Pathogenic and molecular variability among Brassica isolates of Alternaria brassicae collected from different agro-climatic regions of India

The Alternaria blight is one of the most destructive fungal disease of Indian mustard causes severe damage to the crop. Ten isolates of A. brassicae were collected from various agro-climatic location of India viz., Uttar Pradesh (Ab 1 ), Madhya Pradesh (Ab 2 ), Uttarakhand (Ab 3 ), Bihar (Ab 4 ), Jharkhand (Ab 5 ), West Bengal (Ab 6 ), Haryana (Ab 7 ), Rajasthan (Ab 8 ), Chhattisgarh (Ab 9 ) and Gujarat (Ab 10 ) and characterized for pathogenic and molecular variations. All the isolates showed high level of variability. The incubation period of the isolates was recorded on B. juncea 3 to 4 days, B. carinata 6.17 to 6.83 days, B. napus 5.17 to 6.00 days, B. nigra 4.17 to 5.17 days and in B. campestris it was ranged from 3.17 to 4.00 days. The results revealed that the maximum PDI was noted on Brassica juncea followed by B. campestris var yellow sarson, B. nigra, B. napus and B. carinata. Based on PDI ten isolates could be classified into three groups in which group one consist of isolates Ab 3 , Ab 6 , Ab 7 and Ab 5 . Isolates Ab 8 , Ab 2 and Ab 4 fall in second group; while group three include isolates Ab 1 , Ab 9 and Ab 10 . The dendrogram analysis identified two major clusters with 82 per cent similarity. One cluster (group I) comprised of 3 isolates (Ab 1 , Ab 10 and Ab 2 ). Whereas, another cluster (group II) comprised of Ab 3 , Ab 6 , Ab 7 , Ab 5 , Ab 4 , Ab 8 and Ab 9 at 86 per cent similarity. The three isolates (Ab 3 , Ab 6 and Ab 7 ) of group II showed 100 per cent similarity based on molecular basis.