Morphological and pathological variations in isolates of Alternaria brassicae causing leaf blight of rapeseed and mustard

摘要

Based on different morphological characteristics like colony growth, colour, spore size, spore septation and sporulation potential, all the 25 isolates of Alternaria brassicae were grouped into three broad groups viz. AB1, AB2 and AB3. Isolates of group AB1 had whitish brown, appressed fast growing colonies with high sporulation. Isolates of group AB2 had white or whitish with brown margin, slightly fluffy medium growth with sparse to low sporulation. Isolates of group AB3 were greyish white, fluffyslow growing with moderate sporulation. Pathological behavior of representative isolates of A brassicae (from each group) differed on twelve host cultivars of rapeseed and mustard. Ab5 isolate appeared to be most virulent and Ab4 isolate showed least virulence.