Pathogenic Variability Among Alternaria brassicae Population Infecting Oilseed Brassicas in India

Alternaria brassicae (Berk) Sacc., isolates from various Brassica spp. collectedfrom different geographical locations in India were characterized on eleven differential varieties of Brassica spp. indicated the existence of pathogenic variability among the isolates. The isolates viz., BAB-04, BAB-07 and BAB-08 were categorized as highly virulent while BAB-02, BAB-05 and BAB-14 as least virulent. Lesion size was lowest in case of BAB-02 (0.29 to 0.73 cm) on almost all the host differentials. The dendrogram based on the presence or absence of DNA fragments amplified with OPS primer (RAPD-PCR) suggests moderate heterogeneity within the A. brassicae populationfrom rapeseed-mustard. A slight effect of host plant and geographical location on genetic variation in A. brassicae was suggested. The genetic relatedness among the A. brassicae isolates were also examined and BAB-14 and BAB-10, BAB-20 and BAB-02, BAB-08 and BAB-12 were genetically similar.