Evaluation of rice genotypes for resistance against brown spot disease caused by bipolaris oryzae

Brown spot caused by Bipolaris oryzae is one of the destructive diseases of rice in the world and causes severe losses in grain quality and quantity. Use of resistant varieties is the sustainable and eco-friendly way of controlling brown spot disease in rice. In this concern, we evaluated 20 rice genotypes under glasshouse and field conditions during June, 2014-May, 2015 to determine the level of resistance against B. oryzae. Disease assessment was done by calculating disease severity, area under disease progress curve (AUDPC) and AUDPC per day (AUDPC/day). Response of rice genotypes to brown spot disease was found similar under both the field and glasshouse conditions. The tested genotypes showed variable response to the level of resistance. Mean AUDPC value varied from 80.36 to 340.05. Sabitri appeared the most resistant with AUDPC value of (80.36) followed by Radha-4 (108.02), while Sankharika (340.05) was the most susceptible among the tested genotypes. Grain yield ranged from 2.76 to 4.76 t ha-1. Of the tested genotypes, Sabitri and Sankharika yielded the highest (4.76 t ha-1) and the lowest (2.76 t ha-1) grain yields, respectively. Grain yield was negatively correlated with AUDPC (r = -0.628**). Thus, the genotypes Sabitri and Radha-4 could be utilized as a source of resistance for breeding of rice for brown spot resistance.