Histological and Ultrastructural Changes in Leaves and Stems of Resistant and Susceptible Chickpea Cultivars to Ascochyta rabiei

The histo- and cytopathological effects in resistant (ILC-195) and susceptible (Canitez-87) chickpea cultivars were examined by light, transmission and scanning electron microscopy 3, 5 and 7 days after inoculation (d.a.i) of seedlings with Ascochyta rabiei. The fungus produced typical appressoria that penetrated both cuticle and stomata. The resistant plants had physical barriers and a cuticle layer against fungal penetration 3 d.a.i. The fungus spread intercellularly and subepidermally in the leaves and stems of susceptible plants 3 d.a.i., and was followed 5 d.a.i. by cell plasmolysis, degeneration of organelles and of cellulose, but not lignified, walls. Pycnidia formation occurred between 5 and 7 d.a.i. 7 d.a.i., organelle degeneration, pycnidia formation and symptom severity increased. Tracheidal elements, including lignified elements, were almost intact in both resistant and susceptible cultivars. In the susceptible plants, lignin cell walls were slightly degraded after 7 days. There was less cell degeneration and pycnidia formation in resistant plants. Some electron-dense large bodies and lipid granules were observed within intracellular fungal hyphae in infected cells of resistant plants 7 d.a.i.     

Cloning and characterization of the mating type (MAT) locus from Ascochyta rabiei (teleomorph: Didymella rabiei) and a MAT phylogeny of legume-associated Ascochyta spp

Degenerate primers designed to correspond to conserved regions of the high mobility group (HMG) protein encoded by the MAT1-2 gene of Cochliobolus heterostrophus, Cochliobolus sativus, and Alternaria alternata were used to amplify the portion of the sequence corresponding to the HMG box motif from Ascochyta rabiei (teleomorph: Didymella rabiei). A combination of TAIL and inverse PCR extended the MAT1-2 sequence in both directions, then primers designed to MAT1-2 flanking DNA were used to amplify the entire MAT1-1 idiomorph. MAT1-1 and MAT1-2 idiomorphs were 2294 and 2693 bp in length, respectively, and each contained a single putative open reading frame (ORF) and intron similar to MAT loci of other loculoascomycete fungi. MAT genes were expressed at high levels in rich medium. MAT-specific PCR primers were designed for use in a multiplex PCR assay and MAT-specific PCR amplicons correlated perfectly to mating phenotype of 35 ascospore progeny from a cross of MAT1-1 by MAT1-2 isolates and to the mating phenotype of field-collected isolates from diverse geographic locations. MAT-specific PCR was used to rapidly determine the mating type of isolates of A. rabiei sampled from chickpea fields in the US Pacific Northwest. Mating type ratios were not significantly different from 1:1 among isolates sampled from two commercial chickpea fields consistent with the hypothesis that these A. rabiei populations were randomly mating. The mating type ratio among isolates sampled from an experimental chickpea field where asexual reproduction was enforced differed significantly from 1:1. A phylogeny estimated among legume-associated Ascochyta spp. and related loculoascocmycete fungi using sequence data from the nuclear ribosomal internal transcribed spacer (ITS) demonstrated the monophyly of Ascochyta/Didymella spp. associated with legumes but was insufficiently variable to differentiate isolates associated with different legume hosts. In contrast, sequences of the HMG region of MAT1-2 were substantially more variable, revealing seven well-supported clades that correlated to host of isolation. A. rabiei on chickpea is phylogenetically distant from other legume-associated Ascochyta spp. and the specific status of A. rabiei, A. lentis, A. pisi, and A. fabae was confirmed by the HMG phylogeny     

Biocontrol of Ascochyta blight by Azospirillum sp. depending on the degree of resistance of chickpea genotypes

Throughout arable land that was devoted to chickpea (Cicer arietinum L. (Family: Leguminosae) production, Ascochyta blight (Ascochyta rabiei (Pass.) L. (Order: Sphaeriales; Family: Mycosphaerellaceae) is a widespread disease that would lead to significant loss of chickpea yield. This study's purpose was to explain the responses of a resistant chickpea cultivar (ICC 12004) and a susceptible cultivar (Bivanij) in terms of disease resistance, disease symptoms appearance and expression pattern of two defence‐related genes (DEF0442 and Snakin2) after the Azospirillum brasilense seeds inoculation. In this research, the Snakin2 gene expression was affected by Azospirillum inoculation. The gene expression has been enhanced in plants inoculated with Azospirillum in both cultivars in comparison with non‐inoculated plants, but this change in ICC 12004 and Bivanij were significant and non‐significant, respectively. Although, Azospirillum would up regulate the DEF0422 gene expression in ICC 12004, but it would down regulate the expression of this gene in Bivanij. A. brasilense inoculation decreased the A. rabiei disease severity, regardless of the chickpea cultivar. Bivanij still could be classified as susceptible, even if treated with A. brasilense.     

Changes of antioxidative enzymes,lipid peroxidation and chlorophyll content in chickpea types colonized by different <Emphasis Type="Italic">Glomus</Emphasis> species under drought stress

In order to investigate the effects of Glomus species on some physiological characteristics of two chickpea types (Pirouz cultivar of Desi type and ILC-482 of Kabuli type) under non-stress (NS) and drought stress, an experiment was conducted using a factorial arrangement based on completely randomized design with three replications. Drought stress decreased shoot and total dry weight in plants. However inoculation of plants with mycorrhiza improved these traits. Leaf chlorophyll content was decreased, but leaf proline content and guaiacol peroxidases (EC 1.11.1.7) (POD), catalase (EC 1.11.1.6) (CAT), and ascorbate peroxidase (EC 1.11.1.11) (APX) activities were increased as a result of drought stress. Drought stress had no significant effect on soluble protein content and polyphenol oxidase (EC 1.10.3.1) (PPO) enzymatic activity in chickpea plants. In general, drought stress and especially severe drought stress increased membrane lipid peroxidation (MDA) in chickpea plants, which was more evident in non-inoculated than in inoculated plants. Inoculation of chickpea by AM significantly increased POD and PPO activities compared with non-inoculated chickpea, but had no effect on CAT activity and proline content of leaves. The reaction of chickpea cultivars to inoculation by AM species and irrigation levels were different. ILC-482 showed that antioxidant enzymes activities were more and thus less MDA compared with Pirouz cultivar. In general, the most POD and PPO activities were recorded for inoculated plants with G. etunicatum and G. versiform species, and the most APX activity was observed in plants inoculated with G. intraradices.     

Biochemical and molecular biological studies on infection (Ascochyta rabiei)-induced thaumatin-like proteins from chickpea plants (Cicer arietinum L.)

A pathogenesis-related protein induced by infection with Ascochyta rabiei was purified from intercellular washing fluid of chickpea (Cicer arietinum L.) leaves. Amino-terminal sequencing identified the protein, named PR-5a, as a thaumatin-like protein. The isoelectric point was determined with 6.5 and the molecular mass is 16 kDa. Therefore, chickpea PR-5a is the first dicot member of a TLP subgroup containing small TLPs with a molecular weight between 15 and 18 kDa. PR-5a shows no antifungal activity towards A. rabiei. Screening of a chickpea cDNA library led to the isolation of a cDNA clone (p5a-241) for this protein. A second cDNA clone (ELR112) encoding a TLP was isolated using differential hybridisation of cDNA libraries obtained from elicited and water treated cell suspension cultures of chickpea. The deduced protein (PR-5b) has a molecular mass of 22 kDa. PR-5b is postulated to be located in the vacuole due to the presence of a respective N-terminal signal peptide and a carboxy-terminal extension. Southern blot analyses showed that ELR112 and p5a-241 represent single copy genes. During fungal infection of chickpea plants expression of both genes proceeds much faster in an A. rabiei resistant cultivar than in a susceptible one.     

Historical and contemporary multilocus population structure of Ascochyta rabiei (teleomorph: Didymella rabiei) in the Pacific Northwest of the United States

The historical and contemporary population genetic structure of the chickpea Ascochyta blight pathogen, Ascochyta rabiei (teleomorph: Didymella rabiei), was determined in the US Pacific Northwest (PNW) using 17 putative AFLP loci, four genetically characterized, sequence-tagged microsatellite loci (STMS) and the mating type locus (MAT). A single multilocus genotype of A. rabiei (MAT1-1) was detected in 1983, which represented the first recorded appearance of Ascochyta blight of chickpea in the PNW. During the following year many additional alleles, including the other mating type allele (MAT1-2), were detected. By 1987, all alleles currently found in the PNW had been introduced. Highly significant genetic differentiation was detected among contemporary subpopulations from different hosts and geographical locations indicating restricted gene flow and/or genetic drift occurring within and among subpopulations and possible selection by host cultivar. Two distinct populations were inferred with high posterior probability which correlated to host of origin and date of sample using Bayesian model-based population structure analyses of multilocus genotypes. Allele frequencies, genotype distributions and population assignment probabilities were significantly different between the historical and contemporary samples of isolates and between isolates sampled from a resistance screening nursery and those sampled from commercial chickpea fields. A random mating model could not be rejected in any subpopulation, indicating the importance of the sexual stage of the fungus both as a source of primary inoculum for Ascochyta blight epidemics and potentially adaptive genotypic diversity.     

Histology of Disease Development in Resistant and Susceptible Cultivars of Chickpea (Cicer arietinum L.) Inoculated with Spores of Ascochyta rabiei

Abstract Histological studies were performed on a compatible and an incompatible interaction between chickpea ( Cicer arietinum L.) plants and the fungus Ascochyta rabiei (Pass.) Labr. The time course of infection, development on leaflets and stems of susceptible (ILC 1929) and resistant (ILC 3279) plants was monitored by light or scanning electron microscopy with the aim to compare histological changes as the basis for further work on biochemical changes in this plant-pathogen interaction.
Spores of A. rabiei began to germinate from 12 hpi on and developed a polar germ tube; fungal colonization, secretion of a mucilaginous exudate and appressoria formation (1–3 dpi) were identical on both cultivars. Leaves of susceptible plants were invaded by the fungus directly through the cuticle, the fungus then spread subepidermally followed by a rapid collapse of the leaf tissue (4–6 dpi). Development of leaf spots and fungal pycnidia could be observed 6–8 dpi. The resistant cultivarrapidly responded (24–48 hpi) to fungal infection and cells of the palisade parenchyma exhibited autofluorescence. In later stages of the infection (4–5 dpi) fluorescent areas developed to small necrotic spots all over the leaflet. These necrotic areas, were the result of cell death and a subsequent change in the leaf structure and were characterized by the accumulation of phenolic compounds. Leaves of the resistant cultivar were invaded by the fungus to less than 5%.     

Molecular analysis of Ascochyta rabiei (Pass.) Labr., the pathogen of ascochyta blight in chickpea

Genetic diversity in Ascochyta rabiei (Pass.) Labr., the causative agent of ascochyta blight of chickpea, was determined using 37 Indian, five American (USA), three Syrian, and two Pakistani isolates. A total of 48 polymorphic RAPD markers were scored for each isolate and the data used for cluster analysis. Most of the isolates clustered in the dendrogram essentially according to geographic origin. Based on the two major clusters A and B, Indian isolates were grouped into two categories, type-A and type-B. Isolates of A. rabiei within the Punjab state were more diverse than isolates from other states in northwestern India. A DNA marker (ubc756_{1.6 kb}), specific to Indian isolates was identified. This is the first report of a molecular diversity analysis of Indian isolates of A. rabiei. The information may assist Indian chickpea breeders in the proper deployment of blight-resistant cultivars and in disease management. Received: 25 April 2000 / Accepted: 11 July 2000     

Evolutionary relationships among Ascochyta species infecting wild and cultivated hosts in the legume tribes Cicereae and Vicieae

Evolutionary relationships were inferred among a worldwide sample of Ascochyta fungi from wild and cultivated legume hosts based on phylogenetic analyses of DNA sequences from the ribosomal internal transcribed spacer regions (ITS), as well as portions of three protein-coding genes: glyceraldehyde-3-phosphate-dehydrogenase (G3PD), translation elongation factor 1-alpha (EF) and chitin synthase 1 (CHS). All legume-associated Ascochyta species had nearly identical ITS sequences and clustered with other Ascochyta, Phoma and Didymella species from legume and nonlegume hosts. Ascochyta pinodes (teleomorph: Mycosphaerella pinodes [Berk. & Blox.] Vestergen) clustered with Didymella species and not with well characterized Mycosphaerella species from other hosts and we propose that the name Didymella pinodes (Berk. & Blox.) Petrak (anamorph: Ascochyta pinodes L.K. Jones) be used to describe this fungus. Analysis of G3PD revealed two major clades among legume-associated Ascochyta fungi with members of both clades infecting pea ("Ascochyta complex"). Analysis of the combined CHS, EF and G3PD datasets revealed that isolates from cultivated pea (P. sativum), lentil (Lens culinaris), faba bean (Vicia faba) and chickpea (Cicer arietinum) from diverse geographic locations each had identical or similar sequences at all loci. Isolates from these hosts clustered in well supported clades specific for each host, suggesting a co-evolutionary history between pathogen and cultivated host. A. pisi, A. lentis, A. fabae and A. rabiei represent phylogenetic species infecting pea, lentil, faba bean and chickpea, respectively. Ascochyta spp. from wild relatives of pea and chickpea clustered with isolates from related cultivated hosts. Isolates sampled from big-flower vetch (Vicia grandiflora) were polyphyletic suggesting that either this host is colonized by phylogenetically distinct lineages of Ascochyta or that the hosts are polyphyletic and infected by distinct evolutionary lineages of the pathogen. Phylogenetic species identified among legume-associated Ascochyta spp. were fully concordant with previously described morphological and biological species.     

Ion-exchange properties of cell walls in chickpea cultivars with different sensitivities to salinity

Ion-exchange properties of polymeric matrices were compared for cell wall preparations isolated from roots and shoots of two cultivars of Cicer arietinum L. (cvs. Bivanij and ILC 482) with different sensitivities to salinity. Irrespective of growth conditions, the cell walls contained four types of ionogenic groups: amino groups, carboxyl groups of uronic and hydroxycinnamic acids, and phenolic hydroxyl groups. Regardless of the salt concentration in the medium, the cells walls of different chickpea cultivars and from different organs of the same plant were similar in qualitative composition of ionogenic groups, although quantities of ionogenic groups per unit dry wt of cell walls varied depending on external and internal factors. Irrespective of the external medium salinity, the cation-exchange capacity of cell walls, expressed per unit dry wt, decreased in a sequence: stem > root ∼ bottom leaves > upper leaves. The volume of chickpea cell walls was found to vary depending on ionic composition and pH of the incubation medium. The results were analyzed in the context of cell wall involvement in responses of C. arietinum to elevated salinity.     

Production of Ascochyta rabiei lacking solanapyrone A toxin production

Ascochyta rabiei, agent of Ascochyta blight of chickpea produces three toxins, Solanapyrones A, B and C of which solanapyrone A is the most toxic. All isolates of the fungus so far examined produce at least one of the Solanapyrone toxins, usually Solanapyrone A. The universality of solanapyrone production argues strongly for the importance of the toxins in virulence or pathogenicity. However, further evidence for this awaits the development of mutants lacking toxin production. Generation and isolation of fungal mutants defective in pathogenicity has been very useful for understanding the genetic and enzymatic processes responsible for infectivity in a number of pathosystems. Numerous tools have been used to transform plants and micro-organisms but the most widely micro-organism employed is Agrobacterium tumefaciens. In the present experiments, two strains of A. tumefaciens, AGL1 and LBA1126, harbouring two different plasmids, both encoding a gene for hygromycin resistance in the T-DNA region were used to transform isolate Tk21 of A. rabiei. The transformation of Ascochyta rabiei, gave rise to 498 colonies which grew on media supplemented with the selective agent; hygromycin B. The 30 sporulated transformants produced solanapyrone A on the specific medium at different rates. Solanapyrone A production, as demonstrated by the absorption of light at 327 nm, varied from 2.11 microg/ml to 4.32 microg/ml, representing a reduction of 74.11% to 46.99% in comparison with the wild type (8.15 microg/ml).     

Use of a Mini-Dome Bioassay and Grafting to Study Resistance of Chickpea to Ascochyta Blight

A mini‐dome bioassay was developed to study pathogenicity of Ascochyta rabiei and relative resistance of chickpea (Cicer arietanium). It was determined that the best condition for assaying pathogenicity of A. rabiei was to use 2 × 10⁵ spores/ml as inoculum and to maintain a leaf wetness period of 24 h under mini‐domes at a temperature between 16 and 22°C. This mini‐dome pathogenicity assay was used to determine relative resistance of six chickpea cultivars (cvs) to isolates of two pathotypes of A. rabiei. Grafting was employed to detect any translocated factors produced in the chickpea plant that mediate disease response, which could help elucidate possible resistance mechanisms to Ascochyta blight. The six chickpea cv. were grafted in all possible scion–rootstock combinations, and then inoculated with isolates of two pathotypes of A. rabiei using the mini‐dome technique. Results showed that self‐grafted‐resistant plants remained resistant and self‐grafted‐susceptible plants stayed susceptible, indicating the grafting procedure did not alter host response to infection by A. rabiei. Susceptible scions always exhibited high and similar levels of disease severity regardless of rootstock genotypes, and resistant scions always showed low and similar levels of disease severity when they were grafted onto any of the six rootstock genotypes. Orthogonal contrasts showed that scion genotypes determined disease phenotype, and that rootstock genotypes had no contribution to disease phenotype of the scions. The pathogenicity assay did not detect any translocated disease‐mediating agents responsible for susceptibility or resistance in chickpea. Disease phenotypes of Ascochyta blight of chickpea were conditioned locally by scion genotypes.     

Virulence diversity of Ascochyta rabiei the causal agent of Ascochyta blight of chickpea in the western provinces of Iran

Chickpea is the third most important food legume in the world. The most important limiting factor for the chickpea production in the world, including Iran, has been the Ascochyta blight. The pathogenic variation of 40 Ascochyta rabiei isolates from the western provinces of Iran was assessed on eight chickpea differential lines. The results revealed that A. rabiei population is diverse in the western provinces of Iran and the virulence rating of isolates across differential lines showed a large but continuous pathogenic variability. Based on the statistical analysis and the continuous response in differential lines, it was not possible to categorise A. rabiei isolates in the present study into pathotypes or races. Information obtained from the current study can be valuable in developing quarantine methods aimed to prevent dissemination of highly virulent isolates and in the development of durable resistant cultivars against the Ascochyta blight of chickpea.     

Accumulation of phytoalexins and isoflavone glucosides in a resistant and a susceptible cultivar of Cicer arietinum during infection with Ascochyta rabiei

After infection with spores of a virulent strain of Ascochyta rabiei the chickpea (Cicer arietinum) cultivars ILC 1929 (susceptible) and ILC 3279 (resistant) were compared with regard to pterocarpan phytoalexin and isoflavone accumulation. Quantitative HPLC analyses of total extracts of aerial parts were used to measure the induced formation of the phytoalexins medicarpin and maackiain and the accumulation of the constitutive isoflavones biochanin A and formononetin together with their, 7-0-glucosides and their 7-0-glucoside-6″-0-malonates. The two cultivars showed no significant difference in the level of isoflavones and isoflavone conjugates. On the other hand, the resistant cultivar ILC 3279 rapidly accumulated large amounts of both, phytoalexins (20–26 nmole g^?1 fr.w.) whereas cultivar ILC 1929 only produced very small amounts (5 nmole g^?1 fr.w.) of medicarpin. The data are discussed with regard to isoflavonoid metabolism and the significance of induced and constitutive levels of phytoalexins and isoflavones in resistance of chickpea towards A. rabiei.     

An intraspecific linkage map of the chickpea (<Emphasis Type="Italic">Cicer arietinum</Emphasis> L.) genome based on sequence tagged microsatellite site and resistance gene analog markers

An intraspecific linkage map of the chickpea genome based on STMS as anchor markers, was established using an F(2) population of chickpea cultivars with contrasting disease reactions to Ascochyta rabiei (Pass.) Lab. At a LOD-score of 2.0 and a maximum recombination distance of 20 cM, 51 out of 54 chickpea-STMS markers (94.4%), three ISSR markers (100%) and 12 RGA markers (57.1%) were mapped into eight linkage groups. The chickpea-derived STMS markers were distributed throughout the genome, while the RGA markers clustered with the ISSR markers on linkage groups LG I, II and III. The intraspecific linkage map spanned 534.5 cM with an average interval of 8.1 cM between markers. Sixteen markers (19.5%) were unlinked, while l1 chickpea-STMS markers (20.4%) deviated significantly ( P < 0.05) from the expected Mendelian segregation ratio and segregated in favor of the maternal alleles. However, ten of the distorted chickpea-STMS markers were mapped and clustered mostly on LG VII, suggesting the association of these loci in the preferential transmission of the maternal germ line. Preliminary comparative mapping revealed that chickpea may have evolved from Cicer reticulatum, possibly via inversion of DNA sequences and minor chromosomal translocation. At least three linkage groups that spanned a total of approximately 79.2 cM were conserved in the speciation process.     

Isolation of Solanapyrones A, B and C from Culture Filture and Spore Germination Fluids of Ascochyta rabiei and Aspects of Phytotoxin Action

Nine isolates of the fungus Ascochyta rabiei have been assayed for their ability to produce solanapyrone toxins. All isolates formed solanapyrone A, B and C which were secreted into the culture medium. Pronounced production of the toxins only occurred after onset of sporulation. The identification of the fungal products was achieved by cochromatography (TLC, HPLC), ¹H-NMR (solanapyrone A and B) and mass spectrometry (solanapyrone B). Work with A. rabiei isolate X showed that cultivation in chickpea seed extract medium in a surface culture provided best conditions for maximal toxin production. The accumulation of solanapyrones over the growth cycle was monitored. Germinating spores produced solanapyrones C and B whereas solanapyrone A was formed from the 6th day of the culture period on. Application of a mixture of solanapyrones A, B and C to leaflets of intact plants from an A. rabiei resistant cultivar (ILC 3279) and a susceptible cultivar (ILC 1929) led to characteristic changes in leaf morphology which had earlier been obsevad in susceptible plants following infection with spores of A. rabiei. Attempts to demonstrate the occurrence of toxins in the infected leaf were unsuccessful. Application of solanapyrones to solanapyrones to chickpea cell suspension cultures (derived from both cultivars) led to pronounced losses in viability and to plasmolysis of cells.     

Genetic dissection of pathotype-specific resistance to ascochyta blight disease in chickpea (<Emphasis Type="Italic">Cicer arietinum</Emphasis> L.) using microsatellite markers

Ascochyta blight is an economically important disease of chickpea caused by the fungus Ascochyta rabiei. The fungus shows considerable variation for pathogenicity in nature. However, studies on the genetics of pathotype-specific resistance are not available for this plant-pathosystem. The chickpea landrace ILC 3279 has resistance to pathotype I and II of the pathogen. In order to understand the inheritance of pathotype-specific resistance in this crop, both Mendelian and quantitative trait loci analyses were performed using a set of intraspecific, recombinant inbred lines derived from a cross between the susceptible accession ILC 1272 and the resistant ILC 3279, and microsatellite markers. We identified and mapped a major locus (ar1, mapped on linkage group 2), which confers resistance to pathotype I, and two independent recessive major loci (ar2a, mapped on linkage group 2 and ar2b, mapped on linkage group 4), with complementary gene action conferring resistance to pathotype II. Out of two pathotype II-specific resistance loci, one (ar2a) linked very closely with the pathotype I-specific resistance locus, indicating a clustering of resistance genes in that region of the chickpea genome.     

Integration of sequence tagged microsatellite sites to the chickpea genetic map

Fifty sequence-tagged microsatellite site (STMS) markers and a resistant gene-analog (RGA) locus were integrated into a chickpea ( Cicer arietinum L., 2n = 2 x = 16 chromosomes) genetic map that was previously constructed using 142 F(6)-derived recombinant inbred lines (RILs) from a cross of C. arietinum x Cicer reticulatum Lad. The map covers 1,174.5 cM with an average distance of 7.0 cM between markers in nine linkage groups (LGs). Nine markers including the RGA showed distorted segregation ( P < 0.05). The majority of the newly integrated markers were mapped to marker-dense regions of the LGs. Six co-dominant STMS markers were integrated into two previously reported major quantitative trait loci (QTLs) conferring resistance to Ascochyta blight caused by Ascochyta rabiei (Pass.) Labr. Using common STMS markers as anchors, three maps developed from different mapping populations were joined, and genes for resistance to Ascochyta blight, Fusarium wilt (caused by Fusarium oxysporum Schlechtend.: Fr. f. sp. ciceris), and for agronomically important traits were located on the combined linkage map. The integration of co-dominant STMS markers improves the map of chickpea and makes it possible to consider additional fine mapping of the genome and also map-based cloning of important disease resistance genes.     

Some physiological responses of chickpea cultivars to arbuscular mycorrhiza under drought stress

A factorial experiment based on RCB design with three replicates was conducted to investigate changes in some physiological responses of two chickpea (Cicer arietinum L.) cultivars (Pirouz from Desi type and ILC482 from Kabuli type) to arbuscular mycorrhiza (Glomus etunicatum Becker and Gerdman) under different irrigation treatments. The experiment was carried out in the greenhouse of the Agricultural Faculty of Kurdistan University from April to August 2009. The results showed that leaf chlorophyll content of chickpea cultivars was significantly increased by arbuscular mycorrhiza (AM) under both well and limited irrigation conditions. Proline accumulation in chickpea leaves under moderate and severe drought stresses was significantly stronger than that under optimum irrigation. Inoculation of chickpea with mycorrhizal fungi caused an increase in the activities of polyphenol oxidase and peroxidase, but a decrease in the activity of catalase. Comparisons among different irrigation levels showed that chickpea plants under drought stress had the most active lipid peroxidation. Non-AM plants showed stronger lipid peroxidation under moderate and severe water stresses than AM plants. Lipid peroxidation was more active in Pirouz leaves than in ILC₄₈₂ leaves. It seems that Kabuli-type cultivar responded better to mycorrhizal symbiosis under drought stress than Desitype cultivar.