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Background: Fusarium wilt caused by Fusarium oxysporum f. sp. ciceris, a main threat to global chickpea production, is managed mainly by resistant cultivars whose efficiency is curtailed by Fusarium oxysporum f. sp. ciceris races. Methodology: We characterized compatible and incompatible interactions by assessing the spatial-temporal pattern of infection and colonization of chickpea cvs. P-2245, JG-62 and WR-315 by Fusarium oxysporum f. sp. ciceris races 0 and 5 labeled with ZsGreen fluorescent protein using confocal laser scanning microscopy. Findings: The two races colonized the host root surface in both interactions with preferential colonization of the root apex and subapical root zone. In compatible interactions, the pathogen grew intercellularly in the root cortex, reached the xylem, and progressed upwards in the stem xylem, being the rate and intensity of stem colonization directly related with the degree of compatibility among Fusarium oxysporum f. sp. ciceris races and chickpea cultivars. In incompatible interactions, race 0 invaded and colonized ‘JG-62’ xylem vessels of root and stem but in ‘WR-315’, it remained in the intercellular spaces of the root cortex failing to reach the xylem, whereas race 5 progressed up to the hypocotyl. However, all incompatible interactions were asymptomatic. Conclusions: The differential patterns of colonization of chickpea cultivars by Fusarium oxysporum f. sp. ciceris races may be related to the operation of multiple resistance mechanisms. [ABSTRACT FROM AUTHOR]

Forty-seven isolates of Fusarium oxysporum f.sp. ciceris, representative of the different pathogenic races and originating from California, India, Tunisia and Spain, and twenty-five non-pathogenic F. oxysporum isolates obtained from chickpea roots in Algeria, Italy, Morocco, Pakistan and Spain, were analyzed for vegetative compatibility. Only one vegetative compatibility group (VCG) was found among the 47 isolates of F. oxysporum f.sp. ciceris, although some isolates failed to complement with one or more isolates in this VCG. Among the twenty five non-pathogenic isolates, we found three multi-member VCG, each group containing two to five isolates. Pathogenic and non-pathogenic isolates complemented sporadically. Most of the non-pathogenic isolates were compatible with a yellowing-type low virulent F. oxysporum f.sp. ciceris isolate (Foc USA 3/1 JG), thus suggesting the possibility of the existence of transition isolates between pathogenic and non-pathogenic populations. Heterokaryon formation between compatible isolates was shown by both pathogenicity and molecular tests. The virulence pattern displayed by the heterokaryons indicated the presence of genetic factors controlling pathogenicity from both parental races. RAPD-PCR analysis of total DNA of the heterokaryon also showed the presence of the two genomes in it. The existence of a single VCG in the F. oxysporum f.sp. ciceris population support the hypothesis of its monophyletic origin. [ABSTRACT FROM AUTHOR]

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Root-knot nematodes (Meloidogyne spp.) are sedentary, obligate endoparasites in plants, where they induce specialized feeding sites. The feeding sites act as strong metabolic sinks to which photosynthates are mobilized. The histopathological modifications in the nematode-induced feeding sites of artificially inoculated chickpea cv. UC 27 were qualitatively and quantitatively compared using five isolates of M. artiellia and one isolate each of M. arenaria, M. incognita, and M. javanica. All Meloidogyne isolates infected chickpea plants, but root gall thickening was significantly less for M. artiellia isolates than for the other Meloidogyne species. Nevertheless, neither the number of giant cells in the feeding site (averaging four to six) nor the area of individual giant cells was influenced by nematode species or isolate. However, the number of nuclei per giant cell was significantly smaller, and the maximum diameters of nuclei and nucleoli were significantly greater, in giant cells induced by M. artiellia isolates than in those induced by M. arenaria, M. incognita, or M. javanica. In a second experiment, M. artiellia-induced giant cells in faba bean and rapeseed also contained a small number of large nuclei. [ABSTRACT FROM AUTHOR]

The article focuses on the presence of plant-parasitic nematodes in the roots and rhizosphere of chickpea in the major growing regions in the world. However, only certain nematode species are considered constraints to chickpea producing, causing an estimated 14% in annual yield losses. The symptoms and signs of nematode parasitism on chickpea differ depending on the nematode's feeding habit. Symptoms caused by nematode attack are nonspecific and nondescript, and they are largely a consequence of disruption of normal processes of plant growth, and absorption and translocation of water and nutrients.

Use of resistant cultivars and adjustment of sowing dates are important measures for management of Fusarium wilt in chickpeas (Cicer arietinum). In this study, we examined the effect of temperature on resistance of chickpea cultivars to Fusarium wilt caused by various races of Fusarium oxysporum f. sp. ciceris. Greenhouse experiments indicated that the chickpea cultivar Ayala was moderately resistant to F. oxysporum f. sp. ciceris when inoculated plants were maintained at a day/night temperature regime of 24/21°C but was highly susceptible to the pathogen at 27/25°C. Field experiments in Israel over three consecutive years indicated that the high level of resistance of Ayala to Fusarium wilt when sown in mid- to late January differed from a moderately susceptible reaction under warmer temperatures when sowing was delayed to late February or early March. Experiments in growth chambers showed that a temperature increase of 3°C from 24 to 27°C was sufficient for the resistance reaction of cultivars Ayala and PV-1 to race 1A of the pathogen to shift from moderately or highly resistant at constant 24°C to highly susceptible at 27°C. A similar but less pronounced effect was found when Ayala plants were inoculated with E oxysporum f. sp. ciceris race 6. Conversely, the reaction of cultivar JG-62 to races 1A and 6 was not influenced by temperature, but less disease developed on JG-62 plants inoculated with a variant of race 5 of F. oxysporum f. sp. ciceris at 27°C compared with plants inoculated at 24°C. These results indicate the importance of appropriate adjustment of temperature in tests for characterizing the resistance reactions of chickpea cultivars to the pathogen, as well as when determining the races of isolates of E oxysporum f. sp. ciceris. Results from this study may influence choice of sowing date and use of chickpea cultivars for management of Fusarium wilt of chickpea. [ABSTRACT FROM AUTHOR]