tricinctum was not correlated with a high con-tamination of wheat samples with moniliformin, even though almost every tested Isolat of F. avenaceum and F. tricinctum produced moniliformin in vitro. The highest contamination of a wheat sample with 225 ppb was found in 2003, while moniliformin levels of nearly all other samples were below 100 ppb. With low concentrations of Azoxystrobin in the medium, both isolates of F. avenaceum and F. tricinctum showed in vitro only weak inhibition of growth rate, but increased levels of moniliformin. Tebuconazol inhibited the growth of the mycelium strongly without influencing the concentration of moniliformin in the mycelium. Middelschulte, Dierk (2000): Amelioration and Subsequent Farming on Recultivated Loess Soils in the Brown Coal Areas of the Rhineland - Effects on Some Parameters Relevant to Arable Farming. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 175 pages. In the brown coal areas of the Rhineland recultivated loess soils were compacted partly dur-ing recultivation and partly during subsequent farming. Such compacting leads to temporary waterlogging, farming difficulties, reduced rootability of the subsoil and finally to yield reduc-tions. The effects of various amelioration and farming measures on an extremely compacted

area were examined within the framework of three-year field trials with regard to their influ-ence on soil properties, water balance, plant development and yields. Subsoil loosening improved the root penetration of the subsoil by increasing the number of coarse pores in the soil. The amelioration measures did not, however, result in statistically proven higher yields for every year and for every crop. Increased yields as a result of amelio-ration were recorded in 1990 for sugar beet and rye and in 1991 for wheat. The highest yields were achieved as a rule with the combination of subsoil loosening (TLG 12) and 8 m drainage. Correlations between yield and root development and between yield and penetra-tion resistance in the subsoil were only slight. The soil-conserving, non-turning tillage considerably improved the stability of aggregates in the top layer and reduced the probability of ameliorated, recultivated soils recompacting. Nonetheless, the various soil-working measures did not have an effect on yield each year and for each crop. Yield advantages for cereals were achieved with conventional ploughing and for sugar beet with soil-conserving farming. Especially after the cultivation of clover grass as an amelioration crop, a growing stability of aggregates in the top soil layer with re-gard to water was noted as the trials progressed. Clover grass also had a favourable influ-ence on the yields of the subsequent wheat and sugar beet crops. An N fertilisation level based on the N min method did not lead to any nitrate leaching worth mentioning at this site. During the main growth period areas of subsoil loosening showed emptying of nitrate to a large extent and to a great depth in the soil profile, whereas during the vegetation-free pe-riod they tended to more rapid nitrate leaching. Mohammed, Khalaf Ali Hamam (2004): Improving crop varieties of spring barley for drought and heat tolerance with AB-QTL-analysis. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 139 pages. In the years 2002-2003, 323 BC2DH individuals of double haploid (DH) spring barley popula-tion were genotyped with SSRs markers. The BC2DH lines were evaluated in greenhouse trials for drought and heat tolerance. Altogether 13 parameters for the determination of drought tolerance and 12 parameters for the investigation of heat tolerance were examined. There were two treatments for the drought experiment, 50% field capacity (FC) level for drought stress and at 100% FC level for the control. We used two treatments for the heat experiment (normal climate and in greenhouse). The traits measured were: relative leaf wa-ter content, osmotic adjustment, heading date, number of spikes per plant, number of kernels per spike, number of leaves per main tiller, flag leaf area, first leaf area, second leaf area, carbon isotope discrimination (for the drought experiment), yield, biomass and harvest index. The traits were compared to determine the presence of alleles from the wild barley parent by means of the AB-QTL-analysis. The 97 mapped SSRs covered 1013 cM of the barley ge-nome; the mean SSR density is equal to 11.1 cM. Polymorphic SSRs revealed 54 putative QTLs in two groups. The first had 20 putative QTLs for the drought experiment and the sec-ond 34 putative QTLs for the heat experiment. Altogether, 30 (55.5%) favorable allele effects of the Hsp alleles were detected for both drought and heat experiment. 14 (70.0%) favorable

effects were detected for drought tolerance. These traits, osmotic adjustment, yield, biomass, relative leaf water content, carbon isotope discrimination, number of leaves per main tiller and flag leaf area were controlled by 7, 3, 3, 3, 2, 1 and 1 QTL respectively, in the drought experiment. Most of the favorable Hsp alleles were located on chromosomes 1H, 5H and 7H (2, 8 and 3 respectively). Under drought stress first leaf area was positively and strongly cor-related with flag leaf area. Positive correlations were expressed by second leaf area with flag leaf area and first leaf area. Yield was positively correlated with harvest index, number of spikes per plant and number of kernels per spike. Biomass showed correlations with number of spikes per plant, number of leaves per main tiller, flag leaf area, first leaf area, second leaf area and yield. 16 (47.0%) favorable effects of the Hsp alleles were detected for heat toler-ance. Flag leaf area, osmotic adjustment, yield, harvest index, biomass, first leaf area, rela-tive leaf water content, number of spikes per plant and heading date were controlled by 8, 7, 4, 4, 3, 3, 2, 2 and 1 QTL respectively, in heat experiment. Most of the QTLs were located on chromosomes 3H and 4H (3, and 5 respectively). Correlations of heading date with osmotic adjustment, and number of leaves per main tiller were strongly positive. Strong positive cor-relations were expressed by second leaf area with flag leaf area and first leaf area. Yield was positively and strongly correlated with harvest index. Müller, Christina (2000): The contribution of Remote sensing to estimating malting barley quality. Institute for Agricultural Botany, Faculty of Agriculture, University of Bonn, 183 pages. The annual industrial supply with malting barley depends on area, yield and quality of culti-vated barley. Strict quality criteria are laid down by maltsters for acceptance of barley grain for malting, particularly with regard to grain protein content. Grain protein concentration > 11,5% is usually regarded as unsuitable for malting. In order to make decisions on the pur-chase of malting barley, malt industries require timely information on vitality and quality status of the crop. Until now maltsters get informations about the growing status of malting barley by question-ing wholesalers, associations of manufacturers and farmers. But this method is too rough and only possible to carry out within small regions. On the other hand the essential advan-tage of remote sensing is the feasibility of an countinously field-based large-scale observa-tion of the surface. The experiments were carried out in typical cultivation regions of malting barley in Germany which strongly differ in site characteristics and production conditions.. Investigations were focused on optical remote sensing data provided by a ground-based spectoradiometer for monitoring crop vitality throughout the growing season.. Along with the spectral measure-ments detailed analyses of crop parameters were conducted. Essential differences in the spectral signal were given at the ripening period of malting barley and can be described by the normalized difference vegetation index (NDVI). However for a serious interpretation of such data additional informations of the geographical location and soil type are imperative. One important value of graining and therefore of malting barley quality is the leaf-N-content which can be estimated by the NDVI. Additional it is possible to determine the end of the

grain filling by using the NDVI. With these two parameters important informations about mal-ting barley quality can be registered and thus are available for a prediction system for malting barley quality. Müller, Georg (2000): Gravity-dependent signaltransduction of inositol-1,4,5-trisphosphat in sunflower-hypocotylprotoplasts. Institute for Agricultural Botany, Faculty of Agriculture, University of Bonn, 100 pages. Protoplasts of sunflower hypocotyls (HCPs) were used as a model to prove the hypothesis that the PI-System is part of the gravi-induced signal-transduction. Therefore a method had to be developed to isolate a large quantity of vital protoplasts. To investigate the vitality of the protoplasts a further method beside the classical tests (light- microscopy, FDA-test) has been established, which measures the auxin-dependent activa-tion of the PM/H+-ATPase in vivo. This method also considers a defective receptor at the plasmamembrane and is a useful tool to optimise the conditions of the protoplast-system. Using the optimized protoplast-system, a concentration-dependent activation of the PM/H+-ATPase in response to auxin was observed. The effect could be repressed by the H+-ATPase inhibitor DCCD. Since neomycin (an inhibitor of the PI-system) did not inhibit the auxin-dependent activation of the PM/H+-ATPase, there is no evidence that the PI-System is part of the auxin-induced signal-transduction which leads to an activation of the PM/H+-ATPase. Nevertheless, auxin (100 µM) also causes time- dependent changes of free Ins(1,4,5)P3, the main intermediate product of the PI-System dependent signal-transduction, in auxin-stimulated HCPs. To detect and quantify the second messenger Ins(1,4,5)P3 in HCP-extracts a non- radioac-tive method called metal-dye-detection HPLC (mdd-HPLC) has been established. After opti-mising the hardware this highly isomer-specific method could detected Ins(1,4,5)P3 down to 10 pmol. Running HCP-extracts through the alkaline mdd-HPLC one peak showed co-elution with Ins(1,4,5)P3. Three newly developed, independent methods (3-phytase-breakdown, UV-absorption, rechromatography) confirmed the identity. Experiments with simulated weightlessness and micro-gravity gave first indications that HCPs present autonomous units, which are capable of sensing a changing g-vector. More-over, they enforce the hypothesis that the PI-system is part of the signal-transduction-chain, converting the physical stimulus into a chemical signal. Furthermore it has been shown that a simple mechanical stimulation of HCPs leads to an activation of the PI-system. Müller, Susanne (2002): Induced resistance and pathogenic defence by Reynoutria sachalinensis-extract and Physcion: signal pathway in comparison with systemic inducers and relationship to hypersensitive reactions. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 130 pages.

Recently it became obvious that Induced Resistance (IR) in plants proved to be specific for different inducers, for different host plants and against different pathogens. Beneath many known chemical inducers the extract of Reynoutria sachalinensis is a biological one, which is efficacious against downy mildew infections. Physcion, an anthraquinone, could be estab-lished as an important active substance in this extract up to this day. In contrast to chemical activators the signal by Reynoutria-extract and Physcion is not systemic, but the induction is locally restricted. The aim of this thesis was to compare significant properties of the signal pathway of Reynoutria sachalinensis and Physcion with those of systemic inducers (DCINA, DCSA, Bion) in two host-parasite relationships, Cucumis sativus / Sphaerotheca fuliginea and Hordeum vulgare / Blumeria graminis f. sp. hordei, to find out differences and/or confor-mities in monocotyledons and dicotyledons. Continuing former experiments, the first focal point was to investigate the important role of H2O2 in the signal pathway of R. sachalinensis and Physcion. Therefore H2O2-inhibitors and scavengers on the one hand and H2O2-producers on the other were set in different biological assays. Because of their positive/ negative mode of action the first explaining steps of the inducing effect were given. Further-more methods were used to localize and to quantify H2O2 in plant tissue. These results sup-port the presence of an oxidative burst. Two others significant oxygen radicals, named su-peroxide anion and nitric oxide, were embraced in these investigations. O2

- represented a kind of first step for the H2O2-formation apparently, NO could act as a signal and react with elements of the activated H2O2-metabolism. In order to study the peroxide metabolisation H2O2-building and H2O2-reducing enzymes were analysed. Their activities could connected with the oxidative burst partly. Complementary to it enzymes outside the H2O2-metabolism were screened in the API-ZYM-system and isoforms of some selected enzymes were deter-mined by gel electrophoresis. Structural and biochemical experiments have demonstrated the defence reactions of the host tissues. The known histological changes in plant tissues and within the pathogenic developements connected with induced resistance were observed in qualitative and quantitative analysis in form of parameters e. g. hypersensitive reaction, autofluorescence, papilla formation and H2O2-locations. The employment of dyes which are able to stain living or dead cells, reviewed the hypothesis whether the inducing effect of R. sachalinensis is a kind of subliminal hypersensitive reaction. The possibility of having a direct effect on the germination and pathogenic development of S. fuliginea were studied with dif-ferent pathotyps of powdery mildew and by pH-measurements of the leaf surface. Answering the question if there were more inducing or direct working ingredients of R. sachalinensis phenolic substances were established. Münch, Clemens (1996): Improvement of yield formation and symbiotic N2 fixation as well as N dynamics of soils by growing faba beans (Vicia faba L.) as pure crop and intercrop with non-legumes ac-cording to the "CULTAN"-system. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 198 pages. The growing of faba beans is limited by low yields and the risk of N-losses because of high amounts of residual N. To improve the N2 fixation and yields different treatments of N fertiliza-tion, application of straw as well as of plant hormones in pure crops of faba beans were tested.

High amounts of nitrogen diminished the N2 fixation and yields. In contrary, the nodulation and yields as well as a early balance between root and shoot were encouraged by the application of straw. The nodules are not only participating in the N supply of the plants, they also probably improve the growth of the plants by influencing the phytohormonal status. By the application of benzyladenin (cytokinin-analoga) the distribution of assimilates could be temporarily improved in favour of the reproductive organs and as a result the pod setting could be increased. There was no significant increase in yields because benzyladenin diminished the translocation of assimi-lates from the leaves to the pods. Substantial improvements in the yields can be expected from active substances similar to cytokinins, which are transported via phloem, which could promote the sink-strength of pods without limiting the source function of the leaves. The application of NH4-fertilizer as placement in root zone (NH4-depots), also known as "CUL-TAN"-system, has been shown to be an appropriate N fertilization system for mixed cropping of faba beans with non-legumes. In contrast to non-legumes faba beans are not able to use the nitrogen of NH4-depots, since the nodules present above the root tips are the stronger sink for carbohydrates. Therefore, the root tips are not sufficiently supplied with carbohydrates to take over the ammonium in the protein metabolism. As a result the non-legumes can be combined according to their N requirement without inhibiting the symbiotic N2 fixation by the legumes through applied N. Therefore, the "CULTAN"-system is of high interest for intercropping- and agroforestry-systems. Besides higher yields, the risk of N-losses is diminished in such intercropping systems because of a better exploitation of the soil N and lower amounts of N in their residues. The studies have shown, that the higher C/N ratio in such crop res idues results in a significantly higher N immobi-lisation compared to pure faba bean crops. Mukminah, Faridatul (2001): Growth, photosynthetic capacity and yield potential of sweet potato as affected by irrigation levels. Institute for Horticulture, Faculty of Agriculture, University of Bonn, 103 pages. Characterisation of sweet potato (Ipomoea batatas L. (Lam.) to different water regimes was the main topic of the present study. Six sweet potato clones were submitted to five different irrigation levels in order to study growth and yield, carbohydrate content in tubers as well as the chlorophyll and carotene contents in leaves. Furthermore, sweet potato clones were characterised with regard to their photosynthetic capacity of young and fully expanded leaves and their potential to export photoassimilates from leaves using the short-lived radioisotope 11C. Irrigation increased the vegetative growth of sweet potato. More irrigation increased dry matter of leaves, leaf number, dry matter of vines and length of the longest vines of sweet potato clones. On the other hand, irrigation decreased the root-tuber/shoot ratio and dry weight of tuber of the sweet potato clones. Three clones AB94001.8, AB94078.1 and Eland had the highest production of tubers but lowest production of leaves, vines and roots. At final harvest, dry weight of tubers correlated significantly with tuber number, fresh weight per tu-ber, plant dry biomass, dry matter production efficiency and (roots + tubers) / shoots ratio. Dry weight of tubers correlated negatively to leaf dry weight ratio, vine dry weight ratio and root dry weight ratio. Furthermore, plant dry biomass correlated positively to dry weight of

leaves and negatively to leaf dry weight ratio. Total soluble sugar increased with time, whereas drought treatments increased total soluble sugar in sweet potato tubers. At final harvest, there was a significant negative correlation (r = - 0.671) between total soluble sugar and starch content in tubers. Total chlorophyll and carotene contents of leaves varied with clones. The highest chlorophyll content was reached by the control treatment and decreased in the treatments drought and temporary water logging. Water logging treatments decreased carotene content in leaves more than the drought treatments. Net photosynthesis rates (A) of the investigated sweet potato clones, AB94001.8, Eland, CIP-1, AB94065.4, Klon A, and AB94078.1 were correlated with plant dry mass production, but not with tuber production. Net photosynthesis rate of fully expanded leaves was positively correlated with effective quantum yield (∆F/Fm’) of the investigated sweet potato clones. A significant negative correlation be-tween qN (non-photochemical quenching) and g’m (carboxylation efficiency) was recorded. An increase of the ratio tuber dry matter per plant’s leaf area for the clones AB94001.8, Eland, CIP-1, AB94065.4, and Klon A was also correlated with a low qN . In the 11C experi-ment, clone Thai with a developing tuber exported a considerable greater percentage of the recently fixed photoassimilates (70% - 75% = export fraction + respiration) than clones AB95001.4 and Dayak (32% - 50%) without tubers. Only clone Kwarangwana was character-ised by an even smaller loss of 11C from the application leaf. The harvest of clone Thai, 75 min after 11CO2-application and subsequent analysis of the distribution of the radioactive tracer within the plant indicated that nearly 60% of the radioactivity exported from the leaf was stored within the growing tuber, proving the strong sink capacity of that organ. Mulawarman (2002): Use of natural products based on renewable raw materials to stimulate soil health and control Meloidogyne incognita. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 115 pages. New products based on renewable raw materials as well as various sources of Chitin and Chitosan were screened to control plant parasitic nematodes. Chandler Check (20 kg/ha) and TerraPy® (200 kg/ha) significantly suppressed Meloidogyne incognita infection by 21 % to 28 %. For chitinuous compounds, Chitosan oligosacharides suppressed nematode infec-tion by 23 % to 70 %, while those with higher molecular weight were most efficient. All Biosol treatments in general suppressed nematode infestation by 65 %. Control efficiency was even enhanced by combining Biosol with Oligo-Chitin and Oligo-Chitosan resulting in an average increase in control of 62 %. Regarding its origin, Chitosan originated from India and Canada and NM 9316 were shown to give best control of nematodes up to 48 %. The application of organic amendments was optimised by varying application rates, forms and using combinations of organic amendments or combinations of organic amendments with antagonistic microorganisms. Both, high and low rates of Chitosan incorporated into soil at 28 days before planting and at planting caused a reduction in nematode infection and en-hanced plant growth, while no effects were observed with application of Chitosan after plant-ing. In an approach to reduce total amounts of application, Chitosan applied as a seed treat-ment significantly reduced Pratylenchus zeae infection on maize. Similarly, Chitosan also reduced Heterodera schachtii on sugar beets 21 days after inoculation and 35 days after

inoculation. Infection of Globodera pallida was significantly reduced by all treatments of po-tato treated tubers at 35 days after inoculation. The application of Chitosan on tomato as a seed treatment caused only a slight reduction in Meloidogyne incognita infection. An addi-tional reduction of nematode infection was observed for the combination of TerraPy with my-corrhiza. The organic amendments significantly affected soil microorganisms and nematode communi-ties. TerraPy®, Chitosan and to a lesser extent Magic Wet® reduced plant parasitic nematode densities and improved plant growth. The application of N and P in equivalent amounts pre-sent in the formulations did not affect plant growth promotion in the same degree. Properties of the amendments such as improved soil structure, increased soil water retention or in-creased plant nutrient availability may play a key role in plant growth promotion. Further-more, modifications of the microbial community also might contribute to plant growth stimula-tion and nematode control, in that all three compounds TerraPy®, Chitosan and Magic Wet® significantly increased certain genera in the soil. Acinetobacter, for example, plays a key role in the solubilization of phosphate in soils. Therefore, increasing densities of Acinetobacter might result in improved supply of phosphate to the plant. The highest increase of Pseudo-monas, a bacterial genus with plant growth promoting activity was observed following Chito-san application. Other, not yet identified bacteria, might have also contributed to plant growth or health promotion by mechanisms such as stimulation of phytohormones, N-fixation or suppression of deleterious microorganisms. The potential mode of action of Chitosan as an inducer of systemic resistance against Meloi-dogyne incognita was studied on tomato using a split-root system and foliar spray. Chitosan application to one-half of a split-root system caused a significant reduction of egg masses on the other side of the split root system. Similar result were achieved when Chitosan was ap-plied as a foliar spray, indicating that a downward movement of signals associated with the resistance reaction occurs. It is concluded that TerraPy®, Magic Wet® and Chitosan contribute significantly to plant growth and health by stimulating soil microorganisms and thereby suppression of plant para-sitic nematodes. Mulindabigwi Valens (2005): Influence of farming systems on the land use, carbon sequestration and food security in the upper Ouémé catchment in Benin. Institute of Crop Science and Resource Conservation, Faculty of Agriculture, University of Bonn, 153 pages. In this work, the farming systems were described and their impact on the land use, food se-curity and carbon sequestraion was also evaluated. The farming systems are dominated by shifting cultivation. The crops are sown or planted in pure or associations between May and July. The agricultural intensification is limited to the cotton production system. With the increasing shortage of arable land, the farmers tend also to intensify the maize production. The rapide demographic growth and the decline of soil fer-tility of the cultivated areas constitute the principal factors of deforestation (2-3% per annum) in upper Ouémé catchment.

The natural formations remain the best ecosystems for the storage of carbon (forêt dense semi-décidue : 138,5 t ha-1; forêt claire: 71,7 t ha-1 against 33,8 to 35,3 t ha-1 for the agricul-tural surfaces). Contrary to former studies (NYE & GREENLAND, 1960; ROBERT, 2001), the carbon, stored in the first 20 cm of the cultivated areas, does not differ significantly from that of the soils under natural formations or of soils under fallow. This may be explainable by regular bush fires. The evolution of the agricultural areas and the associated degradation of natural resources can be subdivided in five principal phases: (i) Ecological Equilibrium; (ii) Collapse of ecologi-cal equilibrium; (iii) Ecological degradation; (iv) Structural food insecurity; (v) Misery and irre-versible hydrological degradation.The land use around the road « Wari Maro – Doguè » represents the phase 2: Collapse of ecological equilibrium, while the land use in Sérou is in the phase 3 of the ecological degradation. Until 2020, in the case of rain saison shortening, the agricultural area will extend to 79,7% of the total arable area and provide 116% (against 132% in 2000) of the needed calories. On the other hand, a demographic growth reduction from 4,9% to 3,0% and partial intensification of agriculture will allow to reach 147% of the needed calories in 2020 by using only 62% of the arable area. The agricultural intensification depends on the adoption of more productive technologies. These technologies were already developed by various national and regional agricultural research institutions but are not available for the farmers. The objective must be the transfer of these technologies to the farmers. However, the agricultural intensification is not the only strategy to guarantee a durable use of the natural resources. It rather forms part of integrated strategies for rural development which have to be objectively further defined and concretized. Munif, Abdul (2001): Studies on the importance of endophytic bacteria for the biological control of the root-knot nematode Meloidogyne incognita on tomato. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 120 pages. A total of 670 strains of endophytic bacteria were isolated from tomato plants grown in tem-perate and tropical soil from Germany and Indonesia. The isolation procedure was done us-ing surface-sterilization and trituration method with 3% and 6% sodium hypoclorite (NaOCl). The total population density of endophytic bacteria recovered from tomato roots ranged be-tween log 0.45 and log 4.45 cfu/g root fresh weight. Endophyic bacteria were identified based on their fatty acid profile using FAME-GC-MIDI system. Thirty-eight bacterial species in 21 genera and 50 bacterial species in 32 genera were found in association with tomato roots in Germany and Indonesia, respectively. The most abundant endophytic bacterial species in Germany were Pseudomonas putida (11.8%) followed by Bacillus megaterium (10.59%) and in Indonesia B. megaterium (14.31%) followed by P. putida (12.44%). Species richness and diversity was 7.08 and 3.29 for bacteria from Germany and 8.44 and 3.01 for bacteria from Indonesia. A total of 181 bacterial strains in 51 bacterial species were physiologically characterized. Bacterial traits most commonly observed were protease activity (55.74%), cellulose activity (41.53%), solubilization of phosphate (40.44%), chitinase activity (25.14%), HCN (18.03%), fluorescense activity (18.03%), and lipase activity (10.93%). None of the bacteria showed

pectinolytic activity. The 181 bacterial strains were tested for their in vitro antagonism to-wards Rhizoctonia solani, Fusarium oxysporum f.sp. radicis-lycopersici and Fusarium ox-ysporum f.sp. lycopersici and their biocontrol activity against Meloidogyne incognita. Four-teen strains (7.7%) showed antagonism against R. solani, 9 strains (5.0%) against F. ox-ysporum f.sp. radicis-lycopersici and 7 strains (3.9%) against F. oxysporum f. sp. lycopersici and 21 strains (11.6%) significantly reduced the number of galls produced by M. incognita on tomato in screenings studies. Four out of 21 strains, i.e. Pantoea agglomerans MK-29, Cedecea davisae MK-30, Entero-bacter spp. MK-42 and Pseudomonas putida MT-19, significantly reduced M. incognita infes-tation on tomato either as a seed treatment or as a soil drench application. The four endo-phytic bacteria also significantly reduced early root penetration of Meloidogyne juveniles into tomato roots up to 56%, when applied as a root dipping or soil drench. Combination of the four bacterial strains gave a higher reduction in the number of galls than the application of a single strain. Investigation on the mode of action of endophytic bacteria showed that the culture filtrates of endophytic bacteria were able to inactivate and kill M. incognita juveniles in vitro and reduce early root penetration and the number of galls and egg masses of M. incognita on tomato. Application of endophytic bacteria in a split-root system resulted in a significant reduction of the early root penetration and number of galls and egg masses of M. incognita. These results suggest a combination of two active mechanisms by endophytic bacteria, i.e. direct mecha-nisms through the release of metabolites with nematicidal/nematistatic activity and indirect mechanisms based on induced systemic resistance. The population dynamics of endophytic bacteria in the rhizosphere and within plant tissue showed that the introduced endophytic bacteria colonized the tomato rhizosphere continu-ously over 28 days after bacterial application and significantly increased the total bacterial population density. The introduced endophytic bacteria were able to colonize the root interior for a minimum of 6 weeks. The internal population densities of introduced endophytic bacte-ria in tomato roots ranged between log 1.2 and log 5.9 cfu/g root fresh weight. The popula-tion densities of introduced endophytic bacteria were higher in the presence of M. incognita than in the nematode-free control but the differences were not significant. With the exception of Enterobacter spp. MK-42, the applied endophytic bacteria were not detected in the stem of tomato. Mwangi, Maina (2003): Mechanisms of action in biological control of Fusarium oxysporum f.sp. lycopersici in tomato using rhizobacteria. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 159 pages. Seven bacteria isolates with known antagonistic effects against nematodes were evaluated in the greenhouse for ability to reduce Fusarium wilt in tomato. The effective isolates Pseu-domonas fluorescens T58, P. putida 53 and Bacillus sphaericus B43 were selected for fur-ther study and their mechanisms of action were investigated. Results showed that induced systemic resistance (ISR) was the main mechanism of action for all three effective rhizobac-teria while antibiosis did not play a major role. To characterise the ISR changes in phenolic

compounds, lignin content in roots, and activities of the pathogenesis-related (PR-) proteins peroxidase, chitinase and ß-1,3-glucanase, and structural changes in cells were investigated. A new phenolic compound was detected in plants treated only with Fusarium. This new phe-nol was not detected when the plants treated with P. fluorescens T58 or B. sphaericus B43 were infected with Fusarium. Isolate P. putida 53 did not suppress the occurrence of the new phenol. Lignin content in roots was non-significantly increased in plants treated with isolate T58 and B43. Peroxidase activity in stem was increased by all isolates, but the increase due to B. sphaericus B43 occurred earlier and was short-lived. Changes in chitinase activity in leaves were induced by isolates 53 and B43, while ß-1,3-glucanase activity was not affected by any of the rhizobacteria. Isolate T58 induced callose deposition on cell walls while isolates 53 and B43 induced extrusion of occluding material into the lumina of xylem vessels. P. fluo-rescens T58 was observed to be a producer of HCN. The role of HCN and other volatile me-tabolites produced by this isolate in biocontrol of Fusarium was investigated. The volatile metabolites reduced Fusarium spore germination but not mycelia growth, although mycelia lost pigmentation when exposed to the volatiles. The volatiles produced by isolate T58 could significantly reduce the densities of competing bacteria in plant growth substrate while fungal densities were not always significantly reduced. In addition, the volatiles induced increased peroxidase activity in tomato plants which may contribute to biocontrol. The ability of ISR to reduce tomato damage by Fusarium toxin was also investigated. Ion leakage and chlorophyll degradation in the leaves was studied in relation to the content of superoxide anions (O2-) and H2O2, which are active oxygen species (AOS). Superoxide dismutase, catalase, ascor-bate peroxidase and guaiakol peroxidase activities, which regulate AOS metabolism were also studied. Plants treated with isolate T58 had significantly less ion leakage and chlorophyll degradation after treating with Fusaric acid. Isolates 53 and B43 did not effectively protect plants from damage by the toxin. On the overall the effect of toxin on chlorophyll degradation and ion leakage from leaves could be related to the AOS content and the activities of the enzymes regulating AOS metabolism. Neu, Anni (1999): Nitrogen mineralization and immobilization processes in soil from the post harvest period, with special regard to soil microbial biomass. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 144 pages. The nitrogen turnover processes in the soil were studied with a special focus on the functions of microbial biomass as a nutrient storage pool as well as a main transformer of the different N compounds. Interactions between nitrogen, present in the microbial biomass (Nmic) and mineral N (Nmin) pools, were investigated during the course of the post harvest period (from harvest of the main crop until the start of the leaching period in November/December) in rela-tion to the main factors affecting the N turnover during this period (differences in residual Nmin after harvest, soil tillage and rapid changes in soil moisture). Furthermore, to what extent the determination of microbial bound N could be used to quantify the N mineralization potential originating from the microbial biomass was examined. In field studies during 1994, the varying N fertilizer supply to oats and the soil mois ture re-gimes, which were differentiated during the post-harvest-period, modified the Nmin pool during

the post harvest period, whereas Nmic hardly changed. Furthermore, no association between Nmic gradient and depth was found in the topsoil either before or after soil tillage. However, during the 1995 growing season N uptake by summer wheat varied, whereas the Nmic and Nmin remained unchanged. The lack of differentiation in Nmic and Nmin at the start of the follow-ing vegetation period confirms that no variable N supply resulted from these pools. There-fore, N immobilized during 1994 was stored in non-biomass N pools, which were remineral-ized during the 1995 growing season. The assumed contribution of the hot water soluble N pool (Nhws) to the differentiation in N mineralization could not be confirmed in an incubation experiment. In contrast to the minor changes observed in field trials, laboratory studies showed that under changing soil moisture conditions, the greatest part of microbial biomass was killed during drying, resulting in increased mineralization. "In vitro" cultivated 15N labelled microorganisms used for these experiments represented a more labile fraction than native soil biomass. Mi-crobial residual mass -originating from microorganisms destroyed during soil drying - was also increasingly mineralized due to repeated soil drying and rewetting. Increased rhizodepositions were simulated in a pot experiment using oats by continuous ap-plication of microbial available C together with a varying supply of mineral N (as 15N). Immo-bilization of N into microbial biomass was intensified, whereas the plant N uptake was re-duced. During a subsequent pot experiment with rye-grass remineralization of the 15N immo-bilized into microbial biomass was assumed. A possible explanation for the lack of reminer-alization was the short duration of the pot experiment. Although a qualitative correlation between Nmic and Nmin pools was validated by using 15N labelled fertilizer, it was difficult to establish quantitative relationships in order to derive the potential N mineralization capacity resulting from the microbial biomass. Niere, Björn Ilja (2001): Significance of non-pathogenic isolates of Fusarium oxysporum Schlecht.: Fries for the biological control of the burrowing nematode Radopholus similis (Cobb) Thorne on tissue cultured banana. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 118 pages. Bananas are an important commodity in international fruit trade but they are far more impor-tant as a starchy staple in East Africa. Banana production is threatened by a complex of pests and diseases. The burrowing nematode Radopholus similis is the major root rot patho-gen in Africa as well as worldwide. In this study, possibilities for the biological control of the burrowing nematode on tissue cultured banana were investigated. Major parts of this study were conducted at the International Institute of Tropical Agriculture (IITA), Eastern and Southern Africa Regional Center (ESARC) in Uganda. Fungal endophytes were isolated from healthy banana root and rhizome tissue after surface sterilization. Identification of the 285 isolates obtained, revealed that the majority of fungi could not be considered mutualistic fun-gal endophytes. Species of Acremonium and Fusarium were most commonly isolated at a frequency of 20 % and 30 % of all isolates, respectively. Fusarium oxysporum was the pre-dominating fungal species and constituted 10 % of all endophytic isolates. Although the ma-jority of F. oxysporum isolates are non-pathogenic soil colonizers, a number of specialized

forms causing wilts or root rots of crop plants exist. To distinguish isolates of F. oxysporum targeted for the biological control of banana nematodes from F. oxysporum f. sp. cubense, the causal agent of banana wilt, vegetative compatibility grouping (VCG) was applied to the biocontrol strains. None of the strains proved to be genetically related with known tester strains of the banana and tomato pathogens as detected by VCG. The majority of strains was also not compatible with each other, indicating that non-pathogenic endophytes of ba-nana roots represent a heterogeneous fraction of the F. oxysporum population. Non-pathogenic isolates of F. oxysporum were selected for the inoculation of tissue cultured ba-nana plants. The fungal strains tested exhibited various degrees of activity that led to re-duced nematode reproduction in roots of up to six months old banana. Nematode control was considered to be dependent on the host plant genotype and could never be observed on the East African highland cultivar Mbwazirume. Reductions in nematode densities were re-lated to a significant reduction in development of females in roots of inoculated banana. Plant growth in endophyte treated plants was generally not affected. Reduced height was ob-served on the cultivars Enyeru and Valery but at the same time number of nematodes were significantly reduced. Root necrosis in general decreased in plants inoculated with fungal antagonists followed by nematode challenge inoculation supporting the non-pathogenic na-ture of the fungal isolates. The mechanisms of action responsible for nematode control could not be established. Direct microbial antagonism of the nematodes by F. oxysporum, how-ever, seems not to be the cause leading to nematode control. Further studies are needed to elucidate the mode-of-action responsible for nematode control. Inoculation of non-pathogenic isolates of F. oxysporum on tissue cultured banana is currently seen as a technology that complements and can improve tissue culture of Musa spp. Nöthen, Markus (2001): Effect of contact fungicide application on the content of minerals and the vegetative and generative development of apples. Institute for Horticulture, Faculty of Agriculture, University of Bonn, 142 pages. Field studies in fruit orchards showed after repeated applications of Euparen Multi a higher calcium content of fruits and reduced vegetative growth of apple trees. Low levels of calcium and high levels of potassium and magnesium in apples are often correlated with physiologi-cal diseases, e.g. bitter pit. The aim of this study was to investigate the influence and effec-tiveness of Euparen Multi regarding the potential of increasing the calcium content in fruits, reducing bitter pit and influencing leaf and shoot growth. In a three years trial (1998-2000) on the Fruit Experimental Station Klein-Altendorf of Bonn University the fungicides Euparen Multi (50 % Tolylfluanid) and Malvin (83 % Captan) – 0,15 % a. i. in spray solution – were both applied separately and in combination to bitter pit sensitive apple varieties. In 1999 and 2000 additional trials were conducted with fungicides under greenhouse-conditions using `Malus communis´ -seedlings. The determination of nitrogen and phosphate were examined photometrically employing an autoanalyser, potassium, calcium and magnesium content of the leaf and fruit samples were investigated by using an atomicabsorbtionspektrometer (AAS). The rate of assimilation was measured with a portable infrared-gas-analyser and the

leaf-area was determined by using a leaf-scanner. After harvest and grading, apples (75-85 mm) were stored at 1° C in a cooling room. The results can be summarised as follows. 1 Analysis of mineral elements in six weeks old fruit revealed no impact on the mineral content due to the application of the contact-fungicides. However, fully developed and ripe fruit showed a significantly higher amount of calcium after Euparen Multi treatment. There was no influence of contact fungicide application on the content of minerals in leaves. No significant differences in return bloom or fruit set, bloom intensity, average weight of fruit, yield and quality of yield were established after the application of contact-fungicides to the trees. Fruit firmness, sugar/acid ratio and the shelf-life of the examined fruit did not underlie any significant changes after the application of the fungicides. The ground colour of the skin of apples proved higher intensity after single Euparen Multi treatment. The storability had clearly improved after Euparen Multi treatment. The number of fruit showing symptoms of bitter pit was significantly decreased after Euparen Multi application. In open field examinations Euparen Multi treatment reduced the leaf area and postponed the end of shoot growth. Under greenhouse conditions contact fungicide applications re-duced the amount of leaf number and leaf area of `Malus communis´ -seedlings and the leaf area of ´Phaseolus vulgaris’. Examinations without the active ingredient of Euparen Multi showed neither impact on leaf number and leaf area, nor on the stage of shoot-growth of `Malus communis´ and the leaf area of `Phaseolus vulgaris´. In leaves of the contact fungicide treatment group content of total chlorophyll and chlorophyll a- to b-ratio was significantly higher after application of Euparen Multi. Applications without the active ingredient of Euparen Multi resulted in lower content of total chlorophyll and chlo-rophyll a- to b-ratio. During cell division period transpiration and evapotranspiration of fruits treated with Euparen Multi was increased, while transpiration of leaves was reduced after treatment with Euparen Multi. Measurements in August – four weeks before harvest - showed no influence on tran-spiration of leaves after multiple applications of contact fungicides. Nolten, Ralf (1997): The Implementation of Agri-environmental programmes. Institute for Agricultural Botany, Faculty of Agriculture, University of Bonn, 199 pages. The aims of these study are the evaluation of implementation of the north-rhine-westfalian programmes, the finding of positive and negative factors of determining and the deduction of recommendations to improve their implementation. The study basis on the concept of imple-mentation research. Criterions of evaluation are the acceptance of the programmes, the preservation of the common agreement in the programmes and the ability to be implemented by administration. In consideration of relevant research studies two empirical surveys were initialized in 1991 to 1993. The most important results are: a lack of acceptance by the farm-ers, regulations, which are difficult to manage, and the influence of administration have af-fected on the implementation of the several programmes in different ways. The relevance of several determinants of acceptance differs to the programms. A weighting of the influence of the single determinants to the acceptance wasn’t possible. A positive ecological conscious-

ness supports the willing to take part at programmes. It leads to a comparable behavior if aspects of business arrangements of the farm are compatible with a take part. The limitation of fertilizer management, livestock numbers, the late first cut and too small payments in a few programmes were especially impeding factors. The same effect have the uncertainty about the possibilities of husbandry in future and the fear of a lost of worth. The kind of administra-tion has only a little influence. The common agreement about the programmes is endangered in a few cases by determinations or the implementation itself. Different payments for the same restrictions and a different control and punishment of contract violations offend against the order to handle all concerning farmers equal. Especially differences at controlling and documentation of the programme effects can give hints at a not efficient use of financial re-sources. Determinations, which are not or only with difficulties to implement, impair the ad-ministrative implementation of a few programmes. On the background of different budgetory and personally funds of the institutions bureaucratic determinations are leading to a neglect of implementation or to an use of alternative grants. To improve the acceptance a variable handling of restrictions fixed in contracts and a reducing of the determinations on a minimum level is necessary. An improvement of the attractivity of the payments in toto and concerning special determinations is sencefully. A bonus system could be introduced. The programme administrators should act unbureaucratically and only in a short distance of the target areas. A relationship of farmers and programme administrators as it exists between partners, a leg-islative foundation of environmental protection by the instrument of voluntary contracts, simi-lar payments in all programmes and regimes of controlling and documentation improve the public agreement in these programmes. A better exchange of information among the pro-gramme administrators will supply these efforts as well as a change of impeding determina-tions, too. Okorie, Hilary Anyanwu (2001): Furthering the domestication of African pear (Dacryodes edulis (G. Don) HJ Lam). Institute for Horticulture, Faculty of Agriculture, University of Bonn, 92 pages. The African pear (AP) [Dacryodes edulis (G. Don) HJ Lam], also called ´safoutier` or ´bush butter` is one of the most important indigenous African tropical fruit trees species (TFTS). It is a multi-purpose tree used as food, medicine, livestock feed and ornamental purposes. It is also a source of high quality nutritious, non-greasy natural oil with possibly numerous indus-trial uses. The AP is however, yet to be fully domesticated. There is a conspicuous lack of basic information required for the development and improvement of AP. This study was aimed at furthering the domestication and improvement of AP by the species characterisation both at the field and nursery levels, vegetative propagation, analysis of the fatty acid profiles of the identified fruit types, and their post-harvest physiology responses under low tempera-ture storage. An overlapping trend of variation was observed between and within the different fruit types identified. Of the 23 pomological and vegetative characters examined, only fruit length/breadth (L/B) ratio, pulp thickness, fruit stalk length and the shapes of the fruit stem and blossom ends proved to a certain extent reliable in the species characterisation. In the first category of fruits, i.e. the large fruit types, their calculated L/B ratios ranged from 1.46 –

1.82. Variations in their shapes were both at the stem and stylar ends, giving rise to continu-ous variations from oblong shape to lanceolate. The L/B ratios for the medium fruit types var-ied only very slightly, ranging from 1.32 –1.36. Generally, the small fruit types have spherical or oval shapes with very thin pulps. Their L/B ratios ranged from 1.12 –1.28. Some useful correlations between the vegetative and pomological characters were established. Using the low-technology non-mist vegetative propagation system, application of three levels (0.2%, 0.4% & 0.8%) each of indole-butyric acid (IBA) and naphthalene acetic acid (NAA) during the rainy season produced no significant effect on the rooting of the species stem cuttings. Cut-tings rooted in top soil and river washed sand (RWS) had significantly (p < 0.05) higher sur-vival rates of 4.64% & 4.22%, respectively; compared with 1.06% & 3.45% obtained for those rooted in sawdust and sawdust/RWS mixtures, respectively. The species stem exudate was suspected to have inhibited both respiration and water uptake within the propagation me-dium, rendering the applied hormones ineffective. While the total fat content of the AP fruit pulps ranged from 44.4 –55.8%, that of the seeds ranged from 10.7 –15.0%. Four fatty acids: palmitic-, oleic-, linoleic- and stearic acid, make up 98.2% of the AP fruit pulp total fatty acid (TFA) and 88.2% of the seed TFA. The values of these acids in the fruit pulp ranges from 45.6 –49.6%, 28.6 -32.2%, 13.5 –20.4% & 3.1 –3.7% for palmitic, oleic, linoleic and stearic acids, respectively. Their corresponding values in the seeds were 26.8 –33.2%, 18.2 –21.4%, 28.9 –29.1% & 8.0 –11.0%, respectively. High coefficients of variations (CV) ranging from 0.45 – 100% was obtained in the fatty acid pro-files between the different fruit types. Storage at –20°C for 6 months had no significant effect (p < 0.05) on both the fatty acid com-position and organoleptic quality of AP. Fruits stored at 0°C however, deteriorated after the 28th day. The small fruit types had significantly (p < 0.05) higher palatability and acceptability values. A great deal of intraspecific variations of horticultural and genetic interest exists in the AP to warrant the initiation of a selection and improvement programme. If the twin prob-lems of global food security and environmental degradation are to be effectively and concur-rently addressed, the development of these hitherto neglected TFTS and their re-integration into farming systems, is not an option but a necessity. Ortega, Felipe (1994): Influence of induced resistance on the host-parasite-interaction MalusXDomestica Borkh.-Venturia inaequalis (Cke.) Wint. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 124 pages. In the work presented, the efficacy of induced resistance against pathogen strains with dif-ferent genotypes and mixed populations out of them was investigated. For this purpose MalusXDomestica Borkh.-Venturia inaequalis (Cke.) Wint. was used as a model system. First it was necessary to find appropriate induction methods and to characterise induced re-sistance in this host-parasite-interaction. The application of 2,6-Dichlorisonicotinic acid and 3,5-Dichlorsalicylic acid on apple plants lead to a reduction in their scab infestation that amounted to 60-70%. The subcuticular growth of the pathogen was reduced, the latency period prolonged and the sporulation restricted. The effect of induced resistance on the infec-tion cycle of the fungus was investigated by fluorescence microscopy. Induced resistance

interfered with all stages of infection except conidial germination and appressorium forma-tion, but the most relevant effect to the restriction of the disease was the impairment of the first infection stages of the pathogen. The investigations strongly suggest that the main effect of induced resistance on Venturia inaequalis in apple is due to the interference with the pathogen nutrition. To evaluate the variability in pathogen populations towards this crop protection principle, the efficacy of induced resistance was evaluated against pathogen strains with different geno-types. Their sensitivity to triazole-fungicides and Vf-virulence were used as distinctive marks for their differentiation. The investigations resulted in important differences in the activity of induced resistance, but no correlation between its efficacy against a certain strain and the sensitivity of this strain to triazol fungicides nor its Vf-virulence could be identified. When in-duced resistant plants were challenged with a mixed population of these pathogen-genotypes its activity was, either comparable or clearly superior to the efficacy reached against the best controlled strain in the mixture. No selection processes could be identified in competitive studies. The investigation of the dose-response relationship of triazole fungicides against Venturia inaequalis on induced resistant plants allowed the identification of a clear synergism between both active principles. The enhancement of the efficacy of the fungicides on induced resistant plants could be proofed under field conditions as well. This observation delivers a further concept for the use of induced resistance in crop protection. Despite that the utilisation of resistance-inducers in practical crop protection is difficult to handle, due to their indirect mode of action, the active principle of induced resistance widens the possibilities with which plant diseases can be controlled. Ortseifen, Ulrich (2000): Investigation of the applicability of the CaCl2-extractable organic N (Norg) content in the soils of Muensterland in northern Germany for the estimation of soil N mineralisa-tion potential in the Nmin-based fertilisation recommendation system. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 177 pages. The aim of the study was to optimise the Nmin fertiliser recommendation system by, in addi-tion to soil Nmin content, consideration of the CaCl:-NOrg content in the soil as a measure of site-specific soil N mineralisation potential. For the method to be feasible, Norg content in the soil should be sufficiently variable, and should be closely related to the N mineralisation po-tential of the soil. The introduction of such a concept would result in a more environmen-tally-friendly N fertilisation without negative effects on yield or quality of crop produce. The focus of the study was the Frischhofsbachgebiet in Münsterland in northern Germany. Firstly, the CaCl~-NOrg-content of the arable land in the watershed area was investigated. There was a wide range in soil Norg contents between different sites, which was comparable over three years of the study. Norg content within a site was stable, and did not vary greatly between years. A close relationship between soil NOrg-content and the N mineralisation po-tential was found in laboratory incubation tests, and non-fertilised plots in field trials. Based on these results, an Norg class concept was created with four classes.

The NOrg-classes were used to develop a fertilisation concept for cereals based on the Nmin-method. This concept was tested in field trials in 1991 an 1992. It is based on the as-sumption that the Nmin-method considers soil N mineralisation adequately if the NOrg-content is in medium range. In case of a low NOrg-content the mineralisation potential is lower and the fertilisation should be increased. On the other hand if the NOrg-content is high the nitrogen application rate could be lowered. The modification of the late nitrogen applications according to the NOrg-content of the soil had no effect on the crop yield. Nevertheless the N-content in the grain was consistently higher in the higher fertilized treatments. The extent of the nitrogen mineralisation showed a significant relation to the NOrg-content. With increasing N-supply the calculated net minerali-zation clearly decreased probably due to stronger immobilisation processes. Contrary to ex-pectations a reduction of the late N dressing on sites with a high NOrg-content were not to-tally compensated by a higher soil nitrogen mineralisation. This was mainly due to the ex-tremely dry weather conditions during the trials, which did not allow a more clearly differentia-tion of the mineralisation between the treatments. The findings on the nitrogen mineralisation potential of the soils in the investigated area were furthermore used to determine the site specific nitrate leaching potential in the watershed area of the Frischhofsbach. Over, Bettina (2002): Approach to an environmentally friendly utilisation of secondary raw material fertilizer - for example sewage sludge - in agriculture by inclusion of a geographic information system. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 249 pages. The intention of the present work was to build up an information system as a base and deci-sion support system for the administrative decision process for the environmentally compati-ble disposal of sewage sludge in agriculture. With this information system, aspects of soil, water and nature protection are considered over the requirements of the German Sewage Sludge Ordinance (1992) to satisfy the admin-istrative authority of the county of Uckermark and Elbe-Elster of Brandenburg. The designed area register for secondary raw material fertiliser comprises digital data of land use, areas where it is not permitted to use sewage sludge according to §4 AbfKlärV (1992) and results of external models. An evaluation of fields for environmentally friendly sewage sludge use in agriculture is thus possible. A number of criteria are used as the basis for the integration of the external models. The modular design of the entire system warranted the convertibility of the GIS data and the models for actualisation of the area register. For an estimation of suitable and unsuitable areas for local sewage sludge utilisation the Fuzzy-Logic method was used. The model results show that for the model regions, Prenzlau-West and Schraden, a differentiated suitability evaluation is possible. From comparisons of both model regions Schraden shows less suitability for regional sewage sludge use. The participants of the county Uckermark used the information system and have confirmed that the area register is a workable instrument in the procedure to authorise sewage sludge use. Furthermore, it is useful and expandable for other problems. In this context farmers

were interviewed and in the future will use the data in the area register prior to an application of sewage sludge. Until this time none of the farmers interviewed had previously used sew-age sludge. Requirements for the use of regional sewage sludge in particular are, safety of use and economic benefits. Complementary to the sewage sludge quality, the heavy metal and nutrient content of the soil was also investigated in the counties Uckermark and Elbe-Elster. Pacyna, Svea G. M. (2005): Significance of sulphur on the content of ferredoxin and leghemoglobin as well as on the supply of energy to N2-fixing legumes. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 186 pages. In recent years sulphur deficiency has become an increasing problem for agriculture resulting in decreased crop quality parameters and yields. Especially legumes gain in importance as plant protein distributors and are highly sensitive to S-deprivation limiting the synthesis of the S containing amino-acids methionine and cysteine and therefore protein synthesis. Further S deficiency results in reduced chlorophyll contents and therefore in a lower photosynthesis rate. Some investigations with different legumes already assessed that S deficiency results in a decreased nitrogen fixation. The way of influence from S shortage to limited nitrogen fixa-tion is still discussed. In the present study the influence of sulphur supply on S and N concentrations, available amounts of sucrose, glucose and adenylates of shoots, roots and nodules as well as con-tents of ferredoxin and leghemoglobin of nodules were investigated regarding different leg-umes. The effects of S shortage on assimilates and energy as well as proteins in legumes might result in an indirect or direct inhibition on nitrogen fixation. To observe the trend of moderate to severe sulphur deficiency and the effect of late S applications after a time of moderate S shortage trials were carried out in time series. Sulphur deficiency resulted in lower yields as well as in diminished N accumulations corre-sponding to a reduced nitrogen fixation in legumes. As a consequence of S shortage signifi-cant lower S and N concentrations were demonstrated in shoots, roots and nodules of beans, peas and lucerne. Caused by low demands of assimilates by an impaired metabolic nodule activity the amounts of sucrose were increased in roots of S deficient legumes. Ex-pectedly the amounts of sucrose and glucose were indeed decreased in shoots and nodules under S deficiency. The reduced amounts of assimilates resulted in a reduction of ATP-concentrations and of the energy charge shown in shoots, roots, bacteroids and mitochon-dria. Although the level of transcripts for leghemoglobin was even higher in nodules under a moderate S shortage the protein content responsible for O2 availability and creation of a mi-croaerobic environment in nodules was strongly reduced. Compared to leghemoglobin ferre-doxin of bacteroids which are important for electron transport to nitrogenase decreased only under severe S deficiency. The present results suggest that S deficiency indirectly influences nitrogen fixation by reduc-ing assimilates and energy in legumes and nodules and directly by decreasing leghemoglo-bin and ferredoxin content in nodules.

Pätzold, Stefan (1998): Herbicide application in horticulture - Investigation and simulation of degradation, sorption, and leaching of simazine and diuron in loess soils. Institute for Soil Science, Faculty of Agriculture, University of Bonn, 231 pages. Over three years of field trials degradation, sorption and leaching of the herbicides simazine and diuron as well as of the diuron degradation product DCPMU were investigated in orchard soils after applying the recommended amounts with a common spraying device. Most of the research was conducted in a 12 year old apple orchard on a Haplic Luvisol near Bonn, FRG. Diuron degradation and sorption were also studied in corresponding laboratory experiments. Both adsorbed and dissolved amounts of simazine, diuron and DCPMU were analyzed in order to characterize the herbicide mobility in soil. For the same reason sorption isotherms were derived from batch experiments. Degradation and leaching of simazine and diuron were simulated by using the computer model PELMO which is based on the model PRZM; PELMO is used for registration purposes by german authorities. For six months after applying the herbicides, degradation of the chemicals in the 0-5 cm layer conformed to first-order-kinetics. The DT50-values ranged from 20 to 64 days for simazine and from 17 to 30 days for diuron. As the degradation rate gradually decreased, a carry-over of herbicide residues from the preceeding growing season occured at the time of reapplica-tion in the following year. The long-term development of the herbicide residue level was best characterized by two combined exponential functions representing fast and slow degrada-tion. The formation of DCPMU was observed in the laboratory and field investigations. Both soil saturating extracts and CaCl2-extracts were equally suitable for the determination of simazine and diuron mobility. Under natural conditions, mobility of herbicide residues de-creased significantly with time. In sterile soil samples the decrease of diuron mobility dimin-ished after 28 days indicating the importance of simultaneous microbial degradation and dif-fusion processes for the immobilisation of herbicide residues. Soil moisture revealed signifi-cant effects on herbicide mobility and formation of bound residues. Up to 40 % of the previ-ously unextractable residues were remobilised after drying the moist soil. In general, sorption and desorption followed Freundlich-isotherms. Sorption and desorption phenomena at low concentrations were partially best represented by a separate Freundlich-isotherm. This was caused by sorption of small herbicide amounts on inner surfaces of aggregates and organic matter; slow desorption kinetics from these sites was found to be the reason for the observed carry-over phenomena. Formulation additives enhanced simazine and diuron mobility when high concentrations of the herbicides were added in the batch experiments. In autumn only low concentrations of the simazine and diuron applied in the previous spring remained in the upper soil layers. Consequently, only small amounts of these strongly ad-sorbed residues were leached into the subsoil due to convective-dispersive flow during the winter months. In contrast, a few days after the herbicide application in May 1994, while high herbicide concentrations occured in the 0-5 cm soil layer, residues of both chemicals were translocated into the subsoil. This rapid movement was due to preferential flow in soil macro-pores like earthworm channels and shrinkage cracks. The importance of preferential flow was proved by conducting a dye tracer experiment. Small amounts of simazine and diuron were detected in the groundwater.

The simulation model PELMO was capable of predicting degradation and leaching of simaz-ine and diuron, as far as no preferential flow occured. PELMO does not account for this process. The degradation and sorption parameters commonly used in simulation for registra-tion purposes led to less realistic simulation results than optimized parameters for the char-acterization of the chemicals. In particular, the kinetics of herbicide degradation has to be taken into account. The description of herbicide mobility by time-dependent partition coeffi-cients improved simulation results as compared to Freundlich-parameters determined in batch experiments. Pande, Keshab Raj (2005): Managing seasonal soil N-dynamics in rice-wheat rotation systems of Nepal. Institute of Plant Nutrition, Faculty of Agriculture, University of Bonn, 104 pages. The rice-wheat annual double cropping system occupies an estimated 0.5 million hectares in Nepal where it provides food for about 23 million people. The production systems are similar with regards to the prevailing soil types and the agronomic management but differ in terms of the climatic environment, stretching from the hot tropical lowlands to cold temperate moun-tain areas. Current production levels of both rice and wheat are far below their reported po-tential with N-deficiency being the major production constraint. Because of mainly subsis-tence-oriented smallholder agriculture, mineral fertilizer use is negligible and crops have to rely largely on native soil supply for their N nutrition. Between the harvest of winter season wheat and the transplanting of monsoon season rice lies a transition season of variable length (>10 weeks in the lowlands to <5 weeks in the mountains), where the land is typically under bare fallow. During this dry-to-wet season transition period (DWT), the soil aeration status changes from aerobic to anaerobic, resulting in an initial peak of soil N mineralization and its subsequent disappearance upon soil flooding. Protecting this native soil N from being lost is seen to contribute to improve the N nutrition and the currently negative N balances with impact on yield and productivity. Possible options may include the temporary immobili-zation of soil N in the biomass of soil micro-organisms and/or of transition season crops. Pot and field experiments were conducted in the greenhouse and under field conditions at vari-ous sites in Nepal between 2001 and 2003 to assess the potential of wheat straw manage-ment (short DWT in cool mountainous areas), grain and green manure legumes (long DWT in the lowland areas) and combinations of those on soil N dynamics, crop yields and sys-tems’ N balances. When the land was left bare during the transition season (farmers practice), Nmin was ini-tially building up (50-80 kg of nitrate-N) and subsequently lost by nitrate leaching and denitri-fication, resulting in low N uptake and yield of both rice and wheat. The application of wheat straw during DWT significantly reduced soil Nmin at the same rate as soil microbial biomass-N increased and resulted in <1 kg ha-1 of nitrate leaching and minimal nitrous oxide emis-sions from the soil. Increased grain yields were limited to the rice crop and increased with straw application rate and the duration of DWT. A crop cover with legumes reduced leaching losses by half and nitrous oxide emissions by two thirds of those in the bare fallow control, and BNF-N additions by legumes ranged from 27 to 56 kg ha-1. Depending on the type of legume, this resulted in direct (rice) and residual (wheat) increases of 24-42 kg N ha-1 yr-1 in

crop N uptake and of 1.2-2.1 Mg ha-1 yr-1 in grain yield, while improving the overall N balance of the systems. The lower benefits were associated with the grain legume, (50% of the N assimilation removed by grain harvest), while the high benefits were obtained with green manures. About one third of these legume-induced productivity gains could be ascribed di-rectly to the conservation of soil N. We conclude that in environments where the time span between wheat harvest and rice transplanting (DWT) is too short to grow an even short-cycled crop (mid-hills and mountain areas), the incorporation of wheat straw can save native soil N from losses and improve the systems’ nitrogen N balance. Where the DWT is suffi-ciently long, the cultivation of legumes appears economically and ecologically beneficial and should be encouraged. Combinations of straw amendment and green manure use during DWT provide the largest benefits in terms of grain yield, and N balance with possible longer-term benefits for system’s productivity. Pauly, Jörg (2000): Replanting of a vineyard: Aspects of a site-specific and goal-oriented management. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 128 pages. Replanting of a vineyard leads to fundamental changes in the way a vineyard is managed and necessitates a completely different treatment of the soil. These changes can cause in-tensive mineralisation and nitrate leaching. In this thesis variations of management during the replanting (integration of green-fallow, choice of tilling machine, termination of tillage, soil management after planting) were ob-served at different sites on different wine-growing estates. Investigations concentrated on the intensity of mineralisation and on nitrate leaching. Additionally the impact of green cover and soil management and also of site-specific condi-tions on the performance of the young vines after planting (regular root-taking, high vitality, rapid attainment of maximum yield capacity) were analysed. Following tillage and the planting of the vines a higher soil nitrate content was observed; this increase proved more intense in the first year after planting than in the second. During the drain water periods nitrate leaching correlated with the intensity of the preceding mineralisa-tion. Among the different treatments the following hierarchy concerning the amount of nitrate leching can be deduced from the different treatments with regard to the extent of nitrate leaching: spading machine or deep plough > MM100 or cultivator soil mangement after plant-ing: mechanical weed control > winter green cover green cover species: natural green cover > winter rye > crucifers cultivation system:farm-like > extensive > ecological. On-site investigations on farms showed that the site-specific conditions (soil and climate) have a greater impact on nitrogen dynamics in soil and nitrate leaching than green cover and soil management. The data collected from the measurements and investigations helped to develop a computer-based decision-support-model for the replanting of a vineyard.

Pihl, Uwe (2000): Chemical soil parameters as criterians for the prediction of the potential P-leaching in drainage- and groundwater. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 227 pages. In this paper the reliability of a prognosis concerning the extent of a possible endangering of ground- and drainage water contamination via the vertical P-leaching by various chemical soil parameters which characterize the P sorption and the P dynamics was investigated. In a first project representative soils of the most important "soil units" (Bodeneinheiten) were chosen from the Niederrhein and Münsterland for the comparative methodical basic investi-gations. In a second project extensive soil surveys were carried out in three Münsterland counties (Kreise) with intensive lifestock density. The results of this investigation support the dependency of the P-concentration of the soil solution (intensity) on the quantity of the adsorbed phosphate. The adsorbed P with influence on the intensity could be estimated by the Fe/Al-P-fraction (KURMIES), the oxalate-soluble P (Pox), and also by the lactate-soluble P (CAL-P). It could be shown, that the intensity is not only determinated by the quantity of adsorbed P, it is also dependend on the already existing saturation of the P sorbents. Therefore, the P-concentration of the soil solution increases exponentially with increasing saturation degree of the P-sorbents. The ammonium-oxalate extractable poorly cristalline Fe/Al-oxides/hydroxides [(Fe/Al)ox] proved to be the major P-sorbents. In a multiple regression the variance of the P sorption maximum could be explained to 80 % with only these two parameters. Including (Fe/Al)ox and pH together with a parameter of quantity (Pox or CAL-P), coefficients of determination of up to 80 % could be reached in the multiple analysis of regression when estimating the P-concentration of the soil solution. Some soil units (Bodeneinheiten) could be assigned to characteristic ranges of (Fe/Al)ox con-tents and therefore also to P sorption capacities. The soils which were investigated in both projects showed, as a rule, a P supply that was already high to very high in the topsoil. However, a rapid decrease of the P contents could be assigned in all cases with increasing depth of the profile. A closer examination of the layer in the depth of 30 - 60 cm showed that the higher P con-tents in this layer were caused by only few centimetres directly below the topsoil. The potentially most importanted layer for a possible P leaching in ground- and drainage water in the depth of 60 - 90 cm showed a P-concentration above the still tolerable "approxi-mate value" of 0,20 mg P/l predominantly among soils with an already high P supply in com-bination with peculiarities in the P budget (Gleye, Pseudogleye, and Plaggenesche). Pocasangre, Luis (2000): Biological enhancement of banana tissue culture plantlets with endophytic fungi for the control of the burrowing nematode Radopholus similis and the Panama disease (Fusarium oxysporum f.sp. cubense). Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 95 pages.

A total of 132 endophytic fungal isolates were recovered from internal tissues of surface ster-ilized roots and corms from 21 banana cultivars in Central America and Cuba. The antago-nistic activity of 25 endophytic fungi towards Radopholus similis was studied on micropropa-gated banana plantlets of the cultivar Gran Enano (AAA) under greenhouse conditions. Five of these endophytic isolates caused reduction in the number of R. similis /g root greater than 90% in comparison to endophyte-free plantlets. The antagonistic activity of the effective endophytic isolates was retested on different banana cultivars: Williams (AAA), Gros Michel (AAA) and FHIA-23 (AAAA). Reduction in the number of R. similis /g root greater than 76% was recorded on all banana cultivars tested. Also the population density of R. similis in the soil was significantly reduced by the endophytic fungi. Endophytic fungi effectively colonized the roots and corms of the plantlets. Frequency of reisolation greater than 46% in the roots was recorded on three banana cultivars. The presence of endophytic fungi in the roots re-duced the penetration of R. similis into the root tissue up to 74% on the commercial cultivar Gran Enano (AAA) 5, 10 and 15 days after nematode inoculation. In addition in the absence of R. similis inoculation with endophytic fungi increased shoot and root weight as well as root length of the banana cultivar Gran Enano (AAA) Williams (AAA) and FHIA-23 (AAAA) 3 months after inoculation. The Antagonistic activity of endophytic fungi towards race1, 2 and 4 of Fusarium oxysporum f.sp. cubense (FOC) was studied on micropropagated plantlets under greenhouse conditions. The pathogenicity of FOC race 1, 2 and 4 was confirmed on race indicators cultivars. Typical symptoms of Panama disease were observed 6 weeks after inoculation. Antagonistic tests conducted with high and low inoculum densities of FOC race 4, 1x106 and 1x103 cfu/ml re-spectively showed that there were no differences in disease severity between inoculated plantlets with endophytic fungi and control under high inoculum densities of FOC race 4. However, disease severity, internal and external symptoms, was significant different between inoculated plants with endophytes and control under low inoculum density. Portz, Christina (2002): Venturia inaequalis (Cke.) Wint.: Significance of conidia as a source of primary inocu-lum, implications for bud development and alternatives for use of copper for control of leaf and fruit scab incidence. Institute for Horticulture, Faculty of Agriculture, University of Bonn, 158 pages. In the study presented, various strategies for an improvement of the control of Venturia in-aequalis were evaluated: In the fruit growing region of Meckenheim (Bonn) primary infections are decisive for the in-tensity of scab incidence on leaves and fruits during the following growing season. Severe scab attacks at the beginning of the vegetation period resulted in strong reductions of fruit quality at harvest. Four fungicide applications were sufficient to decrease the amount of in-fected fruit significantly. Although treatments were restricted to the early vegetation period, significant differences in leaf and fruit scab incidence still could be established between un-treated and treated trees at the end of the growing season, almost five months later.

Ascospores represented the most important source of primary inoculum in early spring in the region of Meckenheim (Bonn). In addition, overwintering conidia or mycelium of Venturia in-aequalis were present. By means of light and scanning electron microscopy overwintering asexual structures on buds and twigs were identified and documented. Most of the examined conidia originated from overwintering lesions on twigs and outer bud scales. Different stages of wood scab could be exhibit in a new way by using scanning electron microscopy. It could be shown that the development of twig scab depended on apple cultivar and on the condi-tions during the overwintering of infected trees. Venturia inaequalis may affect the development of apple buds in a direct or indirect way. Early scab incidence on leaves, flowers and fruits could be due to overwintering asexual structures of the pathogen being located on the outside or inside of the buds. Severe attack on the leaves may restricted the formation of flower buds for the following year by 30% due to the reduction of the photosynthetically active leaf area. Ammonium fertilizers could be used to decrease the competition between leaf growth and flower bud development for a limited time. The expected ban of use for copper fungicides will aggravate the control of the disease in organic apple production. The application of α-tocopherol on apple seedlings resulted in a reduction of scab incidence that amounted to 80%. Because of changes in leaf surface char-acteristics retention of conidial suspension and duration of leaf wetness were decreased. The conidia which remained on the treated leaves showed modifications in germ tube growth, development of appressoria and penetration of the cuticule. Subcuticular growth and subse-quent sporulation of Venturia inaequalis were reduced. Prange, Alexander (2004): Food mycological and X-ray absorption spectroscopic investigations on the influence of phytopathogenic, mycotoxin producing moulds on the gluten protein structure and baking quality of wheat. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 156 pages. The influence of phytopathogenic, mycotoxin producing moulds on the sulfur speciation of the gluten proteins and thus the baking quality of wheat was systematically investigated. To characterise the sulfur speciation in situ, XANES spectroscopy was established as method for the "wheat gluten" system. XANES spectra were analysed quantitatively using the MINUIT fitting routine. To deal with this interdisciplinary subject comprehensively, different methods and aspects pertaining to mycology, mycotoxinology, molecular biology and cereal chemistry were applied and considered for the investigation of mould infected wheat in sev-eral field and storage trials. XANES spectroscopic measurements allowed for the first time a description of the sulfur speciation of wheat gluten proteins and flours in situ. The oxidation of reduced LMW subunits of glutenin with atmospheric oxygen led to an increased formation of disulfide bridges; in LMW subunits stored in ambient air and temperature conditions for more than two years, virtually nothing but sulfoxide and sulfonate were detected. The investigation of LMW sub-units which were reoxidised with potassium bromate and iodate at different pH values showed that these oxidising agents do not only cause an oxidation of thiol groups to disulfide

bridges, but also an (unwelcome) oxidation of the cysteine residues to sulfoxide and sul-fonate; sulfur as sulfone was not detected. The strongest oxidation was observed with acidic pH values. Field fungi of the genus Fusarium have hardly any influence on the sulfur speciation of the wheat gluten proteins. A reduced functionality of the gluten network and a reduction of the baking volume have not been observed. From the perspective of food safety and consumer protection this is of great importance because the baking quality of flours that were heavily loaded with DON did not allow detecting their contamination with fusaria and/or mycotoxins. Storage fungi of the genera Aspergillus and Penicillium have a direct influence on the sulfur speciation of gluten proteins. In baking tests with flours from the storage trials (20% moisture content/20°C) a considerably reduced baking volume was observed. In this context, an in-creased proportion of sulfonate was found, which is not available for the thiol/disulfane ex-change reaction in the gluten network. From these changes of the composition of the mould flora during suboptimal storage of wheat and from the trichothecene contents it is concluded that microbial interactions play an important role in the development of the mould flora and the mycotoxin contents. Pude, Ralf (1997): The winter hardiness of Miscanthus during establishment. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 112 pages. Field trials with the renewable material Miscanthus were conducted at the institut of plant production of the University of Bonn in the years from 1993 until 1995. The institut of arable farming and plant production of the University of Halle and the chamber of agriculture „Rheinland“ joined the research project in 1994 and 1995, respectively. Effects of plant density and nitrogen fertilization on yield performance of Miscanthus have been tested. Due to the high rate of winter killing during the first experimental year, winter hardiness of Miscanthus was also investigated beside the formation of yield. Winter hardi-ness could be improved by increasing plant densities. For detailed analysis of winter hardiness Miscanthus plants of different provenance were tested in 1995. Except one provenance there was no genetic difference between the Miscan-thus plants of different origin. However, a variance in yield performance and winter hardiness could be detected between the genetic identical plant provenances, probably caused by dif-ferences in the plant conditioning during micro-propagation. Yield formation of Miscanthus is mainly influenced by the amount and distribution of percipi-tation at the site, whereas winter hardiness depends on the temperature course from late autumn throughout the winter. The seasonable relocation of minerals and reserves from aboveground plant material into the rhizomes seems to be of special importance for winter hardiness of Miscanthus. Nitrogen fertilization had no significant influence on yield formation and winter hardiness, where high plant densities effected both characteristics positively.

Reichart, Katrin (1998): The impact of agricultural measures on criterions of soil fertility in the line of cultiva-tion sugar-beet - winter wheat - winter barley. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 119 pages. On the occasion of a soil-tratment trial that was established in the year 1981 on the experi-mental farm Dikopshof of the university Bonn during the years 1993 - 1996 (in the fourth rota-tion) research on the impact of - ploughless soil treatment - rotation fallow ground - produce and quality of sugar-beet, winter wheat and winter barley was accomplished. The ploughing of an 51/2 old endurance fallow ground on a neighbouring soil in the year 1994 made it possible to compare the two forms of the fallow grounds regard-ing their impacts on soil characteristics as well as produce and quality of the succsesion plants. It was indicated that the physical soil properties (pore volume, biopores and stability of sur-face-close ground soil aggregates), chemical soil properties (Ct-, Nt- P2O5-, K2O-contents and the nitrate-dynamics in the ground) and the biological soil properties (micribiological ac-tivity and weed seams potential) were mainly influenced by the soil treatment intensity. Fal-low ground-effects became evident only during the fallowing or in combination with plough-less ground-soil treatment. The fallowness of 11/2 and 51/2 years had only a small influence on the above mentioned soil properties. The ploughless soil treatment had no negative impact on produce and quality of the culti-vated plants; in comparison to the traditional soil treatment with yearly ploughing a tendency to improved produce could be realized. A positve impact of the rotation and endurance fallow ground on produce and quality of suc-cession plants was only recognizable at minor level nitrate fertilization. In this case the culti-vated plants could take advantage of the higher nitrogenous level of the fallow ground. On account of the prevailing positive location properties no correlation between soil charac-teristics and produce was detectable. Reimann, Stephan (2005): The interrelationships between rhizobacteria and arbuscular mycorrhizal fungi and their importance in the integrated management of nematodes and soilborne plant pathogens. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 91 pages. A total of 62 bacterial isolates were isolated from surface sterilized AMF spores, which were previously extracted from tomato fields in Nakhon Ratchasima Province of Thailand. These spore-associated bacteria were tested for their antagonistic potential against the root-knot nematode Meloidogyne incognita and the soilborne plant pathogens Fusarium oxysporum, Pythium aphanidermatum, Pythium ultimum and Rhizoctonia solani.

A high percentage of the bacterial isolates (14,5%) reduced nematode penetration of tomato roots in repeated experiments. Two of these antagonistic bacteria were further tested in a long-term experiment, either alone or in combination with Glomus intraradices. Single inocu-lations resulted in low or even no biological control, but both dual inoculations reduced gall and eggmass production. Twelve bacteria (19,4%) inhibited fungal growth of at least one pathogen in vitro and six iso-lates showed antagonistic potential against all pathogens tested. The seven isolates that inhibited growth of Fusarium oxyporum in vitro were tested in vivo against the same patho-gen. Three of these seven bacteria reduced the reisolation rate of the pathogen and there-fore inhibited fungal spread in the tomato stem. The PHPR Rhizobium etli G12, inducing resistance against M. incognita, was found to pro-mote establishment of G. intraradices on three different tomato cultivars. The bacterium ap-pears to accelerate AMF colonization of the root, and therefore should be regarded a My-corrhiza helper bacterium (MHB). In in vitro studies, R. etli stimulated AMF sporulation and hyphal branching, the latter of which is an important prerequisite for penetration of the host roots. This direct effect of the bacterium on fungal morphology is one explanation for the in-creased mycorrhiza establishment, but a plant-mediated effect can not be excluded. The combination of G. intraradices with R. etli enhanced biocontrol of M. incognita on to-mato, in comparison to single inoculations. The better mycorrhization of the young trans-plants and the combination of different modes of action could be the explanations of the in-creased antagonistic potential. Reissinger, Annette (2000): The interaction of the fungus Chaetomium globosum with the powdery mildew fungus Erysiphe graminis f. sp. hordei on barley (Hordeum vulgare). Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 95 pages. Fungal endophytic colonization of plants can change their metabolic activity leading to a modified defense response to subsequent pathogen attack. It could be shown that the sapro-trophic fungus Chaetomium globosum is able to grow endophytically in barley roots (Hor-deum vulgare). The colonization included symptomatic discoloration of the root cortex if a synthetic culture substrate was used for plant growth. The colonization of the root tissue by C. globosum was investigated with histological and serological techniques. The fungus colo-nized the epidermis intracellularly, while the outermost cortex layer was colonized inter- and intracellularly. The colonization always originated from the rhizosphere. The inter- and intra-cellular growth was accompanied by host responses including autofluorescence and brown discoloration of cell walls adjacent to hyphae and hemispherical or papilla like protuberances of cell walls. Additionally, an anamorphic substance which was found in the intercellular spaces, seemed to block the intercellular growth of the fungus. In contrast to these findings C. globosum could not be reisolated from the roots by means of surface sterilization tech-niques. The only sterilant being effective to ascospores on the plant surface penetrated the epidermal root tissue and caused damage to this area [1]. Consequently, C. globosum hy-phae growing in this tissue could not be detected. Using microscopical and serological meth-ods, no colonization of leaf blades could be found.

To determine the mode of action leading to the reduced disease severity of Erysiphe graminis f. sp. hordei, which was described previously [2], increased plant defense re-sponses in the primary leaves induced by the defense of C. globosum in the roots were in-vestigated. However, on a microscopical level no increased defense responses could be found in plants colonized by C. globosum. Additionally there was no indication for a modified infection process of E. graminis konidiospores 41 h post inoculation. The conidial germina-tion of the pathogen, as well as the appressorium and haustorium formation, i.e. the success-ful penentration of the epidermis, and the reproduction was not altered. However, a general reduction of attached conidia was found on the leaf surfaces of plants colonized by C. globo-sum compared to mock treated controls. This observation indicates for a C. globosum induc-ible, and systemically diffusible signal which acts on early stages of pathogenesis, i.e. the attachment of konidiospores to the leaf surface, via an altered conidial germination. References [1] Reissinger, A., Vilich, V., Sikora, R.A. (2001). Detection of fungi in planta: effective-ness of surface sterilization methods. Mycological Research, in press. [2] Vilich, V., Dolfen, M., Sikora, R.A. (1998). Chaetomium spp. colonization of barley following seed treatment and its effect on plant growth and Erysiphe graminis f. sp. hordei disease severity. Journal of Plant Diseases and Protection 105, 130-139. Renn, Jörg (2005): Medaka (Oryzias latipes) as in vivo model system of osteogenesis. Institute for Agricultural Botany, Faculty of Agriculture, University of Bonn, 134 pages. Osteoporosis, characterized by bone loss, is one of the most important bone diseases of humans worldwide. A high-risk group for the development of osteoporosis is post-menopausal women. Furthermore, osteoporotic alterations are found in the bones of astro-nauts during long-term space flights. The reason is an imbalance of bone formation and bone resorption as a result of decreased estrogen synthesis and reduced gravity, respectively. Bone formation and bone homeostasis is regulated by several known key factors, like e.g. core binding factor α1 (cbfa1) and osteoprotegerin (opg). The transcription factor cbfa1 is crucial for differentiation of osteoblasts, whereas opg inhibits the formation and activation of osteoclasts. Small bony fish, like Medaka (Oryzias latipes), are widely used as vertebrate model systems to investigate molecular biological questions. The experimental advantages of Medaka make it to an ideal in vivo model system for bone research. Several genes of the bone metabolism, e.g. cbfa1, are already identified in Medaka. The aim of the investigations described here was to enlarge the knowledge in Medaka regarding genes that are involved in bone development and bone homeostasis of mammals. The analyses showed a high homology of the amino acid sequence, the genomic organization and the expression of the genes twist-1 and osteonectin in Medaka compared to higher ver-tebrates. Furthermore, two osteoprotegerin genes, opg1 and opg2, have been isolated in Medaka. Both code for amino acids that show highest homology to the functionally important cytein-rich domains of the mammalian opg. In mammals, the expression of opg and cbfa1 is influenced in vitro by exogenous factors like altered gravity and estrogenic substances. The experiments performed here using whole

living Medaka larvae have shown that the expression of opg1, opg2 and cbfa1 were also altered in an in vivo situation by simulated microgravity and estrogens. Taken together the results support the assumption that genes and molecular mechanisms of bone development and bone homeostasis are conserved to a great content between Medaka and higher vertebrates. Furthermore, the results underline the developmental potential of Medaka as an in vivo model to analyse the effect of exogenous factors on the bone of verte-brates. Richter, Sabine (2002): Laboratory- and field-investigations about the efficacy and the insertion of Diadegma semiclausum Hellen against Plutella xylostella L. and Pteromalus puparum L. against Pieris rapae L. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn. The two lepidopterous pests small cabbage white, Pieris rapae (L.) (Lep., Pieridae), and diamondback moth, Plutella xylostella (L.) (Lep., Plutellidae), are able to destroy a large amount of the cabbage, which is cultivated in the region of the Rhein-valley. Increasing resis-tence of the pests against insecticides and the lack of indications for pesticides in the produc-tion of vegetables enlarge the further development of alternative methods to suppress the pests. To keep care to the farmer and the customer as well as to save the environment it is necessary to develop alternatives for the only use of chemical insecticides. The use of bene-ficial arthropods therefore reaches more and more importance as a harmless and purposeful method to control the pests. The present study deals with the biology, the ecology and the parasitation of two parasitoid wasps, which occur naturally in the Rhein-valley: Diadegma semiclausum Hellen (Hym., Ich-neumonidae) is a solitary larvae-parasitoid of the diamondback moth, the gregarious parasi-toid Pteromalus pupa-rum L. (Hym., Pteromalidae) attacks the pupa of the cabbage white. The investigations were done to get information for the development of biologic strategies against both the lepidopterous pests. Aspects of the biology and the parasitation capacity of both parasitoid species were investi-gated under laboratory conditions with the aim of obtaining basic information for the biologi-cal control on cabbage. The maximum parasitation of D. semiclausum and P. puparum was observed at the beginning of the oviposition period. In the first half of the oviposition female offspring predominated over the male one, whereas more male parasitoids were produced towards the end of the oviposition. D. semiclausum showed the highest parasitic capacity when P. xylostella-larvae in the stages L2-L3 were offered. The number of hatched P. puparum-offspring was influenced by the age of P. rapae-pupae. Furthermore the reduced number of parasitized host-pupae dependent on the increasing interval between hatch and copulation of the parasitoid female was perceived. The studies with both parasitoid species leads to the use of those parasitoid females in the pest management, which are at the begin-ning of the oviposition. Their progeny is female biased and may parasitize further genera-tions of the pest. In field trials the results of the laboratory studies were taken to get the optimum parasitoid density and the most favourable moment of release of the parasitoids. In all the three years

of research a parasitation of the cabbage white and the diamondback moth was noticed in the week after the release. An important difference between the number of individuals in the single treated cabbage plots and in the control plots could be registered just at one place. The repeated releases of the parasitoids showed a better effect than to double the number of the inserted wasps, at which these results are statistically not significant. The combination of a parasitoid release and a chemical plant protection could be carried out at one place. A complete reduction of the pests was achieved only in the parts with insecticide spraying. In 1998 a distinct increase of parasitized pest individuals could be noticed in the plots with parasitoid releases against the control plots. During the three years a complete suppression of the population of both pest species in the field trials couldn?t be achieved. Roperia, Surender Singh (1998): Growth, development and yield formation in triticale and wheat as depending on the supply of nitrogen and the application of phytohormones. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 96 pages. In pot experiments, the influence of nitrogen fertilisation and the application of phytohor-mones was studied on growth, development and yield formation in triticale and wheat. The application of urea ammonium sulphate (UAS: 2/3 urea-N; 1/3 ammonium sulphate-N) or ammonium as placement fertiliser at the beginning of tillering up to the beginning of jointing stage under latent N-deficiency stimulated the tillering. The higher grain yields have been achieved through increased rate of tillering despite lower number of grains per ear. Tillering has been impeded by the application of UAS or ammonium plus BA (Benzyladenin) as placement fertiliser after latent N-deficiency at the beginning of jointing stage. The grain yields as well as the number of grains per ear have been increased in comparison to the re-spective treatments without BA. The incorporation of straw in soil in combination with ammonium as placement fertiliser stimulated the tillering in wheat but the presence of BA along with ammonium as placement fertiliser limited the tillering. Higher yields have been achieved through higher tillering as well as through higher test weight. The cutting back of wheat at the beginning of jointing stage followed by ammonium or am-monium plus BA as placement fertiliser stimulated the tillering in wheat significantly as com-pared to UAS or UAS plus BA as placement fertiliser. Tillering has been impeded after the application of mixed fertilisers with urea, ammonium and nitrate if urea and ammonium to-gether exceed 60% N in the mixed fertiliser. After severe N-deficiency during jointing stage, EC 29/30, urea and nitrate have been stored in the shoot for the short period while ammo-nium has been stored considerably delayed. Reduction in the grain formation could be in-duced through delayed uptake of ammonium whereas through urea and nitrate uptake ex-cessive tillering could be possible. The treatment of whole plant or the ears with GA3 (Gibberellin) at the time of anthesis after fertilisation with nitrate in split applications or UAS as placement fertiliser led to increased grain yields which is based on the higher number of grains per ear. The addition of GA3 along with UAS as placement fertiliser led to considerable shoot growth followed by weaker stalk of

wheat within few days and considerable yield losses. A whole plant treatment with auxin at anthesis after UAS plus BA as placement fertiliser led to significant increase in test weight. With regard to the storage of nitrogen in the grains no differences could be established be-tween the applied nitrogen fertiliser forms of urea, ammonium and nitrate. Higher nitrogen fertiliser efficiencies have been achieved after split applications and ammonium sulphate or UAS plus BA as placement fertilisers. These efficiencies could be further improved through the treatment of whole plant with GA3 at anthesis. Roßbach, Jürgen (2000): Effects of input material and degree of decomposition on N-fractions and N-delivery of composts. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 125 pages. With the novella of the german refuse act to the new recycling and refuse act all biogenic wa-stes have to be reused as secondary raw materials. That means this materials have to be prepared as fertilizers (i.e. by composting processes) for recycling to agricultural land accord-ing to the regulations of the german decree of fertilizers (DÜNGEVERORDNUNG 1996). This decree provides an application of organic fertilizers adjusted to the real consumption of nutri-ents during the vegetation periods. For calculation of this consumption the amount of nutri-ents available in soil, supplied by compost application and delivered during the vegetation period has to be taken into account. Especially the effect of nitrogen in composts and the estimation of N-delivery in combination with mineral fertilization still raises questions. Therefore the goal of this study was the investigation of N-effects of composts depending on input material and degree of decomposition, which have directly influence on N-content and N-fractions. N-content, different N-fractions and other parameters of twentyfour composts from different compost plants were investigated. The composts differed in the composition of input material (biorefuse (separately collected organic domestic waste) and plant residues (from park an garden cultivation); percentage composition (v/v): 70/30, 30/70, 0/100) and degree of decomposition (fresh compost and highly matured compost). In fresh composts the total N-content declined with the increase of proportion of plant resi-dues wheras the content of stabile N-fractions arose. In highly matured composts this effect could not be proofed. The C/N relations increased with proportion of plant residues from 16/1 to 30/1 in fresh composts and from 15/1 to 19/1 in highly matured composts. A greenhouse pot bioassay (Italian ryegras, Lolium multiflorum L.) with these composts was conducted to estimate the percentage of short-term apparent bioavailable nitrogen. Fresh composts showed a negative N-supplying capacity, ascribed to a partial biological immobili-zation of soluble soil-N. Highly matured composts reached an exploitation of total organic compost-N from 0,7 to 1,3 percent, dependent on proportion of plant residues. An additional N-supply with mineral fertilizer led to an increase of N-exploitation in highly matured com-posts in the range of 3 to 4 percent. From all investigated N-fractions and compost parame-ters there existed only a significant correlation between the C/N ratio and the N-uptake of ryegras with coefficients of –0,94 (fresh compost) and –0,64 (highly matured compost). So an increase of the C/N ratio led to an negative N-effect of composts ascribed to increasing immobilization processes in soil.

Field experimental studies at three different sites over three years with three different amounts of compost (10 and 20 t dm ha-1 a and 30 t dm ha-1 3a) were conducted to esti-mate the N-effect of compost in combination with additional N supply. A yearly application rate of 10 t compost dm ha-1 according to the official german regulations had no signifikant influence on yield formation in all three vegetation periods. The amount of additional mineral N-fertilizer is calculated with deduction of 10 percent of total compost-N as expected amount of N-delivery in the first year. The results showed a visible lower N-supplying capacity than 10 percent. With aerobic incubation tests the N-mineralization potential of the soils from different treat-ments of long-term field application of composts was investigated. The application of com-post resulted in a significant higher N-delivery compared to the control soils (factor 1,2 – 1,7). It is concluded that applied at moderate rates the N-supplying capacity of compost is very low in the first years of application. However, long-term compost fertilization results in an increase in organic matter (Ct) as well as total nitrogen (Nt) accompanied by a significant higher N-mineralization potential of these soils. As the changing N-supplying capacity of soils with high organic matter content results in in-creasing Nmin-contents this parameter has to be tested periodically and taken into consid-eration when calculating the economically and ecologically optimum N-fertilization of the crops. Only in combination with an adequate mineral fertilization the advantages of an im-proved humus status of the soils with long-term compost application (improved aggregates stability, increased cation exchange capacity and a favourable water holding capacity) can be used effectively. Roth, Annette (1998): Nitrate leaching under excrement patches in relation to the date of grazing and sites. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 151 pages. Nitrate losses in pasture are often caused by highly concentrated N-point-sources from ex-crement patches. A detailed or complete analysis of nitrate leaching in pastures due to the excrement patches is difficult since little information is available on the time of application, the N-concentration and the size of the excrement patches. With a controlled application of urine and dung it is possible to simulate natural conditions in pastures and to investigate the effects of nitrate losses. Our objective was to compare different sites and their potential ni-trate leaching under the excrement patches applied at different times during the grazing sea-son. The effect of excrement patches on nitrate leaching were investigated at two different low mountain sites and one lowland site over three years. Spots of 2,5 kg cattle dung and 2 l artifical urine were applied in four to eight week intervalls during the grazing season on Lolio-Cynosuretum . After each application the N-uptake by biomass was determined. Four weeks after application and during the following winter, soil samples in each treatment were taken on undisturbed plots (n = 4) in four depth from 0 to 90 cm. The results can be summerized as followed: Urine patches cause much greater amounts of mineral-N in soils than dung patches.

Nitrate leaching under urine patches is primarily influenced by the date of application; the site is less significant. The amount of nitrate leached under urine patches is lower after application in spring than in summer or autumn. Dry soil conditions during the growing season caused greater nitrate leaching from urine patches than moist soil conditions. In pastures without N-fertilizer the estimated amounts of nitrate leachate during winter were 10 to 18 kg NO3-N / ha and year depending on the site and 80 to 144 kg NO3-N / ha and year when fertilizer rates of 250 kg N / ha and year are applied. The potential nitrate leaching in pature depends on: ⇒ stocking rate and date of grazing ⇒ conditions in soils for immobilization and mobilization of mineral-N under urine patches ⇒ N-uptake by biomass in patches ⇒ weather conditions after urine secretion in regard to NH3-volatilization and hydrolysis and

mineralization of urine-N during the winter and the amounts of N lost by denitrification. Röttgermann, Martina (1997): Evaluation of stems of silage maize (Zea mays L.) with respect to forage quality by image analysis and conventional methods. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 117 pages. Breeding of silage maize genotypes requires rapid, simple and accurate methods to analyse forage quality of leaf and stem material. The feeding quality of the vegetative plant portion depends on both, the amount of watersoluble carbohydrates and the cell wall content, par-ticularly the incorporation of lignin into the cell walls. The experiments were conducted to investigate the application of image analysis procedures as a screening tool for evaluating forage quality of maize stems. Histochemical reaction of acid-phloroglucinol with phenolic compounds were used to vizualize lignin within maize stem-cross sections. From 1993 to 1995 plants of five maize inbreds and two hybrids were har-vested at late milking stage and silage stage from field plots. Stem-cross sections from the lower seven internodes of the stem were analysed for staining reaction and parenchymal cell density directly after harvest. In addition the contents of lignocellulose, lignin, and water-soluble carbohydrates of the stem material were analysed chemicaly and digestibility of the organic matter were determined by in vitro method. The lignin contents in maize stem tissues were highest in the sclerenchyma (about 7% of the dry matter), that therefore showed a deep red staining reaction with phloroglucinol. The per-cent-area of sclerenchyma tissue in the lower seven internodes of maize stems did not differ between harvest dates and was not related to lignin content and in vitro digestibility of the organic matter when genotypes were compared. Treatments of maize stem-cross sections with phologlucinol resulted in a weakly stained parenchyma tissue in the center of the pith and a brown stained storing parenchyma localized between sclerenchyma and inner paren-chyma. The storing parenchyma was characterized by the highest digestibility due to a 7-10% higher concentration of sucrose and a 3-4% lower concentration of lignocellulose as

compared to the sclerenchyma and the inner parenchyma. The mean percent-area of storing parenchyma of the whole stem and of individual internodes - especially in the third internode from the base of the stem - was positively correlated (r = 0,77 and 0,87) with in vitro digesti-bility of the whole stem of different maize genotypes. Hence, different values of percent-area of storing parenchyma allowed to distinguish between a high, medium, amd low stem di-gestibility of different maize genotypes. During termination of plant growth, the portion of stor-ing parenchyma decreased in favour of parenchyma during maturity. Cell density in the pith of maize stems was not related to in vitro digestibility of the stem material. Saied, Amina Sirag (2003): Differences in NaCl stress tolerance of strawberry cultivars ‘Elsanta’ and ‘Korona’. Institute for Horticulture, Faculty of Agriculture, University of Bonn, 120 pages. In a two-year study (2001 & 2002), strawberry (Fragaria X ananassa Duch.) cvs ‘Elsanta’ and ‘Korona’ showed differences in their sensitivities to NaCl salinity. Frigo plants were were supplied with either (tap water), 30 or 60 mM NaCl applied at a rate of 100 ml four times a week. The results were summarised as follows: 1. Salinity impaired the vegetative growth of both strawberry. The effects were more severe

in the second season than in the first one and the growth of cv. ‘Elsanta’ was found to be more impaired than that of cv. ‘Korona’ indicating a relatively higher sensitivity of cv. ‘El-santa’. Moreover, necrotic symptoms appeared after one month from the start of the salt treatments on ‘Elsanta’ leaves, whereas ‘Korona’ leaves showed no symptoms.

2. Maximum assimilation rates and carboxylation efficiencies, calculated from the A/Ci curves of leaves, were reduced by 39% and 44% in ‘Elsanta’ and by 22% and 34% in ‘Korona’, respectively. Here clear differences between the cultivars in the responses of their photosynthetic systems to salinity could not be detected.

3. A major difference between the two cultivars was found on their leaf Cl- contents. ‘El-santa’ had higher content than ‘Korona’, meanwhile the leaf Na+ content remained unaf-fected by salinity in both cultivars. This suggested that the necrotic symptoms on ‘El-santa’ leaves were due to the accumulation of Cl- ion and that ‘Korona’ was more effec-tive in limiting the Cl- accumulation in leaves compared to ‘Elsanta’. In addition ‘Korona’ was more capable in adjusting its leaf osmotic potential, thus maintaining a lower leaf wa-ter potential than in case of ‘Elsanta’.

4. Strawberry plant may be regarded as a ‘Na-excluder’ as the Na+ content remained rela-tively low on whole plant level. The increase in Cl- content on whole plant was more or less equal in both cultivars. The difference was on the distribution of this mineral among the different plant organs. In ‘Elsanta’ most of the Cl- was found in petioles and leaves, whereas in ‘Korona’ it was found in roots and crowns. So roots of ‘Korona’ were capable in accumulating higher Cl- concentration than ‘Elsanta’ roots and thus preventing it from being further transported to the leaves.

5. Salinity reduced the carbohydrate contents in both strawberry cultivars. The reduction being more pronounced in ‘Elsanta’ than in ‘Korona’. It seemed that the monosaccharides glucose and fructose as well as the disaccharide sucrose were not involved in osmotic adjustment as their contents did not increase.

6. The severe impairment of the vegetative growth in the second season was reflected in the plants’ yield. Both fruit fresh weight and fruit number were reduced by salinity and again ‘Elsanta’ was more affected than ‘Korona’. Salinity also reduced the fruit quality in terms of visual appearance: such as loosing chlorophyll pigment of fruit calyx, which is a measure of fruit freshness, as well as reducing the total soluble solids to titratable acids ratio, which is a measure of fruit taste and flavour.

Saleh, Azzam (2002): Biological and ecological studies on the polyphagous predatory bug Dicyphus taman-inii WAGNER (Heteroptera: Miridae) as a natural enemy of the melon aphid Aphis gos-sypii GLOVER (Homoptera: Aphididae). Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 79 pages. The present research aimed to study the biology and prey consumption by Dicyphus taman-inii WAGNER (Heteroptera: Miridae) by feeding on different age groups of Aphis gossypii GLOVER (Homoptera: Aphididae) as prey at different temperatures in the laboratory. The host plant spectrum for oviposition by the predator was also investigated. Moreover, experiments were conducted to study the interaction of D. tamaninii with other natural enemies and the potential damage it might cause to cucumber. Finally greenhouse experiments were carried out in order to investigate the efficiency of the predator under more natural conditions. The results of the laboratory experiments showed that D. tamaninii was able to successfully feed, develop and reproduce when exclusively fed on A. gossypii as prey at a wide range of low and high temperatures, however a constant temperature of 35+1°C was fatal to the predator. The predatory bug was able to adapt smoothly to fluctuating prey offer and main-tain its capability of oviposition even when the prey was relatively scarce. The average daily prey consumption by the late nymphal instars as well as the adult stage of the predator on A. gossypii was high, where it reached up to 60 aphid/day by the adult female. Although D. ta-maninii showed a clear affinity toward A. gossypii, it accepted also other important pest spe-cies offered as prey. Although cucumber, tobacco and tomato were preferred, the predatory bug seems to occupy a wide plant host range for oviposition. Despite being polyphagous, the predatory bug is not likely going to disrupt the efficiency of some other natural enemies in a biological control program. Investigating the plant-feeding habit of the predator showed that, D. tamaninii preferred leaves to cucumber fruits, a fact that leads to the conclusion that the potential damage to cucumber fruits by the phytophagous predator remains low. In the greenhouse experiments, it was found that the release of 2 D. tamaninii adults per plant was sufficient to achieve up to 90% reduction in A. gossypii population, when the predator was released 1 week after infestation with the aphid. Nevertheless, it is speculated that an earlier release of D. tamaninii would be more effective in the biological control of A. gossypii. In conclusion, D. tamaninii exhibited under laboratory as well as greenhouse conditions many features, which make the predatory bug a very promising natural enemy to be used in framework of a biological control program of the melon aphid on cucumber.

Sausen, Matthias (2001): About the development of a planning concept considering topographic conditions for the use of planting measures in order to prevent soil erosion caused by precipitation in agriculturally used areas with crop rotation. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 223 pages. In order to find the right answers to questions concerning the possibility of an all-year-round vegetation of greenery to provide an effective protection against erosion, a three-year field trial had been carried out during the time from 1987 to 1989. In combination with maize (Zea mays L.) as model plant, 24 by-plants were assessed with a look at their suitability for this purpose. The starting point was the introduction of the different by-plants as catch crops. The evaluation of this field trial showed that particularly hardy by-plants that are able to es-tablish a perennial plant cover, provide a permanent protection from erosion. In order to avoid any impact on the maize´s growth, however, it is required to suppress the high com-petitiveness of these by-plant types during the first development stages of the maize using appropriate soil cultivation measures or the use of herbicides. The currently existing prognosis models quantifying the erosion of the soil offer only insuffi-cient time frames and require expensive empirical examinations. In order to develop a plan-ning concept for the purposeful use of erosion protection measures by planting greenery, an evaluation model was established that offers the possibility to assess the topography- and cut-related risk of erosion within crop rotations on the background of certain land use meth-ods. To determine the specific risk of erosion it is in particular the big variety of land use pa-rameters - resulting from crop rotation and land use - that must be considered besides the main topographic factors. Using rotating model crops it was possible to show - under exemplary topographical and pre-cipitational conditions - which agricultural and vegetational erosion protection measures can be implemented in every single case to decrease the risk of erosion in times of high erosion risk. Schade-Schütze, Anja (2000): Occurrence and biological characterization of Fusarium species in wheat. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 161 pages. In 1995 - 1997 the incidence of Fusarium species and Microdochium nivale in conventional and organic wheat production in the Rhineland area was investigated. The influence of culti-var, nitrogen fertilization and application of fungicides on Fusarium head blight severity and mycotoxin contamination was assessed. The isolation rate of various Fusarium species and M. nivale from plant material was opti-mized using a selective growth medium (Czapek-Dox-Iprodion-Dicloran-Agar). Especially, for low infection levels the isolation rate of pathogens from grain samples was increased signifi-cantly. At harvest, the infection rate of wheat kernels by Fusarium species averaged less than 10 % for all trial sites, whereas kernels were infected by M. nivale by up to 30 %.

In organic wheat production “Toronto” was the most susceptible cultivar tested, whereas “Ba-tis”, with a satisfactory yield level, showed medium susceptibility. During the three years study F. avenaceum was the most common species detected in grains harvested at all sites; there was a tendency of increasing infection rates with F. poae. In organic farming the my-cotoxin level of most of the grain samples was less than 40 µg deoxynivalenol /kg. An in-crease in the infection rate for Fusarium spp. was observed in crops that either received a higher amount of nitrogen fertilization or had been treated with fungicides including active ingredients belonging to the strobilurines. In the latter case increased levels of deoxyniva-lenol were also assessed. For the biological characterization of Fusarium species and M. nivale the pathogenicity and virulence of five Fusarium species and M. nivale on leaves of different wheat cultivars and barley were measured. This method revealed a wide range in virulence among Fusarium species decreasing in the order, F. cerealis, F. culmorum, F. graminearum, F. avenaceum, F. poae and M. nivale. Furthermore, 27 isolates of F. culmorum were characterized using disease severity of had blight of wheat in inoculation experiments, the effect on thousand kernel weight, the virulence of isolates on primary wheat leaves as well as the growth rate on selective media. Analysing these parameters correlations between disease severity at BBCH and the reduction of the thousand kernel weight as well as between thousand kernel weight and the total amount of mycotoxins could be established. In general, deoxynivalenol-producing isolates of F. culmorum reduced the thousand kernel weight to a greater extent than nivalenol-producing isolates. Schäufele, Rudolf (1996): Post-defoliation regrowth of perennial ryegrass (Lolium perenne L.): Cell production, cell growth and C- and N-relations of leaf growth zones. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 96 pages. Post-defoliation regrowth of perennial ryegrass (Lolium pernne L.) was studied in four con-secutive experiments under controlled conditions. After an establishing period of 33 days, which was identical in all four experiments, plants were cut to 5 cm stubble height and ex-posed to different CO2-concentrations, different temperatures, and different nitrogen nutrition during a 14-day post-defoliation regrowth period. The effects of the different growth condi-tions on the development of the above ground plant parts as well as on the supply of the leaf growth zones with C and N were studied. In one of the four experiments the effect of defolia-tion on cellular dynamics within leaf growth zones as well as the contribution of C- and N-reserves to the leaf growth after defoliation was studied in detail. Steady-state labelling tech-niques with 12C/13C and 14N/15N were used to distinguish between pre- and post-defoliation fixed C and N. A new method was developed to study the growth dynamics of cells and the C- and N-relations of leaf growth zones under non-steady growth conditions. Results: Leaf elongation was significantly reduced after defoliation. This was caused by reduced rates of cell production and cell elongation. The changed growth dynamics of cells within the leaf growth zone were, however, not related to a changed supply of the leaf growth zone with C

and N. The reduced tillering rate after defoliation indicated that the available assimilates were preferentially partitioned to existing tillers. The different growth conditions imposed during regrowth differed in their impact on leaf growth and C- and N-relations of the leaf growth zones in the order N >> temperature >> CO2-concentration with the effect of the increased CO2-concentration having an (negative) effect only, when plants were supplied with a N-free nutrient solution after defoliation. Carbohydrate reserves were the main source of carbon for the leaf growth process only dur-ing the first day after defoliation, whereas the supply of the leaf growth zones with nitrogen was at least for two days after the cut mainly dependend on the remobilization on N-reserves. A major fraction of the C-reserves imported into the basal part of the leaf growth zone during this time was associated with nitrogeneous reserves. The results of the present experiment strongly suggest that the contribution of C- and N-reserves to the leaf growth process after defoliation was greatly overestimated in the past. Schelling, Klaus (2000): Aufbau eines operationellen fernerkundungs- und GIS-gestützten Systems zur Zu-standsbeschreibung, Ertrags- und Qualitätsabschätzung von Braugerstenbeständen. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 134 pages. Timely information about the production of malting barley is of great significance for the malting industry in Germany. The supply situation depends on the area cultivated to spring barley, yield, protein content and the graded proportion which is suitable for malting. Yield and quality are strongly influenced by environmental factors - weather being the most impor-tant. In the current thesis it was investigated, how optical-near-infrared satellite images and non remotely sensed data can be utilised in an operational GIS-based system for the estima-tion of barley yields and quality. The analysis of monthly NDVI-maximum value composites from coarse resolution NOAA AVHRR data spanning 5 years indicated a good relationship to the regional average yields. Yield differences between fields can be identified by means of high resolution optical-near-infrared satellite images. In order to derive estimates of the protein contents, a differentiated analysis of the remote sensing data according to the water holding capacity of the soils is indicated. Currently, atmospheric effects and the limited availability of images considerably restrict the operational utilisation of high resolution remote sensing data. Phenological observations turned out to be a valuable source of information. The duration of the grain filling period derived from these data proved to be temperature dependent. Knowl-edge about the length of this development period allows good assessments of the yield level, by means of which quality parameters can be estimated with relatively high precision. In years with high yields, the protein contents and the screening percentages are usually low. The most meaningful parameter for yield estimations is the mean daily temperature between ear emergence and yellow ripeness. The relative humidity proved to be an informative pa-rameter to assess the protein content. It is recommended to evaluate the effects of precipita-tion in conjunction with the relative air humidity.

By means of multiple linear regression approaches using phenological and meteorological data, all three target factors - regional average yields, protein contents and screening per-centages - could be predicted with deviations to the observed values of well below 5 % at the time of yellow ripeness. For an operational application it is recommended to integrate the various information layers into a Geographic Information System. Schenk, Frhr. von Jörg (1998): Investigations about the connection between the site factors, components and sen-sory evaluation of Riesling-wines from the Rheingau area. Institute for Soil Science, Faculty of Agriculture, University of Bonn, 265 pages. In the following research the connection between various site factors and the chemical com-position (wine-chemical compounds, organic acids, minerals, trace elements) as well as the sensory evaluation of Riesling-wines of several vintages (1990-1992) from the Rheingau area has been investigated. The findings of the investigation are as follows: The Vintage can be looked upon as most the important factor for the quantity and distribution of nearly all different fractions, organic acids and minerals in wine. Wines from vintage 1990 have - in connection with below-average grape yields - more ripeness, a higher sugar-free extract and a higher concentration of malic acid, citric acid, N, P, K, Mg, Zn and Mn than the other vintages (1991 und 1992). From climate factors, a high insolation on the sites reduces the sugar-free extract, malic acid and N content and tends to reduce the acid-content of wines. Futhermore, the relationship between organic acids and the trace element contends (Zn, Mn) in wine is sightly influenced by local climate conditions. Among the soil factors calcium carbonate has a direct correlation to the pH-value, but a strong inverse correlation to P content in wines. Besides, a slight influence on the acid and trace element content of wines can be found. A high field capacity on the sites results in a higher pH-value as well as in a higher sugar-free extract, malic acid, N and K content in wines. The P and partly the tartric acid concentration of wines show an inverse correlation to the factor field capacidity. Wines with high pH-values, malic acid, N and K contents grow on loamy, silty soils. Moreover, the Zn and Mn content of wines are influenced by soil conditions of sites, but without any clear tendency. The viticulture region is of great importance for the distribution and amount of the most inves-tigated components in wines. According to the analysis data, especially the sugar-free ex-tract, malic acid, N, K an Mg content of wines increase from the west to the east part of the Rheingau area, whereas the pH-value, tartric acid and P content decrease in the same se-quence. The sensory evaluation shows that there are no extreme sensoric differences in character of the wines grown in various regions of the Rheingau area. Wines from the western part of the Rheingau region represent a light, elegant and sometimes slate taste with pronounced acid-ity and small body, whereas wines from the middle and east Rheingau area as well as Main-gau region have are riper, rounder taste with more body and less acidity.

Scherer, Rafael Alejandro (2001): Mass and Nursery Selection of Yerba Mate (Ilex paraguariensis St. Hil.) for Quality Im-provement in Argentina. Institute for Horticulture, Faculty of Agriculture, University of Bonn, 203 pages. In 1999, an improvement program for Mate quality was initiated among some argentine pro-ducers with the support of INTA Cerro Azul and the University of Bonn, Germany. The main objective was to improve the quality of the yerba mate. Mass selection of superior trees in five different sites as well as combined selection in the INTA breeding material was carried out. Several new characteristics related to the quality and the yield potential were measured both in the field and in the laboratory. Moreover, early selection at the nursery stage was carried out during summer 2001. In this context, it was concluded that: New parameters were determined at field level. However, phenotypic correlations between field observed quality parameters and the most remarkable quality parameters like caffeine content, theobromine content and index saponine were low. New quality indicators at field level should be identified. Marked reversals were found between phenotypic correlations and their corresponding genetic correlations. The genetic nature of caffeine and saponine was strongly additive, contrary to theobromine. The heritabilities of caffeine and saponine were rather high, (h2

ns = 0.83, y h2ns = 0.59 respectively). The theobromine showed itself to be

more dependent on the environment than both other studied characteristics. The high co-heritability of the bound between caffeine and theobromine suggests that additive effects are concurring in the same direction. Mass selection in yerba mate was promising and brings acceptable genetic gains either for the quality parameters or for the production parameters. The genetic progresses in mass selection were generally high and in many instances correlated genetic progress was even higher than the direct genetic progress. A co-related genetic progress of up to 58% for the diameter of the dominant shoot was obtained by selecting for the index saponine. Higher correlated genetic progresses in the males than in the females could be obtained by means combining mass selection with selection index. The heritabilities of the different characters measured in the field were not very encouraging, and all the parameters related to the domi-nant shoots were greatly affected by the environment. However, new parameters should be studied either for the quality or for the production. Cluster analysis proved to be informative in grouping genotypes according to different desired ideotypes. At the nursery level, it is possible to achieve a genetic progress up to 57% for the plants’ height by means of selection indexes and a genetic progress of up to 31% for the number of leaves. The phenotypic correlations among the measured characters in the nursery were higher than the parameters measured in the fields. The parent-offspring regressions yielded unreliable heritability estimates. Up to this point, many of the yerba mate quality and production related desirable characteris-tics could be improved by means of the direct or indirect selection either in the nursery or on the adult mother plants. Four multi-local progeny tests and five large seed gardens were es-tablished for further recurrent selection.

Schick, Hans-Peter (1997): Ecological analysis, assessment in nature conservation and balance of a Westeifel grassland region with regard to the protection of biotic and abiotic resources. Institute for Agricultural Botany, Faculty of Agriculture, University of Bonn, 159 pages. An overall assessment and appraisal of the biotic and abiotic resources has been carried out in the highlands of the Eifel (Municipal of Hellenthal, Northrhine-Westfalia). The investiga-tions concerned a consolidation area of 5 km2, predominantly covered with grassland. The criteria for the assessment of biotic resources were naturalness, intactness, replaceabil-ity, rareness or threat, and their importance for the ecosystem. The evaluation was based on intensive investigations of flora and fauna with special regard to their ecology. The abiotic resources were evaluated by looking at the effects of specific land uses on the regulatory functions of soils on ground- and surface waters, as well as on the atmosphere. Therefore, many chemical parameters of soils and watercourses were analysed. Furthermore, written sources and information of local farmers about fertilisation intensities and crop yields were taken into account. The analyses show that 1.7% of the consolidation area have very high, 33.3% high, 22.2% medium, 44.0% low and 0.8% very low or no importance to the preservation and protection of biotic resources. 95.4% of the analysed area have very high, high and medium importance to the preservation and protection of abiotic resources. The results demonstrate that the cultural landscape is intact and worthy of protection, meet-ing todays standards of nature and environmental conservation in almost the entire study area. Considering the present socio-economic circumstances it seems unlikely that similar results will be found in agricultural landscapes with intensive production levels. The report gives suggestions of possibilities for protecting biotic and abiotic resources in re-gions of significant ecological importance, employing new, comprehensive, and integrated consolidation methods as indicated in Paragraph 1 of the Landscape Consolidation Law (Flurbereinigungs-Gesetz). They include the principle of paying for ecological achievements in agriculture and forestry. Schindler, Matthias (2004): Biology of kleptoparasitic bees and their hosts (Hymenoptera, Apiformes): Field and laboratory studies on Nomada and Andrena. Institute for Agricultural Zoology and Bee Biology, Faculty of Agriculture, University of Bonn, 120 pages. Cuckoo bees of the genus Nomada are obligatory kleptoparasites predominantly associated with hypogeous Andrena species. Field and laboratory studies on the biology of Nomada fucata Panz. and Andrena flavipes Panz. as well as on Nomada fabriciana (L.) and Andrena bicolor Fabr. were conducted. Rearing methods facilitating observations outside the nest and in the underground nest were established. The study focussed on the interactions of parasite and host bees. Moreover mating behaviour of N. fucata and Nomada lathburiana K. was ex-amined.

The kleptoparasitic bees N. fabriciana und N. fucata were established successfully in the cages in the greenhouse and in the field. Observation nests were suitable for N. fabriciana and A. bicolor. The searching behaviour of N. fucata females at host nests followed characteristic se-quences. Parasite females are guided to the host nests by visual and olfactory signals. An-tagonistic behaviour between host females and cuckoo bee was observed at the nest en-trance and within the underground nest. Analysis of phenological data suggests that females which emerge early in the flight season and females with a longer lifespan can provision off-spring under lower pressure of parasites. The comparison of the diurnal activity of N. fucata and A. flavipes females showed no significant difference. The results of morphometric ex-amination do not allow a conclusion as to whether females of N. fucata are able to evaluate the size of brood cells or the quantity of larval food. Studies with emergence traps revealed a female biased sex ratio of A. bicolor and A. flavipes. In the field nests of A. flavipes were parasitized by N. fucata as well as by flies of the families Bombyliidae and Anthomyiidae, those of A. bicolor exclusively by N. fabriciana. Rates of parasitism of host species in the field and in greenhouses did not differ significantly. Compared with single nests nest aggre-gations of A. flavipes were parasitized more intensively. Analysis of the phenological data of N. fabriciana showed three groups which presumably represent two taxa. Further studies suggest that phenological barriers prevent taxon 1 and taxon 2 from interbreeding. Field studies on mating behaviour revealed that males of N. fucata patrol together with males of Andrena flavipes Panz., the host species, at foraging plants and above entrances of the fossorial host nests. Males of N. lathburiana did not patrol potential rendezvous sites. In the lab details of the courtship behaviour of N. fucata und N. lathburiana could be recorded for the first time. Males repeatedly wind their flagella around the females’ antennae and then pull their flagella upwards so that they glide over the females antennae. Results of morphological (LM and SEM) and histological studies of the males’ antennae indicate that Nomada males communicate sexual pheromones excreted from antennal glands to the antennae of females during courtship. Schlüter, Bernd (1997): Development of a methodology for measurable and reproducible summary evaluation of the repercussions of crop rotation and cultivation systems on the agricultural-ecological system of a location. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 111 pages. Evaluating of the repercussions of croprotation and cultivation systems on the agricultural-ecological system of a location requires necessarily a system approach, which covers in a first step all the objectively relevant influencing systems and thus avoids a subjective pre-filtering of influencing systems having potentially an impact on the result. In order to allow that system approach all the influencing systems, which have a direct or indirect effect on the agricultural-ecological system, are determined to begin with. The individual influencing sys-tems have to be recorded in such a way that comprehensive characterisation of the entire system is possible. In this respect, at least one characteristic per influencing system is re-

quired. If several characteristics are recorded for one influencing system, then only the mean value of these characteristcs is entered in the evaluation. On the one hand the problem of unifying the various dimensions of the characteristics arises, on the other hand a reference value, by which the evaluation can be determined by means of its difference to the promi-nence of the characteristics that was actually measured, is needed for each of the character-istics examined. Accordingly, the distinctive features of the characteristics that were measured are converted into rating numbers. At the same time, the difference between the distinctive feature found in each case and the mean value of the data collected in the characteristic group is put into relation to the spread (variation range) determined of the respective characteristic. The refer-ence values are also converted into rating numbers. Determining the individual reference values takes place either as a result of statutory specifications (for example, no nitrate in drinking water) or as a result of rationally specified dimensions. The presentation of all influencing systems and the relevant reference values of an agricul-tural-ecological system in just one network diagram allows the observer, according to the type of efficiency analysis, an evaluation at a glance. Since he sees how far away the value of an influencing system that was actually measured is from the reference value, he can in addition individually consider whether he decides against a specific crop rotation (or a culti-vation system), because in a certain influencing system one reference value remains under-shot or whether as a result of the distinctiveness of other influencing systems this is compen-sated to such an extent that the decision can nevertheless be made in favour of the specific crop rotation (or a cultivation system). In most cases therefore, this kind of evaluation amounts to finding a compromise. Schlüter, Wilhelm (1997): Cations and anions contents in the soil solution and in the high level ground water under organically and conventionally cultivated farm land of the river flood plain Sieg as well as the simulation of the nitrogen-dynamic and nitrate-leaching. Institute for Soil Science, Faculty of Agriculture, University of Bonn, 203 pages. Over a period of two years the dynamics of cations and anions were investigated in weakly to moderately acidic Fluvi-Eutric Cambisols of a river flood plain of the Rhine tributary Sieg (Nordrhein-Westfalen, Germany). The soils were cultivated according to organic and conven-tional farming systems. Under a surface area of 9 m² in different depth (every 30 cm) of dif-ferent thick soils (up to 180 cm) soil solutions were sampled by ceramic suction cups and analyzed for the contents of selected elements. The investigation of the small scale variability in different depths of two soils showed, that the installation of 6 suction cups per depth step was sufficient to get representative values of the Na+-, Mg2+-, Ca2+-, NO3

--, SO42-- and Cl--concentrations, whereas the values of the K+- and

DOC-concentrations are partly uncertain. For the most of the analyzed soil solution contents the investigations showed typical time series which reflect the seasonal and agricultural conditions very well. The leaching of the cations Na+, K+, Mg2+ and Ca2+ as well as the leaching of the anions SO4

2- and Cl- were quantified with the help of their concentrations in the soil solutions underneath the rooting

zone. The interpetation of the NO3--dynamic was possible by model calculations using the

DELPHI model, which first had been calibrated by tracer experiments with Cl-, Br-, NO3- and

SO42-.

During the tracer experiments in addition to the sampling of soil solution by suction cups at definite time intervalls soil material was taken from different depth to produce soil saturation extracts. The concentrations of the non-adsorbed anions Cl-, Br- and NO3

- were very similar in the suction cup solutions and in the saturation extracts, whereas the concentrations of the weakly adsorbed SO4

2- partially showed considerable differences. Obviously both methods extract in acid soils different fractions of the dissolved sulfate. By comparing marked sulfate peaks with those of chloride, bromide or nitrate, which occur at the same time in different soil depth, a Kd value for sulfate of 0,16 l/kg can be calculated for the Ap horizon and of 0,02 kg/l for the subsurface horizons of one Fluvi-Eutric Cambisol. Values of the dispersivity of the different horizons were estimated by varying the values of the dispersivity reported in the literature until the best fit of the simulated anion depth distri-bution to the measured values was found. The estimated dispersivities varied between 1 cm in the Ap horizon and 10 cm in the subsurface horizons. In the course of simulating the NO3

--dynamic by means of the calibrated model N-mineralization and N-leaching were quantified. For different crop residues reaction coeffi-cients for the mineralization of the easily decomposed organic material were calculated. They were extremly high for bean residues (19.0 × 1012 × exp (-9800/T)) and mustard-vetch resi-dues (12.0 × 1012 × exp (-9800/T)). The lowest reaction coefficient of 3.0 × 1012 × exp (-9800/T) was calculated for the decomposition process during winter time. For the two farming systems a detailed N-balance was calculated. It is shown that under conventional farming over a time period of two years 199 kg N/ha were leached. Within the same period 53 kg N/ha were leached under organic farming with the cultivation of intercrop, which reduced the leaching of nitrate. The partly considerable losses of NO3

- in the investigated soils results in increasing NO3--

concentrations in the high level ground water under conventional and organic farming. Tem-porary the treshold value for NO3

--concentration of the drinking-water was exceeded. Schmid, Joachim (1998): Sap flow measurements in grapevines. Institute for Horticulture, Faculty of Agriculture, University of Bonn, 164 pages. The Granier system for measuring sap flow in intact plants was adapted to grapevines. Cut stem segments were used to test the system with known flow rates. The relation between sap flux density (u) and sap flux value (K) was confirmed for flow rates up to 17 m * h-1. E-ven higher flow rates of up to 29 m * h-1 resulted in a systematic underestimation up to 7,2 %. A long time comparison showed good agreement between sap flow measurements and gravimetrically determined water loss. The difference between both measurements was generally less than 10 % for daily values and between 10 and 25 % for hourly values. Over a continuous measuring period of 84 days close agreement was found between both meas-urements.

Large differences were found in water use between different vines in the field. However, when calculating water loss on the basis of leaf area, differences between vines could be eliminated. Sap flux density was thus directly related to leaf area of individual vines. Stem cross sectional area did not limit water use. The daily course of sap flow was closely related to environmental factors of which light and vapour pressure deficit had the greatest influence. High rates of sap flow were always correlated with high rates of photosynthesis. Water stress inhibited both, sap flow and photosynthesis. A high rate of sap flow at night was always cor-related with high respiration rates. A sudden reduction in leaf area resulted in a proportional increase in sap flow per unit leaf area. In a comparison of different rootstocks large differences in growth were seen between these rootstocks. However, when calculating sap flow on a leaf area basis, no differences were found. During a period of 85 days vines on "Sori" used around 91 l * m-2 of ground area, whereas those on "Börner", "5 BB" and "SO4" used between 117 and 130 l * m-2 of ground area. Schmitz, Astrid (2005): Suitability of different remote sensing techniques for the detection of Heterodera schachtii infestation on sugar beets and possibilities for site-specific nematode con-trol. Institute of Crop Science and Resource Conservation, Faculty of Agriculture, University of Bonn, 113 pages. Greenhouse experiments with increasing H. schachtii densities and with different sugar beet varieties were conducted to detect H. schachtii infestation and to differentiate between vary-ing nematode infestation levels using remote sensing methods. Gas exchange parameters, nitrogen and chlorophyll content of sugar beet leaves as well as SPAD values were meas-ured in intervals up to seven days after nematode inoculation. Parallely, high resolution re-mote sensing images were taken from a near distance by a multispectral and a thermal cam-era. In addition, laser induced and pulse amplitude modulated chlorophyll fluorescence data was collected. Sugar beet plants reacted to H. schachtii infestation initially with a decrease in photosynthesis rate and later with an additional reduction in nitrogen uptake and chlorophyll concentration. In this study, sugar beet leaves infested with 500, 1000 or 1500 juveniles/100 ml of soil did not differ either in reduction of nitrogen or chlorophyll content nor in photosyn-thesis and transpiration rate. During early stages of nematode infestation it was possible to differentiate H. schachtii infested sugar beets from uninfested control plants with LIF parame-ters F740 and 'Integral of spectrum'. Later stages of infection were accompanied with degra-dation of chlorophyll content that led to an increase of F686/F740 ratio and ground fluores-cence (Fo) and a decrease in photochemical efficiency (Fv/Fm). However, a discrimination of the different H. schachtii infestation levels was impossible by means of applied fluorescence techniques. Multispectral images of infested plants showed significantly lower NDVI and GNDVI values at later stages of infection, 28 and 35 days after inoculation. At this stage a differentiation between infestation levels was possible by means of multispectral imaging. Only during early stages of nematode infestation, 7 days after inoculation, the sugar beets

showed higher transpiration rates and leaf temperatures compared to healthy plants. Sugar beets infested with 500, 1000 and 1500 juveniles/100 ml soil did not differ in their leaf tem-peratures. To detect H. schachtii infestations in the field, crop canopy temperature of two different sugar beet fields infested with increasing nematode densities were measured from a helicopter with a thermal infrared camera at 8000 to 12000 nm. At one experimental site, high nematode infestation (> 1500 eggs + juveniles/100 ml soil) led to an increase in canopy temperature of the sugar beets up to 0.83° C compared to low infestation levels (< 500 eggs + juveniles/100 ml soil). Temperature differences were only evident when adequate soil moisture was available for proper crop development. Although environmental conditions of both experimental sites were similar, data from the second field experiment did not show any temperature differences between low and high infested sugar beets. This demonstrated the difficulties in reliability using airborne thermal images for detecting nematode infestation. Should differentiation between different nematode infestation levels within a field be possible, growers could vary use of resistant cultivars, break crops as well as biological or chemical nematicides. In this study, the egg parasitic fungus Paecilomyces lilacinus strain 251 (PL251) was tested for control of H. schachtii. In pot trials cysts were exposed to different concentra-tions of PL251. Higher doses of PL251-conidia resulted in increased egg parasitism and mor-tality of H. schachtii juveniles as well as in significant lower numbers of juveniles penetrating the root system. The best level of biological control of H. schachtii was achieved at tempera-tures above 25° C and at densities of 107 conidia/g soil. Schneiders, Markus (1998): Studies on the significance of nonexchangeable ammonium in wetland rice with atten-tion to the influence of redox potential in the root zone. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 178 pages. A series of pot experiments was conducted to evaluate the effect of waterlogging on the dy-namics of nonexchangeable ammonium in soils, and on the availability of this N fraction to rice plants and its contribution to N nutrition. Apart from studying the influence of certain soil characteristics on the fixation of ammonium special attention was given to the role of soil redox potential. Waterlogging of soils did not generally lead to a decrease in the concentration of fixed am-monium, nor did it lessen the NH4+-fixing capacity. In fact, high net mineralization of soil N caused a significant increase in nonexchangeable NH4+ even without mineral N fertilization. Nitrogen amounts applied with ammonium sulphate solution were completely fixed by clay minerals although only a small part of the freshly fixed NH4+ originated from the 15N labelled fertilizer itself, because of a pronounced N pool substitution. Timing of NH4+-fertilizer appli-cation appears to have little impact on ammonium fixation in submerged soil while puddling may enhance interlayer adsorption of ammonium. Content of illite and potassium saturation were major influential factors for the dynamics of nonexchangeable ammonium in flooded soils. Recently fixed ammonium was not released in fallow soils over a period of 15 weeks of sub-mergence and showed little variation during drying and rewetting of soils. On the other hand it was highly available for rice plants. In the rhizosphere release of recently fixed NH4+ was

complete and a concentration gradient developed around the roots. Dense root growth caused the depletion of newly fixed ammonium even with high levels of mineral N fertiliza-tion. Release of interlayer ammonium correlated with the nitrogen uptake of plants and its contribution to rice N nutrition ranged up to a maximum of 89 %. Dynamics of nonexchangeable ammonium significantly correlated with soil redox potenital: Fixation of ammonium occurred when the Eh declined to reducing conditions, while NH4+ mobilization was promoted by the oxidation of the rice rhizosphere. Rice cultivars differed in oxidizing power and ability to release fixed ammonium. Some possible explanations of the dependence of ammonium fixation on redox potential in waterlogged soils are thoroughly discussed in the present study. Schoene, Philip (2003): Ulocladium atrum as an antagonist of grey mould (Botrytis cinerea) in grapevine. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 104 pages. Plant diseases inhibiting cultivation of crops are typical of intensive agriculture and plant pro-tection measures with frequent applications of pesticides are therefore required. Problems occur by using chemical pesticides: e.g. development of resistance to pesticides and side-effects on beneficials and the environment, which calls for new strategies of crop protection. Botrytis cinerea (Pers.), one of the main pathogens in grapevine, Vitis vinifera L., is capable of infecting leaves, stems, flowers and fruits and reduces quality and quantity of yield. The saprophytic hyphomycet Ulocladium atrum (Pers.) proved to be antagonistic to B. cinerea in some crops, reducing growth and sporulation of the pathogen by competition for nutrients and space, limiting the epidemic spread of B. cinerea on plants and within the crop. The efficacy of U. atrum for biological control of grey mould in grapevine was assessed un-der controlled conditions and in field studies. The antagonist reduced the development of B. cinerea in vitro and on necrotic and healthy grapevine leaf material, respectively. U. atrum reduced spore production of the pathogen on mature grapevine berries as well as sporulation of sclerotia. Competition for nutrients and space proved to be the principal mode of action. The antagonist showed, similar to the pathogen, an ecological fitness persisting unfavourable climatic conditions under controlled conditions and in field experiments. Moreover, a low sensitivity of U. atrum to many pesticides enabled an integration of the antagonist into con-ventional crop protection measures. Direct combination with some pesticides as tank mixture resulted in a lower vitality of the antagonist and therefore reduced its efficacy. Nonetheless, alternating treatments with pesticides and the biocontrol agent are a potential strategy to enrich strategies of integrated crop protection. Large-scale experiments on biological control of grey mould by U. atrum were carried out in white grapes in 1997-99 in three German vine-growing areas. Three to four applications of the antagonist reduced B. cinerea effectively on plant tissue during the season and on ber-ries at harvest. Furthermore, a reduced air-load of B. cinerea conidia was measured before vintage in 1997. This indicates that an effect of U. atrum could be enhanced when the an-tagonist is applied over a much larger area. The potential of this biocontrol agent was shown applied alone or combined with botryticides. In all three seasons with low to moderately high disease pressure, grey mould was reduced by U. atrum alike chemical botryticide treatments.

Nonetheless, at a high disease pressure of grey mould, an integrated approach together with chemical control and biological control measures should be envisioned. Negative effects of U. atrum were observed neither on plants, inflorescences and berries nor on vinification. Hence, the antagonist provides a suitable biocontrol agent for grey mould in grapevine, and it can be used in both, biological and integrated crop protection. Schöning, Alexander (2000): Influence of chemical properties of forest soils on earthworm populations – implica-tions for soil liming. Institute for Soil Science, Faculty of Agriculture, University of Bonn, 343 pages. The influence of soil-chemical properties on earthworms was investigated in soils of loess in the Kottenforst area near Bonn. Limed and partly P,K-fertilized plots as well as untreated plots were used for this purpose. The investigation focused on the mobile, i.e. potentially bio-available element fractions. For the liming-/fertilizing-experiment, six differently treated plots each in deciduous and spruce forest were established at acidic Stagnic Alisol sites in 1994/95. The treatments were 0, 3, 6 t dolomite ha-1 without P,K-fertilizer and 6, 9, 15 t dolomite ha-1 combined with P,K-fertilizer. In order to re-establish endogeic and anecic lumbricid species, we tried to colo-nise these species in the different plots. Samples were taken every six months during 1993 to 1998. Depending on the amount of lime, especially in the deciduous forest, the treatments led to significant positive changes in soil chemical properties. In the soil depths which were influenced by liming both the pH(CaCl2) and the content of mobile Ca and Mg increased, whereas the content of mobile heavy metals and Al was reduced. The content of mobile P, K and S only changed negligibly even in the P,K-fertilized plots. Neither decomposition of hu-mus stock nor leaching of NO3 could be observed with the sampling method used in our in-vestigations. However, a slight leaching of some heavy metals and Al could not be ruled out. Corresponding to the different depth effects of the treatments on the soil chemical properties, their influence on the lumbricids was also different in deciduous and spruce forest. In the deciduous forest the number of species as well as abundance and biomass, especially of the endogeic species, already increased during the first year after the treatments. In the spruce forest, however, lumbricid abundance and biomass increased only 3 years after the treat-ments. The investigation of the untreated plots showed a large variation of soil chemical properties. Accordingly, big differences in the earthworm populations were observed. Repre-sentatives of epigeic, intermediate, endogeic and anecic lumbricids were found. The correlation analysis for the whole data indicated that there is a strong relationship between the genus Aporrectodea and soil chemical properties of the top soil. The “acid com-ponent” extracted by major component analysis was found to be the main factor of influence. This component includes the pH(CaCl2) as well as the content of mobile Ca, K, Fe, Zn, Al, Cd and Pb. The genus Dendrobaena and the species L. rubellus proved to be highly inde-pendent from the examined soil chemical properties. The anecic species L. terrestris also showed no close relationship to soil chemical properties in the top soil. Obviously L. terrestris

is able to compensate for relatively unfavourable conditions in the top soil by favourable con-ditions in the bottom soil. We concluded that a significant improvement of soil chemical properties with simulta-neous promotion of especially endogeic lumbricids can only be achieved at pH values of at least 4.5. In order to attain this target pH value, different amounts of lime are required de-pending on the soil properties. In any case liming should be repeated at intervals of a few years. Scholz, Uwe (2001): Biology, pathogenicity and control of the cereal cyst nematode Heterodera latipons Franklin on wheat and barley under semiarid conditions, and interactions with com-mon root rot Bipolaris sorokiniana (Sacc.) Shoemaker [teleomorph: Cochliobolus sati-vus (Ito et Kurib.) Drechs. ex Dastur.]. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 159 pages. The results are presented in eight chapters. The introduction (Chapter I) gives an overview about the agro-ecological conditions for cereal production in the Near East as well as litera-ture review specifically related to the research topics investigated in this work. The second and third chapter describes the hatching behavior and life cycle of H. latipons. Experiments demonstrate the adaptation of H. latipons to low temperatures (5°C - 10°C) with maximum hatch of 45% of the cyst content per vegetation period. The juveniles of H. latipons emerge from the cysts in December and reach the highest concentration in soil in January and February. H. latipons multiplies on seminal and nodal roots of barley. The host range status of barley, oat, durum and bread wheat varieties is investigated in the fourth chapter. Almost 40% of the barley and most oat varieties of the International Differen-tial Set for cereal cyst nematodes as well as the majority of barley varieties adapted to the Mediterranean environment are good hosts for H. latipons from the dry agro-ecological zone. All wheat varieties investigated are resistant to this population. Pathotype I from the dry zone is prevalent on barley and pathotype II from the wet zone is able to attack barley and wheat. In chapter V the pathogenicity of B. sorokiniana to barley under controlled conditions is de-monstrated for the application of mycelium and conidia of the fungus. Pathogenicity is ac-companied by severe infection of the crown of barley. The joint and separate impact of nematode and fungus on barley is investigated in chapter VI, VII and VIII. The early infection by H. latipons followed by B. sorokiniana nine weeks later as well as the simultaneous attack of nematode and fungus result in the strongest reduction of grain and straw yield and increased the B. sorokiniana infection of crown and subcrown internode compared to the application of the fungus alone. Under the presence of B. soroki-niana, the multiplication of H. latipons was reduced. H. latipons has a severe impact on grain and straw yield of barley under unrestricted water supply and a slight impact under drought stress, while the pathogenicity of B. sorokiniana is only expressed under drought stress con-ditions. Root length and root weight is reduced by the nematode under unrestricted water supply and the fungus reduces root weight and root length as well as the number of heads under drought stress. H. latipons reduces the water use efficiency related to grain and straw

yield regardless the water supply level, while B. sorokiniana reduces the water use efficiency only at unrestricted water supply. The damage threshold of H. latipons for barley and durum wheat is 5 e+j/g and 10 e+j/g soil in the dry and wet zone respectively. Barley and durum wheat grain yield is reduced in the dry and wet agro-ecological zone, respectively, while bread wheat tolerated the infection in both zones (Chapter IX). Schröder, Stefan (2001): Automated Identification of bee species (Apidae, Hymenoptera) using image analysis of the wing venation and statistical classification procedures. The usefulness of modern computer technology as a method for species identification was examined in this study. The classification concept is based exclusively on characters of the forewing venation. These are extracted from digital wing images by automated image analy-sis. It should be possible to use the system to identify living bees in the field. The hardware of the system consisted of a laptop computer connected to a CCD camera mounted on a stereomicroscope. The image analysis used in this work involved two steps. First, the user had to mark defined vein junctions by a mouseclick. The program then auto-matically connected the junctions by line-following and thus digitised the whole venation. Identification tests were made for closely related species of the bee genera Colletes and Bombus. The investigations provided the following results: With a training set of approximately 30 well-classified specimens per species, the rate of cor-rect identification was 98,5% for morphologically very similar Colletes species. These spe-cies have a solitary mode of living. The recognition rate was 94,8% for the tested Bombus species, which have a social mode of living. Males and females showed a great conformity in venation characteristics. Clusters of males and females of one species had smaller distances in cluster analysis than the clusters of dif-ferent species. Most reliable species identification was achieved when males and females were classified together in the discriminant analysis. The field investigations revealed the following results: The system performed well under field conditions. It was possible to make wing images of living bees. Individuals of Colletes cunicularius from different sample locations less than 20 km apart showed very small or no differences in the characteristics of wing venation. Individuals from locations separated by a distance of 750 km, however, showed significant differences. These experiments proofed that wing venation can be used as an exclusive indicator for the identification of closely related bee species. Apart from species identification, further applica-tions for the automated morphometry of wing venation were demonstrated. These include the rapid generation of hypothetical phylogenetic trees, the assignment of a previously unknown sex to its species, and zoogeography.

Schulte auf’m Erley, Gunda (2001): The Nitrogen and Carbon Allocation of Grasses with differing Growth Dynamics (Lo-lium perenne L. and Festuca rubra L.). Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 82 pages. The species composition on permanent grassland is influenced by environmental effects like climate and soil. Especially a high intensity of nitrogen fertilization leads to a shift of the spe-cies composition to nitrophilic species. Environmental effects on the floristic composition of a grassland sward are sufficiently documented; however, the physiological and morphological features that contribute to the adaptation of the dominating species in a habitat, are not well understood. In the present work stable nitrogen and carbon isotopes were used to compare the carbon- and nitrogen-economy of two grass species (Lolium perenne and Festuca rubra), that differ strongly in their nitrogen demand. The allocation of nitrogen and carbon within the plant dur-ing seedling establishment were of special interest in this study. Both species were raised at high (N+) and low (N-) nitrogen availability on nutrient solution and under controlled condi-tions. It was assumed, that the species do hardly differ in their instantaneous efficiency of the nitrogen- and carbon-economy, but that there are differences in the reutilization of previously gained assimilates. L. perenne had a 20 % higher relative growth rate (mg g-1 d-1) than F. rubra, when grown under N+. Under N- there was almost no difference in the relative growth rate between both species. The potentially higher growth rate of L. perenne was caused mainly by a higher specific leaf area (mm2 mg-1) of this species. The nitrogen efficiency (g g-1 N d-1) of L. perenne under N+ was about 10 % higher compared to F. rubra, but approximately the same between both species under N-. The photosynthetic nitrogen use efficiency of the individual leaves of L. perenne was under N+ nearly two times higher than in F. rubra, but nearly the same in both species under N-. A reutilization of nitrogen and carbon assimilates from senescing leaves could be detected for both species. Differences between the species in the quantity of the retranslocated car-bon or nitrogen or any preference in the site of allocation could not be proved. However it was detected in a partial experiment, that F. rubra was able to export and thus reuse clearly bigger proportions of the nitrogen assimilates, that were present in the fully expanded leaf. Siepen, Achim (1999): Suitabilitiy of the CaCl2 extractable Norg-fraction to characterize the easily mineralizable N in soils and the effects of additional consideration of this index in the Nmin-supported fertilizer recommendation to maize. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 169 pages. The aim of this study was to investigate, if the site-specific capacity of N-mineralization of soils can be characterized by the CaCl2-soluble organic N-fraction (Norg) and if this index can provide information about the nitrogen mineralization to be expected under field conditions. Further it

should be analyzed if the nitrogen fertilizer recommendation of maize according to the Nmin-method could be improved by taking the Norg-content of soil into account on sites with over- or underaverage mineralization potential. Laboratory and field experiments were conducted in the years 1992-1994. The trials were located in a bordered natural area with homogeneous and predominately sandy soils in the Northwest Münsterland. A relationship between the CaCl2-extractable Norg-fraction and the nitrogen mineralization of soil could be shown by incubation under laboratory conditions for the investigated locations. Under field conditions there were also references to a causal connection between these indices. On plots without nitrogen fertilization nearly half of the variation of nitrogen mineralization (47%) could be explained by the CaCl2-Norg-content. Principally the correlation between this index and the nitrogen mineralization increases during the vegetation period. Consequently, the Norg-fraction possibly can be used to consider nitrogen mineralization of different locations in the fertilizer recommendation especially for cultures with growth periods until autumn. In several nitrogen fertilization experiments to maize the effects of modifying the Nmin-supported fertilizer recommendation in regard to a Norg-content-classification-system on the yield of maize and the risk of nitrate leaching were investigated. This classification system means that the nitrogen fertilization according to the Nmin-method has to be reduced on sites with high Norg-contents and increased on locations with low Norg-contents. Evaluating those field experiments, there were only low differences between the several variants of nitrogen fertilization in regard to the yield of maize and to the Nmin-content of soil after harvest. However it was conspicuous that in the trials only negative N-balances were determined. Taking into consideration these N-balances, the Norg-content-classification-system on the groundwater sensitive soils in the investigated area is positively to be judged, because on the one hand the nitrogen reserve on high supplied soils could be reduced without negative effects on the yield of maize and consequently, the medium-term risk of N-losses out of the soil-plant system could be decreased. On the other hand an increased N fertilization on locations with lower nitrogen reserves leads to equalized N-balances and so the risk of decreasing soil fertility could be reduced. In supplementing experiments on maize plots without nitrogen fertilization outside of the abovementioned area there were no sufficient references to a relationship between the CaCl2-Norg-content and the nitrogen mineralization of soil. Therefore a transfer of the results to other and possibly greater natural areas is not practicable without additional detailed research in those special regions. Singh, Parmjit (1998): Carbon uptake and biomass production as affected by leaf area development and pho-tosynthetic rate in kohlrabi and strawberry under adequate and low phosphorus sup-ply. Institute for Horticulture, Faculty of Agriculture, University of Bonn, 126 pages. Carbon uptake and biomass production of plants depend on the size of CO2 assimilating leaf area, height of photosynthetic as well as respiration rates. On the other hand, all these are affected by the availability and uptake of essential nutrients as phosphorus (P). P may be-

come a limiting factor due to declining P reserves and a quick increase of demand to fulfill the rising food requirement of a fast growing world population. P fertilization of crops and knowledge about threshold values of P concentration in plant organs for optimal vegetative and reproductive growth is necessary. A minimum threshold P concentration was to be found for leaf area development, net photosynthesis, chlorophyll fluorescence, dry matter accumu-lation, nutrient uptake and carbohydrate partitioning between different plant organs of kohl-rabi (Brassica oleracea var. gongylodes L. cv. Quickstar) and strawberry (Fragaria x ananassa Duch. cv. Elsanta). The plants were cultivated in plastic containers filled with acid-washed sand and supplied with adequate (0.5 mM) or very low (0.005 mM) P over a 28 day period. All plants during the experimental period were placed in a greenhouse and random-ized in blocks. Leaf area per plant in kohlrabi declined when leaf P concentration was 0.40% and in straw-berry when leaf P concentration was 0.15% on dry weight basis. Net photosynthesis, transpi-ration rate and stomatal conductance in kohlrabi and strawberry declined at leaf P concentra-tion of 0.15% and 0.09%, respectively. Minimum fluorescence yield of dark-adapted leaves (Fo), maximum fluorescence yield of dark-adapted leaves (Fm), and non-photochemical quenching (qN) increased, while optimal quantum yield of PS II (Fv/Fm), actual quantum yield of PS II (∈F/Fm )́, and photochemical quenching (qP) decreased under low P. The pho-tosynthetic capacity at leaf P concentration of 0.15% in kohlrabi and 0.09% in strawberry was limited by processes associated with dark reactions of photosynthesis, while at 0.10% (in kohlrabi) and at 0.05% (in strawberry) leaf P concentration, photosynthetic capacity of leaves was affected by both light as well as dark reactions of photosynthesis. Chlorophyll contents and the a/b ratios declined when leaf P concentration was as low as 0.003% in kohlrabi and 0.05% in strawberry. Low P resulted in decreased dry weight of leaves, petioles, fruit, stem and roots. Relatively more dry matter was accumulated into the roots than in the shoots. Relative growth rate, leaf weight ratio, tuber weight ratio and tuber root ratio decreased, while specific leaf weight and root shoot ratio increased under low P in comparison to control. Low P rapidly reduced tissue P concentration as well as total uptake of C, N, P, K, Ca and Mg and increased the partition-ing of photosynthates from shoots to the roots. Low P resulted in the accumulation of carbo-hydrates especially starch in all the plant organs particularly in the leaf blades of both the species. Under low P in kohlrabi and strawberry, total carbon as well as uptake of carbohy-drates was reduced as a result of decline in leaf area development and then further de-creased by the reduction in leaf P concentration because of its effects on photosynthesis. Skrobek, Anke (2001): Investigations on the effect of entomopathogenic fungi on whiteflies. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 128 pages. The entomopathogenic fungus Paecilomyces fumosoroseus is well-known for its broad host-spectrum and efficacy against many kinds of insects. Although its effectiveness against soil-borne arthropods has already been described over 100 years ago, Metarhizium anisopliae has only recently been cited as pathogenic to homopteran pests. In the present study diffe-rent isolates of both microbial control agents were evaluated for their potential to control the

whitefly species Trialeurodes vaporariorum and Bemisia argentifolii. Whiteflies are one of the most important arthropod pests of greenhouse and field crops, B. argentifolii occurring mostly in tropical and subtropical climates and T. vaporariorum being the pre-dominant species in Northern Europe. Many isolates of P. fumosoroseus and M. anisopliae, originating in different climatic regions, were found to be effective against all larval stages of both whitefly species. For the integration of this biological control agent into crop protection systems, a possible synergism between the entomopathogens and insecticides from the group of the chitin syn-thesis inhibitors was investigated. Although fungi and insecticide acted synergistically when applied with a time interval, control of whiteflies was not sufficient for an effective, practical pest control. In contrast, corresponding investigations on Spodoptera littoralis, the Egyptian cotton leafworm, gave high mortality levels and thus offered good prospects for reducing the pesticide input. Different oils, waxes and polymeric additives were examined for their ability to enhance the efficacy of the biological control agents. Two polymeric additives were found to increase the shelf-life at room temperature of conidia of M. anisopliae when conidia were dried within the formulation. Microscopical studies using fluorescence, low temperature scanning electron and confocal laser scanning microscope indicated positive effects of Addit ® (Koppert, Neth-erlands) and a polymeric additive on the distribution of formulations –and hence conidia- on leaf and insect surfaces. Spore germination, speed of kill and mortality of the target insect were also found to be enhanced. Both additives offered good prospects for optimising the efficacy of entomopathogenic fungi against B. argentifolii and T. vaporariorum, thus indicat-ing high potential for the integration in the framework of an IPM strategy. Sökefeld, Markus (1997): Automatic identification of weed seedlings using digital image analysis. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 60 pages. Digital image analysis was used to identify weed seedlings of 25 species. Those species are typical of a weed vegetation in Western European sugar beet fields. Images were taken with a black-and-white CCD-camera sensible for near-infrared light. A band filter (740 nm) was mounted in front of the camera lense to exclude visible light below 740 nm. All images were digitized with a personal computer (66 MHz) and a video-board. Identification was based on shape parameters including roundness, compactness, area and 40 Fourier descriptors of the external contour. These parameters were calculated for all weed seedlings in the image. A data base of characteristic seedlings for all species was created to compare and identify weed seedlings of the same species in the field with two classification methods. The average rate of identification was 69,3%, ranging from 100% for Brassica napus to 44% for Viola ar-vensis. The rate of identification depends on the classification method and the number, weight and order of parameters which were calculated from the external contour. The aver-age identification rate was 80,2% when all species were grouped into classes with similar sensitivity to herbicides commonly applied in sugar beet fields.

The system was automated to allow the analysis of larger numbers of images. This is impor-tant for future applications of the system in the field with a camera mounted in front of the tractor. Weed species identification is needed to select postemergence herbicides and to assess weed seedlings distribution in the fields. It is expected that herbicide use can be re-duced when only selective herbicides are applied and when weed control is limited to field areas where weeds are present. Sonntag, Maria M. (2003): Accelerated Microbial Degradation of Fenamiphos (a.i. Nemacur®) in Soils: Soil Re-covery Study with Identification of Some Microorganisms Responsible for Degrada-tion. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 187 pages. Accelerated microbial degradation (AMD) of the nematicide fenamiphos (a.i. of Nemacur®) in field soils is due to a selective build-up of microbial species capable of degrading the com-pound at very high rates. Fenamiphos-AMD is provoked by the overuse of Nemacur® in the field, and in most cases, the high rates of degradation cause a reduction or elimination of Nemacur® efficacy. Stopping Nemacur® treatment allows “soil recovery” from fenamiphos-AMD. This work had three main objectives: to study time dependent recovery in 4 soils from different geographical locations (Australia, Greece, Italy, and Martinique) under different temperature regimes (-20°C, 4°C, 10°C, 20°C, and 30°C), to determine if fenamiphos degra-dation patterns change during soil recovery, and to isolate and identify soil microorganisms that are involved in fenamiphos degradation. In the soil recovery study, 14C-labelled fenami-phos was used to follow fenamiphos (f) degradation to 14CO2 and its toxic (f-sulfoxide, f-sulfone) and non-toxic (f-sulfoxidephenol, f-sulfonephenol) metabolites over time. Within 10 months, all soils recovered from fenamiphos-AMD when stored at 30°C, one soil recovered when stored at 20°C, and two soils recovered when stored at 4°C. At 30°C storage tempera-ture, soil recovery was probably a result of nutrient-resource-limited overall microbial activity, and not due to a specific temperature effect on fenamiphos degrading microorganisms. At lower temperatures, total microbial activity was not severely reduced. At 4°C storage tem-perature, soil recovery was most likely due to a specific inhibition of fenamiphos degrading microorganisms, related to suboptimum temperature. The degradation pathways of fenami-phos in AMD-soils and a previously untreated control soil showed significant quantitative dif-ferences. The quantity of fenamiphos degraded in an alkaline AMD-soil with high carbonate content was greater than in the acidic AMD-soils, and metabolites found in the acidic soils could not be detected in the alkaline soil. Only in this alkaline soil, a non-defined f-metabolite, which appeared to be f-sulfoneanisole, was detected. A microbial consortium was isolated from each AMD-soil using agar plates containing fenamiphos. These consortia were tested for their capability to degrade 14C-labelled fenamiphos to 14CO2 in a fluid test system contain-ing soil extract. 37 bacterial genera were identified in the microbial consortia able to degrade fenamiphos. 6 bacterial species/strains occurred in consortia originating from at least two different AMD-soils. Only one fungus in each microbial consortium could be identified. How-ever, it cannot be excluded that further fungal species were involved in fenamiphos degrada-tion. Single bacterial or fungal species that were isolated from each fenamiphos degrading

microbial consortium could not degrade the compound. Recombined microbial consortia of previously individualized species did not restore the ability to degrade fenamiphos. It was proposed that extrachromosomal DNA-/RNA-pieces like plasmids or transposons code for enzymes which are necessary for fenamiphos degradation. Sonwa, Denis J. (2004): Biomass management and diversification within cocoa agroforests in the humid forest zone of Southern Cameroon. Institute for Horticulture, Faculty of Agriculture, University of Bonn, 112 pages. The aim of this work was to study diversification and evaluate biomass management in co-coa agroforests of Southern Cameroon. More specifically, research efforts were focused on (1) characteristics of farmers and their species preferences, (2) diversity of the plants associ-ated with cocoa, (3) structure and typology, (4) phytomass, (5) litter dynamics, (6) cocoa production and (7) Carbon stock of the cocoa agroforests. To collect all this information, 300 farmers were interviewed, vegetation survey was conducted in 60 cocoa agroforests, and experimental plots followed during two years in 8 representatives cocoa plantations. The fol-lowing findings were then obtained: Each farmer used on average six companion plant species for intensification and diversifica-tion of his cocoa agroforest. Among farmers, 93% use fruits and 81 % use non-fruit species. Among the species used by farmers, 63% of fruits are exotic and 17% of non-fruits are high value timber (i.e. regularly exported from Cameroon). Within each cocoa agroforest, 21 species are found on average. A total of 206 were found in all the agroforests. In fragmented forest landscapes, agroforests are less diverse. Food spe-cies tend to be more frequent while timber species are among the best shade providers (i.e. having enough basal area). Among all food plant species listed in these agroforests, 2/3 are species yielding non-wood forest products (NWFP). The average basal area of an agroforest is 36 m2.ha-1 out of which 85% are taken up by the plants associated with cocoa. Food species tend to be denser around Yaounde, while timber and medicinal species are more likely to be found in forested areas. A cluster analysis, taking into consideration the age of plantations and the densities of cocoa and other trees (including Musa species and oil palms), allowed the identification of three classes of cocoa plantations. Types A and C have lower densities of cocoa, - 918 and 1060 plants/ha -, against 1757 in type B. In contrast, type A plantations have a higher density of Musa spp. and oil palms, while type C contains more high-value timber and indigenous fruit trees. Total tree density is highest in type B plantations. The phytomass average is 451 Mg.ha-1 whereby associated plants account for 83% of this value. Unshaded cocoa orchards contain only 56 Mg.ha-1 of phytomass. In the phytomass contribution of plants associated with cocoa, food plants account for 15% and timber for 25%. The carbon stock obtained was 243 Mg.ha-1, with above ground carbon accounting for 50 to 75 % under shading conditions. Beside cocoa, the first 10 associated species account for more than half of the phytomass of the companion plants. Agroforests with high timber and NWFP plants (Type C) store two to three times the amount of carbon as stored under shade types A and B. Unshaded cocoa orchards stored 60 Mg.ha-1 of carbon.

A total of 10.7 Mg.ha-1of litter fell, on average, in cocoa agroforests on a yearly basis. In the absence of shade, only 4.78 Mg.ha-1 was recorded. As a result of slashing by farmers, a complement of 1.21 Mg.ha-1 of weeds is returning to the soil. The absence of shade in-creases this weed biomass to 3.3 Mg.ha-1.Year-1. The Olson degradation rate (K) is 1.7 on average in the entire area (1.3 under unshaded conditions). Each cocoa tree produces on average 11 healthy pods per year when cocoa trees are well treated against black pod disease and 5 when they are not treated. Production of 258 to 445 Kg.ha-1 could be obtained under shade against 768 under direct sun when fungicide is ap-plied. When pesticides are not applied, densification of cocoa is harmful to production (only 80 Kg.ha-1.year-1) against 194 or 169 where cocoa density is lower. Black pod incidence was more than 61% when fungicide was not applied. The structure and characteristics of cocoa agroforests are affected by farmers' management methods and are influenced by the surrounding forest landscape. Understanding interactions between cocoa agroforests and other land uses as well as interactions between components within the system will help fulfilling household needs, conserving forest resources and provid-ing ecosystem services in an improved way. Key words: Cocoa agroforest, Southern Cameroon, biodiversity, biomass, carbon, cocoa production, litter dynamics. Spang, Günter (2000): Measurement and modelling of sorption and diffusion processes in a loess soil – Batch- and column-experiments with ions of different matrix affinity. Institute for Soil Science, Faculty of Agriculture, University of Bonn, 272 pages. Laboratory experiments were used to measure the processes of sorption and diffusion for selected ions in a loess soil. The work was conducted to characterize the influence of these processes on the transport of the ions in soil columns. The data obtained in the experiments were used for calibration and validation of new simulation models ESORP and ESTIM. An extended version of the Freundlich sorption isotherm (s = c1/n – Q) gave the best descrip-tion of the data from the ad-/desorption batch experiments (24 h agitation). The adsorption of the different ions in the Ah soil horizon increased in the following manner: SO4

2- < Na+ < Mg2+ < K+ < phosphate-P < MoO4

2- < Zn2+ < Cd2+. In the subsoil, stronger adsorption was observed for all ions - with exception of MoO4

2- - compared to Ah horizon. All ions investigated - with exception of SO4

2- and Na+ - revealed a sorption hysteresis. The batch experiments showed bimodal sorption kinetics, which demonstrated the temporal dependence of phosphate and zinc sorption. This sorption behavior could be described by a sorption/diffusion model that was developed, i.e. ESORP, which assumed spontaneous ad-sorption on outer surfaces and, subsequently, a long term solid state diffusion to the inner surfaces of soil particles, especially iron oxides. The sorption hysteresis observed during desorption of phosphate was also accurately described by the applied diffusion equations. In column percolation experiments breakthrough curves (BTC’s) were derived. The BTC’s for the conservative tracer Br, obtained in water saturated flow experiments, were simulated using the transport model ESTIM. The model calculations were based on the convective-dispersive equation and proved to be successful. In the column experiments that were con-

ducted with higher flow velocity, a physical nonequilibrium was observed and could be de-scribed with ESTIM, considering the concept of mobile/immobile pore regions in soil. The simple linear adsorption of sulfate in the soil columns was very accurately simulated with ESTIM using a Freundlich type sorption isotherm. The sorption nonequilibrium observed dur-ing phosphate transport could be adequately described in most of cases by the model, ES-TIM, using coupled sorption/diffusion equations. The BTC’s for Zn, Ca and Mg showed a strong impact of cation exchange processes. The Zn-BTC’s revealed snowplow effects as a reflection of the fast displacement of the adsorbed ions from outer surfaces. The sulfate sorption parameters determined in batch- and column-experiments dif-fered only by a small degree. However, Freundlich sorption parameters derived from phos-phate BTC’s showed the strong influence of transport conditions and revealed a wider range than the Freundlich coefficients determined in batch studies. Stadeler, Cerstin (1998): The interaction of nutrition and the immune system examined in the case of the com-mon cold and vitamin C intervention. Institute for Agricultural Botany, Faculty of Agriculture, University of Bonn, 170 pages. The existence of a relationship between nutrition and immunity is generally accepted. The aim of the present study was to evaluate this interaction using the common cold as a stress factor by describing alterations in the nutritional and immunological status of young, healthy adults infected with a common cold and after their recovery. The common cold is the most frequent cause of acute morbidity in society and is associated with major socio-economic costs. Most remedies offer only minimal or symptomatic relief. A long-standing controversy exists concerning the possible efficacy of ascorbic acid in treating the common cold and in sustaining the immune response. The test subjects (n=40) participated in a clinical study at the University of Bonn at the onset of their colds. Treatment was double-blinded and subjects took either 500mg/d vitamin C or placebo for 7 days. Blood samples were taken on an empty stomach, both during the illness (7 days) and after recovery (day 21). The following parameters were investigated: serum vitamin C, intracellular vitamin C in PMN and MN cells, serum folic acid, vitamin B6, vitamin E, iron, zinc, leukocyte count and distribution, phagocytosis, respiratory burst, lymphocyte phenotypes, proliferative response of lymphocytes and the severity and duration of cold symptoms. Assessment of vitamins, trace elements and body-mass-index indicated that the nutritional status on average was adequately balanced for all subjects. The intraindividual comparison as well as the comparison between placebo group and intervention group revealed no rele-vant alteration of the nutritional and immunological status during the common cold and after recovery. Furthermore, no significant correlation between nutritional factors and relevant im-munological parameters were found. Intervention with ascorbic acid showed no clear benefit in regard to the immune response or the duration and severity of common cold symptoms. It can be stated that in the present study the nutritional and immunological status of young, healthy adults was not significantly affected by a common cold or by vitamin C intervention. Obviously, the human immune system and the nutritional status of this particular group were

adequately balanced to combat a stress situation like a common cold. This might not be valid for other age groups or people with consumptive diseases or malnutrition. In this particular group the common cold as stress factor was not able to demonstrate an interaction between nutrition and immunity analytically. Ascorbic acid failed to notably affect any of the measured immunological responses. Even though a number of reviews concluded that extra ascorbic acid may reduce the duration and severity of symptoms, no significant reduction was found in the intervention group. Therefore, further studies are needed to clarify the pathology of the common cold and to establish more sensitive methods to assess the immune response. Steingießer, Roland (1997): Estimation of fresh and dry winter barley and maize biomass within different regions in Europe using multitemporal, multifrequency and fullpolarimetric radar data - a con-tribution to the mission X-SAR/SIR-C - . Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 118 pages. Radar remote sensing using airborne and space-borne sensors is well-suited for the obser-vation of agricultural crops due to the weather independence of the latter. However the inter-pretation of radar backscatter signatures in terms of the recognition of different crops and their states still poses problems, since the dependence of the backscatter characteristics on sensor parameters, vegetation and soil are not well understood. In this respect the X-SAR/SIR-C shuttle mission provided the first opportunity for evaluating multitemporal, multi-frequency and full-polarimetric satellite radar sensors for civilian use. This also provided the opportunity for studying agricultural crops under identical sensor parameters. In order to ob-tain significant differences in growth stages for identical crop types during the ten-day long shuttle missions, which took place in April and October of 1994, winter barley fields were chosen along a gradient from southern Italy to southern Germany for the first mission, and maize parcels were chosen in southern Germany and in the Netherlands for the second mis-sion. These test fields were surveyed coincidentally with shuttle passes over them. One of the main results was that the spread in fresh biomass measured in (g/m2) between winter barley and maize fields as a function of their different growth stages, could be de-tected with great precision from the backscatter data. The best parameter for the measure-ment of winter barley and maize biomass was the ratio HH/VV at L-band. For the extraction of dry biomass in winter barley fields, the cross-polar polarisation HV at C-band showed the best results. The dry biomass of maize was shown to be strongly correlated with L-band HV backscatter coefficients. Backscatter parameters not containing any information about the observed biomasses or other crop parameters, were seen for oblique incidence angles, drenched crops or for plant row orientations perpendicular to viewing geometry of the radar sensor. Stierl, Reinhard (1999): Comparative Investigations of the Mechanisms of Induced Resistance.

Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 107 pages. The mechanisms of chemically induced resistance to Alternaria solani, Phytophthora in-festans and Oidium lycopersium in tomatoes were investigated and compared. These phyto-pathogenic fungi differ fundamentally in their life-cycles and modes of nutrition. The resis-tance inducers used were Dichlorosalicylic acid (DCSA), Dichloroisonicotinic acid (DCINA), Benzothiadiazole (BTH), ß-Aminobutyric acid (BABA) and a synthetic inducer designated RI 108. In greenhouse experiments with P. infestans all the inducers caused clear reductions in the severity of infection, which were also largely reproducible in field trials. With the exception of RI 108, the inducers were also able to reduce infection by O. lycopersium. They were least effective against A. solani and in some experiments no effects could be observed with this organism. The application of BABA invariably failed to induce any degree of resistance to A. solani. The mechanisms of induced resistance at the cellular level were investigated using conven-tional light and fluorescence microscopy and confocal laser scanning microscopy. On DCSA-, DCINA- and BTH-treated leaves the penetration of O. lycopersium was almost completely prevented by the increased formation of papillae, whereas BABA treatment reduced penetra-tion without any visible plant reaction. Reduced penetration by P. infestans could also not be attributed to stronger papillae formation. The limited development of both O. lycopersium and P. infestans on induced resistant plants could mainly be attributed to the hypersensitive re-sponse of infected cells. In contrast, hypersensitive responses were not able to restrict the development of A. solani. Timed investigations revealed that cytoplasmic aggregation and alterations in the cytoskele-ton were already evident in the cells of induced plants during the penetration phase. These reactions, which are probably the earliest symptoms of the defence mechanism, occurred sooner and more strongly in induced plants. This indicates improved pathogen recognition in induced plants. The differences in the frequency and efficacy of papillae formation and of the hypersensitive response to different pathogens indicate that, in addition to the penetration event itself, in-duced defence reactions are also influenced by the life cycle and mode of nutrition of the pathogen. It must therefore be concluded that induced resistance cannot be attributed to a single mechanism. Straßer, Hans Bernhard (2004): The influence of subsurface banded Phosphate on the P dynamics in the diffusion area, the root development and the P uptake of the plant. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 219 pages. The aim of this work was to give causal explaination of the differences concerning the P uptake by the plant between DAP and TSP when subsurface band applied. For this the differences between the influencing factors P binding strength, spatial extension of the diffusion area, movement to the root in the diffusion area and the rhizosphere, root development and physio-logical effects as well as the chemically responsible parameters had to be determined sepa-

rately and their particular proportion had to be estimated. For this model diffusion experiments, combined diffusion-/rhizosphere experiments, pot- and rhizothrone experiments were carried out with rape, maize, sweet sorghum and sun flowers in a slightly acidic, P deficient silt derived from Loess. The results of these experiments show, that fertilizing with DAP leads to a higher P uptake than with TSP, especially when subsurface band applied. The following essential reasons for this have been determined: At equal spatial extension of the diffusion area phosphorus in the dif-fusion area of the DAP band is less strongly bound because of the initially higher pH and hence more mobile compared with TSP. As a result of this more P is moved towards the root, besides via diffusion, to a considerable degree by mass flow. Furthermore the depletion zone is replen-ished to a greater extend while the concentration gradient is higher. Placement of nitrogen, es-pecially the ammonia contained in DAP, results in a multiplication of the root length density in the diffusion area and contributes causally to a substantional, additional uptake of P. Placement of phosphorus alone does not influence the root length density at all and it affects the P uptake only to a little extent. Besides, Ammonia has a physiologically caused, benificial effect on the P uptake. Mainly the superiority of DAP placement compared to TSP is due to a better spatial develop-ment of the diffusion area by a raise of the root length density caused by placement of ammo-nia. To a distinctly less extent and in each case to the same proportion the lower adsorptive strength as well as the synergistical effect of the ammonia contribute to this superiority. Terhardt, Josef (1999): Influencing microbial communities of the rhizosphere through the treatment of plant leaves and biological control of Fusarium oxysporum f. sp. lycopersici and Meloi-dogyne incognita with bacterial antagonists. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 136 pages. The text is divided into four chapters. Chapters A an B deal with influenncing microbial com-munities of the rhizosphere through the treatment of plant leaves. Chapter A refers back to the plate count method. Individual variations in leaf treatment led to the changes in the com-bination of the rhizosphere community, in that a portion of the pseudomonads in the total amount of bacteria increase over time. In chapter B, alternative methods of characterizing microbial communities, including gas chromatography analysis of fatty acids, will be presented. The potential of double analytical approaches will be tested in thorough examinations, for example, analyzing the fatty acid composition of the phosholid fraction previously extractet from bulk soil or combining fatty acid analysis with the dilution plate count method, and compared to various microorganism communities from soil extracted from both potato und bean plots. With assistance from prin-cipal component and cluster analysis, the differences in the fatty acid spectra can be identi-fied, and thereby the relevance of individual fatty acids can be derived. The resulting informa-tion would then be used as follows in the examinations to determine the influence of leaf treatments. The effects of individual leaf treatment substances (Milsana and Bion) on the microbial rhizosphere communities could be shown with the aforementioned techniques. Possibilities and limits of the fatty acid analysis method will be discussed.

Chapter C describes the examinations to biologically control Fusarium oxysporum f. sp. ly-copersici with the help of antangonistic bacteria. Of the 62 tested bacteria types, three showed a repeated reduction in the re-isolation rates of the pathogenic mold from the plant tissue when compared to the control group. Expanded examinations of the gas-exchange, chlorophyll content, and chlorophyll fluorescence as well as the organic substances of the plants will be caried out. Chapter D describes an ad planta test against the root-knot nematodes Meloidogyne incog-nita following the application of bacteria in the rhizosphere of the plants. Here, one bacteria type led to a reduction in root galls. Five samples reduced the number of egg sacs. A com-pleted leaf treatment test with Bion and jacmonic acid had no impact on the intensity of nematode root infestation. Thiele, Sören (1997): PAHs in polluted soils: Investigations on the characterization, optimization and prog-nosis of the microbial degradation of PAHs as well as the estimation of the PAH-fraction available to plants. Institute for Soil Science, Faculty of Agriculture, University of Bonn, 318 pages. To investigate the microbial PAH decomposition pot experiments were conducted under field conditions completed by laboratory studies. Easily degradable organic substances, mineral nu-trients, in part lime and synthetic surfactants were added in varied combinations to ten different soil samples from polluted industrial sites. In preliminary experiments 20 surfactants were tested. Four nonionic products were selected according to their good PAH solubilization proper-ties and low toxicity for microorganisms. Soil samples sterilized by HgCl2 were set up to quantify abiotic processes of the PAH decrease. 15 out of 16 PAHs listed on the US EPA list (1979; without Acenaphthylene) were determined. Depending on the kind and quantity of the amendments the biological activity of the soil sam-ples could considerably be increased. Thus an essential decrease of the contaminants' toxicity for soil microorganisms and cultivated plants was achieved. By increasing the (co-)metabolic decomposition activity of the microorganisms and depending on the different treatments, a de-crease of the PAH contents between 4.6 and 90.9% was achieved within 74 weeks. Still after 121 weeks, an in parts remarkable further decrease of the PAH contents could be observed. Above all, the decrease of the PAHs is based on the microbial decomposition and bonding and for the most part can be fitted by two coupled exponential functions. Effects like the removal by plants or leaching by percolating water are not relevant. Abiotic processes make up less than about 30% of the PAH decrease. On the other hand mobilizations of PAHs could also be ob-served. Apart from solubilizing agents of pedo-, and biogenic as well as technical origin, this is caused by the fluctuating water content of the soils. Higher PAH contents lead to higher PAH decreases. However, they end at higher remainder contents. The persistence of PAHs is mainly determined by their availability, which in turn can approximately be described by their KF values as a determinant of their adsorption. Therefore lower condensed PAHs with low KF values are more available and are decomposed more strongly. In contrast the contents of the higher condensed 5- and 6-ring PAHs are primarily in-

fluenced by fixation and remobilization processes with the quantity of the soil exchange sites being less important than their quality. The PAH degradation is increased by the soil treatments. However, the effects are only in parts statistically significant. The addition of easily degradable organic matter (C/N < 20) in a higher quantity (3%w/w) combined with the addition of nitrate and a surfactant most effectively in-creases the degradation of the PAHs. Raising the pH of a very strong acid soil sample revealed an optimum PAH decomposition at pH 6. Valid data on the microbial PAH degradation were available from the pot experiments. The PAH uptake from soil by food plants was investigated by lysimeter trials of the LUA NRW (DEL-SCHEN et al. 1996). It therefore was possible to use the appropriate soil samples for the devel-opment of laboratory methods for the determination of the degradable as well as the plant avail-able PAH portions. Screening tests were carried out with different extractants: H2O (bidest.), and salt solutions, 0.02 - 5% concentrated solutions of nonionic surfactants, organic solvents and solvent mixtures. The most important selection criterion was the correlation between the results of the extractions and the target parameters. In addition different variations of the extrac-tion procedure were tested. More detailed experiments on the determination of the degradable PAH contents were con-ducted with three variants of each of the ten pot trial samples. On the basis of the screening tests toluene/acetone (3:2) and the single as well as the twice repeated extraction with 0.5% concentrated surfactant solutions (Genapol UDD 88 or Synperonic LF/RA 30, resp.) were cho-sen. The results of these extractions describe the contents of the degradable PAHs well with r = 0.615 - 0.878. For that purpose the PAHs were classified in groups depending on the degree of condensation and an equation of regression was calculated for each group. However, closer correlations to the soil characteristics or physicochemical parameters of the PAHs are not exis-tant. Nine soil samples from the lysimeter experiments were used to characterize the PAH por-tion in soils available to plants. The uptake of PAHs by plants was measured on the basis of their contents in spinach surveyed with the soils. The PAH contents extractable with etha-nol/water (1:4v/v) and 1M NH4NO3 correlate closely with the contents of the different PAH groups in the spinach with r = 0.697 - 0.930. The tested extraction procedures can be recom-mended for application. Timmermann, Christian (2001): Site-specific weed control in precision farming considering yield data and soil pa-rameters. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 78 pages. In this study, site-specific weed control was conducted over four years in a rotation of winter wheat, winter barley, maize and sugar beet. The results allowed an evaluation of the eco-nomic efficiency, the environmental sustainability and the technical requirements of site-specific weed control. The amount of herbicide savings varied between the crops, depending on the different thres-holds for weed control and the weed populations associated with each crop. For grass herbi-cides, the savings were 90 % in winter cereals, 78 % in maize, and 36 % in sugar beet. For

For herbicides against broadleaf weeds, 60 % were saved in winter cereals, 11 % in maize, and 41 % in sugar beets. The monetary savings resulting from the reduction in herbicide use varied between the crops, depending on the amount of herbicides saved and the price of the herbicides. In maize, savings of 42 €/ha were realised, in winter wheat of 32 €/ha, in winter barley of 27 €/ha and in sugar beet of 20 €/ha. Besides cost reduction, due to the reduced amount of applied herbicides, site-specific weed control resulted also in positive ecological effects. Large sections of the fields, furthermore, needed herbicide treatment significantly less frequently. In those areas where weed density remained below the weed control threshold, flora and fauna was allowed to establish largely without disturbances. Requirements for the technical realisation of site-specific weed control in practice are the development of automatic systems for weed detection as well as sprayers that allow changes of herbicides and herbicide rates in the process of spraying. New decision models that consider heterogeneous soil parameters in addition to heteroge-neities in the weed distribution within fields have the potential to increase the efficiency of site-specific weed control. The causes of the yield variations within fields were analysed with the purpose of including site-specific weed control in the wider framework of precision farming and of optimising the input of resources. As limiting factors for the yield were identified: soil properties and topog-raphies that influenced a field’s water supply; the management history of the field, affecting the soil’s nutrient and carbon contents; and high weed densities in certain sections of the field. If there are naturally occurring sources for yield variations, input of fertilisers and seeding density are to be adapted to the heterogeneous yield expectations. This means in practice that site-specific fertiliser input has to be varied according to the changing nutrient uptake and that in field sections with low yield expectations seeding rate has to be lower then in sec-tions in which a high yield is expected. In fields in which the yield variations are management-induced, the factors that caused the variations have to be overcome by applying site-specific management strategies. Suitable long-term measures include the compensation for nutrient deficits within fields by site-specific fertilization and the reduction of weed density in weed patches. Trapmann, Stefanie (1999): Detection of Herbicide Contamination by means of a Thylakoid Bioassay: Optimisation and Characterisation of the biological unit. Institute for Agricultural Botany, Faculty of Agriculture, University of Bonn, 174 pages. The use of thylakoids as biosensors to detect photosynthetic active herbicides was optimised and characterised. The isolation method for thylakoids was improved by an increased addition of the scavenger ascorbate to the isolation media and a reproducible quality of the thylakoids could be guaran-teed. Lettuce, readily available from markets, can be used as donator plant for thylakoids. Osmotic rupture during isolation proved to be important for the sensitivity of the biosensor.

Technique and evaluation of fluorescence measurements was adapted to the needs of an in vitro method and led to an initial improvement of the detection limit. The use of minimal thy-lakoid concentrations per measurement proved to be advantageous for the detection of her-bicides. Measuring procedure could be simplified due to changes of the constituents. Comparison of different photosynthetic active herbicides showed their selective detection and their varying inhibition efficiencies, which can be expressed in equivalents. Since it could be proven that only additive interactions take place, the calculation of activity equivalents based on Diuron was possible. The thylakoid bioassay tolerates pH values between 2 and 12 and is insensitive towards most other elements. Even high concentrations of heavy metals, which may occur in aque-ous extracts of compost samples, did not lead to interference of the detection. Photosystem-II-herbicides can be detected by means of fluorescence or oxygen consump-tion measurements with a detection limit of 0.3 or 10.7 µg Diuron/L. Photosytem-I-herbicides can only be detected with the help of oxygen consumption measurements (detection limit of 2.7 µg Diquat/L). In principle it is possible to concentrate herbicide containing water samples by use of a Vi-greux column. This method results in a recovery of around 80 %, but is very time consuming. Photosynthetic activity of thylakoids decreases significantly during freeze-drying procedure. Sensitivity of the lyophilised products does not change. Therefore the more temperature in-sensitive, lyophilised thylakoids can be used for field applications. The potential of the bioassay and the lyophilised thylakoids could be shown with the help of waste water samples. Despite high contamination of the samples with other elements photo-sytem-II-herbicides were detected reliable in a sum parameter. Trimborn, Manfred (2002): Denitrification, production and consumption of N2O in hydromorphic soils. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 136 pages. The influence of the soil moisture regime of hydromorphic soils under agricultural use on the N-turnover was examined in field studies and in a laboratory experiment with undisturbed soil columns. The investigations were focused on the denitrification in the topsoil and in the sub-soil. In addition to this the dynamics of the microbial biomass, the mineral nitrogen and dis-solved organic matter were studied. The field studies proved that the quantity and quality of the microbial biomass and dissolved organic matter in the topsoil was highly influenced by the dynamics of the soil moisture. N-uptake and yield of crops were reduced in soils with stronger hydromorphic properties. Nev-ertheless, this hardly influenced the amounts of soil nitrate and dissolved organic matter in soil. It is assumed that the decomposition of the organic matter was restricted when water logging conditions increased. The amounts of microbial biomass and dissolved organic mat-ter were very low in the dense layer of the subsoil. The rates of denitrification in the topsoil, measured with the acetylene-inhibition-method, were strongly influenced by the stagnic con-ditions. Furthermore the denitrification was influenced by the amount of the dissolved organic matter, but no correlation between denitrification and the amount of nitrate in soil could be found.

In the laboratory experiment with undisturbed soil columns, different soil moisture conditions (drying, rewetting, wet and alternating moisture) were adjusted in order to examine their in-fluence on the production of N2O and on denitrification. The amounts of N2O emitted during the periods with constant soil moisture conditions were consistent with the known relation between soil moisture and denitrification. However, the emissions during the wet period were small compared to emission peaks occurring at changing soil moisture conditions. While dur-ing rewetting high N2O concentration were found for only a few days and mainly in the deeper topsoil, during the wet period or the period with alternating moisture very high N2O concentrations occurred in the subsoil directly above the dense layer. The local origin of the emitted N2O could be quantified in the soil profile by labeling the soil columns with 15N. This pointed out the significance of subsoil denitrification of hydromorphic soils. Furthermore a significant consumption of N2O during diffusion to soil surface was detected in the soil profile. Therefore the N2O emissions not necessarily reflect the rates of N2O production in soil. Prior to the laboratory experiment a method was developed to analyze the 15N abundance of nitrate. It is based on the reduction of NO3

- to N2O by Hydrazinium Sulphate and copperized Cadmium. The method requires a sample volume of 200 µl and is very sensitive, with a de-tection limit of 20 ng NO3

--N in comparison to other methods which require 200 µg NO3--N for

a 15N analysis. The precision of 15N determination, the selectivity against other N-compounds and the handling made the method were very suitable for the analyse of soil solution sam-pled form the undisturbed soil columns. Tu-Rapp, Tieu Hoang (2004): Studies of the role of CD95 in the pathogenesis of murine collagen-induced arthritis. Institute for Agricultural Botany, Faculty of Agriculture, University of Bonn, 107 pages. Collagen-induced arthritis (CIA), the animal model of rheumatoid arthritis (RA), is a chronic inflammatory disease bearing all the hallmarks of RA like e.g. polyarthritis, synovitis, and subsequent cartilage/bone erosions. One feature of the disease thought to contribute to joint damage is synovial hyperplasia. Factors contributing to this phenomenon are unknown, however, imbalance between rates of cell proliferation and cell death (apoptosis) has been suggested. Apoptosis is induced by interaction of CD95-ligand and CD95 (Fas), a trans-membrane protein. However, an anti-apoptotic effect after Fas-ligation has previously been observed. In addition, it has been discussed, that the soluble form of CD95 (sFas) has pro-tecting features against Fas-mediated apoptosis. Increased sFas was found in synovial fluids and sera of patients with RA. These observations suggest a role of Fas in the disease proc-ess of RA. To evaluate the role of Fas in the pathogenesis of CIA we determined the susceptibility of Fas-mutant mice (DBA/1J-lpr/lpr) and of soluble Fas transgenic mice (sFas-DBA/1J) to CIA. Disease was induced by immunizing mice with bovine type II collagen (CII) in complete Freund’s adjuvant. Contrary to expectation, DBA/1J-lpr/lpr mice developed statistically sig-nificant milder disease with lower incidence than the control mice in spite of increased im-mune responses to CII. On the other hand, sFas-DBA/1J mice developed CIA with mean date of onset and an average score comparable to their control littermates despite increased immune response and impaired susceptibility to Fas- and activation-induced apoptosis. Fur-

thermore, the critical pro-inflammatory cytokines like tumor necrosis factor-a (TNF-a), inter-leukin-6, and -1ß (IL-6, IL-1ß) were increased in DBA/1J-lpr/lpr mouse paws on the onset of disease despite of milder arthritis suggesting less efficient activation through these cytokines when Fas signalling is deficient. In addition, synovial fibroblast was stimulated by interaction with anti-Fas antibody as evidenced by the expression of pro-inflammatory cytokines and less susceptibility to anti-Fas-induced apoptosis in mouse fibroblast cell line NIH3T3. These observations clearly show that tolerance impairment does not lead to enhanced susceptibility to CIA and that Fas contributes to damage in CIA synovium by inducing proliferation of local cells, in particular synovial fibroblasts. Furthermore, there is a delicate balance between the soluble and membrane form of Fas and the apoptotic and stimulatory Fas pathways. The regulation of this balance may be important to autoimmune diseases. Untiedt, Ralf (2000): CO2 gas exchange of apple trees in dependence of growth regulators, pesticides, wa-ter stress and flooding. Institute for Horticulture, Faculty of Agriculture, University of Bonn, 109 pages. The outdoor measurings were carried out at the institute of fruit-growing and vegetable-growing of the university Bonn from 1994 to 1995. Three year old apple trees cv. Golden Delicious and Elstar on M9 rootstock grown in 60 litres pots containing sand. They were en-closed in six transparent assimilation chambers made of 0,1 mm thick polyethylene film. An infrared gas analysator measured at intervals of one minute the carbon dioxide exchange rates. Growth regulators, commonly used pesticides combinations, water stress and flooding were tested to their influence on net photosynthesis and dark respiration of whole apple trees. The following results have to be emphasized: The precision of the equipment for measuring the photosynthesis and dark respiration into open top chambers was examined and improved. Applications of growth regulators such as Amidthin, Ethrel, Rhodofix and Alar led to decreas-ing photosynthesis and increasing dark respiration. The increase of dark respiration was stronger than the decrease of photosynthesis. Use of the pesticide combination from Dithane Ultra, Benocap and Metasystox led to de-creasing photosynthesis of the apple trees as well as increasing dark respiration. The in-crease of the dark respiration was stronger than the decrease of the photosynthesis. Use of the practice usual pesticide combination from Delan and Pirimor led to an decrease of the photosynthesis as well as of the dark respiration. Water stress in September led not before 15 days to an decrease of the photosynthesis of apple trees, but already after a week to an increase the dark respiration. Flooding led not to any reaction of the photosynthesis and dark respiration of apple trees. Vedder, Gottfried (1995): Controlled supply of water and nutrients in new apple plantations with fertigation.

Institute for Horticulture, Faculty of Agriculture, University of Bonn, 151 pages. In autumn 1989, an experiment was installed, combining a range of fertigation and soil cultiva-tion methods, at the experimental orchards of the Institut für Obstbau und Gemüsebau, Univer-sity Bonn. Apple trees of cvs 'Graf Ezzo', 'Roter Cox', 'Roter Berlepsch' and 'Gloria' on M9 were planted at distances of 1.50 m x 3.45 m and trained to slender spindle. The 1 m wide tree alleys were treated with either herbicide 'BASTA' or 'ROUND UP'. Alternatively, they were either mulched with wooden chips, mechanically weeded or grassed, with or without additional fertigation. Plots without fertigation received nitrogen in form of granular fertilizer such as OSMOCOTE, CALCIU-MAMMONNITRAT or NITROPHOSKA STABIL, with or without irrigation. Fertigation comprised HAKAPHOS SPEZIAL or AMMONNITRAT-HARNSTOFF. Since spring frosts in 1990 and 1991 damaged many flowers, trees of cv. 'Graf Ezzo' produced a small yield, and vegetative growth was primarily assessed with the other cvs. Irrigation with granular fertilizer and fertigation enhanced reproductive para-meters in cv. 'Graf Ezzo' viz. fruit yield, average fruit weight and retarded ripening, irrespective of soil management. In herbicide-treated plots, vegetative growth was unaffected by both granular fertilizer or fertigation, but there was a positive effect of irrigation. Similarly, leaf mineral content appeared unaffected by fertiliza-tion. Overall, irrigation increased vegetative growth, which in all treatments was highly correlated with subsequent flowering next spring. Irrigation also increased fruit yields in 1990 to 1993 with differences easing with time. Trees of cv. 'Graf Ezzo' produced the largest yields of the cvs ex-amined in 1992, which were strongly reduced in 1993 due to alternate bearing. Chip mulching conserved water by reducing evaporation which enhanced vegetative and repro-ductive growth with earlier flowering and consequently a greater risk of frost damage. The num-ber of flowers was reduced in cvs 'Cox' and 'Berlepsch' due to nitrogen fixation in the soil caused by wood decomposition. Cv. 'Graf Ezzo' also produced greatest yields in plots of com-bined chip mulch and irrigation, without inducing alternate bearing. In general, mechanical weeding reduced generative and vegetative growth compared to herbici-de treatment which was partially compensated for by irrigation. Trees in mechanically managed strips with complete fertilization and irrigation showed comparable results with respect to the numbers of flowers with trees in the herbicide strip, but the former produced smaller yields. Plots with combined grass and irrigation appeared nitrogen deficient when growth was com-pared with that in the herbicide strip. Trees without irrigation grew slower and produced smaller yields. The results have shown that the positive fertigation effects were mainly due to its water compo-nent. Vianden, Hanno (1998): Contribution of reserve and current uptake of C and N to post-defoliation regrowth of perennial ryegrass (Lolium perenne L.) assessed by 13C and 15N steady-state labelling. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 94 pages.

The aim of the present study was: (i) to quantify carbon and nitrogen mobilization in senesc-ing stubble tissue and in roots of Lolium perenne L., (ii) to investigate the allocation and utili-zation of pre-defoliation fixed carbon and nitrogen during regrowth, (iii) to determine current photosynthate accumulation and current nitrogen uptake and the pattern of current allocation within plants as it changed during regrowth and (iv) to assess the contributions of currently and pre-defoliation fixed carbon and nitrogen to leaf growth. Further experiments were con-ducted in order to assess the impact of increasing CO2 and temperature level on of C and N during a post-defoliation regrowth period of miniature swards of perennial ryegrass. The pre-sent data clearly show three major sources of carbon for leaf growth following defoliation, (i) carbon already present within the growing tissue, (ii) carbon redistributed from senescing stubble tissue and (iii) current photosynthate. Already during day 2 after cutting the contribu-tion of actual photosynthesis amounted 81% of the net carbon influx into young leaves. More than 87% of the net amount of carbon fixed by the plants during the first two days following defoliation was partitioned to young leaves. Mobilization of carbon originating from pre-defoliation photosynthesis was most prominent in senescing stubble tissue but was also evi-dent in roots. Only about 43% of the total amount of pre-defoliation carbon was allocated to young leaves. Approx. 57% of the redistributed carbon was lost to the environment. Most of this was likely associated mainly with covering substrate needs of maintenance processes. However, the presented data show clearly that the dependence of regrowth on stored re-serves persisted longer for nitrogen than for carbon. Even at day 5 after defoliation 30% of the total net influx of nitrogen into young leaves was derived from redistribution. Dry matter yield of Lolium perenne was generally promoted by high CO2 and this effect was significant when nitrogen was supplied during regrowth. Net carbon accumulation at elevated CO2 was approx. 23% higher than at ambient CO2 on the basis of C contained in the plants at the time of defoliation. This effect was less (i.e. approx. +15%) when no fertilizer was added. In-creased CO2 and temperature led to approx. 27% and 4%, respectively, increases in net up-take of swards during the 14-day regrowth period when nitrogen was added. Most of the ni-trogen taken up after defoliation was partitioned to the shoot (73 to 78%). Partitioning pattern of nitrogen was not affected by CO2 concentration during regrowth. Vorsatz, Carsten (2000): Cultivation of outdoor vegetables by the Cultan-System. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 155 pages. In the cultivation of outdoor vegetables, because of the nitrification of different nitrogen forms in the soil, the supply of nitrogen takes place independently of the offered nitrogen forms as nitrate, in the CULTAN-system as ammonium. This is offered to the plants in their root zone as depots. For the reason of its phytotoxicity, ammonium is taken up controlled from the boarders of the depots according to the intensity of growth of the plant. CULTAN = Conrolled Uptake Long Term Ammonium Nutrition. Essential aims of the system are to solve the prob-lems of nitrate in the plants and soils, to make the production of vegetables easier and more safe, to stabilize the yield on high level independent from weathering and to improve the qualities according to the contents of dry matter, mineral nutrients, ingredients as well as to its stability in transport and storing.

Basic investigations for the cultivation of vegetables based on the CULTAN-system were started 15 years ago. The aim of our investigations was to bring the CULTAN-system to praxis on the present knowledge. In these investigations the following problems for the appli-cation of the CULTAN-system under field conditions were predominat: the calculation of the level of N-fertilazition on the basis of nitogen release of the soil, the right placement of the CULTAN-depots according to the kind of vegetables and their typical root systems, the examination of the different fertilazation techniques according to the kind of their usefulness for the combination of nitrogen fertilazition with the planting or sowing of vegetables. As spezial results of these investigations the following shall be mentioned: for the CULTAN-system air pressure tanks, pressure pumps or tube pumps are suited for the application of liquid fertilizers and offer individual advantages. The right system may be dif-ferent for the farms. In the comparsion to common fertilazition, a nitrogen fertilazition according to the CULTAN-system achieved higher yields and better quality by less work and less risk of cultivation in all tested vegetables, like e.g. lettuce, cabbage, carrots and leak, especially cauliflower reacted very well to the CULTAN-treatment, so that noticeably higher marketing amounts can be reckoned on in comparision to conventional treatment. Nitrogen treatments reduced by 20 % in the CULTAN.system were equal in yields and quali-ties in comparison to common treatments according to the KNS-system (Kulturbegleitendes N-Sollwerte-System). The Nmin residues after harvesting the crops are less with remarkable release in the surplus of nitrogen in the soil. The uptake of phosphate and magnesium was not changed by the CULTAN-system in com-parison to common fertilazition. The uptake of calcium was increased remarkably with higher contents calculated on the basis of fresh weight. An antagonistic behavior in nutrient uptake in presence of ammonium could be observed in the field. The quality for storing vegetables was improved by the CULTAN-system in comparison to common fertilazation. This is probably due to the higher contents of dry matter and stronger cells. After the fertilazition of REA-gypsum in combination with the CULTAN-system higher weights per head were received by cabbages as well as higher uptakes of nitrogen and calcium. Vrochte, Wilfred (2003): Crop rotation effects of perennial ryegrass for grasseed production. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 200 pages. The seed production of perennial ryegrass is an economic interesting alternative to winter barley in the crop system of the crop rotation in the so called “Rhine Land Crop Rotation”. In the agricultural practise exact informations are missing how perennial ryegrass can be opti-mal included in the crop rotation and which crop rotation effects are resulting for the follow crops sugar beets and winter wheat. This was tested in a three years field trial.

Perennial ryegrass, growing with the objective for seed production, has a six weeks longer vegetation time as the comparing crop winter barley and the harvest of the seeds is normally 4 weeks later as winter barley. Grass seed production supplies the soil with an enormous quantity of organic matter. The root length density of perennial ryegrass is higher than in winter barley and it links to the as-sumption that the root mass is also higher. Plant residues and straw quantities are also higher in comparison to winter barley. The result of the grass seed production is an improved organic matter saldo. Is the plant straw removed from the field after grass production, the organic matter saldo is still higher than after winter barley without removing straw in combination with a green manure crop of mustard. An equalized organic matter saldo can be achieved after grass production for the case the plant straw material is not removed. Differences in the N consumption of the follow crop can be expected only after late ploughing of the fields or under very dry autumn conditions. Sugar beets after grass seed production showed in comparison to winter barley a tendency to a better quality. Differences in yield were hardly to measure. Winter wheat as the second follow crop after grass seed production showed a tendency to higher yields as after winter barley. The yield components, which linked to the yield differences, varied distinctively. N fertilisation in autumn on the stopples of winter barley or perennial ryegrass influenced the quality of the follow crop sugar beets negatively. The sugar beet or the winter wheat yields were not influenced. An improved soil structure, through the increased input of organic matter and an intensive root development after grass seed production, was measured first at the second follow crop winter wheat. The effects of the grass seed stopples and the straw fertilisation were in-creased through a late ploughing. For the stopple tillage of grass seed production fields all fundamental soil tillage gears can be used. A very shallow tillage is for the very hard and intensive rooted top soil necessary. Ro-tating tillage gears or disc harrows are suitable to work the intensive rooted top soil better and easier. Vu Thi Thanh, Tam (2005): Modes of action of non-pathogenic Fusarium oxysporum endophytes for bio-enhancement of banana toward Radopholus similis. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 101 pages. Four mutualistic endophytic Fusarium isolates with known antagonistic effects were studied for modes of action in bio-enhancement of banana toward R. similis. Greenhouse experiments were conducted to test the effects of the endophytes on R. similis penetration. R. similis penetration was reduced significantly by 29 – 39 % or by 22 – 41 % five or fifteen days after nematode inoculation. Isolates A1, Fo162 and V5W2 not only af-fected nematode penetration, but also reduced significantly by 54.5 – 57.8 % nematode population density in long term experiments. Timing, inoculum concentration and the ability of the fungus to colonize banana tissues influence the levels of biological control activity.

F. oxysporum isolates colonized 40 to 45 % of the roots beginning two weeks after endo-phyte application but also persisted in the root tissues for over 14 weeks at high levels of 47.5 % to 94.3 %. The isolates promoted banana growth in long term experiments in the ab-sence of nematodes which indicates cross reactions between nematode control and growth promotion activity. The pathogenicity of Fusarium isolates toward R. similis in vitro showed no direct parasitism. However, nematode mortality in the in vitro tests with Fusarium increased by 20 – 36 % due to toxic metabolites. Fungal metabolites in the soil without banana caused a 5 – 16 % level of mortality. F. oxysporum isolates also produced toxins in culture filtrates that induced mobility 41.5 – 67.8 % in vitro. However the toxic effect was not lethal. The metabolites when applied to the soil did not affect nematode infestation in banana roots. The influence of F. oxysporum on attraction and penetration behaviour was demonstrated with a Linked Twin-pot Chamber experiment. The isolates decreased significantly by 46.7 – 58.7 % the host finding ability of R. similis. F. oxysporum may stimulate the banana to pro-duce specific substances or change root exudates that obstruct attraction to banana or affect nematode host recognition. The isolates induced systemic resistance against R. similis infestation in banana. R. similis penetration in untreated Split-root tests was reduced significantly by 30 – 38.5 % or 26.7 – 47 % five or fifteen days after nematode inoculation. Induced systemic resistance due to F. oxysporum also reduced by 33 – 49 % the host finding ability of R. similis. Induced sys-temic resistance was therefore clearly demonstrated to be present and protection and it initi-ates the main mode of action which is alteration of host finding ability. It was demonstrated that the F. oxysporum isolates are unrelated genetically to the important pathogenic Fusarium wilt diseases bananas and tomatoes caused by F. oxysporum sp. cubense, F. oxysporum sp. lycopersici and F. oxysporum f.sp. radicis-lycopersici. Therefore, these mutualistic endophytic isolates are not only beneficial and non-pathogenic on bananas but also are not pathogenic to the other crops in the field. Wang, Huajun (2005): AB-QTL analysis for two populations of winter barley sharing the donor of Hordeum vulgare ssp. spontaneum. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 169 pages. The objective of the present study was to detect favourable exotic QTL alleles for the im-provement of agronomic traits, pathogen resistance and non-parasitic browning in two BC2DH populations derived from the crosses of two German winter barley varieties, Carola and Theresa {Hordeum vulgare ssp. vulgare, in the following abbreviated Hv), with the wild barley accession ISR101-23 (Hordeum vulgare ssp. spontaneum, in the following abbrevi-ated Hsp) from Israel. The two BC2DH populations (termed C101 and T101) were genotyped with 82 and 78 SSR markers, respectively. C101 and T101 consisted of 282 and 104 BC2DH lines, respectively. Sixteen agronomic traits, four pathogen resistances and the non-parasitic browning were evaluated at up to six different locations and in two consecutive years. QTL analysis was carried out with a three-factorial ANOVA including the marker as fixed effect

and the environment and lines nested in the marker genotype as well as the respective inter-actions as random effects. In addition, cold damage (COD) and neighbouring plots of the seriously cold-damaged plots (N) were used as co-variables for those traits which were sig-nificantly affected by COD and N. In C101, 35 favorable exotic QTL effects out of 183 puta-tive QTLs were detected for ten agronomic traits, four pathogen resistances and non-parasitic browning. Among these putative QTLs, 22 (19.1) of 115 QTLs detected for agro-nomic traits exhibited favorable effects and 13 (19.1) of 68 QTLs identified for disease resis-tances and non-parasitic browning were associated with improvements. A crossover interac-tion QTL effect of the Hsp allele on yield, detected on chromosome 6H in C101, was associ-ated with a yield increase of 8.2 averaged across three environments. However, in the re-maining two environments the Hsp effect was associated with a yield reduction of 4.6. In ad-dition, favourable effects of exotic alleles were detected for all pathogen resistances and non-parasitic browning in this study. For instance, the symptoms of leaf rust, net blotch, powdery mildew, scald and non-parasitic browning symptoms at QlrC101-3H, QnbC101-6Hd, QpmC101-2H, QrhC101-7Ha and QnpbC101-5Ha were reduced by 26.2 , 20.8 , 17.8 , 4.9 and 14.9 in C101, respectively (Table 17). In T101, 85 putative QTLs were discovered for eleven agronomic traits, four pathogen resistances and non-parasitic browning. The exotic genotype improved the performance at 13 (19.4) of 67 QTLs detected for agronomic traits and no favorable QTL effect was identified for disease resistances and non-parasitic brown-ing in T101 (Table 19). Thirty-nine putative QTLs detected in C101 were confirmed by 40 QTLs detected in T101. Altogether, 65 (24.3) QTL effects among 268 putative QTLs local-ized in both populations and 21 (43.8) favorable QTL effects among 48 favorable QTL effects identified in both populations were verified in other barley QTL and linkage analyses. About 56 favorable exotic QTL alleles identified in this study were so far not detected in other barley QTL studies. These favorable Hsp alleles may be new alleles. Weber, Ralf-Peter (2004): Potentialities and limitations of integrating contractually-agreed nature conservation in wetlands cultivation using the example of the Middle Elbe Biosphere Reserve. Department of Geobotany and Nature Conservation, Faculty of Agriculture, University of Bonn, 162 pages. The following work investigates just how much the instrument of nature conservation through contractual agreement has made a contribution to reach the goals of nature conservation on the Middle Elbe floodplain between Dessau and Gommern. First and foremost are the re-quirements that nature conservation has of grassland cultivation in the Elbe valley wetlands and how these can be realized through their integration in agricultural operating procedures. The great ecological and economic importance of grassland cultivation in the area investi-gated is underscored through the large percentage of agricultural area in use, about 70% of which is more or less regularly flooded. The percentage of cultivated land which falls under the category “contractually-agreed nature conservation” is very high (50%); this emphasizes the great importance of nature conservation through contractual agreement to the local agri-culture.

In addition to the ecological tests of contractually-agreed nature conservation projects, more than three hundred vegetation samples of the grassland were prepared, the feed value of selected areas was investigated, nineteen areas under long-term observation of the bio-sphere reserve administration were audited with regard to their vegetative development, the local developments of the populations were examined using cartographic analysis, and a survey of ten agricultural businesses was conducted to ascertain the acceptance, willingness to participate, and the relevance of utilisation restrictions which result from contractually-agreed nature conservation. The most important deficits found were an abrupt clearing of the landscape due to the pre-dominantly cutting every June 15 as well as the overwhelming lack of correlation between the goals of nature conservation and the actions actually taken. In addition, the area suffers from underutilisation which results in a matted overgrowth of the turf and the associated lack of species richness. Investigation of the feed quality of the extensive grassland outgrowths also showed that plant communities with a high species richness – first used in mid-June – also contain considerable energy potential, which would allow their partial use in cow feed. There was advice on defining and optimising the measures taken to protect, maintain and develop the floodplain grasslands as well as constructive recommendations on applying for loan programs. All in all it can be concluded that contractually agreed nature conservation plays a large role in the preservation, protection and fostering of the grassland populations of the middle Elbe. Weickel, Barbara (1997): Studies on the isolation, identification and biological characterization of arbuscular mycorrhizal fungi. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 116 pages. Arbuscular mycorrhizal fungi show differences in their infectivity and symbiotic activity. The aim of this study was to identify criteria for the biological characterization of mycorrhizal fungi that are relevant for practical use of the symbiosis. The influence of various factors on my-corrhizal formation where investigated to demonstrate their impact on the symbiotic effi-ciency. Arbuscular mycorrhizal fungi of the genus Glomus were isolated from different soils and cul-tivated using trap plants. Taxonomic classification was carried out on the basis of morpho-logical and biochemical characteristics of the chlamydospores. Morphological features were described using the Expert System of the European Bank of Glomales (BEG) as a reference. The isozyme profiles after native polyacrylamide gel electrophoresis (PAGE) and the RFLP patterns of PCR-amplified ITS-DNA were used for molecular identification of Glomus-species. In greenhouse experiments, the isolates were differentiated in their dynamics of develop-ment, infection rates and symbiotic efficiency. The inoculation of different host plants with a Glomus caledonium isolate significantly increased plant growth. Differences in the metabolic activity of mycorrhizal fungi were detected after histochemical staining for enzyme activities in the intraradical and extraradical fungal structures. The expression of fungal metabolic ac-tivity in relation to plant development is discussed. Isozyme analysis was used for isolate-

specific detection of mycorrhizal fungi in the roots of the host plant. Mycorrhiza-specific malate dehydrogenases showed clear differences to host plant isozymes. Their occurrence and intensity were related to the fungal development stage. The pre-inoculation of Allium cepa with an isolate selected on the basis of the greenhouse data clearly improved mycorrhizal formation and plant growth in the field. The described ap-proach can be useful in screening-programs for inoculation potential of mycorrhizal fungi. Weimar, Stefan (1995): Dynamics of nonexchangeable ammonium in slurry amended field of the Nothern Rhine River Region. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 245 pages. The present pot, field and laboratory investigations dealed with the influence of slurry amend-ments on the dynamics of nonexchangeable NH4-N. The selection of the experimental soils based on the determination of the contents of nonexchangeable NH4-N of 17 representative agricultural sites in the soil layer form 0 cm to 30 cm. Additionally 6 of these sites were sam-pled in the layer from 30 cm to 60 cm. In the topsoils the contents of nonexchangeable NH4-N ranged between 95 mg kg-1 and 313 mg kg-1 and in the subsoils between 112 mg kg-1 and 271 kg kg-1. The amounts of nonex-changeable NH4-N and the clay content (r2 = 0,66**) and illite content (r2 = 0,66**), respec-tively, were correlated significantly. However, the contents of this N fraction and the vermiculite and smectite contents were not correlated. In the pot experiment with 15 topsoils and 6 subsoils the influence the fixation and release of nonexchangeable NH4-N were investigated after slurry amendments in a spring wheat, corn, winter wheat and ryegrass rotation. The topsoils were grouped according the potassium con-tent of the soils and the proportion of smectites plus vermiculite of the clay fraction, respec-tively. The amounts of NH4

+ fixed by clay minerals after slurry application decreased with in-creasing contents of exchangeable K. Continous substitution of NH4

+ by K+ in the intercalary binding positions during the experimental period was suggested to be the main reason for de-creasing NH4

+ fixing capacity in the soils. Even the NH4+ fixation after slurry application in-

creased with increasing proportions of smectites plus vermiculite only a weak relationship could be established between both parameters. During the crop rotation NH4-N fixed after slurry application was released and no net accumu-lation of nonexchangeable NH4-N occured. In the 3 year field experiment (crop rotation: winter wheat, winter barley, clover ryegrass inter-crop, sugar beets) on 2 farmer's sites (orthic luvisol; distric gleysol) the dynamics of nonex-changeable NH4-N and Nmin after application of slurry and mineral fertilizer, respectively, was investigated. In the orthic luvisol the dynamics of the nonexchangeable NH4-N tended to be similiar in the soil depth from 0 cm to 75 cm. In the distric gleysol the amounts of nonexchangeable NH4-N in the topsoil and in the subsoil layer 75 cm to 90 cm remained nearly constant during the ex-periment. Markable dynamics of the nonexchangeable NH4-N were observed in the 30 cm to 75 cm subsoil increments depending on synergistic effects of layer charge characteristics in the subsoil, a weaker K competition at the specific binding sites and more favourable soil mois-

ture conditions. Higher contents of exchangeable K were suggested to decrease the fixiation of NH4-N. DCD application showed a limited effectiveness in increasing the rate of NH4-N fixed after the autumn amendment of pig slurry to winter barley grown in 1990/91 because high amounts of NH4-N provided with slurry were immedeatly converted to nitrate in the late autumn. Neither the slurry amended nor the mineral fertilized field plots left a net accumulation of non-exchangeable NH4-N at both sites. In a laboratory column experiment with soil material from a long-term slurry amended farmer's site the downward movement of labelled 15NH4

+ of a synthetically composed slurry was investi-gated as influenced by simulated rainfall intensity and the amounts of exchangeable K. The applied N amounted to 208 kg ha-1. After a 8 week percolation period nonexchangeable NH4-N in the soil columns was analyzed by increments of 5 cm. In the presence of nitrapyrin diffusion of 15NH4

+ could be determined up to a column soil depth of 15 cm to 20 cm. The 15NH4-N movement pattern showing a specific gradient was influenced significantly by the rainfall inten-sity, whereas the exchangeable K had no significant influence. However only 6 to 7 % of the 15NH4-N was determined to be fixed 15NH4-N after the percolation period. Obviously a striking difference exists between the absolute increase of fixed NH4-N after the percolation period and the proprotional increase of 15NH4-N in the soil columns. Weis, Jürgen (2001): Contractual nature conservation programmes – inspection of measures and results in the northern Eifel area. Institute for Agricultural Botany, Faculty of Agriculture, University of Bonn, 270 pages. The presented study is aiming towards an overall assessment of the results of biotope man-agement by farmers in the northern part of the Eifel (Northrhine-Westfalia). For more than 15 years meadows, pastures, meagre grasslands and other biotopes have been cultivated within the scope of contractual conservation programmes comprising a variety of conversa-tion measures and various sites. Whether or not the protective objectives of these measures have been achieved, is to be inspected on different spatial levels according to criteria such as their effects on the landscape, the development of plant societies and the populations of rare plant species. Taking into account the diversity of sites and land utilization, the results of the study are demonstrated for pastures and meadows as well as for meagre grasslands on limestone being a characteristic biotope in the Eifel. The analysis of aerial survey photographs illustrates the immense decline of limestone grass-lands since the fifties due to afforestation, succession or – in places – intensified agriculture. But the analysis also shows that this trend could not only be brought to a halt by the conser-vation measures taken, but even be inverted when areas were regenerated that had already been covered by shrubs. The observation of permanent vegetation plots around Alendorf e.g. proved the positive effects of sheep grazing. Today these grasslands are once more intact and well-structured. The populations of characteristic plant species in these grazed or mo-wed chalk-grasslands are well-protected. For some orchids – very rare and endangered species in Northrhine-Westfalia or throughout Germany – very impressing increases of popu-lations could be recorded.

In addition, it has to be noted that since the sixties meadows and pastures on more produc-tive sites have also been intensified and unified. This development can be traced in the Dah-lem area by means of two historic vegetation-mappings dating from 1975 and 1986. A recent repetition of these mappings demonstrates the positive effects of a conservation program started in 1986. The inspection of a representative number of sites managed by farmers un-der conservation treaties has proven that they predominantly contain plant societies and species of the ‘red lists’ of Northrhine-Westfalia. As expected, the floristic diversity of these sites is conspicuously higher than of surrounding sites that are subject to intensive management. The sites managed according to the program show a very rich and complete range of species. With the presented inspection of the results of different conservation measures performed by farmers in the Eifel, it can be summarized that the protective objectives of these measures, which are settled on different levels, have been fulfilled to a high degree. Weissteiner, Christof J. (2004): Use of Remote Sensing and Soilborne Data for Regional Yield Predictions of Malting Barley (Hordeum vulgare L.). Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 117 pages. Yield forecasts are of high interest to the malting and brewing industry in order to allow the most convenient organisation of the respective purchasing policy of raw materials. Since malting barley, due to its special requirements, is predominantly cultivated in a limited set of growing regions, yield predictions can be limited to these regions of interest. Within this in-vestigation, malting barley yield forecasts (Hordeum vulgare L.), in Germany mostly grown as spring barley, are performed for typical growing regions in South-Western Germany. Multitemporal remote sensing data on one hand and ancillary data such as meteorological, phenological, pedological, agrostatistical and administrative data on the other hand are used as input data for two versions of prediction models, which were based on an empirical-statistical modelling approach. Since spring barley production is depending on acreage and on the yield per area, classifica-tion is needed, which was performed by a supervised multitemporal classification algorithm, utilizing optical Remote Sensing data (LANDSAT TM/ETM+). The classification algorithm is considering spectral data, topographical data (Digital Elevation Model) and expert knowledge input. The latter is important with regard to the particular phenological development of the observed crop, an expertise which was used to distinguish it from similar crops. A pixel-based and an object-oriented classification algorithm were used for classification. For field plots larger than 2 ha up to 73 % of the spring barley area were classified. The basic version of the yield estimation model was conducted by means of linear correlation of remote sensing data (NOAA-AVHRR NDVI Maximum Value Composites), CORINE land cover data and agrostatistical data. In an extended version meteorological data (temperature, evapotranspiration) and soil data were incorporated. Yield predictions were significantly af-fected by the selected time span for NDVI integration. For NDVI time-integration across the

corn-filling period, the mean deviation of reported and simulated yield was 7.0 % and 6.4 % for the basic and extended yield estimation model, respectively. Wessel-Bothe, Stefan (2002): Simultaneous transport of ions with different matrix affinity in loess soils under field conditions - measurement and simulation. Institute for Soil Science, Faculty of Agriculture, University of Bonn, 218 pages. For the purpose of measuring leaching processes in field soils and developing a related simulation model the anions Br, NO3, SO4, H2PO4 and MoO4 and the cations Na, K, Mg, and Zn were applied on the surface of a cambisol. Leaching processes were observed over a period of 22 months by analyzing suction cup solutions and saturation extracts. A transport influenced by preferential flow was detected after a period of 30 days. During this short period the applied ions had already migrated into different soil depths due to their heterogeneous sorption properties. After 22 months the following leaching depths were observed: Bromide and nitrate ≥ 135 cm, magnesium approximately 100 cm, sulfate ap-proximately 90 cm, sodium approximately 60 cm. Zinc, potassium, phosphate und molybdate had only been transported over very short distances. In most cases, the concentrations in the suction cup solutions for bromide, nitrate, sulfate, sodium, and magnesium were much higher than in saturation extracts that were taken simultaneously. Phosphate, molybdate, potassium and zinc, however, showed high concentrations in suction cup solutions only at the beginning of the transport experiment. At the end of it, their concentrations were in most cases much lower than those of saturation extracts, as they had been decreasing during the experiment. The different matrix affinity of the applied ions and the flow conditions in soil were identified as the main reasons for those deviations. Calculations of metal species in the soil solution supported the presumption of co-transport of magnesium and calcium together with sulfate and thus the unexpected high transport velocity of magnesium in the field experiment could be explained. Alterations of the pH value by applying elemental sulfure and lime on two plots con-siderably affected the concentration of some of the solutes. Nevertheless, no effects on the leaching velocity of those solutes could be observed. On the basis of field and simultaneously conducted laboratory studies (Spang 2000) a model for simulation of solute transport on field scale was developed (Klennert & Helfrich 1997, Niemeyer 2000). In this model, the water transport is calculated based on measure-ments of the pressure head in different soil depths and spontaneous adsorption is computed by different adsorption isotherms. An important innovation of the model is the estimation of solid state diffusion using different equations for computing the diffusion of soluble ions into rod-shaped, spherical, and cylindrical particles. After calibration of the model with the observed tracer transport a satisfying simulation of water transport could be realized. Transport simulations of adsorbed solutes showed that some isotherm parameters determined by laboratory studies can be transferred to field con-ditions with satisfying results, while others may be transferred only with restrictions.

Transport simulations of phosphate, potassium and zinc were only possible by con-sidering the solid state diffusion. For transport processes under natural conditions diffusion coefficients were observed, that were one to four dimensions smaller than those of laboratory studies. Reasons for these deviations might be the varying temperature and water content in the soil and the influence of various chemical parameters which affect the solubility of ions, i.e. pH value and DOC concentration. Only adsorption and diffusion coefficients which were determined within a cinetic batch experiment for zinc (Kuhl 2002) lead to simulations that were in accordance with field results. All in all the consideration of solid state diffusion for modeling transport processes in the field seems to be a useful alternative to estimating ad-sorption cinetics by equations of any order and therefore an improvement. Wilbois, Klaus-Peter (1998): Growth, and Carbon and Nitrogen Economy of spring under elevated atmospheric CO2. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 96 pages. As part of the present climate change, the atmospheric CO2 concentration is considered to rise to a level of about 700 µl l-1 by the middle of the next century (Gribbin 1981). Plants may profit from elevated CO2 by increased rates of photosynthesis. These enhanced rates of pho-tosynthesis increase the availability of C within the carbon economy of the plant, which may in turn boost the biomass production. A further utilization of the additional available C is the storage of carbon reserves in the vegetative plant organs. It is known that elevated CO2-concentrations not only affect the plants carbon economy but also decrease the percentage N, mainly in the green plant parts. During grain filling, the cereal plant resorts to reserve pools of carbon and nitrogen in the vegetative plant organs. It is as yet not known how an elevated atmospheric CO2 concentration affects the resort to this reserves during grain filling. To elucidate this question experiments with wheat plants were carried out in growth cabinets in 1994 and 1995. Wheat plants (Triticum aestivum L., cv. Munk) were grown in growth cabinets either under 353 µl l-1 (ambient) or 700µl l -1 (elevated) CO2 in combination with a low and a high nitrogen fertilizer level. To determine the contribution of pre-anthesis reserves to grain filling, one part of the plants entered the growth chamber not earlier as the plants reached anthesis. The CO2 entering the growth cabinets was labelled by using a 13C-steady-state-labelling-technique. Nitrogen was supplied via Hoagland nutrient solution and was also labelled by 15N enrich-ment. The relative contribution of both carbon and nitrogen, which was accumulated in the vegetative organs before flowering and redistributed during grain filling, was calculated from C and N analysis by means of mass spectrometry. CO2 enrichment resulted in an average biomass increase of about 25% at the ample N lev-els. This increase was mainly due to enhanced tillering. Both, sub- and superoptimal nitrogen application, led to a reduced response of biomass to CO2 enrichment. Since the grain weight rose stronger than the total biomass did (29% to 26%), the harvest index augmented under elevated CO2 by about 0.2 units. Furthermore, there was a substantial positive effect of CO2 on root to shoot ratio. The root growth stimulation, due to CO2 enrichment, amounted to

135% when severe N stress was imposed. While the percentage of leaf N dropped by up to 18% under elevated CO2, declined the grain N concentration only in the low N treatment of the 1995 experiment (-26%), where the N supply via nutrient solution was drastically reduced after anthesis. During grain filling, the current photosynthesis of CO2 enriched plants provided distinctly higher amounts of carbohydrates than under ambient CO2. In the 1994 experiment the per-centage carbon contribution, from transient storage in the vegetative plant parts to grain fill-ing, amounted to 27% and to 20% for the low N and high N levels respectively. In the 1995 experiment on the other hand, where only the low N treatment was sampled, this relative contribution was about 10%. In both years, the relative contribution of pre-anthesis assimi-lates to grain filling was not significantly influenced by elevated CO2, although the absolute C importes into the grain were up to 70% higher than under ambient CO2 concentrations. At a non-limiting N supply via nutrient solution after anthesis, nitrogen assimilation improved con-siderably under elevated CO2, which consequently led to a lower reliance of grain filling on pre-anthesis reserve N from vegetative organs. In 1995, when the inorganic N availability in the rooting medium after anthesis was lowered, the grain N concentration substantially de-creased due to an insufficient nitrogen remobilization from the vegetative organs of CO2 en-riched plants for grain filling, because of the distinctly lowered N concentration in these plant parts. Averaged over both experimental years and treatments, about two third of the N, lost from vegetative plant parts during grain filling, were recovered in the grain at maturity, indi-cating a nitrogen remobilization efficiency of 66%. Wissing, Albert (2000): Movement of Vydate (a. i. oxamyl) at insecticidal and nematicidal/nematostatic con-centrations to the site of action and the effect on pests and the plant. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 150 pages. The integration of several control strategies for managing plant-parasitic nematodes and foliar feeding pests is a necessary approach to minimise potential environmental contamina-tion with chemical plant protection agents. The possibility of a multiple delivery of pesticides via a drip irrigation system provides an effective strategy to position minimised amounts of the active agent by means of the tubing close to the plants near the target soil region of highest root and nematode abundance. Oxamyl (Vydate, E. I. Du Pont de Nemours & Co. Inc.), as a highly water-soluble and systemic nematicide, insecticide and acaricide provides an effective tool in this drip irrigation strategy to give agricultural and horticultural crops an all-round protection against sub-terrestrial nematodes and a wide range of aerial sucking and piercing pests. To optimise this strategy for effective pest control and a minimum burden for the environment it is imperative to understand the systemic movement capabilities of oxamyl in the crop itself. It is necessary to quantify the amount of active ingredient moving in time acropetal in the apoplast (upwards in the xylem) and basipetal in the symplast (downwards in the phloem) of the plant. This study demonstrates very pronounced systemic properties of the active agent oxamyl. Applied to the soil it is taken up passive and quantitatively very efficient by the plant root sys-tem. The translocation in the plant flows primarily to the sites of highest transpiration, the

main metabolic source regions of the growing plant. The subsequent accumulation of oxamyl in the vascular tissue above the applied concentration level guaranties a high lethal effect against pests at the site of action in the foliage. The foliar pest control after soil application is obtained in a short time. A comparison of the extent of pest control after a corresponding foliar application reveals limited systemic translocation between different foliar plant levels at insecticidal concentrations, but apparent sufficient basipetal movement of oxamyl for root protection against nematode invasion. For effective plant protection against nematodes a prophylactic treatment is imperative. These conclusions on the movement of oxamyl in the plant are based on various analytical and in vitro experiments. Furthermore ad planta bioassays in a special designed, multifunc-tional test system, in which several pest groups (nematodes, insects and acaria) were com-bined on different test plant species, demonstrated the oxamyl distribution in the plant. Stud-ies on insects and acaria in a ‘biomembrane feeding system’ and experiments with radio-labelled 14C-oxamyl, inter alia in a ‘split-root system’ on tomato against Meloidogyne incog-nita, provided intrinsic information on the unique systemic properties of oxamyl. According to the results with radiolabelled oxamyl in the ‘split-root system’; it was evidenced that not only oxamyl or any radioactive degradation product elicits the plant protection against nematode species at the roots. Based on this conclusion different hypothesis on possible supplemen-tary modes of plant protection against nematodes by oxamyl are described. Plant growth stimulation has been reported to take place after a treatment with oxime-carbamates in absence of nematodes or other major pests or pathogens. This “carbamate effect“ was examined for oxamyl and other nematicides, but it has been shown to occur not in all plant growth situations. Wodsak, Hans-Peter (1998): Investigations of the organic nitrogen content and nitrogen mineralization potential of soils in water protection areas in the Rhineland. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 140 pages. In the present thesis it was investigated if N-fertiliser recommendations according to the Nmin-method can be further improved by additional consideration of the site-specific N-mineralization potential of the soil. N-mineralization potential can be determined by different methods of soil analysis. These methods measure soluble organic N-compounds or N-fractions (Norg-fractions), which are expected to be closely related to the mineralization of organic nitrogen in the soil. Examples of methods under discussion are the hot-water extrac-tion according to BRONNER AND BACHLER (1979), the Electro-Ultrafiltration (EUF) according to NEMETH (1976) and the CaCl2-extraction suggested by HOUBA ET AL. (1986). Inclusion of such a method to refine the N-fertiliser recommendations according to the Nmin-method de-pending on Norg-content of the soil can be preferably best effected through creation of a soil Norg content classification system. First, the three different organic N-fractions extracted using the different methods were tested for their ability to characterize N mineralization potential of the soils. In contrast to the Nmin-method, the soil samples have to be dried before extraction. Because drying temperature and drying period were found to influence the amount of extractable Norg and by this possi-

bly the ability to characterize N mineralization potential, the different standard methods used for drying soils (24 hours at 40 °C and 4 hours at 105 °C) were compared. The results showed that N mineralization potential can be characterized with sufficient accu-racy by organic N-fractions. The CaCl2-extraction was found to be the most appropriate method, because the CaCl2-Norg-fraction was more closely related to N-mineralization than the two other Norg-fractions, and because this method is much better suited to routine analy-sis concerning practicability and costs. Also Norg extracted by CaCl2-method after drying of soil at 40 °C was more closely related to N mineralization than Norg extracted after drying at 105°C. Investigations showed that the CaCl2-Norg values in soils in the investigated Rhenish area were sufficiently well differentiated to ensure the creation of a soil Norg content classification system. Because of the closer relation of CaCl2-Norg-fraction after drying at 40 °C to N-mineralization, a preliminary N-recommendation concept combining Nmin and CaCl2-Norg was created, using the frequency of these Norg values. A concluding assessment of the use-fulness of this concept needs further research and investigations, particularly in field trials. Wölfel, Diana (1997): Comparative investigations on plant tolerance and biological efficacy of vitamin E on French bean and apple. Institute for Horticulture, Faculty of Agriculture, University of Bonn, 148 pages. Vitamin E (? -tocopherol) and vitamin E–acetate (? -tocopherylacetate) were evaluated for their effects on plant tolerance and antioxidative capacity using Phaseolus vulgaris and Malus do-mestica as test plants. The active ingredient (? -tocopherol, ? -tocopherylacetate) was formu-lated as an emulsifable emulsion concentrate. The results are summarized as follows: 1) Vitamin E applied to P. vulgaris primary leaves reduced the negative effects of the formula-tion blank (= formulation without a.i.) on photosynthesis and membrane permeability. 2) Biological effectiveness of exogeneously applied vitamin E was confirmed by vacuum-infiltration of solutions containing the non-ionic surfactant Triton X-100 (octylphenoxy polyeth-oxyethanol) and the herbicide paraquat. Both chemicals damage biological membranes. Leaf disks of P. vulgaris were infiltrated and surfactant and herbicide toxicity was determined by measurement of chlorophyll fluorescence. Surfactant-induced effects on the stress-sensitive electron transport in the chloroplasts were most effectively documented by the groundfluores-cence Fo. In contrast the Fx-value [(Fp-Fi)/Fp] of chlorophyll fluorescence showed a high sen-sitivity to paraquat-induced stress. 3) Vitamin E (0.1% a.i.) increased tolerance of primary leaves of P. vulgaris infiltrated with Tri-ton X-100 (0.01%). This was demonstrated by measurement of chlorophyll fluorescence (Fo). There was no membrane protecting effect of vitamin E (0.1-5.0% a.i.) against infiltration with the radical forming herbicide paraquat (0.01 and 0.025 mmol/l). 4) Vitamin E acted as an antioxidant. To establish plants with a defined level of oxidative stress, plant tissue was treated with paraquat (01, 0.2 and 0.3 mmol/l). Different methods of stress detection (e.g. measurements of ethylene production, chlorophyll fluorescence and membrane permeability) were compared. Chlorophyll fluorescence proved to be the best

suited. The Fx-value of chlorophyll-fluorescence of P. vulgaris and M. domestica showed a high sensitivity to herbicide-induced stress, being markely reduced after paraquat application. 5) An increased tolerance of leaves of P. vulgaris and M. domestica against paraquat was ob-served following application of vitamin E and vitamin E-acetate (pretreatment). Investigations on chlorophyll fluorescence activity of P. vulgaris-leaves showed that maximum protection against paraquat (0.1 and 0.2 mmol/l) was reached 48h after application of vitamin E (0.1% a.i.) and 24h after application of the acetate form (0.1% a.i.) or the mixture of both forms of vitamin E α-T´OHAc (0.1% a.i.). As compared to the paraquat-control the vitamin-treated leaf areas showed significantly higher Fx-values. In some cases the pretreatment influenced paraquat-sensitivity of adjacent leaf tisssue and the opposite primary leaf. There was no effect of the formulation blank. Under field conditions, an application of α-T´OHAc (0.1% a.i.) 24h before exposure to paraquat (0.3 mmol/l) resulted in a greater tolerance of apple leaves to the herbicide. 6) The treatment of apple (cultivars Jonagold, Cox Orange, Boskoop) and sour cherry branches (cv. Schattenmorelle) with vitamin E and/or the cryoprotector glycerol minimized freezing injury in flowers exposed to low temperatures (Tmax = -1.5°C, Tmin = –3°C) under con-trolled conditions. The combination of vitamin E (α-tocopherol, 0.25% a.i.) and glycerol (5%) provided greater protection than either chemical alone. Time-course studies established that the optimum time of application was between 24 and 48 h before the freezing event. Transport studies established that glycerol penetrated fruit cuticles, thus acting as a penetrating cryopro-tective substance. Wolf, Andreas (2001): Water Protecting Agriculture Subject to Typical Arable Soils and Field Crops in a Wa-ter Reservation Area Northwest of Cologne. Institute for Soil Science, Faculty of Agriculture, University of Bonn, 161 pages. In the catchment area of the water extraction system „Weiler and Langel/Worringen“ of the GEW Köln AG, the nitrate levels increased in the ground water rapidly in the 1970`s. The concern was that either the supply systems would have to be closed or expensive processing steps would have to be undertaken. For these reasons, a study in water protecting agricul-ture has been developed combining the „Arbeitskreis Ackerbau und Wasser im linksrheinischen Kölner Norden e. V.“. After selecting agricultural steps, which show potential decreases in nitrate and pesticide output levels, their effectivness on ground water was stud-ied within a framework of field tests. Typical soils of the test area, the widespread Luvisols, two Cambisols and two Arenosols were selected for the field tests. The latter ones have the tendency to leach nitrates and pes-ticides, which are unfavourable characteristics (lower field capacity and higher water conduc-tivity). This manifests in ground water as a high nitrate level. After forming two test groups with three different soils, two crop rotations with four variants each were observed for a pe-riod of three years. Simultanously to the field tests, in which nitrate and pesticides were de-tected in the soils, ground water and in the crops (sugar beets and grain), the development in the respective water quality parameters was measured. The results were as followed:

The sandy soils, which were studied, did not only show a worse nitrate saving level but also a lower nutrient utilisation level. This was shown in lower yields and a higher Nmin-level after harvesting. According to N-fertiliser prognosis, an increase in N-fertiliser is normally recom-mended for sandy soils. This defined increase from the agricultural viewpoint is paradox to water protection. This is because porous soils with a low potential for production receive hig-her fertiliser values. Different harvest times as well as the timing and intensity of soil tillage have an important influence in the winter nitrate levels. The reduction of soil tillage in order to decrease N-seepage is, nevertheless, tied to optimal weather conditions which can not be controlled by the farmers. The investigated mulch seeding procedure led to an increase in available N for the interme-diate crops, a higher N-assimilation through the intermediate crops and a lower Nmin-level in late autumn. The mulch-seeded beets extracted more nitrogen from the soil than the variants with conventional intermediate crops and the nitrate level could be reduced by as much as 64 %. The ground water in the Water Reserve Weiler is well protected against contamination from pesticides (0.27 % positive). However the only surface water, the Pulheimer Pond, was more polluted till 1993 (7.68 % positive). A waste water treatment plant exit drain in which the pol-luted water, containing pesticide residues and cleaning water for the farm machinery, was identified as the main source of contamination. Based on the acquired results, a replacement of chemical pesticides with mechanical processes of weed control in the test area is neither necessary from the viewpoint of water supply and distribution nor feasible under the current agrarpolitic conditions. Wolf, Wilfried (2000): About the „intermediate farming“ of recultivated loess-soils in the north-west German brown coal mining area. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 127 pages. In the north-west German brown coal mining area large tracts of fertile arable soils, mostly loess cambisols, are used for the extraction of brown coal and then recultivated. After the mining operations the responsible company takes care of an „intermediate farming“ for at least seven years. Farmers then take the soils over and handle them according to the „farm-ing-recommendations for recultivated soils“. The silt-rich soils are characterised by low nutri-ent and humus contents with their well known effects on load-bearing capabilities, surface sealing and compaction. In order to promote the genesis of the virgin soils the cultivation must take place with as much conservation tillage as possible. Research during the „intermediate farming“ was conducted to find indications for the appro-priate tillage and crop management systems, which would allow the build up of the soil struc-ture and avoid structural damage. One result was that the current low level of nutrients could to a large extent be compensated for by levels of fertilizers lying well above the needs and uptake of the crops. A lasting stabilisation of the soil structure through the provision of or-ganic matter was not achieved in this short period, although the Ct-content increased dis-

tinctly through mulching with surface plant residues or through the application of sewage sludge. This had positive effects on biological and physical soil properties. In terms of soil fertility, the cultivation of perennial crops, particularly alfalfa, was especially favourable, even though this effect was not statistically significant. The resulting long period in which the soils were not tilled - in comparison to annual tillage within a crop rotation - fos-tered the stabilisation of the soil structure and the proliferation of Lumbricus terrestris. The distinct tap root of alfalfa contributed to the development of the subsoil. Furthermore, the en-larged pore volume promoted water infiltration and gas exchange. Nitrate leaching and a contamination of the soil with weed seeds could effectively be avoided by a grass-legume mixture. Summarizing the results, it can be said that following the „intermediate farming“ these reculti-vated loess soils are absolutely comparable to cambisols in productivity, although substan-tially more unstable in structure and more sensitive to pressure. Therefore the promotion of a stable soil structure in the following cultivation by farmers must be taken into consideration. This can be realised through an optimal provision of soil organic matter on the one hand and a reduced tillage-intensity as well as a reduction of axle loads and field traffic on the other hand. Wüstemeyer, Arndt (2000): Degradation and Transport of Ethidimuron and Methabenzthiauron in an Orthic Luvi-sol - Contribution towards Validating the Lysimeter Concept. Institute for Plant Nutrition, Faculty of Agriculture, University of Bonn, 178 pages. The transferibility of laboratory/lysimeter date concerning the environmental behaviour of pesticides on a filed scale is invcstigated by the FELS study (FIELD_LysimEter-Laboratory-Simulation) thus making a contribution to validating the lysimeter concept. Within the frame-work of this study, two herbicide active ingredients in concentrations of 1,6 kg ha-1 [thiadia-zol-2-14C]ethidimuron (ETD) and 1,8 kg ha-1 methabenzthiazuron (MBT) as well as 45 g/m -2 KBr were applied on 13-11-1997 to twelve lysimeters (10 x 1 m², 2 x 0.5 m², profile depth 1,1m, Orthic Luvisol), six of which were situated at the Institute's (ICG-5) open-air grounds an six at the field site in Merzenhausen (MRZ). In a prior test phase, 2,6-difluorobenzoic acid (DFB) was applied on 03-03-1997 to all lysimeters (6,3 g m-2). One lysimeter at each of the sites was equipped with soil tmperature and soil moisture sensors at different depths, the lysimeter in question at MRZ was additionally fitted with a weighinh device. In supplementary laboratory experiments, the degradation behaviour of the test substances was characterized as a function of numerous parameteres. For ETD it was shown that degradation after soil incorporation provided results in agreement with the more practice-oriented variant after surface application to soil cylinders. In general, a slight degradation as observed for the two test substances in further studies with disturbed soil. Under standard conditions (20 °C, 40 % WHCmax), a DT50 value of 414 d was determined for ETD and 78 d for MBT in the topsoil (0 – 5 cm). The temperature dependence of the deg-radation was discribed for both substances in the Arrhenius diagram (temperature range: 5 – 25°C). The activation energy for the degradation in the expected range with 55,7 – 59,2 kJ mol-1 for ETD and 33,8 – 37,2 jk mol-1 for MBT. A distinct increase in degradation rate for

both substances was observed with a rise in soil moisture in the range from 25 to 60 % WHCmax. After double-logarithmic plotting of the reaction rate constant against the soil mois-ture for MBT, it was possible to derive a linear relationship (r=0,99). A correction term was introduces for ETD, which did not display any linearity as a consequence of a distinctly lower rise in degradation rate at higher soil moisture. The parameters obtained displayed a high soil moisture sensitivity during degradation. In the subsoil (70 – 80 cm), a doubling of the DT50 value was measured for ETD with a simultaneous decrease in microbial activity (factor of 10) and Corg content (factor of 3,5). The quotient of Corg content and microbial activity is probably responsible for the degradation rate in deeper sil layers. With the aid of the degra-dation data, it was possible to construct correlation areas in a three-dimensional diagram permitting the description of the reaction rate constant a function of soil temperature and soil moisture. By means of the mathematical fit, it was possible to estimate degradation rate coef-ficients forming the basis for calculating the DT50 value under field conditions. In the topsoil, these values rangeed from 162 – 2059 d for ETD and 24 – 230 d for MBT. The metabolization processes of ETD and MBT in soil can be attributed to the activity of aerobic microorganisms. For example, after 90 d of incubation no metabolites were deter-mined for either test substance in sterile soil. However, after doubling the microbial activity by adding wheat straw (80 dt ha-1) the DT50 value for MBT was reduces by a factor of 2,1 and for ETD by a factor of 1,8. A high KBr concentration in the soil (56 mg 100 g-1 DM soil) inhib-ited, in particular, MBT degradation with the DT50 value increasing 2,6-fold (1,4-fold for ETD). Due to the fallow period, the soil water contents in the lysimeters were very high for te 45 – 100 cm layer at 33 – 38 vol.% and displayed hardly any spatial or temporal variance. Even extended periods of drought merely led to a reduction of the soil moisture in teh topsoil so that in Summer 1998 the soil water reserves had only decreased slightly by 60 mm. Conse-quently, in the replenishing phase, leachate formation began unusually rapidly and high leachate discharges were recorded with 40 – 46,5 % of the precipitation volume. After an experimental period of 1 ½ years, significant differences in the averaged discharge from the six lysimeters at the respective sites were found involving 49,4% (ICG-5) and 39,7% (MRZ) of the applied quantity of DFB. After one year, the Br- discharge already reached on average 48,9% of the applied quantity for all lysimeters with no significant differ-ences concerning the sites. DFB therefore displayed retarding properties and thus cannot be regarded as an ideal water tracer in this soil under field conditions. The mean ETD and MBT concentration in the leachate from the lysimeters of one site was at the same level on an annual average (ICG-5: 0,65 µg L-1 ETD, 0,56 µg L-1 MBT; MRZ: 2,94 µg L-1 MBT). The relative standard deviation was up to 127% for one site. Assuming a log normal distribution, the t-test nevertheless confirms that the annual average concentrations of the test substances in the leachates differ significantly in a comparison between the two sides. Moreover, there is a correlation of 0,85 between the average determined ETD and MBT concentrations in the leachate of all lysimeters. The amount of discharge of both test substances in the first year was basically influenced by the concentration of the test sub-stances in the commencing Br- breakthrough, induces by matrix flow (ca. 120 – 200 mm of the cummulated leachate). This discharge was independent of the KOC value of both test substances and differed considerably between the lysimeters. A distinctly smaller quota of the discharge of the test substances is yielded by preferential flow events via water-saturated soil macropores. The extent to which the absence of plants in these lysimeter experiments influenced this result is still unclear.

Young-Keun, Lee (1999): Plant sociological position, natural rejuvenation and establishment of plant communi-ties of Picea abies L. and Pinus sylvestris L. on acid soils in the Rhenish Slate lower mountain region (Rheinisches Schiefergebirge). Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 135 pages. Anthropogenic spruce- and pine- woodlands comprise 60% of all wooded areas of the Eifel and Bergisches Land (spruce: 47%, pine: 13%). The federal state Nordrhein-Westfalen stri-ves for converting these coniferous woodlands into mixed or deciduous woodlands. These types of woodland are thought to be more natural and ecological stable. This report examines the differentiation of vegetation communities by taking in consideration the historical use and management factors, the vegetation differences of pine- and spruce- woodlands as well as the ability for natural rejuvenation, dynamic and establishment of both species. Long lasting woodland pasture, straw extraction, Rottwirtschaft and Schiffelwirtschaft (these two are management systems related to shifting cultivation) and charcoal production for the iron industry lead to the development of coppice and heathlands on large areas of the Rheinische Schiefergebirge. In the mid 18 hundreds these areas were largely converted into coniferous woodlands. The spruce-woodlands, also called Galium harcynicum-Picea abies communities by a plant sociologist, can be divided up into three types: I) typical formation, 2) nutrient-rich formation with Oxalis acetosella, and 3) formation under shifting soil moisture conditions with Deschampsia flexuosa. According to soil- and topographic-characteristics pine-woodlands can be differentiated into four different communities: 1) Vaccinium myrtillus-Pinus sylvestris woodland, 2) Pteridium aquilinium-Pinus sylvestris woodland, 3) Molinia caerulea-Pinus syl-vestris woodland, and 4) Festuca ovina-Pinus sylvestris woodland. Due to the cool and humid climate good natural rejuvenation in spruce-woodlands is pre-dominantly found in the higher regions. Important factors for a good natural rejuvenation of pine woodlands are ground cover and humus characteristics. The height increase of both species mainly depends on the amount of light received. Picea abies can be found in areas of high rainfall located higher than 500 m above sea-level. Pinus sylvestris, on the other hand, occurs on drier, south-facing slopes and cliffs (rocky sites), such as in the Rur Valley near Nideggen and the Urft Valley near Gemünd. Both spe-cies should be classified as agriophytes, i.e. they are part of the potential natural vegetation and the potential local climax vegetation. Yu Jing, Zhu (2005): Efficiency of Bacillus thuringiensis with Abamectin on different agricultural pests and their natural enemies. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 82 pages.

The present work aimed to study firstly in the laboratory the characteristic of a new type bio-cide GCSC-BtA (Germany-China Scientific Cooperation-Bacillus thuringiensis-Abamectin) by using HPLC as well as its efficiency on different agricultural pests and their natural enemies. The modes of action of GCSC-BtA on insecticidal activity, antifeedant effect and sublethal effect were also determined. Further experiments were devoted to investigate the factors affecting its efficiency to pests. Finally, field experiments were carried out to estimate the efficiency of GCSC-BtA against pests and its side-effect on natural enemies in alfalfa pas-ture, tea garden and broccoli field. All these experiments have the goals to enrich application characteristics of this promising biocide and so its use in biological control programs against agricultural arthropod pests. The results of the laboratory experiments showed that in the bioconjugation system where B.t. protoxin, Abamectin-COONa and EDC presented at the same time, existed the bioconju-gation product GCSC-BtA, which had a HPLC characteristic peak at retention time about 12 min. GCSC-BtA displayed high efficiency against different pest species from orders of Acari, Thysanoptera, Homoptera, Coleoptera and Lepidoptera as well as relatively safety to their natural enemies. It possessed a combination of strong stomach toxicity and high contact tox-icity property, and also acted as a good antifeedant with lower feeding damage and higher deterrent effect than B.t. toxin crystal and Abamectin. With sublethal concentrations, it sho-wed highly suppression on egg hatching and subsequent progeny formation of pests. Its efficiency to pests varied to different arthropod species, decreased significantly at the older developmental stages except that egg stage had the highest tolerance, and tended to per-form better under warmer condition and with longer exposure time. A single application of GCSC-BtA might control pests with up to 6-d persistence. It was found in the field experiments that biocide GCSC-BtA showed higher efficacy against arthropod pests and was comparatively less toxic to natural enemies than the synthetic py-rothroid Cypermethrin in alfalfa pasture, tea garden and broccoli field. Zacharias, Arndt Karl (2002): AB-QTL analysis for the introgression of wild form alleles in barley. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 161 pages. In today´s barley varieties the production increase, through breeding, is mainly based on the new combination of genes, respectively alleles, of the already adapted cultivated species Hordeum vulgare ssp. vulgare. However, in the long term this can lead to an impoverishment of genetic diversity, as the crossing of successively improved varieties among themselves may lead to a displacement of alleles from the available gene pool. The specific use of alleles from the wild species could represent a solution to this problem, not only in regard to the transfer of new resistance properties, but also in regard to the im-provement of quantitative traits. Using the method of the AB-QTL analysis, developed by Tanksley & Nelson (1996), specific alleles from the wild forms could be identified for the im-provement of quantitative traits of the two spring barley varieties Apex and Harry.

For this purpose, two BC2 backcross populations comprising of 300 genotypes were avail-able. For construction of the backcross populations, the varieties Apex and Harry (Hordeum vulgare ssp. vulgare) were used as the recurrent parents. The wild form ISR 101-23 (Hor-deum vulgare ssp. spontaneum) functioned in both cases as the donor of wild form alleles. During the years 1997-1999 the BC2F2-derived lines were evaluated on the experimental farm Dikopshof of the University of Bonn for the following quantitative traits: plant height, ear length, ear/plant, grain/ear, thousand kernel weight (TKW), grain yield/plant, biomass/plant, harvest-index and yield. To identify the introgression of the wild form in both backcross populations, 102 microsatel-lites and 12 AFLP-markers were used. The determination of putative QTL took place on the basis of the linear regression from genotype on phenotype, and by means of the analysis of variance (ANOVA) for the years 1998 and 1999. Applying to the two QTL definitions, 20 QTL in the Apex-backcross population and 25 QTL in the Harry-backcross population could be detected. By the introgression of the wild form allele in the marker region HvUDPGPP (5 H), the trait TKW could be increased by approx. 8 %. The comparison of markers mapped in both backcross populations showed that specific al-leles from the wild form can lead in different genetic backgrounds to different effects on the evaluated traits. Nevertheless, it has been demonstrated that the improvement of quantitative traits of today´s barley varieties is possible by the introgression of alleles from the wild form Hordeum vulgare ssp. spontaneum. Thereby, the method of the AB-QTL analysis is shown to be an effective tool for the identification of trait improving QTL alleles from wild forms. Zegula, Thorsten (2004): Suitability of different predatory arthropod species for the biological control of Frank-liniella occidentalis (PERGANDE) (Thysanoptera: Thripidae) and a survey of the spread-ing of Thrips palmi KARNY (Thysanoptera: Thripidae) in European greenhouses. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 89 pages. The aim of the present study was to assess the suitability of different predatory arthropod species for the biological control of the western flower thrips Frankliniella occidentalis (PER-

GANDE) (Thysanoptera: Thripidae) under greenhouse conditions. Furthermore, the introduc-tion of the melon thrips, Thrips palmi KARNY (Thysanoptera: Thripidae) - a quarantine pest - into Europe was investigated via literature reviews and a survey of the quarantine offices of various European nations. In the laboratory experiments, twelve predatory mites, two predatory thrips and five predatory bugs were taken into stock culture as potential beneficial arthropods. Later on, experiments on the biology, reproduction and predation with F. occidentalis and T. urticae as prey were conducted. All the predatory mites developed by exclusive feeding on F. occidentalis larvae, except C. fortis, C. malaccensis and E. addoensis. Reproduction of A. cucumeris was high-est by exclusive feeding on F. occidentalis larvae and lowest for A. womersleyi and A. degenerans. C. malaccensis was not able to lay eggs with this prey. Despite their small size the predatory mites showed good predation success. During the 18-day experimental

period, the prey consumption was highest in E. addoensis and A. cucumeris. The predatory thrips F. vespiformis developed with F. occidentalis larvae as prey. On the contrary, A. intermedius could not develop with this prey species. While F. vespiformis was able to lay eggs with F. occidentalis larvae as prey, A. intermedius was not able to do so. Both the thrips species proved themselves to be more efficient predators against F. occidentalis larvae than the predatory mites during the experimental period. The five predatory bugs could develop completely by feeding alone on F. occidentalis larvae. The daily reproduction period was lower in D. tamaninii and M. pygmaeus than in the three Orius species. The prey consump-tion was clearly higher in the predatory bugs than in the predatory mites and predatory thrips. In the greenhouse experiments, population development of F. occidentalis was recorded in the years 1999 - 2001. Infestation by the pest thrips showed great differences in the three-year study period due to the variations in plantations and operations. For the experiments on the suitability of the biological control of F. occidentalis under greenhouse conditions a predatory thrips (F. vespiformis ), a predatory mite (A. cucumeris) and two predatory bug species (D. tamaninii, M. pygmaeus ) were selected. In the present studies, the predatory mite showed no effect against the pest thrips. However, the release of the predatory thrips F. vespiformis as well as that of the predatory bugs D. tamaninii and M. pygmaeus yielded satisfactory results. The results of the survey of the introduction of and damage by the quarantine pest T. palmi revealed that this pest has been introduced to the Netherlands, Slovakian Republic and in England. Additionally, sporadic appearances have been reported in Poland. However, since all infested crops were properly disposed of, establishment of the pest has not been recorded in Europe, to date. Zens, Irene (2000): Occurrence and control of root of sugar beet caused by Rhizoctonia solani. Institute for Plant Diseases, Faculty of Agriculture, University of Bonn, 120 pages. The symptoms of root rot of sugar beet frequently affect single plants and cause losses that are negligible. For a few years in Germany extensive damages become apparent. The causative agent is member of the complex of pathogens Rhizoctonia solani. It is a world-wide known and extremely diverse fungus occurring in numerous biotypes. In this paper the root rot pathogen was characterised and first attempts of control were elaborated. The german pathogen was assigned to anastomosis group AG 2-2. This AG was even isolated in very early stages of growth of sugar beet. The AG 2-2 can be subdivided according to the most common host plants into AG 2-2IIIB, a ´gramineae-type´ and AG 2-2IV characterised as ´chenopodiaceae-type´. Investigations into the root pathogen by means of RAPD-PCR showed that further subgroups within AG 2-2 can be differentiated. Out of these the majority was assigned to the ´gramineae pathogen´. This type furthermore was isolated from fields with high losses much more frequently. Biological characteristics supported the importance of differentiating several types. They did not only differ in temperature tolerance but also in fungicide sensitivity and especially virulence. In a single attacked field in spite of distant dis-ease patches a very homogenous population was proofed. This population consisted of a single pathotype remaining unchanged over a period of several years. The reason could be

that either the predominant type suppressed other ones or these types occurred in so small frequencies that detection was impossible with the employed methods. Corresponding types appeared not only within different fields but also in different sites of Germany and the Nether-lands. Distant fields showing the same pathotype showed further common qualities. With a high percentage of maize in the rotation isolation frequency of type 4 increased. This type was classified as particularly aggressive against sugar beet seedlings in ´mini tests´ and caused the largest damages in the fields. Rhizoctonia solani AG 2-2 owns a great potential of damage. However in Germany hitherto protection of plants is restricted to indirect control. The occurrence of diverse pathotypes is problematic for control means. It is imaginable that even resistant sugar beet cultivars become less effective when a new pathotype becomes predominant. Spraying of fungicides showed some success but only with high application rates. For this reason seed treatments with the antagonistic bacterium ´FZB24´ and several fungicides were tested. The disease suppressive effect of seed dressing was provable up to the end of the growing season. Combinations of fungicides and antagonist especially were effective. Spraying of fungicides targeted on the seed line a few centimetres under the soil surface, the depths where sugar beets are attacked first, was evenly successful. Zimmer, Stefan (2003): The domestication of medicinal plants; - establishment, fertilization harvest -. Institute for Crop Science and Plant Breeding, Faculty of Agriculture, University of Bonn, 173 pages. From 1999 to 2002 the WELEDA AG, Schwäbisch Gmünd, in cooperation with the Insti-tut für Pflanzenbau, University of Bonn carried out pot and field trials for the domestication of selected medicinal plants. The aim of the project was to grow meadow saffron (Colchicum autumnale), white dead nettle (Lamium album), bearberry (Arctostaphylos uva-ursi), lily of the valley (Convallaria majalis) and dog’s mercury (Mercurialis perennis) under field condi-tions according to the guidelines of organic farming. The main aim was the establishment, fertilization and harvest of the medicinal plants. For this purpose the effects of soil type, plant material, planting date, fertilization, cultivation system and harvest time on growth and yield structure were investigated. To be able to describe and compare the growth of these plants with other scientific results, a scale for the different growth stages was developed for each species. The growth of the me-dicinal plants was assessed regularly with this scale, and the specific yield parameters were measured. The experimental results were used to provide recommendations for the cultiva-tion of each plant. The establishment of meadow saffron, bearberry and dog’s mercury in the trial was success-ful leading to stable yields. The cultivation of the lily of the valley in the field was not satisfy-ing. The white dead nettle was only tested in pot trials, hence no field results are available. The nutrient removal by the medicinal plants occurred at a very low level, except the white dead nettle. Interestingly, only the meadow saffron responded to fertilization with a yield in-crease. Compared to the other medicinal plants the white dead nettle was the most suscepti-ble to diseases and parasites. Small changes of the cultivation system, e.g. the shading of the dog’s mercury, resulted in substantially better plant growth. In a mechanisation experi-

ment the meadow saffron could be grown using the machinery for normal vegetable cultiva-tion, which led to a reduction of manual labour. The yields of the medicinal plants gained under experimental conditions provide only a guideline of what can be expected in practice.