Response of maize varieties to the effects of acidic soils under glasshouse conditions in the Eastern Cape

1

TABLE OF CONTENTS

ABSTRACT ............................................................................................................................................ 3

ACKNOWLEDGEMENTS .................................................................................................................... 4

CHAPTER 1 ........................................................................................................................................... 5

1.1. INTRODUCTION .................................................................................................................. 5

1.2 OBJECTIVE ................................................................................................................................. 6

1. 3 HYPOTHESIS ........................................................................................................................... 6

CHAPTER 2 ........................................................................................................................................... 7

2.1 LITERATURE REVIEW ............................................................................................................. 7

2.1.1 Importance of maize in the Eastern Cape .............................................................................. 7

2.1.2 Occurrence of acidic soils in SA ............................................................................................ 7

2.1.3 Methods used to combat soil acidity ...................................................................................... 8

2.4 Methods used to screen for tolerance to soil acidity ..................................................................... 9

2.4.1 Nutrient solution .................................................................................................................... 9

2.4.2 Hematoxylin ........................................................................................................................... 9

2.4.3 Growth chambers ................................................................................................................... 9

2.4.4 Acid soil pots ....................................................................................................................... 10

2.4.5 Sand culture ......................................................................................................................... 11

2.4.6 Soil –Agar Assay ................................................................................................................. 11

CHAPTER 3 ..................................................................................................................................... 12

3.1 MATERIALS AND METHODS ................................................................................................ 12

3.1.1 Soils used in the assay .......................................................................................................... 12

3.1.3 Treatments and experimental design. ................................................................................... 13

3.1.4 Planting and trial management ............................................................................................. 13

Fig.1.1 Maize plants growing on pots ................................................................................................... 13

CHAPTER 4 ......................................................................................................................................... 14

4.1 RESULTS ................................................................................................................................... 14

Fig. 2.1 Fresh root weights (FRW) ...................................................................................................... 14

Fig. 2.2 Dry root weights(DRW) ......................................................................................................... 14

Fig. 2.3 Number of lateral roots of maize varieties.............................................................................. 15

Fig. 2.4 Primary root lengths of maize varieties ................................................................................... 15

Fig.2.5 Dry plant weights of the maize varieties .................................................................................. 16

Fig 2.7 Variety 2 (32W71) and Variety 4 (SAHARA) ......................................................................... 17

2

Fig.2.9 Maize variety 5 (PAN 6110) ..................................................................................................... 17

Table 3: Fresh root weight averages ..................................................................................................... 18

Table 4: Means of Primary root length of five maize varieties ............................................................. 18

Table 5: Means of Number of lateral roots of five maize varieties...................................................... 18

Table 6: Dry root weights of five maize varieties ................................................................................. 19

Levels not connected by same letter are significantly different. ........................................................... 19

Table 7 Soil chemical properties ........................................................................................................... 19

CHAPTER 5 ......................................................................................................................................... 21

5.1 Discussion ................................................................................................................................... 21

5.1.1Dry plant weight ................................................................................................................... 21

5.1.2 Dry root weight .................................................................................................................... 21

5.1.3 Primary root length .............................................................................................................. 22

5.1.4 Number of lateral roots ........................................................................................................ 22

5.2 Conclusions and Recommendations ........................................................................................... 23

CHAPTER 6 : REFERENCES ............................................................................................................. 24

3

ABSTRACT

The experiment was to screen five maize varieties on pots containing acid soils in a

glasshouse. The maize varieties that were used are NGOYI (V1) (local variety), 32 W71

(V2), 33 H 56 (V3), SAHARA (local variety) and PAN 6110 (Control). The maize varieties

were used as treatments in this experiment, the soils used had Aluminium saturation. The

experiment was allowed to run for a period of 20 days. The objective of the experiment was

to screen different maize varieties for tolerance to acidic soils in a glasshouse. It was

observed that the five maize varieties had different performance in terms of top-growth and

root growth. Where PAN 6110 and 32W71 were the most tolerance varieties and SAHARA

was more sensitive to acid soils in pots. The seedlings were uprooted and washed with tap

water. They were taken to the laboratory and measured and weighed. Parameters that were

measured are plant height, stem length, leaf length, number of leaves and leaf width. The root

growth was determined by measuring primary root length, number of lateral roots, root

weight and plant weights were also measured. The control in this experiment showed to be

tolerant to acid soils. The soils that were used were collected from Tsolo and soil

characteristics were measured.

4

ACKNOWLEDGEMENTS

I give my sincere gratitude to my supervisor Dr. Mutengwa for giving me the opportunity to

work on this project. To Mr. Makhafula and Mr. Vacu for giving me advice and guidance to

the implementation of this project.

I would like to thank the department of agronomy for availing their facilities necessary to the

success of this research. To my friends, classmates, and staff members who have been

motivation to encourage me to complete this study. I would to give unique special

appreciation to Miss K. Mtshengu for her loyal support to me to carry out this research your

role is highly appreciated without your support and motivation this project would have never

been successful.

Wish to thank the Financial Aid department for the financial support in the academic year

2014.

5

CHAPTER 1

1.1. INTRODUCTION

Dominant component of acid soil infertility is South Africa is Al toxicity, soils developed

under cool humid climates like Tsolo have humic topsoil horizon that contains up to 23 C

molc Al kg-1

(Buhmann et al. 2006). Geochemical composition of parent material, natural

acidification and leaching of nutrients under high rainfall as well as exploitative farming

activities produced soils that are unproductive in these smallholder farmers in the EC

Province. An increase in the population and its challenge to food security around the world,

particularly in developing countries is a major concern. There is little or no research

conducted to evaluate the performance of maize in these soils in terms of tolerance to acid

soil toxicity. Farmers in the Eastern Cape are resource limited because of different reasons.

The province is dominated by smallholder farmers that produce maize as a main staple food

source. Research conducted in most parts of EC show that maize is the most important

summer crop for resource poor farmers (Musunda, 2012). The need to reduce the effects of

soil acid toxicity as a major yield limiting factor in rural areas has never been more urgent

than now.

Research conducted revealed that plants differ in their tolerance to acid soils; this allows

plant breeders to develop cultivars that are more tolerant to acid soils (Miao et al, 2013).

Selection and breeding programs for Al tolerance are important. In many crop species, a

range of Al tolerance has been identified and selective breeding programs have produced

crop varieties with increased Al tolerance. Physiological and molecular characterisation of

these plants has led to better understanding of the mechanisms of Al tolerance. The degree of

Al- induced root growth inhibition can be used to discriminate plants at the seedling stage for

their relative Al sensitivity to Al toxic soils (Giaveno and Filho, 2000).

There is considerable genetic variability in sensitivity in the major crops and the evaluation of

root elongation in nutrient solution has been useful in developing Al-tolerant varieties

(Giaveno and Filho, 2000).

In order for plant breeders to be successful in their breeding programs, they must have an

understanding of the physiological, genetics and gene regulatory information of soil

tolerance.

There are different methodologies that are used to screen plants for their tolerance and

sensitivity to acidic soils or Al saturated soils

6

Field trials have proved to be effective in selecting resistance but are very expensive and time

consuming (Giaveno and Filho, 2000). Screening methods such as field trials and glasshouse

experiments are regarded as expensive and slow for screening of large numbers of entries

(Mendes et al, 2013).

If breeders are to make practical use of differential Al tolerance in breeding programs it is

essential that rapid and inexpensive screening procedures be developed and used. A rapid and

reliable screening procedure is required to discriminate sensitive and resistant genotypes.

Plant performance must to a large degree be dependent on the variable seed reserves of

nutrients. Although encouraging advances have been made in the development of rapid

screening procedures, there have been very few reports of correlative studies with plant

performance under field conditions and doubts persist regarding the selection of

discriminatory growth parameters. Among the indices of performance which have been

proposed for various crops are top growth and root mass, seminal root length, the differences

between seminal root length prior to Al stress and after a period of Al stress, total root length

and the relative seminal root length of plants grown simultaneously in nutrient solution with

acid and without Al. qualitative assessments based on visual symptoms of toxicity have also

been proposed (Mendes et al, 2013).

1.2 OBJECTIVE

To screen different maize varieties on acid soils for tolerance to Aluminium saturation

1. 3 HYPOTHESIS

Different maize varieties have the same response to acidic soils

7

CHAPTER 2

2.1 LITERATURE REVIEW

2.1.1 Importance of maize in the Eastern Cape

Maize is the largest locally produced field crop and an important source of carbohydrates in

SA and South African Developmental Community (SADC) for both Human and Animal

consumption (Trigurtha, 2009). Maize production can help ensure food security in the

Eastern Cape Province. Agricultural Stats revealed that in 2011-2012 the Eastern Cape (EC)

Province produced a total of 92 tonnes of maize.

Maize (Zea mays L.) is the most valuable grain crop in South Africa and it is produced

throughout the country under diverse environments (Du Plessis, 2003). In a developing

country like South Africa maize is consumed directly as a staple diet. It is estimated that 8.0

million tons of maize grain are produced in South Africa (SA) annually; approximately 3.1

million Ha of land is planted with maize (Du Plessis, 2003). Maize is reported to be an

important field crop in SA for both commercial and smallholder farmers (Beukes et al, 2011).

Maize is one of the field crops that SA exports to other countries which contribute 3% of SA

agriculture Gross Domestic Product (GDP) (Trigurtha, 2009; Stats SA, 2013). In 2011-2012

season research work shows that 3141 Ha of land in SA was used to grow maize.

2.1

11

2.4.5 Sand culture

Sand culture is an alternative assay that could be used to supplement hydroponic assays for

Al tolerance. This procedure has the advantage of allowing examination of Al tolerance with

some older plants and as solid substrate, it is more viable because the results of this assay can

be comparable to those in the field conditions (vallagarcia et al..2001). In sand culture

assays Al and nutrient are applied to the pots plants in a solution form and sand is considered

inert therefore amounts of Al applied can be controlled and can be reproduced.Shortcomings

of using sand culture, the complex interactions of Al and nutrients has resulted to limitation

to the use of this screening method. This can be avoided because stored nutrients in the

cotyledons can sustain growth for the first days after germination.

2.4.6 Soil –Agar Assay

A modified screening media that involves a soil on-agar assay was described by Voigt as

cited by Deborah et al (2003). When plants with small seeds that would have difficult

germinating in acid soil. This modified method requires only a small layer of acid soil to be

placed on top of agar layer. A difference in the time required to grow into an agar layer was

observed among cultivars of a number of forage legumes, which is presumed to reflect a

difference in Al tolerance (Voigt & Mosjidis, 2002).

12

CHAPTER 3

3.1 MATERIALS AND METHODS

3.1.1 Soils used in the assay

The soils used in this assay were collected from Tsolo area that is characterised with acidic

soils due to high rainfall in this region. The soils were sampled from 0-250mm plough layer.

The soils were sieved under 2mm sieve. Sandy soils and red soils were used. The soils were

sampled and analysed in the University of Fort Hare soil Science laboratory. The soils were

tested for the following soil characteristics.

pH (KCl)

Total P (mg/L)

Total N (mg/L)

Organic C (%)

Clay (%)

Ca (mg/L)

Mg (mg/L)

Exchangeable acidity (cmol/L)

Total cations (cmol/L)

Acid saturation (%)

Zn (mg/L)

Mn (mg/L)

Cu (mg/L)

13

3.1.2 Experimental site

The experiment was conducted in a glasshouse with temperature control (280 C), wet wall

and fans at University of Fort Hare School of Agriculture. The glasshouse is located near

Alice town that is 320 46’ S and 260 50’ E at an altitude of 535 m above sea level

(Nciizah,2011).The experiment will be established on 02 November to 21 November.

3.1.3 Treatments and experimental design.

The five maize varieties were selected among ten maize varieties that were initially grown on

nutrient culture in a laboratory environment. The best performing varieties were selected for

further testing on acid soil pots (ASP) and a one that showed signs of tolerance were selected

and used as control. Maize seeds were grown in pots with aluminium saturated soils.

Varieties that were used in this bioassay are (1) Ngoyi (Local variety), (2) 32 W 71, (3) 33H

56, (4) SAHARA, (5) PAN 6110. The experiment was laid out in a randomized complete

block design in a glasshouse with temperature control (280 C), wet wall and fans at

University of Fort Hare School of Agriculture.

3.1.4 Planting and trial management

The seeds were collected from the cold room in the Agronomy department of the University

of Fort Hare (UFH). They were submerged in water for 24 hours at 250 C. the seedlings were

transplanted after priming into pots with saturated Al concentration. The pots were watered

with tap water two times a day in the morning and afternoon for a period of 20 days. Each pot

was planted with three seeds of each variety; after 50 % emergence the seedlings were

thinned to leave one plant per pot in the three replicates.

Fig.1.1 Maize plants growing on pots

14

CHAPTER 4

4.1 RESULTS

Fig. 2.1 Fresh root weights (FRW)

Fig. 2.2 Dry root weights(DRW)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

NGOYI 32W71 33H56 PAN 6110 SAHARA

FRW

FRW

0

0.1

0.2

0.3

0.4

0.5

0.6

NGOYI 32 W 71 33H56 SAHARA PAN 6110

D

R

W

m

e

a

n

s

VARIETIES

DRW

DRW

15

Fig. 2.3 Number of lateral roots of maize varieties

Fig. 2.4 Primary root lengths of maize varieties

0

2

4

6

8

10

12

14

16

NGOYI 32 W71 33 H 56 SAHARA PAN 6110

N.LR

N.LR

0

5

10

15

20

25

30

NGOYI 32 W 71 33H56 SAHARA PAN 6110

PRL

PRL

16

Fig.2.5 Dry plant weights of the maize varieties

Fig. 2.6 Variety 1 Ngoyi plant

0

0.2

0.4

0.6

0.8

1

1.2

1.4

NGOYI 32W71 33H56 SAHARA PAN 6110

DPW

DPW

19

Table 6: Dry root weights of five maize varieties

Level Least Sq

Mean

2 A 0.55

5 A 0.54

1 A 0.53

3 A B 0.48

4 B 0.38

Levels not connected by same letter are significantly different.

Table 7 Soil chemical properties

Soil Characterisation

Soil Properties Mbinja (Red soil) Qumbu (sandy soil)

pH (KCl) 3.85 4.15

Total P (mg/L) 4 7

Total N (mg/L) 0.09 <0.05

Organic C (%) 0.6 <0.05

Clay (%) 29 7

Ca (mg/L) 236 145

Mg (mg/L) 61 24

Exchangeable acidity

(cmol/L)

1.17 0.35

Total cations (cmol/L) 3.29 1.43

Acid saturation (%) 36 24

Zn (mg/L) 0.5 1.6

20

Mn (mg/L) 39 16

Cu (mg/L) 4.5 1.2

21

CHAPTER 5

5.1 Discussion

The experiment was to screen different maize varieties for Aluminium tolerance under acidic

soils in a glasshouse at the University Of Fort Hare School Of Agriculture. (Miao et al,

2013).. It was hypothesised that different maize varieties have the same response to acidic

soils. The results of the experiment proved that the five maize varieties had different

responses to the exposure to acid soils; therefore we reject the null hypothesis in this

experiment.

The main findings in this experiment are that in terms of vegetative growth (biomass) fresh

plant weight and dry plant weight, where the fresh plant and the roots were weighed on a

weighing balance scale in the laboratory.

In this experiment it was observed that the averages of the maize varieties showed

differences among the parameters that were measured (Giaveno and Filho, 2000). . The data

that was collected during the experiment was the plant height, stem length, leaf length and the

leaf width this was according the study by (Deborah et al 2003). These were used to analyse

the effect of Aluminium toxicity on the seedling growth. Parameters such as dry plant weight

and dry root weight will be discussed on this paper for analysing the tolerance of the five

maize varieties that were screened (Deborah et al 2003).

5.1.1Dry plant weight

PAN 6110 (V5) showed an average of 1.20 which was the highest average among the five

varieties under study. The second most performing variety in this experiment on dry plant

weight was the 33 H 56 (V3) which was 1.16 and 32 W 71(V2) which was 1.12 these have

been bred for tolerance. PAN 6110 which was used as a control in this experiment showed

that it was tolerant to acid soils. SAHARA showed the lowest average for dry plant weight in

the experiment, which showed that this variety is more susceptible to acid soils.

5.1.2 Dry root weight

The root weights of the five varieties were measured from the three replicates that were

growth, the averages show that varieties PAN 6110 (V5) 0.54, NGOYI (V1), 0.53 and 32 W

71 (V2) 0.55 were best performing varieties in terms of root growth which indicates that they

can best tolerate exposure to Aluminium saturated soils. SAHARA showed to be susceptible

to acid soils because they had reduced root growth because the observed that average for this

variety was 0.38.

22

5.1.3 Primary root length

A study conducted by Villagarcia el at (2001) the primary root lengths of the maize varieties

were measured and were analysed, the average means of each variety are discussed in this

section. PAN 6110(V5) had average mean of 27.17 followed by 32 W 71(V2) and 33H56

(V3) these maize varieties are not affected by the Aluminium because their root growth is not

reduced. The SAHARA (V4) and NGOYI (V1) show reduced root length which indicates

that these varieties are sensitive to the effects of Aluminium saturation.

5.1.4 Number of lateral roots

The number of lateral roots shows that the root growth of the plant was high or low,

SAHARA had a high amount of number of lateral roots. NGOYI,32 W 71 and PAN 6110 had

averages ranging from 12.22, 13.67 and 12.11 respectively which was a good number of

lateral roots.

The data that was collected in the experiment can allow for conclusions to make about the

response of maize varieties screened for Aluminium tolerance. . Miao et al (2013) further

indicated that a visual observation of symptoms on plant growth is reduced root length. The

main challenge with this experiment is that the soils used were uniform. A study conducted

by Villagarcia el at (2001) it is reports that soil based screening procedures for Aluminium

tolerance may be dependent on soil type. There was no soil used to compare the response of

these maize varieties. The soils used were acidic collected from Qumbu location in the Tsolo

town. This experiment requires more factors to be added in order to make comprehensive

conclusions about the tolerance of these soils. The study design of this experiment was poorly

not accurate enough to allow for true tolerance. In literature it is reported that different maize

genotypes have different tolerance and sensitivity levels to Aluminium tolerance (Deborah et

al 2003). The maize varieties that were screened showed different responses to the effects of

Al saturation. It can be concluded that maize varieties have different responses to the effects

of acidic soils. Exposure to Al causes stunting of the primary root and inhibition of lateral

root formation. Affected root tips are stubby due to inhibition of cell elongation and cell

division. The resulting restricted root system is impaired in nutrient and water uptake, making

the plant more susceptible to drought stress. Plants sensitive to Al toxicity have greatly

reduced yield and crop quality ( Samac and Tesfaye, 2003).

The maize varieties used in this experiment have variation of responses based on the

parameters measured, PAN 6110 (V5) which was used a controlled show best performance in

terms root growth.

23

5.2 Conclusions and Recommendations

Variety 5 PAN 6110 is a resistant variety to acidic soils. Variety 2 32 W 71 is also resistant to

acid soils. Root growth is a parameter that was used to evaluate the tolerance of the five

varieties because the effect of Aluminium toxicity is the inhibition of root growth. Varieties

that are tolerance to acidic soils will have a good root growth. SAHARA is the most sensitive

variety among the five varieties.

The results obtained from this study are not enough to make conclusions about the

performance of the maize varieties under field conditions. Further investigation is required to

screen for more parameters such as leaf area and stem diameter to have more treatments in

the experiment. Farmers must be assisted with screening of varieties such PAN 6110, 32 W

71, NGOYI which show tolerance to the acidic soils. There are other tests that must be

conducted using other methodologies to screen for varieties that show tolerance to acidic

soils conditions.

24

CHAPTER 6 : REFERENCES

BEUKES, D.J, MAPUMULO, T.C, FYFIELD, T.P AND JEZILE, G.G. 2012. Effects of

liming and inorganic fertilizer application on soil properties and maize growth and yield in

the rural agriculture in the Mbizana area, Eastern Cape, South Africa. South African Journal

of Plant and Soil.29 (3 & 4): 127-133.

CHOUDHARY, A. K., SINGH, D., KUMAR, J. 2011. A comparative study screening

methods for tolerance to Al toxicity in Pigeonpea [ Cajanus cajan (L) Millspaugh]. Australian

Journal of Crop Sci. 41:14-18

DEBORAH, A., SAMAC AND MESFIN T. 2003. Plant improvement for tolerance to Al in

acid soils-A review. Plant cell, tissue and organ culture 75: 189-207.

GIAVENO, C.D., AND FILHO, J.B.M. 2000. Rapid screening for Al tolerance in maize

(Zea Mays, L). Genetics and Molecular biology. 23,4. 847-850.

LANDZELA, B, 2013. A study of effects of Bt maize (MON 810) crop and its residues on

selected soil biological properties and N and P release in a sandy loam soil from Alice,

Eastern Cape, South Africa. Thesis. University of Fort Hare.

MENDES, P., FARINA M.P.W AND CHANNON, P. 2013. Assessment of Aluminium

(Al) tolerance in maize using a rapid screening procedure. South African Journal of Plant and

Soil. 1:3, 83-86.

MIAO, B.,MEIXUE, Z., DONGFA, S.,CHENGDAO, L., 2013. Molecular approaches

unravel the mechanism of acid soil tolerance in plants. The crop journal. 1 (2013) 91-104.

THE, C., CALBA, H., ZONKENG, C., NGONKEU, E.L.M., ADETIMIRIN, V.O.,

MAFOUASSON, H.A., MERA, S.S AND HORST, W.Y. 2006. Responses of maize grain

yield to changes in acid soil charecteristics after soil amendment. Plant and Soil . 284: 45-57.

VILLAGARCIA, M.R., THOMAS, E., CARTER, Jr., RUFTY, T.N., NIEWOEHNER,

A.S., JENNETTE, M.W AND ARRELLANO S. 2001. Genotypic ranking for Al tolerance

of soybean roots grown in hydroponics and sand culture. Published by crop science. 41:

1499-1507.