Isolation, Pathogenicity and Effect of Different Culture Media on Growth and Sporulation of Alternaria brassicae (berk.) Sacc. causing Alternaria Leaf Spot Disease in Cauliflower

Abstract

The leaf spot disease of Cauliflower (Brassica oleracae L. var. Botrytis) caused by A. brassicae (Berk.) Sacc. was noticed in moderate to severe form on farm of College of Agriculture Engineering and Technology, Dapoli during 2014-2016. The pathogenic fungus was isolated on potato dextrose agar medium from infected leaves of cauliflower. The pathogenicity of the isolated fungus was proved by inoculating healthy seedlings of cauliflower. On the basis of typical symptoms on foliage, microscopic observations and cultural characteristics of the fungus, it was identified as Alternaria spp. The Chief Mycologist, Agharkar Research Institute, Pune identified the pathogenic fungus as Alternaria brassicae (Berk.) Sacc. Eight culture media were tested among that, the potato dextrose agar medium was found most suitable and encouraged maximum radial mycelial growth (90.00 mm) of A. brassicae. The second best culture medium found was host leaf extract agar medium (87.00 mm). This was followed by Richard’s agar medium (75.33 mm) and oat meal agar medium (71.66 mm). Carrot potato agar medium (55.00 mm), Asthana and Hawker’s agar medium (51.66 mm) and Czapek’s Dox agar medium (39.00 mm) were moderate in mycelial growth of A. brassicae. Poor mycelial growth was recorded in V8 juice agar medium (32.66 mm). Introduction