Diversity in Alternaria brassicae (Berk.) Sacc. isolates and characterization of host response in different oilseed Brassica species

Alternaria brassicae (Berk.) Sacc., a necrotrophic fungus devastating oilseed Brassica crops in India, causes up to 47% reduction in seed yield. So the study is conducting to develop the knowledge about the variability of A. brassicae in terms of cultural, morphological, pathogenic characters and their effects on different Brassica species of rapeseed mustard, for minimizing the losses caused by A. brassicae and help to stabilize the rapeseed mustard production. In variability study, all the isolates showed cultural, morphological variability. Average conidial length was maximum in isolate Ab2 (21.7μ) followed by Ab4 (20.7μ) and minimum in Ab8 (15.6μ). Septation in conidia, both horizontal and vertical also showed variation in different isolates. Finally it was revealed that smallest size of conidia in isolates Ab8 and longest size of conidia in isolates Ab4 were observed. On solid medium, maximum sporulation was observed in Ab7 followed while minimum sporulation recorded in Ab8. On liquid medium, maximum sporulation was observed in Ab7 while minimum sporulation recorded in Ab8. All the isolates showed the variability in qualitative characters i.e. spot colour, presence or absence of central point, concentric rings and yellow halo and as well as in quantitative characters i.e. incubation period and Percent Disease Index.