Rice sheath rot disease etiology and characterization of the pathogen

Abstract

Rice sheath rot disease in Indonesia caused by Sarocladium oryzae is currently become a major pathogen. The objectives of this research was to describe disease etiology and characterization of rice sheath rot pathogen. Characterization was conducted by isolation followed by morphology-based identification, and observation of rice sheath rot symptoms. The fungal colonies has 5 different morphotypes, namely KP, KP2, KP3, PW03, and PW3 which all were pathogenic to rice. Morphotypes of KP3 and PW3 colonies had yellowish color; while KP, KP2 and PW03 colonies had orange color. Microscopically conidia of KP, PW3, and PW03 had longer and thinner form; while KP2 and KP3 were shorter and wider. PCR confirmation using specific primer for S. oryzae resulted that all tested isolates were S. oryzae. The disease occured on uppermost leaf sheath enclosing the young panicles. The lesions appeared as oblong with brown margins and grey centres. The panicles infected by S. oryzae were chaffy, discoloured, and shrivelled. The incubation period of this disease was 3 to 4 d.