Pathogenic variation and compatibility groups in Sclerotium rolfsii isolates causing collar rot on chickpea (Cicer arietinum L.)

Pathogenic variability of fifty one isolates of Sclerotium rolfsii collected from collar rot infected plants of chickpea were broadly grouped into three pathotypes on the basis of number of days taken to initiate plant mortality and causing 100 per cent mortality. The isolates belonging into three groups were studied for mycelial compatibility and the pathotypes showed three reactions i.e. compatible reaction, antagonistic reaction and mycelial incompatibility. In their mycelial compatibility 1273 pairing combinations were observed, out of which 203 combinations (15.9%) were found compatible and 175 (28.0%) incompatible and 84 per cent combinations (1070) showed antagonistic effect. Microscopic observations on mycelial interaction revealed hyphal thinning followed by protoplast lysis, vacuole formation and hyphal thickness at the interaction zone.