Journal
Journal of Applied Horticulture, 14(2): 134-138, 2012
Appl
Resistance evaluation of the pistachio rootstocks to
Meloidogyne species in Iran
Mehrdad Madani1*, Ahmad Akhiani2, Mahmoud Damadzadeh2 and Ahmad Kheiri3
1
University of Tarbiat Modares, College of Agriculture, Plant Pathology Department, Tehran, Iran. Present address: University of Manitoba, Soil Science Department, Winnipeg, MB, Canada. 2Plant Pest and Disease Research Institute. Ministry
of Agriculture and Jahad, Esfahan, Iran, 3University of Tehran, College of Agriculture, Plant pathology department, Karaj,
Iran. *E-mail: madanims@cc.umanitoba.ca.
Abstract
Pistachio (Pistacia vera) is a edible nut native to Iran, the country that ranks first in worldwide pistachio production. Root-knot
nematodes (RKN), Meloidogyne species, are among the most important pathogens that restrict the cultivation of pistachio in Iran. The
objective of this study was to evaluate resistance of native pistachio rootstocks for resistance to isolates of M. incognita. Greenhouse
experiment was conducted to determine the reaction of eleven cultivars of P. vera and six accessions of wild pistachio viz P. mutica,
P. khinjuk, P. terebintus, P. atlantica, P. atlantica sub sp mutica and P. atlantica sub sp cabilica, against five selected populations of
RKN. Meloidogyne incognita and M. javanica were identified based on the morphological characters, and esterase isozyme phenotype.
Resistance was characterized based on root gall and egg mass indices and nematode reproduction. Resistance to M. incognita was
detected among the cultivars and wild accessions of pistachio. There was a significant interaction among nematode populations and
host genotypes, suggesting the presence of virulent pathotypes among the M. incognita isolates. These data suggest that it will be
possible to development cultivars with resistance as a means of suppressing damage to pistachio that is caused by RKN.
Key words: Pistachio vera, root knot nematodes, gall index, eggmass index, cultivar
Pistachio originated from central part of the Middle East located
in North Eastern part of the Iran. The pistachio tree (Pistacia vera
L.) is heterozygous, deciduous, dioucious with separate male
and female plants and is cross-pollinated. Iran is the leading
producer of pistachio nuts with more than 252,790 hectares under
cultivation with an annual production of 190,000 metric tons. The
main areas of pistachio cultivation are located in central Iran in
the provinces of Kerman and Esfahan; however, the provinces
of Yazd, Semnan and Ghazvin also produce pistachio. The wild
species P. khinjuk and P. mutica are found in mountainous regions
of the country especially in the west and south.
Root-knot nematodes (RKN) Meloidogyne (Nematoda:
Heteroderidae), including M. incognita and M. javanica are the
most destructive plant-parasitic nematodes found throughout subtropical, tropical and temperate regions of the world. Pistachio
vera is the principal rootstock used and is susceptible to both of
these species. Estimated production losses in pistachio worldwide
caused by Meloidogyne species is US $118 million (Koenning
et al., 1994). In Iran, M. incognita and M. javanicva has been
reported attacking pistachio roots (Abivardi et al., 1979; Akhiani
et al., 1986; Banihashemi and Kheiri, 1995; Kargar, 1989,
Mojtahedi and Barooti, 1976; Madani et al., 1988). These species
were also reported from pistachio roots in California (McKenry
and Kretsch, 1984).
Although several reports indicate wide presence of RKN in
pistachio orchards in Iran and the occurrence of M. incognita
and M. javanica, there is no systematic study on damage caused
by RKN and/or resistance/susceptibility of pistachio cultivars
and species in Iran. Therefore, the objective of this study was to
screen diffierent pistachio cultivars including P. vera and wild
relative accessions against Meloidogyne spp.
Materials and methods
Complementary Copy
Introduction
The experiments were carried out at the Plant Pest and Disease
Institute of Ministry of Agriculture, Esfahan, Iran. Test for
identification of nematodes were performed at the Plant Research
International, Wageningen, The Netherlands. A survey was
conducted in the main cultivation areas of pistachio in Iran to
collect pistachio seeds and nematode isolates. Infested trees were
easily identified based on stunted growth habit with moderate to
severely necrotic and chlorotic leaves. Thirteen seed samples from
different cultivars of P. vera and 16 samples of wild species were
collected from trees or provided by local growers. Additionally,
three samples of wild pistachio seeds previously identified as
P. atlantica, P. terebintus and P. sp. were received from Dr.
Sh. Dehghani, University of Adelaide, Australia). A sample of
wild species collected from Hormozgan province were kindly
provided by Dr. Z. Banihashemi, Shiraz University, Shiraz, Iran.
Sampling location and information on host plants are presented
in Table 1. Collected seeds were kept in paper bags, placed in a
cool dry container and transferred to the laboratory where they
were maintained at 4°C until use. Nematode isolates were isolated
from 30 soil and root samples collected from naturally infested
pistachio orchards from different locations in Iran (Table 2). Two
or three sub-samples were collected from different parts of each
orchard, and mixed together to make a composite sample of about
1 kg containing feeder roots with rhizosphere and bulk soil from a
depth of 50-70 cm. One composite sample was taken from each
Resistance evaluation of the Pistachio rootstocks to Meloidogyne species in Iran
No. Code
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Pv-Mes
Pv-Jan
Pv-Fa-Kh
Pv-Bo1
Pv-Bo2
Pv-Bad-Ra
Pv-Fa-Ra
Pv-Kh-Ra
Pv-Sar
Pv-Ard
Pv-DM
Pv-Kh-Dam
Pv-Gh
Pw-Kh-sem
Pw-Mu-sem
Pw-Kh-Bam
Pw-Mu-Bam
Pw-Kh-Jir
Pw-At-Jir
Seed source
(Province- location)
Esfahan-Mesr
Esfahan-Jandagh
Esfahan-Khor Va Biabanak
Esfahan-Borkhar
Esfahan-Borkhar
Kerman-Rafsanjan
Kerman-Rafsanjan
Kerman-Rafsanjan
Khorasan-Sarakhs
Yazd-Ardekan
Semnan-Damghan
Semnan-Damghan
Ghazvin
Esfahan-Semirom
Esfahan-Semirom
Kerman-Bam
Kerman-Bam
Kerman-Jiroft
Kerman-Jiroft
20
21
22
23
24
25
26
27
28
Pw-Kh-Sar
Pw-Mu-Sar
Pw-Mu-Mar
Pw-Mu-Mok
Pw-Mu-Ghir
Pw-Mu-Siv
Pw-Mu-Khan
Pw-Mu-Koh
Pw-At-Cab
Khorasan-Sarakhs
Khorasan-Sarakhs
Fars-Marvdasht
Fars-Mok va kavar
Fars-Ghir
Fars-Sivand
Fars-Khanemein
Fars-Kohanjan
Hormozgan-Geno
29
30
31
32
33
Pw-Mu-Ker
Pw-Mu-Koh
Pw-Ter-Aus2
Pw-At-Aus3
Pw-sp
Kermanshah
Kohkiloieh
Australia
Australia
Australia
Species / cultivar
P. vera-Mesri
P. vera-Jandaghi
P. vera-Fandoghi-Khor
P. vera-Borkhar
P. vera-Borkhar
P. vera-Badami
P. vera-Fandoghi
P. vera-Khanjari
P. vera-Sarakhs
P. vera-Ardekani
P. vera-Mamoli
P. vera-Khanjari
P. vera-Ghazvini
P. khinjuk
P. mutica
P. khinjuk
P. mutica
P. khinjuk
P. atlantica sub sp
mutica
P. khinjuk
P. mutica
P. mutica
P. mutica
P. mutica
P. mutica
P. mutica
P. mutica
P. atlantica sub sp
cabulica
P. mutica
P. mutica
P. terebinhtus
P. atlantica
Pistachio sp
orchard and placed in a plastic bag and transported to laboratory
in cooler box at 7-12°C. For locations where no distinct gall
symptoms were observed on pistachio roots, an extra soil samples
were collected from weeds infected with RKN close to trees. No
soil sample was collected from wild Pistachio spp.
Collected seeds were surface sterilized with 1% NaOCl solution
for 5 minutes followed by soaking overnight in sterilized
water. Seeds of P. vera cultivars were then placed between two
layers of wet cotton tissue in a plastic tray and kept at 23-28°C
until germination. To prevent contamination with common
saprophytic fungi, seeds were sprayed with solution of 0.002%
pentachloronitrobenzene (PCNB) fungicide every two days
during the incubation period. After one week, germinated seeds
were transferred to plastic containers (20×25×10 cm), filled with
a sterilized mixture of sand, Perlite and peat moss (50:25:50
v/v) and then covered with 1 cm layer of sand. Containers were
then kept in a greenhouse at 25-27°C until seedlings emerged.
Seedlings with two leaves were then transplanted to a steam
pasteurized clay pot (15×25 cm) containing approximately 500
cm 3 of sterilized river sand, vermiculate and peat moss (50:25:25
v/v). Pots were kept in a greenhouse with temperature ranging
from 22 to 28 °C and 65-85% relative humidity, for a week, and
then inoculated with nematodes.
Seeds of wild species were dormant, therefore, they were soaked
overnight in water and green coat was removed. Seeds were
then transferred to plastic container filled with sterile river sand,
wrapped container with aluminum sheets and maintained at 4°C
for 30 to 40 days until germination. Each germinated seed with
two leaves were then transplanted to a clay pots and kept at
greenhouse under conditions described above. As an alternative,
a method based on H2SO4 treatment was also tested to overcome
the seed dormancy. For this, seeds were subjected to a solution of
1% acid for 1-2 minutes, rinsed with water and then planted.
To obtain pure populations of nematodes, a single egg mass from
each sample was collected and used to inoculate a susceptible
tomato (Lycopersicum esculantum Mill. cv. Rutgers) seedling.
Several egg masses from pistachio roots were used separately for
inoculation of tomato seedlings at 2-4 leaf stage. For pistachio
root samples, where it was difficult to find an egg mass, tomato
seedlings were planted in collected soil and/or an egg mass
was picked from the roots of weeds. Inoculated tomatoes were
maintained in a greenhouse, separated from each other by plastic
sheets to prevent any cross contamination of the nematode
species. After 55 days tomato plants were harvested, soil washed
from the roots and several egg masses and female nematodes were
collected for species identification.
Perineal pattern from at least 20 mature females were prepared
using lactic acid, mounted in glycerin (Brito et al., 2004) and
examined for identification of species of each RKN isolate. Based
on preliminary species identification, four isolates identified as
M. incognita from the main geographical region of pistachio
production including (Kerman, Davaran (RD), Esfahan, Khor Va
Biabanak (KH) and Kashan, (K and P) and one M. javanica isolate
(MJ) from the province of the Yazd (Ardekan). Only M. incognita
isolates were selected for subsequent experiments. Further
confirmation of species was performed on these isolates using
esterase and malate dehydrogenase protein isoelectrophoresis
(IEF) of white female (Karssen et al., 1995), electron microscopy
examination of perineal pattern and J2 morphology and
morphometric characters (Courtney et al., 1995).
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Table 1. Origin, species and location of pistachio seeds used
135
Populations of the selected isolates of M. incognita population
collected from Kashan, race 2, (Mi-K), Kashan race 4 (Mi-P),
Khor Va Biabanak, Esfahan, (Mi-KH), and Rafsanja, Davaran
(Mi-RD) and M. pistachio from Ardekan, Yazd (MJ) were raised
from single egg masses and propagated on tomato seedlings for
two generations. Inocula were prepared by macerating infected
roots using a blender. Eggs and J2 were collected on a 25-μm pore
sieve and gently rinsed with sterilized water into a 250-mL glass
beaker. Three 1-mL samples were taken with a pipette to estimate
numbers of eggs and J2 under a stereomicroscope.
Eleven cultivars of P. vera and six accessions of wild Pistachio
spp. were selected for evaluation of resistance to these isolates.
Seedling pots were arranged in a randomized complete block
design with four replications of each plant genotype and nematode
isolate combination. P. vera seedlings were at the 4-6 leaf stage
of development and wild accessions were 3-month-old seedlings
when inoculation was done. Each seedling was inoculated with
1x104 eggs and J2 of nematode isolate. Control plants were
inoculated with water and maintained in a greenhouse. Pots
were watered every three days and fertilized weekly with a 0.5%
Hoagland solution for 135 days.
136
Resistance evaluation of the Pistachio rootstocks to Meloidogyne species in Iran
population, soil from each pot was
transferred onto a tray, mixed and
Species
Species identification
a sub sample of 250 cm3 taken for
Perineqal pattern, J2
M. incognita
nematodes extraction by elutriation and
Peineal pattern, J2
M. incognita
centrifuge (Lo´pez-Pe´rez et al., 2005).
M. incognita
Peineal pattern, J2-IEF* The host reaction was determined as
resistant (GI ≤ 2, RF <1), tolerant (GI
Peineal pattern, J2
M. incognita
≤ 2, RF >1), hyper-susceptible (GI ≥
M. sp (un identified) Peineal pattern, J2
2, RF <1), and susceptible (GI > 2, RF
Peineal pattern, J2
M. incognita
>1) (Canto-Saenz, 1987). Rootstock
reaction was interpreted either based
Peineal pattern, J2
M. incognita
on GI and EI (Taylor and Sasser, 1978),
Peineal pattern, J2
M. incognita
or using index of R (Trudgill, 1991).
Table 2. Nematode sampling location, host and test applied to identify Meloidogyne population used
No. Province-Location
Host
1
Esfahan-Ardestan
P. vera
2
Esfahan-Natanz
P. vera
3
Esfahan-Khor va Biabanak
P. vera
4
Esfahan-Khoram dasht-1
P. vera
5
Esfahan- Khoram dasht-2
P. vera
6
Esfahan-Chopanan
P. vera
7
Esfahan-Mazrae Nemoneh
P. vera
8
Esfahan-Alah Abad
P. vera
9
Esfahan-Amir Abad
P. vera
M. incognita
Peineal pattern, J2
10
Esfahan-Mesr
P. vera, Cabbage M. incognita
Peineal pattern, J2
11
Esfahan-Frah zad
P. vera, Cabbage M. incognita
Peineal pattern, J2
12
Esfahan-Jandagh
P. vera, weeds
M. incognita
Peineal pattern, J2
13
Esfahan-Arosan
P. vera
M. incognita
Peineal pattern, J2
14
Esfahan-Golestan
P. vera
M. incognita
Peineal pattern, J2
15
Esfahan-Neishabor
P. vera
M. incognita
Peineal pattern, J2
16
Esfahan-Kashan-Sabahi
P. vera
M. incognita
Peineal pattern, J2-IEF
17
Esfahan-Kashan-Kaghazi
P. vera
M. incognita
Peineal pattern, J2-IEF
18
Esfahan-Kashan-Ghale gosheh P. vera
M. incognita
Peineal pattern, J2
19
Yazd-Ardekan
P. vera
M. javanica
Peineal pattern, J2-IEF
20
Kerman-Zarand
P. vera
M. incognita
Peineal pattern, J2
21
Kerman-Zarand
P. vera
M. sp (un identified) Peineal pattern, J2
22
Kerman-Anar
P. vera
M. incognita
Data analysis: Data on gall and egg
mass numbers (GN and EN) per root
system were subjected to analysis of
variance using SAS, version 7.1. Mean
comparison of data were performed
and significance differences in
means of nematode reproduction
were separated using Duncan’s test
with significant differences at 5%
probability and differences among
treatments were determined for each
nematode population by cultivar.
Results
A total of 36 indigenous P. vera and
16 wild accessions were collected
during the survey, from which 11
Peineal pattern, J2
P. vera
M. incognita
23 Kerman-Rafsanjan
cultivars and six wild accessions were
Peineal pattern, J2
P. vera
M. incognita
24 Kerman-Heidar abad
selected for resistance assessment
Peineal pattern, J2
P. vera
M. incognita
25 Kerman-Heidar abad
(Table 1). Preliminary identification
of RKN from soil samples revealed
P. vera
M. incognita
Peineal pattern-IEF
26 Kerman-Davaran
the presence of two species, M.
Peineal pattern, J2
P. vera
M. javanica
27 Kerman-Davaran
incognita and M. pistachio in 27
Peineal pattern, J2
P. vera
Meloidogyne (un
28 Kerman-Davaran
of sampling locations (Table 2).
Peineal pattern, J2 , J2
P. vera
M. incognita
29 Kerman-Naserieh
Meloidogyne incognita was identified
in 25 sampling areas from either
Kerman-Naserieh
Peineal
pattern,
J2
P.
vera
M.
incognita
30
pistachio roots or weeds, whereas
Species in bold were used for the final experiment on resistance test. *IEF: Isoelctrofocusing
M. javanica was identified from the
pistachio roots in two locations from Yazd province (Ardekan)
After harvest, the roots were gently washed with tap water, and
and Kerman province (Davaran). Three populations collected
placed in beakers containing approximately 400 mL of 0.05 %
from pistachio roots, one from province of Esfahan (Khoramdasht
Phloxin B solution for 10 to 15 min to stain the egg masses a
2), and two from province of Kerman (Zarand and Davaran),
bright red color. Each root system was scored for nematode galls
could not be identified to species level due their unusual perineal
(gall index=GI) based on 0 to 5 scale where 0= no gall, 1=1 to
pattern morphology. Esterase and malate dehydrogenase IEF
2, 2=3 to 10, 3=11 to 30, 4=31 to 100 and 5= >100 galls (Safdar
protein profile, electron microscopy of perineal pattern, J2
and McKenry, 2007). The length and weight of each root and
morphology and morphometric obtained for the selected isolates
stem were measured.
of M. incognita (Mi-K, Mi-P, Mi-KH, Mi-RD) and M. javanica
The reproduction factor (RF) was quantified based on R=Pf/Pi,
(MJ), were in agreement with published data (Karssen et al.,
where Pf and Pi were final and initial population densities,
1995) and confirmed the identity of these isolates.
respectively (Zhou and Starr, 2003). For calculation of Pf, the
In the greenhouse screening test, egg mass number per seedling
J2 per root system was estimated by macerating the roots using
ranged from 1 to 167 for P. vera cultivars inoculated with M.
a blender with 1% NaOCl solution. Because eggs viability was
incognita (Table 3). The mean number of eggs masses across
not a concern the higher concentration of 1% NaOCl was used to
increase the extraction efficiency (Zhou et al., 2000). Released
all pistachio cultivars for the four isolates of M. incognita ranged
eggs and J2 were collected on a 25-μm pore sieve and then
from 41.4 to 61.4, whereas the means across all four nematode
counted under a stereomicroscope. To quantify the soil nematode
isolates for the cultivars ranged from 11 to 114.7. For the egg
Complementary Copy
Peineal pattern, J2
Resistance evaluation of the Pistachio rootstocks to Meloidogyne species in Iran
Table 3. Egg mass production by four isolates of M. incognita on eleven
cultivars of pistachio in a greenhouse test. Abbreviation for pistachio
cultivar are given in table 1. Cultivars with the same letter not differ
significantly (P <0.05)
Mi-Kh
Mi-RD
Mi-K
Mi-P
137
Table 4. Root gall production by four isolates of M. incognita on eleven
cultivars of pistachio in a greenhouse test. Abbreviation for pistachio
cultivar are given in table 1. Cultivars with the same letter not differ
significantly (P <0.05)
Mean
Mi - Kh
Mi-RD
Mi-K
Mi-P
Mean
Kh-Ra
28.0
4.0
1.0
3.3
11a
Kh-Ra
147.5
30.8
39.0
21.3
59.7c
Bad-Ra
139.7
65.5
24.3
12.5
60.5d
Bad-Ra
281.5
170.7
69.0
22.8
136.0ab
Ard
29.3
18.5
37.7
21.3
26.7b
Ard
51.7
67.5
75.7
48.7
60.9c
Gh
7.3
7.0
4.0
52.5
17.7a
Gh
15.8
29.5
10.0
58.3
28.4d
Bo1
54.0
57.7
21.7
25.0
39.6bc
Bo1
82.6
89.8
72.7
56.5
75.4bc
Dam-Mam
15.3
16.7
15.0
72.0
29.8b
Dam-Mam
47.0
47.0
21.0
93.5
52.1c
Fa-Ra
10.5
68.5
73.5
20.7
43.3c
Fa-Ra
190.0
147.3
88.0
55.0
120.1b
Bo2
30.3
50.5
72.3
28.0
45.3c
Bo2
71.7
143.0
85.5
58.0
89.6c
Sar
28.5
9.5
15.3
39.3
23.2b
Sar
69.3
34.7
18.5
42.5
41.3d
Fa-Kh
54.0
58.7
68.0
33.8
53.6c
Fa-Kh
130.0
98.5
167.0
63.3
114.7e
61.4a
42.3c
Mean
47.9a
41.4a
45.4a
mass production in P. vera cultivars, there was no significant
differences among isolates across the cultivars; however, a
significant difference in mean value of egg mass number was
observed by cultivar among the four nematode isolates (Table
3). Two-way analysis of variance for the gall number also
revealed significant differences in gall production among cultivars
across all nematode isolates. Differences were observed in gall
production among nematode. Nematodes isolate of Mi-K and
Mi-P both collected from Kashan province were significantly
different in gall production and separated from the rest of
populations (Table 4).
Analysis of data from the wild accessions showed there were
no significant differences among nematodes isolates across
the accessions for either gall and egg mass production (Table
5). Mean value of gall number in Pw-Te-Aus3 and Pw-AtCab accessions showed significant differences with the rest of
accession. Mean value of egg mass number in Pw-At-Mu and
Pw-At-Aus2 accession showed significant difference compared
to other accessions for production of egg mass.
Discussion
The main aim of the present study was to identifying possible
source of resistance through screening of cultivated pistachio root
stocks and wild accession. During the survey and based on our
observation and results of the experiments, RKNs obviously are
among the most important pistachio root disease in Iran which
51.5
113.7
80.0
117.0
Kh-Dam
187.5
148.7
237.5
89.3
Mean
108.7a
93.0b
72.4abc
60.3c
90.6bc
165.8a
83.6ab
can restrict planting of pistachio, especially in loamy sandy soil.
Although sites with potential infestation of RKN were targeted
in this study, wide distribution of RKN in pistachio orchards,
especially in nurseries, were observed causing damage and
reduction of yield in pistachio trees. M. incognita was identified
in most of the sampling areas and detected in more than 80% of
soil samples. This species was the most prevalent RKNs found
in pistachio orchards. Although M. javanica was identified only
in two locations, it appears to be the second important member
of RKNs in terms of spreading and causing damage in pistachio
orchards. Possible presence of other Meloidogyne species on
pistachio is likely, where an unusual perineal patterns morphology
in three populations collected from pistachio roots in Esfahan
province (Khoramdasht 2), and Kerman province (Zarand and
Davaran) was observed. More study needed to confirm the
identity of these populations.
Complementary Copy
Kh-Dam
Usefulness of wild germplasm as source of resistance to plant
parasitic nematodes has been emphasized by other researches
(Yaghoobi, et al., 1995). From this preliminary study it appears
that a wide range of reaction from resistance to highly susceptible
is present in pistachio root stocks against M. incognita. In addition,
identifying the pistachio cultivar used as rootstocks is crucial in
resistance experiments, especially when study of different flora from
Iran and neighbor countries showed the differences in nomenclature
or speciation of pistachio cultivars. In resistance experiments, study
of cultivars and nematodes originated from the same geographic
Table 5. Mean comparison of egg mass (EN) and gall numbers (GN), of six accessions of wild Pistachio species against Meloidogyne incognita in
green house experiment. Data are from four replicates. Abbreviation for pistachio cultivar are given in Table 1. Cultivars with the same letter not
differ significantly (P <0.05)
Cultivar/code
Pw-At-Aus2
Pw-Te-Aus3
Pw-At-Mu
Pw-At-Cab
Pw-Kh1
Pw-Kh2
Mean
Mi-Kh
GN
22.3
7
6.5
7.5
8.3
9.3
10.2a
EN
30.3
1.5
22
2.3
29.8
31.8
19.6a
Mi-RD
GN
EN
27
23.5
7
1.8
5.8
6.3
5.5
8
9.3
28.5
7.3
30.5
10.3a
16.4a
Mi-K
GN
23.5
6.3
6.3
4.5
9
9.8
9.9a
Mi-P
EN
20
1.3
1.5
0.5
45.3
46.5
19.2a
GN
26.8
3
36
7.5
9
9.5
15.3a
Mean
EN
27
3.5
24.5
12
28.5
17.8
20.6a
GN
25.2c
2.0a
13.6b
5.7a
33.0c
34.2c
EN
24.9c
5.8a
13.7b
6.3a
8.9a
9.00a
Resistance evaluation of the Pistachio rootstocks to Meloidogyne species in Iran
0region is more validated due to co-evolution of the two organisms.
In this study pistachio seeds and nematode samples were collected
from the same location. It is assumed that the root galling is not
more accurate indicator for the stability of RKN resistance (Safdar
and McKenry, 2007; Zhou et al., 2000), therefore, in this study the
virtual number of egg mass were also used for analysis of root stocks
reaction. Nematode population from soil and roots were extracted
and used for study of virulence and pathogenicity of the different
population (data not shown). This provide valuable data for further
study on resistance of pistachio root stocks against RKNs.
In some sampling area severe disease symptoms were observed
on above ground parts of pistachio trees while infestation of RKN
was low and in some areas trees showing mild symptoms had
severely infested roots to nematodes. This was in accordance with
greenhouse experiments where the same phenomenon was observed
in some of the cultivar nematode interaction. This indicates the
presence of varying level of resistance/susceptibility among cultivars
and existence of variation in nematode population in terms of
pathogenicity and virulence. Range of variation was more limited in
wild accession compare to the domestic pistachio cultivars.
For most of the nematode cultivar interaction there was a positive
correlation between gall and eggmass numbers, however it was
observed that some cultivar with high number of galls did not
support nematode reproduction. In addition, less variability
in mean value of eggmass production was observed between
nematode isolates than between cultivars. This shows that
cultivars represent more variability in terms of supporting
nematode reproduction. The same was observed for wild
accession with nematodes isolates. Almost all of the nematode
isolates caused galling and high rate of reproduction on pistachio
cultivars. This is the first report on evaluation of pistachio
cultivars used as root stocks in Iran. This provides preliminary
information on identifying source of resistance. More studies are
needed to understand the host pathogen interaction in orchard and
trial plot. Study of differential interaction of nematode population
will reveal more details on this phenomenon.
Acknowledgements
Authors are thankful to James, L. Starr and C. Abivardi for
reviewing this paper carefully, Z. Banihashemi and Sh. Dehghani
for providing some of the pistachio seeds. This work is dedicated
to Ahmad Akhiani for his major participation in this work, who
passed away while this research was being conducted.
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Received: March, 2012; Revised: July, 2012; Accepted: October, 2012