Morphological variability in the Indian isolates of Ascochyta rabiei causing blight in chickpea and evaluation of chickpea cultivars

Abstract

Ascochyta blight caused by Ascochyta rabiei is a serious disease of chickpea world wide. Twenty five Indian isolates of A. rabiei were evaluated for their morphological variability and 91 chickpea cultivars were screened for their reactions to Ascochyta blight. The populations of A. rabiei showed variations in various morphological characters like conidia size and density, colony colour and growth rate. Colonies of the isolates on artificial media were flat, submerged with sparse mycelium. The mycelium was pale cream at first but later turned greyish white or green to greenish dark. In Chickpea dextrose agar (CDA) medium, the isolate AR1 (Delhi) grew the largest followed by the isolates AR14 (Punjab), AR5 (Himachal Pradesh), AR9 (Jammu and Kashmir) and AR20 (Rajasthan) with statistically similar colony diameter at 20 days after incubation. Thus, the growth rate was significantly highest in isolate AR1 (Delhi) followed by the isolates AR14 (Punjab), AR5 (Himachal Pradesh), AR9 (Jammu and  ashmir), and AR20 (Rajasthan). More or less similar growth patterns of the isolates were observed on PDA medium with comparatively less growth as compared to CDA. The size of the conidia in all the isolates ranged from 9.19-12.51 x 3.36-4.32 μm whereas the density of conidia in A. rabiei isolates ranged from 0.5-7.2 x 106 conidia ml-1. Three cultivars namely, ICC 76, ICC 3996 and ICC 15978were identified as highly resistant to Ascochyta blight. Thirty cultivars showed resistant and 14 cultivars showed moderately resistant reactions against the disease. These cultivars may be used for cultivation or resistant breeding programs.