Variability in Alternaria brassicae isolates in relation to resistance components of host genotypes of Indian Mustard (Brassica juncea)

Laboratory and glass house experiments were conducted to study the variability among the three (A, C & D) isolates of Alternaria brassicae affecting rapeseed-mustard in relation to resistance components of host genotypes. The cotyledon and true leaf (attached & detached) inoculation on pot grown plants of nine genotypes of Brassica species revealed differential reaction response to three isolates. The results revealed that isolate showed shortest incubation and latent periods, largest spot size, and significantly more sporulation index under. Isolate C showed longer incubation and latent periods larger spot size and moderate sporulation index, while Isolate D showed shortest incubation and latent periods, pin head size spots and did not sporulate both attached and detached techniques. The results indicated that isolate A was virulent, isolate C was moderately virulent while isolate D was avirulent. Based on resistance components genotypes PR-9024, PR-8988, Kranti were resistant, PR-8943, Divya and Krishna were moderately resistant and PR-9301, PR-9650 and Varuna were susceptible genotypes.