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HISTOLOGICAL RESPONSE OF SUSCEPTIBLE AND RESISTANTDATE-PALM
CULTIVARS TO THE ROOT-KNOT NEMATODE,
MELOIDOGYNE INCOGNITA INFECTION.
Eissa*, M.F.MI.; EI-Sherief, M.A2.; Abdel-Gawad, M.M.I.; Ismail,
A.AI.;and EI-Nagdi, W.M.AI.
1.Nematology Unit, Plant Pathology Dept., National Research
Centre.
2. Nematology Dept., Fac. Agric., Cairo Univ.
ABSTRACT
The cellular alteration in M incognite infected roots of
susceptible andresistant date-palm cultivars were histologically
studied. The most obvious cellreaction of the susceptible cultivar
"Zaghlool" was the giant cell formation. Inresistant cultivars
"Deglet Noor" and "Samani" the infected roots reacted to
thenematode infection by forming necrotic area around the invading
nematodelocalities. Deformed portions of dead nematodes were found
surrounded bydeeply stained necrotic cells. In few cases, malformed
small giant cells wereobserved in association with nematode larval
stages.
INTRODUCTION
Numerous nematode pests were reported to attack date-palm
rootscausing considerable damage to the plants especially in their
early stages. Theroot-knot nematodes, Meloidogyne spp. are some of
the serious date-palmnematode pests. In 1993 Buhrer et al reported
the occurrence of root-knotnematodes on date-palm in USA. Carpenter
(1964) proved that cultivars ofDeglet-Noor and Amhat were tolerant
to root-knot nematode infection, whileBraim, Hayany and Honey were
rated as susceptible cultivars. Lamberti andGreco (1977) reported
Deglet-Noor cultivar as least susceptible to Mjavanicain Algeria.
Minz (1963) from Palestine; Stephan (1986) ITomIraq; Eissa et
a1.(1979) from Saudi Arabia and Ismail & Eissa (1993) and
Youssef & Eissa(1994) from Egypt reported root-knot
pathogenicity to date-palm. Griffin andKoshy (1990) stated that
young seedlings of date-palm were killed (90%) inheavily ifested
soil by root-knot nematodes.
Objective of this work is to illustrate the histological
alterations of theinfected date-palm roots.
MATERIALS AND METHODS
Date-palm seeds cvs. Zaghlool, Deglet Noor (Tunisian source)
andSamani was prepared and planted . One inoculum level of M
incognita wasintroduced to the 4-weeks-old seedlings of each
cultivar grown in 20 cm
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diameter clay pots. The inculum level was 5000 newly hatched M
incognitalarvae/plant. For each cultivar four replicates were made.
Inoculation was madeby pipetting the proper aliquot into three
holes around the root system of eachseedling. All pots were kept in
a greenhouse at 30 :!: 5°C in a completerandomized block design and
agronomically treated the same. After fourmonths from inoculation
time, the experiment was terminated and plants wereuprooted and
data on plant growth criteria and nematode populations
weredetermined.
Portions of M incognita infested roots of date-palm cvs.
Zaghlool,Deglet Noor and Samani were fixed in F.A.A. and processed
for histologicaltechnique according to the standard methods
ofSass(1964). Dehydration wascarried out : in a serial
concentrations of known volume of ethanol and butanolalcohols.
Dehydrated root tissues were then infiltrated and imbedded in
paraffinwax at 52°C for 10 days. During the wax
infiltrationprocess, air bubbles wereremoved from root tissues by
vacuum. Sectioning of the processed root partswas made by a rotary
microtome at 12 microns thickness. Staining was made bySafranin and
Fast green and the stained sections were mounted in canadabalsam.
Sections were then examined under a light microscope.
RESULTS AND DISCUSSION
Stained root sections of the susceptible (Zaghlool) and
resistant (DegletNoor and Samani) cultivars of date-palm were
examined under stereoscopicmicroscope. Cross and longitudinal
sections of the susceptible cultivar rootrevealed that the nematode
developed and reproduced normally within the roottissues. The most
obvious cell reactions to the nematode infection were cell
hyperplaisa and hypertrophy in comparison with the healthy
date-palm rootsection (Fig.I). The hypertrophied giant cells were
initiated in both cortical andstelar regions of the roots which
then developed abnormal xylem elementsexpanding into the cortex
(Fig.2). Parenchyma type cells bordering the giantcells were small,
have dense protoplasm, and irregular in shape. The welldevloped
giant cell had uniformly dense cytoplasm, numerous large nuclei
andthickened walls. The number of nuclei per giant cell ranged from
10 to 18,which were scattered within the giant cell or aggregated
in the center (Fig.2) . agroup of giant cells consisting many
clusters are usually located close toanterior part of the nematode.
The giant cells were irregular in shape, however,they tend to be
elongated or rounded (Figs. 2b and 2c).
On the other hand, the root tissues in the resistant cultivars
reacted in adifferent way. It seems that as the nematode have
invaded the cortical layer, anegative reaction to nematode
existence was exhibited by forming a necroticarea around the
nematode body (Figs. 3 and 4). In few cases, the nematodesucceeded
to survive for a while, hence a slight host reaction was noticed.
Insuch cases, vaculated and empty giant cells were found. Vacuoles.
andapparently empty regions were often associated with the
cytoplasm of such
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giant cells and frequently seemed to lack turgidity, in
comparison to adjacenthealthy tissues. Poorly developed larvae
usually observed in association withthose giant cells (Figs.
3and4). Ismail 1985 obtained similar results on cornplants.
Observations on M incognita infected roots of the highly
susceptiblecultivar Zaghlool indicated an acute histological
respons. Differentdevelopmental stages could be easily observed
within the infected root tissueeither in cortex or in close
vicinity to the stelar regions (Fig. 2). The cells sitesbecame
hypertrophied with several swollen nuclei (Fig. 2). The formation
ofcharacteristic multinucleate and well developed giant cells was
found at theanterior part of the the nematode in the infected plant
tissues with the root-knotnematode, M incognita (Fig.2). The
secreted nematode enzyme throughparasitism dissolved cell walls in
susceptible host. Such host do not secreteample or any phenols
and/or other nematistatic compounds to contradictnematode
parasitism.
In unsuitable host, nematodes are always faced with
antagonisticreaction initiated by the host plant. The most common
reaction in resistant orless suceptible (Deglet Noor and Samani)
cultivars was cell necrosis (Figs.3and 4). Often, after inducing
necrosis, the nematodejuveniles migrated to non-necrotic cells and
commended feeding these cells subsequently became
..necrotic. Necrosis can result in death of the nematode either
through directtoxicity or by destruction of the plant tissues, thus
causing starvation.
LITERATURE CITED- Buhere, E.M.; C.K. Cooper and G. Steiner 1933.
A list of plantsattacked by the root-knot nematode (Heterodera
marioni) Plant Diseasereporter 17: 64-96.
- - Carpenter, J.B. 1964. Root-knot nematode damage to
date-palmseedlings in relation to germination and stage of
development. DateGrowers Inst., Ann. Rept., 44:10-14.
- Eissa,M.F.M.; G.B. Beinhart and S.AI-Uyayed 1979.
Co-operationwith the International Meloidogyne Project in the
Kingdom of SaudiArabia. Proc. 2nd. Res. Planning Cont: on root-knot
nematode,Meloidogyne spp., Athens, Greece, Nov. 26-30, 1979,
p.l05-112.
- Griffth, R. and P.K. Koshy 1990. Nematode parasites of coconut
andother palms. In: Plant Parasitic Nematodes in subtropical and
TropicalAgriculture (M.Luc, R.A. Sikora and J.Bridge eds.) C.A.B.
International,363-386.
- Ismail, A.E. (1985). Biological and Pathological studies on
pathogenicnematodes of some field crops in Egypt. M. Se., ZooI.
Dept, Fac. Agric.,Cairo Univ., PP 121.
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- Ismail, A.E. and M.F.M. Eissa1993.Plant parasitic
nematodesassociated with ornamental palms in three botanical
gardens. Pak.J.Nematol., 11 (1):53-59.
- Lamberti, F. and E.N. Greco1977.Pathogenecity of two species
ofMeloidagyne on four varities of date-palm. Nematol. Medit., 5:
159-172.
Minz, G. 1963. Additional hosts of the root-knot
nematode,Meloidogyne spp. recorded in Israel during 1960/1962.
Israel J. Agric.Res., 13:133-134.
- Sass,J.E. 1964.Botanical Microtechnique. The Iowa State Univ.
Press,228 p.
- Stephan, Z. 1986. Host status of cyst nematodes in Iraq. NATO
AsiSeries. A, Life Sciences, Vol. 121.Proc. NATO Advanced study on
cystnematodes, Sept. 21-0ct. 30 , New York, 1985.
- Youssef, M.M.A. and M.F.M. Eissa 1994. Population dynamics
ofcertain nematodes associated with date-palm in Egypt. Afro-Asian
J.Nematol. 4: 68-72.
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Figure 1: Cross section of healthy date-palm root.
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B
~ . ."~r:. .~" 1ift. ill ~ ~ ~ o.iiiiiiiiIiio;'_-
S
A
Figure 2: Cellular reaction of the susceptible Zaghlool
date-palm cultivar to. M. incognitainfection.
A. Cross section of Zaghlool cultivar infected root showing
thehypertrophied cells
B. Cross section of Zaghlool cultivar infected root (note the
groupsof giant cells and abnormal xylem).
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c
D
Figure 2: Cellular reaction of the susceptible Zaghlool
date-palm cultivar toM. incognita infection.
C. Longitudinal section of zaghlool dultivar infected root (note
themature females and giant cells inside stellar tissues).
D. Cross section of Zaghlool cultivar infected root (note
themature female and egg-mass).
ax =abnormal xylem; ge= giant cell; ne=nematode;em= egg-mass;
ht= hypertrophy.
-
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A
B
Figure 3: Cellular reaction of the resistant Deglet Noor
date-palm cultivarto M. incognita infection.
A,B= Cross section of cv. Deglet Noor infected root by
M.incognita (note the necrotic tissues around nematode body).
--
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,.
c ..
Figure 3: Cellular reaction of the resistant Deglet Noor
date-palm cuItivarto M. incognita infection.
C= Cross section of cv. Deglet Noor infected root by M.
incognita(note the necrotic tissues around nematode body).
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B
A
..
Figure 4: Cellular reaction of the resistant Samani date-palm
cultivar toM. incognita infection.
A,B= Cross section of cv. Samni infected root by M.
incognita(note the necrotic tissues around nematode body).
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c.
_,10
II
1..,....
Figure 4: Cellular reaction of the resistant Samani date-palm
cultivar toM. incognita infection.
C= Cross section of cv. Samni infected root by M. incognita
(notethe necrotic tissues around nematode body).
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