Disease components influencing Ascochyta blight of chickpea

In Punjab chickpea occupied 66 thousand hectares in 1987–88 which in 2007–08 has reduced to a single digit 2.7 thousand hectares. The major phytopathological reason for this decline in acreage is Ascochyta blight (AB) caused by Ascochyta rabiei. The disease can successfully be kept under control through use of resistant variety and chemical means. But it has been noticed that there is not an absolute resistance against this disease and also the resistant varieties succumb to the disease after few years of release. There is a need to explore disease resistant components which have lasting effect on the durability of the genotype/variety. Though some host components such as trichomes on leaves, waxiness of leaf lamina, size of lamina and malic acid production have been integrated with disease resistance. But disease components such as lesion number and size of lesions on leaves and stems, total area covered by disease on leaves and stems, girdling of stem and pycnidia formation on the lesions have not been exploited for pre empty breeding for resistance against Ascochyta blight. Hence 61 chickpea genotypes with diverse but consistent disease reaction were evaluated for above disease components against 10 isolates of A. rabiei. The seedling of these 61 genotypes were raised in polyethylene bags 9” x 4” containing sandy-loam soil. 25 days old seedlings were spray inoculated with these isolates separately in sets of three using cloth chamber screening technique for creating disease epidemic. The genotypes after 13 days of inoculation were observed for the above components visually and using a calibrated hand micrometer. The disease reaction of these genotypes was observed on 1–9 point scale. A simple correlation matrix was worked out to co-relate disease severity with disease components as well the correlation with in these 10 AB isolates. All the components were positively co-related with disease severity. Genotypes without lesions or very small lesions on leaves only, no-girdling on stem, with no pycnidia formed on lesions with any of the AB isolate were considered as good sources of durable resistance. These genotypes were GL nos. 99015, 98005, 97016, 97015, 96047, 95078, 94048, 93011, 91061, 91059, 91058, 90178, 90169, 90158, 90135, 84098, 84038 and ICC 1069.