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Abstract: Ascochyta blight (AB) caused by the fungal pathogen Ascochyta rabiei is a serious foliar disease of chickpea (Cicer arietinum L.). Despite many genetic studies on chickpea‐Ascochyta interaction, genome‐wide scan of chickpea for the identification of AB‐associated quantitative trait loci (QTLs) and their gene(s) has not been accomplished. To elucidate narrow QTLs for AB resistance, here, we report the use of multiple QTL‐sequencing approach on 2 sets of extreme AB phenotype bulks derived from Cicer intraspecific and interspecific crosses. Two major QTLs, qABR4.1 and qABR4.2, and a minor QTL, qABR4.3, were identified on assembled chickpea pseudomolecule 4. We narrowed qABR4.1 to a “robust region” at 4.568–4.618 Mb through mapping on a larger intraspecific cross‐derived population and comparative analysis. Among 4 genes, the CaAHL18 gene showed higher expression under Ascochyta stress in AB resistant parent suggesting that it is the candidate gene under “robust qABR4.1.” Dual‐luciferase assay with CaAHL18 polymorphic cis‐regulatory sequences showed that allelic variation is associated with higher expression. Thus, our findings on chickpea‐Ascochyta interaction have narrowed down AB resistance associated QTLs on chickpea physical map. The narrowed QTLs and gene‐associated markers will help in biotechnological and breeding programs for chickpea improvement. [ABSTRACT FROM AUTHOR]

Gram is an important pulse crop extensively grown in the arid and semi-arid zones of Pakistan.Ascochytablight is a devastating disease of the gram. Thirty varieties/lines were screened against gram blight disease to evaluate the resistant germplam. None of the varieties/lines were immune to infection. 8032, Thal-2006, 06001 and 5CC-109 were resistant in response. Four varieties/line, Bital-98, 03008, PB-2000 and Noor-91, were moderately resistant while 12 were moderately susceptible. Susceptible response was observed in seven (05030, 900156, C-88, M-2008, Balkassar-2000, and Punjab-2000) varieties/lines and three (K8000, 03009 and 05014) were highly susceptible. Two consecutive sprays of five bio-products were done on five gram lines, i.e. 06001, 03008, 093127, 05007 and 05014. Minimum disease incidence was noted on the 06001 line. Vampire was most effective in disease controlling after seven and 14 days of both sprays. [ABSTRACT FROM PUBLISHER]

Twenty-four cultivars of chickpea were evaluated for their susceptibility to the grey mould fungus Botrytis cinerea using foliar, seed and soil inoculation at 2, 4 and 8 g fungus per plant, per kg seed or per kg soil. At 8 g the inoculum caused necrotic lesions to all 24 cultivars with foliar inoculation, to 23 cultivars except cv. CH-2007-22 with seed inoculation and to 17 cultivars with soil inoculation, and reduced yield by 7-43% (foliar inoculation), 3-34% (seed inoculation) and 3-26% (soil inoculation). Foliar or seed inoculation with 4 g of the fungus significantly reduced the yield of all cultivars tested except CH-2007-22 with foliar inoculation, and 4 cultivars with seed inoculation. Soil inoculation at 4 g fungus kg-1 soil, significantly reduced the yield of eight cultivars. Foliar and seed inoculations at 2 g of the fungus significantly reduced the yield of 16 and 7 cultivars of chickpea respectively; but soil inoculation at this concentration, did not significantly reduce yield in any cultivar. The greatest significant decline in yield was recorded with foliar inoculation in the cv. BG-256, 43% at 8 g, 40% at 4 g and 26% at 2 g inoculum level. The cv. CH-2007-22 was tolerant to B. cinerea as it exhibited only 3-7% yield loss at 8 g inoculum. The fungal population, especially that on the phylloplane, increased exponentially from January to March and declined drastically in April. At the high inoculum level of 8 g fungus kg-1 soil, B. cinerea may initiate infection through the soil. There was a positive correlation between disease severity and yield decline, and a disease severity above 2 significantly reduced yield. [ABSTRACT FROM AUTHOR]

For millennia, chickpea (Cicer arietinum) has been grown in the Levant sympatrically with wild Cicer species. Chickpea is traditionally spring-sown, while its wild relatives germinate in the autumn and develop in the winter. It has been hypothesized that the human-directed shift of domesticated chickpea to summer production was an attempt to escape the devastating Ascochyta disease caused by Didymella rabiei. We estimated genetic divergence between D. rabiei isolates sampled from wild Cicerjudaicum and domesticated C. arietinum and the potential role of temperature adaptation in this divergence. Neutral genetic markers showed strong differentiation between pathogen samples from the two hosts. Isolates from domesticated chickpea demonstrated increased adaptation to higher temperatures when grown in vitro compared with isolates from the wild host. The distribution of temperature responses among progeny from crosses of isolates from C. judaicum with isolates from C. arietinum was continuous, suggesting polygenic control of this trait. In vivo inoculations of host plants indicated that pathogenic fitness of the native isolates was higher than that of their hybrid progeny. The results indicate that there is a potential for adaptation to higher temperatures; however, the chances for formation of hybrids which are capable of parasitizing both hosts over a broad temperature range are low. We hypothesize that this pathogenic fitness cost is due to breakdown of coadapted gene complexes controlling pathogenic fitness on each host and may be responsible for maintenance of genetic differentiation between the pathogen demes. [ABSTRACT FROM AUTHOR]

Genetic variation among the isolates of Fusarium oxysporum f. sp. ciceris, the causal agent of chickpea wilt worldwide, was analysed using pathogenicity tests and molecular markers – random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR) polymorphism. Hundred and eight isolates were obtained from diseased chickpea plants in 13 different provinces of Turkey, out of which 74 isolates were assessed using 30 arbitrary decamer primers and 20 ISSR primers. Unweighted pair-grouped method by arithmetic average cluster analysis of RAPD, ISSR and RAPD + ISSR datasets provided a substantially similar discrimination among Turkish isolates and divided into three major groups. Group 1, 2 and 3 consisted of 41, 18 and 15 isolates, respectively. These methods revealed a considerable genetic variation among Turkish isolates, but no correlation with regard to the clustering of isolates from different geographic regions. Analysis of molecular variance confirmed that most genetic variability resulted from the differences among isolates within regions. Our results also indicated that the low-genetic differentiation (FST) and high gene flow (Nm) among populations had a significant effect on the emergence and evolutionary development of F. oxysporum f. sp. ciceris. This is the first report on genetic diversity and population structure of F. oxysporum isolates on chickpea in Turkey. [ABSTRACT FROM AUTHOR]

Ascochyta rabiei, causal agent of Ascochyta blight on chickpea (Cicer arietinum), can cause severe yield loss in the United States. Growers rely on applications of fungicides with site- specific modes of action such as the quinone outside inhibiting (Qol) fungicides azoxystrobin and pyraclostrobin, and the carboximide fungicide boscalid, to manage disease. In all, 51 isolates collected prior to Qol fungicide registration and 71 isolates collected prior to boscalid registration in the United States were tested in an in vitro assay to determine the effective fungicide concentration at which 50% of conidial germination was inhibited (EC50) for each isolate-fungicide combination. The effect of salicylhydroxamic acid (SHAM) on conidia of A. rabiei in the presence and absence of azoxystrobin also was assessed to determine whether the fungus is capable of using alternative respiration. Five of nine A. rabiei isolates tested had significantly higher (P ⩽ 0.05) EC50 values when SHAM was not included in media amended with azoxystrobin, indicating that A. rabiei has the potential to use alternative respiration to overcome fungicide toxicity in vitro. EC50 values of azoxystrobin and pyraclostrobin ranged from 0.0182 to 0.0338 μg/mI and from 0.0012 to 0.0033 μg/mI, with mean values of 0.0272 and 0.0023 μg/mI, respectively. EC50 values of boscalid ranged from 0.0177 to 0.4960 μg/mI, with a mean of 0.1903 μg/mI. Establishment of these baselines is the first step in developing a monitoring program to determine whether shifts in sensitivity to these fungicides are occurring in the A. rabiei pathogen population. [ABSTRACT FROM AUTHOR]

The effect of Glomus intraradices, Pseudomonas putida and Paenibacillus polymyxa on the growth, chlorophyll, nitrogen, phosphorus and potassium contents and on the root-rot disease complex of chickpea (caused by Meloidogyne incognita and Macrophomina phaseolina) were observed. Inoculation of plants with G. intraradices, P. putida and P. polymyxa alone and in combination significantly increased plant growth, pod number, chlorophyll, nitrogen, phosphorus and potassium contents and reduced galling, nematode multiplication and root-rot index. Inoculation of plants with P. putida most effectively reduced galling and nematode multiplication, followed by G. intraradices and P. polymyxa. Combined inoculation of plants with G. intraradices, P. putida and P. polymyxa caused the greatest reduction in galling, nematode multiplication and root-rot index. Pathogens had adverse effects on root colonisation by G. intraradices, while root colonisation by arbuscular mycorrhizal fungus was increased in the presence of P. putida and P. polymyxa. [ABSTRACT FROM AUTHOR]

Randomly amplified polymorphic DNA (RAPD) was used to examine the genetic variability among 10 isolates of Trichoderma representing three species and their ability to antagonize Fusarium oxysporum f. sp. ciceris causing chickpea wilt using dual culture assay and volatile and non-volatile compound production. Using 10 oligonucleotide primers, we are able to distinguish among the species of Trichoderma. Primer OPA 13 efficiently differentiated all the isolates of Trichoderma in to their species except T2 of Trichoderma viride. Some of the other primer as Primer OPA 10 also showed species-specific banding pattern. These species of Trichoderma were evaluated against the pathogen. All the isolates of the fungal antagonists caused significant reduction in the mycelial growth of the pathogen in vitro. The principle mechanism of mycoparasitism was observed as coiling of antagonistic hyphae around the pathogen hyphae and lysis. [ABSTRACT FROM AUTHOR]

Host plant resistance is the major component in the management of fungal diseases in chickpea (Cicer arietinum). We screened a chickpea mini-core collection composed of 211 germ plasm accessions representing the diversity of the global chickpea germ plasm collection of 16,991, maintained at the International Crops Research Institute for the Semi-Arid Tropics to identify sources of multiple disease resistance. The accessions were screened for resistance against Ascochyta blight (Ascochyta rabiei), Botrytis gray mold (Botrytis cinerea), Fusarium wilt (Fusarium oxysporum f. sp. ciceris), and dry root rot (Rhizoctonia bataticola) under a controlled environment. High levels of resistance were observed to Fusarium wilt (FW), where 21 accessions were asymptomatic and 25 resistant. In all, 3, 55, and 6 accessions were moderately resistant to Ascochyta blight (AB), Botrytis gray mold (BGM), and dry root rot (DRR) respectively. ICC 11284 was the only accession moderately resistant to both AB and BGM. Combined resistance also was identified for DRR and FW in 4 accessions, and for BGM and FW in 11 accessions. Through this study, chickpea germ plasm accessions were identified that possess high levels of resistance to more than one fungal disease and would be useful in chickpea multiple disease resistance breeding programs. [ABSTRACT FROM AUTHOR]

Temperature and wetness conditions required for development and maturation of Didymella rabiei pseudothecia were determined in a series of experiments conducted in controlled-environmental conditions. Initial stages of pseudothecium formation occurred at temperatures ranging from 5 to 15°C. Incubation at low temperatures was essential for subsequent pseudothecium maturation. This requirement was satisfied for chickpea stem segments incubated at 5 or 10°C for three consecutive weeks or during periods of 3 or 5 days, separated by periods at higher temperatures. Following the low-temperature requirement, subsequent pseudothecium development was independent of temperature in the range tested (5 to 20°C). Wetness was essential for pseudothecium production: pseudothecia formed and matured on stem segments maintained continuously wet but also on those exposed to periods of three or five wet days, separated by dry periods. The dispersal of D. rabiei ascospores was studied using chickpea plants as living traps in the field. Trap plants were infected mainly when exposed during rain but also in rainless periods. Results of this study enabled us to describe the developmental events leading to the production of the teleomorph stage and the dispersal of ascospores by D. rabiei in the Mediterranean climate of Israel. [ABSTRACT FROM AUTHOR]

Fusarium yellow disease of chickpea (Cicer arietinum), caused by the vascular wilt pathogenFusarium oxysporum, is a major production constraint in chickpea-growing regions of Iran. Fifteen isolates ofF. oxysporumwere classified on the basis of vegetative compatibility (the ability to form heterokaryons). Vegetative compatibility was assessed by pairingnitmutants. The isolates were assigned to three vegetative compatibility groups (VCGs): VCG1, VCG2, and VCG3 with 5, 3, and 7 members, respectively. These isolates were also characterized by virulence assay. On the basis of disease severity on chickpea seedlings, they were divided into three groups: highly virulent (HV), moderately virulent (MV) and weakly virulent (WV). Twelve arbitrary decamer primers were tested on the fungal isolates by polymerase chain reaction. Random amplified polymorphic DNA (RAPD) analysis indicated considerable genetic variation among these isolates. Comparison of the results of VCG tests and the virulence assay indicated that all seven HV isolates belong to a single vegetative compatibility group (VCG3), and all three WV isolates are placed in VCG1. There was no relationship between RAPD groups and the other two characteristics of IranianF. oxysporumisolates. [ABSTRACT FROM AUTHOR]

Helicoverpa armigera , commonly called gram pod borer, is a serious pest of pulses in India and damages chickpea. On average a 30% crop loss is reported. Due to absence of true resistant varieties in both the crops, resorting to chemicals had been the only alternative. But this has resulted in environmental disaster in the form of manifold resistance against insecticide and other social problems. Among the various biocontrol agents, Ha NPV is the most practicable solution and has been found efficacious in laboratory as well as research farms. In order to popularize this technique, large-scale farmers' field demonstrations were laid out during 2000 - 1 and 2001 - 2 in villages around IIPR Kanpur, spread over six villages in three districts in chickpea. The result was very promising. In 2000 - 1 the reduction percentage was 77.6. Treated plots gave 36% increase in yield (ranging between 32.0 to 38.6%). Average cost benefit ratio was 1 : 3.3. In 2001 - 2, the avoidable loss due to the treatment of Ha NPV was in the range of 2.4 to 14.0% with a mean value of 8.8%. Treated plots gave 44% increase in yield (range 10 to 70%). The average cost - benefit ratio was 1 : 3.4. [ABSTRACT FROM AUTHOR]

Presents several abstracts on plant pathology published in the April 2004 issue of "Plant Disease." Occurrence of Arabic Mosaic Virus and Grapevine Leaf Roll Associated Virus-3 on Grapevines in Iran," by R. Pourrahim, A. Ahoonmanesh, Sh. Farzadfar and F. Rakhshandehro; "First Occurrence of Downy Mildew on Boxleaf Veronica Caused by Peronospora Grisea in Italy," by G. Polizzi, A. Vitale and G. Parlavecchio; "First Report of Chickpea Chlorotic Dwarf Virus Infecting Spring Chickpea in Syria," by S. G. Kumari, K. M. Makkouk, N. Attar and W. Ghulam.

In both controlled environment and the field, six QTLs for ascochyta blight resistance were identified in three regions of the genome of an intraspecific population of chickpea using the IDS and AUDPC disease scoring systems. One QTL-region was detected from both environments, whereas the other two regions were detected from each environment. All the QTL-regions were significantly associated with ascochyta blight resistance using either of the disease scoring systems. The QTLs were verified by multiple interval mapping, and a two-QTL genetic model with considerable epistasis was established for both environments. The major QTLs generally showed additive gene action, as well as dominance inter-locus interaction in the multiple genetic model. All the QTLs were mapped near a RGA marker. The major QTLs were located on LG III, which was mapped with five different types of RGA markers. A CLRR-RGA marker and a STMS marker flanked QTL 6 for controlled environment resistance at 0.06 and 0.04 cM, respectively. Other STMS markers flanked QTL 1 for field resistance at a 5.6 cM interval. After validation, these flanking markers may be used in marker-assisted selection to breed for elite chickpea cultivars with durable resistance to ascochyta blight. The tight linkage of RGA markers to the major QTL on LG III will allow map-based cloning of the underlying resistance genes. [ABSTRACT FROM AUTHOR]

The effect of soil solarization on chickpea wilt, caused by Fusarium oxysporum f. sp. ciceri, was examined during the summer of 1985 and 1986. Preplant solarization for 45 days in 1985 significantly (P = 0.5) decreased the incidence of wilt in two subsequent chickpea crops. Additional solarization of sub-plots of the same soil during the summer of 1986 further reduced the disease and the pathogen. Yield and nodulation in the solarized plots were significantly (P = 0.05) higher than untreated plots. No pronounced differences in maximum temperature, percentage of diseased plants, plant height at maturity, and xylem discoloration indices were observed between solarized irrigated and non-irrigated treatments. However, the above parameters differed significantly (P = 0.05) between solarized irrigated and nonsolarized non-irrigated soil. Solarization significantly reduced both the population of F. oxysporum f. sp. ciceri, and viability of conidia and chlamydospores. These reductions were proportional to soil temperatures achieved during solarization. [ABSTRACT FROM AUTHOR]

Didymella rabiei grew saprophytically on pieces of infested chickpea stems and pods, and formed pycnidia and pseudothecia. The extent of saprophytic growth and production of viable spores were determined by the incubation conditions. On debris left on the soil surface under natural conditions, the fungus rapidly colonized the tissues, formed abundant pseudothecia and pycnidia, and remained viable throughout the 2 years of the study. When plant debris was buried, D. rabiei was restricted to the original lesions, in which it formed new pycnidia and was viable for 2 to 5 months. Under controlled conditions in the laboratory, D. rabiei extensively colonized plant debris spread over the soil surface. On the other hand, the fungus did not grow on buried debris, or showed only very limited development when the artificially infested debris was buried between two layers of sterilized soil. Incubation temperature was the principal factor associated with the production of conidia and especially ascospores. [ABSTRACT FROM AUTHOR]

The phytotoxic solanapyrones A, B and C, were produced by Ascochyia rabiei when grown on Czapek Dox nutrients supplemented with an aqueous extract of chickpea seed but not when grown on Czapek Dox nutrients alone. Addition of amino acids, vitamins and inorganic ions to Czapek Dox nutrients allowed the production of the solanapyrones in good yields. By systematic elimination of components of this medium, the constituents essential for toxin production were identified as the divalent metal cations Zn2+, Ca2+, Mn2+ and Cu2+. When these ions were added to Czapek Dox nutrients in the same concentrations as those found in chickpea extract, concentrations of the phslotoxins similar to those found in Czapek Dox nutrients supplemented with chickpea extract were detected. Removal of cations from the chickpea supplement by a cation exchange resin did not affect the growth of the fungus compared with growth on the medium containing the complete supplement, but no toxin was produced. A defined medium and cultural conditions suitable for solanapyrone production by A. rabiei are described. [ABSTRACT FROM AUTHOR]

This preliminary study indicated that the resistance to race 2 of fusarium wilt is controlled by two genes, the first of which must be present in the homozygous recessive form, and the other in the dominant form, whether homozygous or heterozygous for complete resistance. Early wilting results if the other gene is homozygous recessive. Late wilting occurs if both loci are dominant. The existence of differences among chickpea cultivars in the time taken to express the initial symptoms of fusarium wilt were observed. [ABSTRACT FROM AUTHOR]

The article focuses on the chickpea phyllody disease associated with phytoplasma in Pakistan. Plants affected by the disease have developed smaller leaflets on the branches giving it a bushy appearance and the development of abnormal green structures or phyllody in the flowers. Transmission electron microscope was used to examine tissues from affected and unaffected plants. The process has discovered typical pleomorphic bodies (phytoplasma) with opaque, low density cytoplasm having ribosome like granules. DNAs from affected plants were also extracted for amplification of PCR primers P1/P7 followed by R16F2n/R16R2. In addition, chickpea plants inoculated by grafting were also submitted for Koch's postulate for further investigation.

Discusses the abstract of the article "Genetic and chemical control of Rhizoctonia solani on chickpea," by E.B. Connor and R. Hall, submitted to the 2003 Canadian Phytopathological Society Annual Meeting in Montreal, Quebec.

Discusses the abstract of the article "Persistence of Ascochyta rabiei in chickpea residue in Saskatchewan," by B.D. Gossen, submitted to the 2003 Canadian Phytopathological Society Annual Meeting in Montreal, Quebec.