BEHAVIOR OF BIPOLARIS ORYZAE AT DIFFERENT TEMPERATURES, CULTURE MEDIA, FUNGICIDES AND RICE GERMPLASM FOR RESISTANCE

Abstract

Brown leaf spot of rice, caused by Bipolaris oryzae, is one of the most destructive diseases of rice. This study aimed to characterize the B. oryzae with respect to its pathogenicity, best growth media, temperature sensitivity and its management through resistant variety and fungicides.  The best culture medium and the optimum temperature were determined in vitro. Among five culture media, maximum growth of B. oryzae was observed on Malt Extract and Potato Dextrose Agar after 96 hours of incubation with optimum temperature at 28^oC. Development of resistant lines is the best way to overcome the disease. Among 28 entries/varieties evaluated for two years, RSP- 4 was found resistant and PS-2 moderately resistant against B. oryza. Ridomil and Dithane M-45 were found more effective at 50ppm when compared to eight fungicides for the reduction in colony growth of B. oryzae. In view of present investigation, it may be suggested that RSP- 4 and PS-2 could be used for development of resistant variety against brown spot disease. Ridomil and Dithane M-45 although effective in vitro, need to be evaluated also under field condition.