Analysis of morphological and cultural variability among thirteen isolates of Alternaria brassicae provides information about morphological variation and favorable cultural conditions in vitro when such situations become available under cropping environment, which could result in severe infection of Alternaria blight due to isolates existing in different geographical regions of India. This also reflected the adaptation of the respective isolates to the ambient conditions in the different cropping areas, where the disease occurs in varied proportions in different years, which may have also induced the available cultural variability. This work discusses the possible disease scenario in view of global warming and climate change. Although genetic variability could be found by RAPD, no genetic variability could be located among A. brassicae isolates by ITS-AFLP. So, variability did exist at genomic level but not in the highly conserved region of the genome and pathogenic variability also existed among isolates of A. brassicae from different parts of India where oilseed Brassicas are grown and this information may help in easier development of Alternaria blight resistant Brassica.