Chickpea Wilt Research Articles

Sustainable Plant Disease Management of Wilt of Chickpea Caused by Fungi-Nematode Interaction

Fungi and bacteria are being developed into biological pesticides in agriculture. Pseudomonas fluorescence and Trichoderma viride were tested against M. incognita and Fusarium oxysporum f. sp. ciceri in pots and in infested field. In the pots Trichoderma viride were applied in seed, soil and foliar. The results indicated a significantly remarkable reduction of M. incognita population in the treatment of Trichoderma viride (soil) followed by (seed) and (foliar) application. Further it was also observed the Trichoderma viride enhanced plant growth parameters of chickpea and reduced the incidence of Fusarium wilt disease of chickpea up to 70% in soil treatment followed by 66% seed treatment 49% foliar application form control. In the infested (fusarium wilt and M. incognita) field microplot Trichoderma viride and Pseudomonas fluorescence were applied @ 3kg /ha in soil and @ 3g/kg in seed. Results indicate that both bio-agents treatments significantly reduced the formation of root-knot population as compared to control. Application of both the bio-agents significantly enhanced plant growth parameters and no. of grain pods/ plant as compared with control. Both the bio-agents also reduced significantly incidence of Fusarium oxysporum f. sp ciceri as compared to control. In comparing the two bio-agents it was observed that wilt incidence was lowest in the treatments of Pseudomonas fluorescence (soil treatment) 15.1% followed by Pseudomonas fluorescence (seed treatment) 20.8%, Trichoderma viride (soil treatment) 26.2%, and Trichoderma viride (seed treatment) 31.6%.

Field evaluation of eco-friendly biocontrol package for the management of pod borer, Helicoverpa armigera Hubner, and fusarium wilt in chickpea, Cicer arietinum

Helicoverpa armigera is a serious pest of chickpea and causes great damage to crop. Extensive and indiscriminate use of insecticides has led to the development of resistance in H. armigera. Among the several alternative methods for management of H. armigera, the nuclear polyhedrosis virus (NPV) is promising, whereas Trichoderma sp. have shown promising results against chickpea wilt. The experiments to evaluate biocontrol package against H. armigera and wilt disease under field conditions were conducted. Lowest H. armigera larval population (0.71 larvae/plant) was recorded in chemical control, which was at a par with biocontrol package (0.91 larvae/plant), and both the treatments were significantly better than control. Lowest per cent pod damage (3.85%) was recorded in chemical control followed by biocontrol treatment (5.08%) and unsprayed control (8.61%). The yields from biocontrol package (13.45 q/ha) and chemical control (15.37 q/ha) were significantly higher than unsprayed control (10.7 q/ha). There was no disease incidence in all treatments in both 2008 and 2009.

Effect of Brassica carinata (L.) biofumigants (seed meal) on chickpea wilt (Fusarium oxysporum f.sp. ciceris), growth, yield and yield component in Ethiopia

Pot experiments were carried out in the green house at Amhara Regional Agriculture Research Institute (ARARI) Bahirdar, Ethiopia to evaluate the potential of Brassica carinata cultivars namely; Holleta-l, S-67 and Yellow Dodola in 2007 and 2008. The treatment effects of B. carinata (L.) cultivars Holleta–1, S-67 and Yellow Dodola seed meals on chickpea fusarium wilt (Fusarium oxysporum f.sp. ciceris) were studied. Six rates of seed (0, 5, 10, 15, 20 and 25 g/kg of infested soil) were used. Infested soil without B.carinata cultivars amendments as a control and susceptible check variety JG-62 also without amendments were used in all the experiments. For each seed meal experiment, the treatments were arranged in factorial randomised complete block design in three replications. Data on seedling emergence, wilt incidence, fresh weight, dry weight, pod per plant, seed per pod, hundred seed weight and yield per hectare were collected. The amendments of infested soil with B.carinata cultivars seed meal reduced the incidence of chickpea fusarium wilt and increased yield per hectare. The interaction of the seed meal Holleta-1, S-67 and Yellow Dodola at 10–25 g/kg infested soil were effective in reducing wilt incidences on chickpea. However, the interaction of Yellow Dodola with 20 and 25 g seed meal per kg infested soil were the best combination in reducing significantly wilt incidence. The three cultivars incorporated at different level of doses significantly affected the influence of Fusarium wilt on the fresh weight, dry weight, pod per plant, seed per pod, hundred seed weight and yield per hectare. The highest yield kg/ha was recorded in combination of Yellow Dodola seed meal at 20 and 25 g followed by S-67 and Holleta-1 at 25 g /kg infested soil, respectively. The interaction of Holleta-1 at 5–25 infested soil significantly reduced disease incidence up to 16.7–43.3% and increased yield per hectare with mean by (30%) over the control. Seed meal amendment S-67 significantly reduce disease incidence 26.7–46.7% and increased yield kg/ha with mean by (36.7%) from the unamended control. Yellow dodola reduces disease incidence with 26.7–63.3% and increased yield kg/ha with mean by (45%) from the unamended control. The result indicates the potential of using Brassica crop seed meal amendment as useful component of integrated chickpea wilt management.

Status of chickpea fusarium wilt (Fusarium oxysporum f.sp. ciceris) in northwestern Ethiopia

Surveys for incidence of fusarium wilt of chickpea were carried out in six districts of North and South Gondar, and East Gojam administrative zones, Amhara National Regional State in northwestern Ethiopia in 2006–2007 and 2007–2008 main cropping seasons. In each district, five representative peasant administrations (PAs) were selected based mainly on chickpea-growing area coverage, and, in each PA, disease was assessed in five randomly selected farmers’ fields. In the two cropping seasons, the mean incidences recorded in each district were as follows: Gondar Zuria, 34.16% and 34.11%; Dembia, 37.90% and 35.36%; Libo-Kemkem, 34.74% and 28.81%; Fogera, 34.74% and 28.81%; Dejen, 34.74% and 28.81% and Enemay, 33.34% and 37.64%. The result indicated that fusarium wilt is currently highly distributed in all surveyed chickpea-growing areas of northwestern part of Ethiopia. Therefore, possible management options are vital to alleviate the problem.

Effect of amphotericin B nanodisks on plant fungal diseases

The development of water-soluble nanodevices extends the potential use of compounds developed for other purposes (e.g. antifungal drugs or antibiotics) for applications in agriculture. For example, the broad-spectrum, water-insoluble, macrolide polyene antibiotic amphotericin B (AMB) could be used to inhibit phytopathogenic fungi. A new formulation embedding AMB in nanodisks (NDs) enhances antibiotic solubility and confers protection against environmental damage. In the present study, AMB-NDs were tested for efficacy against several phytopathogenic fungi in vitro and on infected living plants (chickpea and wheat). Compared with AMB in dimethylsulfoxide (DMSO), AMB-NDs increased the sensitivity of several fungal species to this antimycotic in vitro. Sensitivity varied with fungal species as well as with the forma specialis. Phytophthora cinnamomi, previously reported as insensitive to other polyene antimycotics, remained unaffected at the doses examined. Some effect against disease symptoms were obtained with AMB-NDs against fusarium wilt in chickpea, whereas the results were highly variable in wheat, depending on both the species and treatment regimen. The results confirm that formulation of AMB into ND increases its effectiveness against phytopathogenic fungi in vitro, opening the possibility for its use on infected plants in the field.

Pathogenicity of indole-3-acetic acid producing fungus Fusarium delphinoides strain GPK towards chickpea and pigeon pea

An indole-3-acetic acid (IAA) producing fungal strain was isolated from chickpea grown rhizospheric soil samples. Based on morphological and Internal Transcribed Spacer (ITS) region sequence analysis the new isolate was identified as Fusarium delphinoides. The Fusarium delphinoides strain produces and secretes IAA in-vitro as identified by HPLC and Mass spectrometry. The IAA production is dependent on tryptophan (Trp) as a nitrogen source in the medium. The IAA production is influenced by growth conditions such as pH of the medium, concentration of Trp and the nature of the carbon source. Additional nitrogen sources repress Trp dependent IAA production. Glucose and Trp served as the best carbon and nitrogen sources respectively. Pathogenicity of Fusarium delphinoides towards the plants was tested by electrolyte, nutrient leakage analysis and also by scoring the disease symptoms. Two cultivars of chickpea (ICCV-10 and L-550) and two cultivars of pigeon pea (Maruti and PT-221) were assessed for the pathogenicity by inoculating with spores of Fusarium delphinoides. The inoculation induced symptoms of Fusarium wilt as in the case of Fusarium oxysporum f. sp. ciceris (FOC), a known pathogen causing Fusarium wilt in chickpea. Electrolyte and nutrient leakage from the infected plants were used to assess the resistance, tolerance (moderately resistance) and susceptibility of the plants to the infection. Based on the results, both the pigeon pea cultivars (Maruti and PT-221) were rated as resistant, and ICCV-10 was rated as a tolerant cultivar of chickpea. However, chickpea cultivar L −550 was found to be a susceptible host for infection by Fusarium delphinoides. These results suggest that Fusarium delphinoides, which belongs to the Fusarium dimerum species group, is an IAA producing plant pathogen and causes wilt in chickpea. Further, along with pathogenicity tests, electrolyte and nutrient leakage analysis can be used to assess the pathogenicity of pathogenic fungi.

Survey, surveillance and cultural characteristics of chickpea wilt caused by Fusarium oxysporium f. sp. ciceri

Survey and surveillance of chickpea wilt in the Latur district revealed average wilt complex to the tune of 12.26%. Tashilwise survey report indicated maximum wilt incidence in Tashil Ausa (15.4%) followed by Jalkot (14.8%) and Renapur (14.0%). Further study indicated thatFusarium oxysporium f. sp. ciceri was associated with majority of the cases. The pathogen was isolated, purified and its pathogenicity was proven in pot culture. Further, on the basis of morphological, cultural characteristics of the pathogen and symptomatology, the fungal pathogen was identified as Fusarium oxysporium f. sp. ciceri. Key words: Survey, chickpea wilt, Fusarium oxysporium f. sp. ciceri

Evaluation of actinomycete isolates obtained from herbal vermicompost for the biological control of Fusarium wilt of chickpea

A total of 137 actinomycetes cultures, isolated from 25 different herbal vermicomposts, were characterized for their antagonistic potential against Fusarium oxysporum f. sp. ciceri (FOC) by dual-culture assay. Of the isolates, five most promising FOC antagonistic isolates (CAI-24, CAI-121, CAI-127, KAI-32 and KAI-90) were characterized for the production of siderophore, cellulase, protease, hydrocyanic acid (HCN), indole acetic acid (IAA) and antagonistic potential against Rhizoctonia bataticola, which causes dry root rot in chickpea (three strains viz. RB-6, RB-24 and RB-115) and sorghum (one strain). All of the five FOC antagonistic isolates produced siderophore and HCN, four of them (except KAI-90) produced IAA, KAI-32 and KAI-90 produced cellulase and CAI-24 and CAI-127 produced protease. In the dual-culture assay, three of the isolates, CAI-24, KAI-32 and KAI-90, also inhibited all three strains of R. bataticola in chickpea, while two of them (KAI-32 and KAI-90) inhibited the tested strain in sorghum. When the FOC antagonistic isolates were evaluated further for their antagonistic potential in the greenhouse and wilt-sick field conditions on chickpea, 45–76% and 4–19% reduction of disease incidence were observed, respectively compared to the control. The sequences of 16S rDNA gene of the isolates CAI-24, CAI-121, CAI-127, KAI-32 and KAI-90 were matched with Streptomyces tsusimaensis, Streptomyces caviscabies, Streptomyces setonii, Streptomyces africanus and an identified species of Streptomyces, respectively using the BLAST searching. This study indicated that the selected actinomycete isolates have the potential for biological control of Fusarium wilt disease in chickpea.

Effect of Abiotic Stress on Phosphate Solubilization by Biocontrol Fungus Trichoderma sp.

This study was undertaken to explore the role of Trichoderma sp. in phosphate (P) solubilization and antagonism against fungal phytopathogens. All fungal isolates (SE(6), KT(6), KT(28), and BRT(11)) and a standard culture of T. harzianum (Th-std) were able to antagonize two fungal phytopathogens (Sclerotium rolfsii and Rhizoctonia solani) of chickpea (Cicer arietinum L.) wilt complex. Transmission electron microscopic studies (TEM) further confirmed ultra-cytological changes in the sclerotia of S. rolfsii parasitized by Trichoderma sp. All fungal cultures exhibited production of NH(3) and siderophore, but only BRT(11), SE(6), and Th-std could produce HCN. Among all the cultures tested, isolate KT(6) was found to be most effective for solubilization of ferric phosphate releasing 398.4 μg ml(-1) phosphate while isolates BRT(11) and SE(6) showed more potential for tricalcium phosphate (TCP) solubilization releasing 449.05 and 412.64 μg ml(-1) phosphate, respectively, in their culture filtrates. Part of this study focused on the influence of abiotic stress conditions such as pH, temperature, and heavy metal (cadmium) on phosphate (TCP) solubilizing efficiency. Two selected cultures KT(6) and T. harzianum retained their P solubilizing potential at varying concentrations of cadmium (0-1000 μg ml(-1)). Isolate KT(6) and standard culture of T. harzianum released 278.4 and 287.6 μg ml(-1) phosphate, respectively, at 1000 μg ml(-1)cadmium. Maximum solubilization of TCP was obtained at alkaline pH and at 28°C temperature. Isolate BRT(11) was found most alkalo-tolerant releasing 448.0 μg ml(-1) phosphate at pH 9.

In Planta and Soil Quantification of Fusarium oxysporum f. sp. ciceris and Evaluation of Fusarium Wilt Resistance in Chickpea with a Newly Developed Quantitative Polymerase Chain Reaction Assay

Fusarium wilt of chickpea caused by Fusarium oxysporum f. sp. ciceris can be managed by risk assessment and use of resistant cultivars. A reliable method for the detection and quantification of F. oxysporum f. sp. ciceris in soil and chickpea tissues would contribute much to implementation of those disease management strategies. In this study, we developed a real-time quantitative polymerase chain reaction (q-PCR) protocol that allows quantifying F. oxysporum f. sp. ciceris DNA down to 1 pg in soil, as well as in the plant root and stem. Use of the q-PCR protocol allowed quantifying as low as 45 colony forming units of F. oxysporum f. sp. ciceris per gram of dry soil from a field plot infested with several races of the pathogen. Moreover, the q-PCR protocol clearly differentiated susceptible from resistant chickpea reactions to the pathogen at 15 days after sowing in artificially infested soil, as well as the degree of virulence between two F. oxysporum f. sp. ciceris races. Also, the protocol detected early asymptomatic root infections and distinguished significant differences in the level of resistance of 12 chickpea cultivars that grew in that same field plot infested with several races of the pathogen. Use of this protocol for fast, reliable, and cost-effective quantification of F. oxysporum f. sp. ciceris in asymptomatic chickpea tissues at early stages of the infection process can be of great value for chickpea breeders and for epidemiological studies in growth chambers, greenhouses and field-scale plots.

Transmission electron microscopic study of the cytological changes in Sclerotium rolfsii parasitized by a biocontrol fungus Trichoderma sp

There is a recent trend towards the use of eco-friendly biological control agents for protecting crops from pest and disease, especially soil-borne plant pathogens, as an alternative to existing chemical methods. Among various biocontrol agents, Trichoderma, which has multiple mechanisms for the biocontrol of phytopathogens, is used widely. The present study explores the role of Trichoderma sp. in inducing cytological changes in fungal plant pathogens during parasitization. In dual culture plates, all the fungal isolates (SE6, KT6, KT28, and BRT11) along with a standard culture of T. harzianum were able to antagonize and mycoparasitize two soil-borne fungal phytopathogens (Sclerotium rolfsii and Rhizoctonia solani) of chickpea wilt complex. The suppression of S. rolfsii was slower than that of R. solani. The interaction between T. harzianum and sclerotia of S. rolfsii was studied by light microscopy and transmission electron microscopy (TEM). Ultra-structural examinations revealed that growth and development of Trichoderma resulted in extensive host cell alterations, such as retraction, aggregation and disintegration of cytoplasmic contents. Lysis and deformation of hyphal cell wall, degradation and disappearance of cytoplasmic contents and loss of cellular integrity in sclerotia of S. rolfsii paratisized by T. harzianum is clearly apparent from transmission electron micrographs.

English

The demand for products and technologies based on plants to control plant pathogens has increased in recent years due to concern about the use of hazardous pesticides. In the present investigation, washings of vermicompost (called biowash) prepared from foliage of Jatropha (Jatropha curcas), Annona (Annona squamosa) and Parthenium (Parthenium hysterophorus) were evaluated against fungal pathogens viz. Fusarium oxysporum f. sp. ciceri (FOC; causes wilt in chickpea), Sclerotium rolfsii (causes collar rot in chickpea) and Macrophomina phaseolina (causes charcoal rot in sorghum). Crude biowash of the botanicals were partitioned against ethyl acetate and the resultant organic and aqueous fractions were tested against the fungi. Similarly, crude biowash was also passed through C18 solid phase extraction cartridges and the resultant adsorbed and non-adsorbed fractions were tested against the fungi. Organic fractions of all the three biowash at 0.5% inhibited the growth of S. rolfsii between 78 and 87%, M. phaseolina between 62 and 65%, whereas only Parthenium was able to effectively inhibit FOC (91%), compared to control.  Adsorbed fractions of all the three biowash at 0.5% inhibited the growth of S. rolfsii between 81 and 92%, M. phaseolinabetween 76 and 77% and FOC between 26 and 49%, compared to control. Both aqueous and non-adsorbed fractions of all the three biowash did not inhibit any of the fungi. Since Jatropha biowash showed consistently higher levels of inhibition (>80%) in both fractionation methods on S. rolfsii, this was selected for further purification of their secondary metabolites. When the organic fraction of Jatropha biowash was further fractionated by C18 open column chromatography with eluent 5, 10, 20, 40, 60, 80 and 100% MeOH fractions, only 80% methanol (MeOH) fraction was found to inhibit S. rolfsii. The active 80% MeOH fraction showed three clear bands when chromatographed on Silica Gel 60 F254 thin layer chromatography (TLC) plates with Rf values 0.95, 0.90 and 0.70. Hence, it was concluded that one of these three bands could be the active ingredients that inhibited S. rolfsii and can be further exploited as a bio-fungicide.   Key words: Botanicals, jatropha, annona, parthenium, biowash, Sclerotium rolfsii,Fusarium oxysporum f. sp. ciceri, Macrophomina phaseolina, secondary metabolites.

ITS-RFLP fingerprinting and molecular marker for detection of Fusarium oxysporum f.sp. ciceris

Genetic diversity of 11 representative isolates of Fusarium oxysporum f.sp. ciceris causing chickpea wilt was determined through internal transcribed spacer (ITS) region of the ribosomal DNA-restriction fragment length polymorphism (ITS-RFLP). ITS1+5.8s+ITS2 regions of the isolates were amplified with a set of primers ITS1 and ITS4 and amplified products were digested with 4 restriction enzymes (AluI, MboI, RsaI, MseI). Six different kinds of ITS-RFLP patterns were obtained. The ITS region of these isolates was sequenced and deposited to NCBI GeneBank. The nucleotide sequence homology of ITS region grouped the isolates into 5 categories. Primers were designed with sequence information using Primer 3 software. F. oxysporum f.sp. ciceris specific markers (FOC F2 and FOC R2) based on ITS region were developed for the first time for detection of the pathogen. The markers produced an amplicon of 292 bp; they were validated against the isolates of the pathogen collected from different locations of India.

Biocontrol of Fusarium Wilt of Chickpea using Arbuscular Mycorrhizal Fungi andRhizobium leguminosorumBiovar

Abstract Present study deals with the biocontrol of Fusarium wilt of chickpea using arbuscular mycorrhizal fungi (AMF) Glomus hoi (Gh), Glomus fasciculatum (Gf) and Rhizobium leguminosorum Biovar. (Rl), which are the important members of rhizosphere and biological control agents, were examined on both the patho- system of Fusarium oxysporum f. sp. ciceris (Foc) and chickpea (Cicer arietinum). The colonization and nodulation of two biocontrol agents exhibited differences as a result of reciprocal interactions of these items as well as the effect of the Foc. Nodulation of Rl particularly decreased in triple inoculation. In addition, colonization of AMF significantly decreased in treatment of Foc+AMF than control, AMF. It was determined that single biological control agents inoculations were more effective than dual inoculations (AMF+Rl). When the morphological parameters of chickpea were considered, all of the morphological values were decreased in treatments which present Foc. Beside this all biological co...

Variability in Fusarium oxysporum f. sp. ciceri causing vascular wilt in chickpea

The variability in cultural characteristics and the virulence among three isolates of Fusarium oxysporum f. sp. ciceri causing vascular wilt in chickpea was studied under laboratory conditions. The three isolates (Foc-1, Foc-2 and Foc-3) did not show any significant difference in their mycelial dry weight production at any temperature regimes, pH level or the growth media tested. The radial growth on PDA also did not differ significantly in the three isolates. However, some quantitative differences were noted in colony characters and septations in macroconidia of these isolates. The isolate Foc-1 exhibited dull white, thin and flat hairy growth, spreading out like thread, Foc-2 showed a white fluffy colony with irregular aerial margin, while Foc-3 exhibited a pinkish white, slightly fluffy colony with regular margin. Conidia also differed with regard to septation. Three to six septa were present in Foc-2, while there were 2–3 in isolates Foc-1 and Foc-2. These isolates differed significantly with regard to their virulence on test varieties. Isolate Foc-1 was more virulent that Foc-2 or Foc-3 and produced abundant spores.

First Report of Clonostachys rhizophaga as a Pathogen of Dendrocalamus giganteus in Mozambique.

Dendrocalamus giganteus Wall. ex Munro, a wild plant belonging to the family Poaceae, is widespread in Mozambique where it is used as a construction material. At the end of 2007, disease symptoms have been observed on D. giganteus plants growing in the neighborhood of Maputo. Diseased plants showed longitudinal dark streaks on the stem surface to which corresponded internal vascular browning and chlorosis in wide leaves that gradually developed into necrosis. At the final stage of the disease plants died. To isolate the pathogen, stem segments collected during September 2008 were surface sterilized with 1% HgCl2 for 30 s, rinsed with sterile deionized water for 30 s, and incubated on potato dextrose agar (PDA) medium at 22°C in the dark for 2 weeks. Monosporic cultures of the isolated fungus formed dimorphic Verticillium-like (primary) or penicillate (secondary) conidiophores and ovoidal to elongate, minutely curved, hyaline conidia, 5 to 9.5 × 2.5 to 4.5 μm, with laterally displaced hilum. These characteristics are typical of Clonostachys rhizophaga Schroers (3). Identification was confirmed by the Centraalbureau voor Schimmelcultures (Utrecht, the Netherlands) on the basis of the β-tubulin (tub2) gene sequence (3). For our isolate CBS 125416, the tub2 sequence was 100% similar to that of the C. rizhophaga strain CBS 124511 (GenBank Accession No. FJ 593883) (1). To verify the pathogenicity of the fungus, a 5-mm-diameter mycelial plug obtained from 2-week-old colonies grown on PDA was affixed to a portion of the stem of D. giganteus from which the superficial tissues had been removed and the inoculation site was covered with wet cotton and wrapped with Parafilm. Control plants were treated by the same method but using PDA plugs without mycelium. Twenty plants were used, ten of which were controls. They were grown in a controlled climatic chamber at 22°C with a photoperiod of 16 h at 40 μE·m-2·s-1. Two months after inoculation, all plants showed a dark area surrounded by an idropic halo on the stem surface and internal browning, whereas control plants remained healthy. C. rhizophaga was recovered from all infected plants. C. rhizophaga is apparently rare. The fungus (as Verticillium rhizophagum Tehon & Jacobs, nom. invalid.) has been previously reported from the United States, Chile, and Ecuador (4) and as a culture contaminant in Switzerland (3). More recently C. rhizophaga has been found to be associated with Pinus canariensis in Argentina (2) and it has been reported as a causal agent of chickpea wilt in Syria (1). To our knowledge, this is the first report of C. rhizophaga for subsaharian Africa. It may be under reported and more common than has been thought because of the difficulty in identifying Clonostachys species, but with the ability to identify species using tub2 (3), there can be no doubt of its identity.

Morphological and pathogenic variability of Indian isolates of Fusarium oxysporum f. sp. ciceris causing chickpea wilt

Wilt of chickpea (Cicer arietinum) caused by Fusarium oxysporum f. sp. ciceris is prevalent in almost all chickpea growing areas of the world and its incidence varied from 14.1 to 32.0% in the different states of India surveyed. The isolates were highly variable in their colony growth pattern, size of colony and pigmentations. The size of microconidia varied from 5.1–12.8 × 2.5–5.0 μm, whereas macroconidia ranged from 16.5–37.9 × 4.0–5.9 μm with 1–5 septations. One hundred and twelve isolates were grouped into 12 categories on the basis of their radial growth, size of macroconidia and growth pattern. Majority of the isolates were highly pathogenic causing more than 50% wilt in chickpea cultivar JG 62. Virulence analysis of 56 representative isolates on a set of 18 cultivars of chickpea, including 10 international differentials, grouped them into three categories. Chickpea cultivar KWR 108 differentiated all isolates of Punjab, Haryana and Delhi states and a few isolates of Rajasthan from others by showing resistant reactions and were placed in the first group. The rest of the isolates of Rajasthan state showed susceptible reactions on KWR 108 placed in a second group. Cultivar CPS 1 distinguished the isolates of Jharkhand state and placed them into a third group. An international set of cultivars recommended for race differentiation were not able to distinguish all the isolates into known races of the pathogen, therefore cultivar KWR 108 should be included in the existing differential set of cultivars.

A Molecular Insight into the Early Events of Chickpea (Cicer arietinum) and Fusarium oxysporum f. sp. ciceri (Race 1) Interaction Through cDNA-AFLP Analysis

Wilt of chickpea caused by Fusarium oxysporum f. sp. ciceris is one of the most severe diseases of chickpea throughout the world. Variability of pathotypes of F. oxysporum f. sp. ciceris and breakdown of natural resistance are the main hindrances to developing resistant plants by applying resistant breeding strategies. Additionally, lack of information of potential resistant genes limits gene-transfer technology. A thorough understanding of Fusarium spp.-chickpea interaction at a cellular and molecular level is essential for isolation of potential genes involved in counteracting disease progression. Experiments were designed to trigger the pathogen-challenged disease responses in both susceptible and resistant plants and monitor the expression of stress induced genes or gene fragments at the transcript level. cDNA amplified fragment length polymorphism followed by homology search helped in differentiating and analyzing the up- and downregulated gene fragments. Several detected DNA fragments appeared to have relevance with pathogen-mediated defense. Some of the important transcript-derived fragments were homologous to genes for sucrose synthase, isoflavonoid biosynthesis, drought stress response, serine threonine kinases, cystatins, arginase, and so on. Reverse-transcriptase polymerase chain reaction performed with samples collected at 48 and 96 h postinfection confirmed a similar type of differential expression pattern. Based on these results, interacting pathways of cellular processes were generated. This study has an implication toward functional identification of genes involved in wilt resistance.

First Report of Chickpea Wilt Caused by Clonostachys rhizophaga in Syria.

In 2007 and 2008, disease symptoms were observed on four cultivars of chickpea (Cicer arietinum L.), including two of the most popular cultivars grown in Syria (Ghab 3 and Ghab 4), in a replicated on-farm trial conducted in the fertile Al Ghab Plains. Affected plants exhibited chlorosis of the foliage, vascular discoloration, and death. In both years, plant mortality reached 100% in plots of cvs. ICC 12004, Ghab 3, and Ghab 4, but only 60% in plots of cv. ILC 97-706. Five monosporic isolates obtained from surface-disinfested stems and roots were identified morphologically. All micromorphological characteristics indicated that the isolated fungi fit the description of Clonostachys rhizophaga Schroers (1). Wilting of chickpea was widespread in the area, and fungal isolations from a random sample of diseased plants in neighboring farmers' fields revealed the presence of C. rhizophaga. In culture, isolates formed dimorphic, Verticillium-like (primary) or penicillate (secondary) conidiophores and ovoidal to elongate, slightly curved or asymmetrical, 5 to 9 μm long and 2.5 to 3.5 μm wide conidia showing a slightly laterally displaced hilum. The identification of the five isolates as C. rhizophaga was supported by sequencing approximately 600 bp of the β-tubulin gene (tub2). Two representative sequences have been deposited under GenBank, Accession No. FJ593882 for strain CBS 124507 and No. FJ593883 for CBS 124511. Both were 100% similar to the sequence of C. rhizophaga strain CBS 361.77 (GenBank Accession No. AF358158) but differed by a deletion of 2 nucleotides relative to the ex-type strain of C. rhizophaga, CBS 202.37 (GenBank Accession No. AF358156). Two methods were used to inoculate plants and complete Koch's postulates. Method 1 used a 10-mm-diameter mycelial plug to inoculate healthy 3-day-old seedlings grown on 40 ml of Hoagland nutrient agar medium in a glass tube (one seedling per tube). The plug was placed mycelial-side down on the surface of the medium, and the fungus subsequently colonized the medium and penetrated the plant roots. Method 2 involved mixing autoclaved seed that had been colonized by each isolate with sterilized soil (1:12 vol/vol) prior to transplanting healthy seedlings into the soil mix. Thirty plants of each cultivar were tested per isolate per method, and controls received sterile agar plugs or autoclaved chickpea seed only. Irrespective of inoculation method, all five isolates caused wilt and plant death of all cultivars within 15 days (method 1) or 2 months (method 2) postinoculation. Symptoms were similar to those originally observed in the field and controls remained healthy. C. rhizophaga was recovered from all affected plants. To our knowledge, this is the first report of C. rhizophaga as a pathogen of chickpea. In an earlier report, C. rhizophaga (as Verticillium rhizophagum Tehon & Jacobs, nom. invalid.) was identified as the causal agent of a disastrous disease of Ulmus americana in Ohio (2). C. rhizophaga has been reported from Chile, Ecuador, the United States, and Switzerland (1).

Changes in the redox status of chickpea roots in response to infection by Fusarium oxysporum f. sp. ciceris: apoplastic antioxidant enzyme activities and expression of oxidative stress‐related genes

Activity levels of oxidative stress-related enzymes in the root apoplast during the interaction of WR315 (resistant) and JG62 (susceptible) chickpeas (Cicer arietinum L.) with the highly virulent race 5 of Fusarium oxysporum f. sp. ciceris were compared. Because this fungus develops asymptomatic infections in the chickpea root cortex in both susceptible and resistant plants, but only intrudes into the root xylem in the susceptible variety, the interactions were compared at three specific stages during disease development in JG62: (i) before symptom development (10 days after inoculation); (ii) at the time of appearance of the first disease symptoms (15-17 days after inoculation) and (iii) when all plants had developed disease symptoms (20-22 days after inoculation). Diamine oxidase (DAO), ascorbate peroxidase (APX), glutathione reductase (GR), guaiacol-dependent peroxidase and superoxide dismutase (SOD), but not catalase (CAT), were found in the apoplast of chickpea roots. In terms of APX activity, infection by the pathogen caused a different response in the incompatible compared to the compatible plant. In the case of GR, SOD and DAO activities, the pathogen caused the same response, but it developed earlier (i.e. GR and SOD) or to higher levels (i.e. DAO) in the incompatible interaction. Expression of apx, cat, sod, lipoxygenase (lox) and actin genes was also analysed in infected roots. Infection by F. oxysporum f. sp. ciceris race 5 only caused a significant change in the root expression of lox and actin genes. This up-regulation was earlier (lox) or higher (actin) in the incompatible than in the compatible interaction. Thus, changes in oxidative metabolism differ in compatible and incompatible interactions in Fusarium wilt of chickpea.