Abstract

Potato dextrose and malt extract agar were found to be suitable for culturing different isolates of Pyricularia oryzae. Colonies of P. oryzae appeared as white on oat meal, rice polish and malt extract agar, grey on potato dextrose agar and whitish grey on rice agar. Spore induction was hastened on maize stem pieces than on rice and Panicum repens. Spore density on maize was 3420/ml of water as against 500/ml on P. repens. When spores of 11 isolates of P. oryzae were compared, conidia of the isolate from Pennisetum purpureum were significantly bigger than the other isolates. The spores of rice isolates from Erode and Gopichettipalayam were significantly smaller in length and width.Fingerprinting of 11 isolates of P. oryzae by retrotransposon - microsatellite amplified polymorphism (REMAP) showed a high level of variability and polymorphism among them. Phylogenetic analysis using REMAP markers grouped out one rice isolate from others. Two isolates of Tirunelveli region were grouped together like Erode and Gopichettipalayam isolates. Isolates causing leaf and neck blast showed 52.9% similarity. Isolates from Coimbatore and Gudalore were 32.7% similar; likewise two non-rice host isolates were grouped together with 27.6% similarity.

Key words: Variability, culture media, rice blast, Pyricularia oryzae, retrotransposon, microsatellite.