Article

Some fungi belonging to genus Alternaria are plant parasites that easily can change when exposed under different conditions. Variability of Alternaria alternata tobacco pathotype includes morphology, physiology, sporulation and pathogenicity of this fungus. Diversity in color of colonies appeared even in a single spore isolate used in this study. Numerous of spores were obtained when the pathogen was grown under near UV light at 25oC. The spores germinated on leaf surface in 24 hr in high humidity and infection hyphae of germinating spores penetrated epidermal cells directly.