Mustard is one of the important oilseed crop in the country. It contributes % to the total domestic edible oil production. Alternaria blight is one of the major factor in the reduction of yield and quality which ranges from 15-71 % depending upon the severity of the disease. The present study was undertaken to evaluate diversity among different isolates of Alternaria brassicicola collected from various regions of Bihar and adjoining parts. A total of sixteen isolates were collected from Saharsa, Supaul, Darbhanga, Khagaria, Samastipur, Bhagalpur, Gaya, Munger and Varanasi and its cultural, morphological, pathological, biochemical and genetic variability were studied. | Variability in the population of Alternaria brassicicola causing dark spot of mustard
