HOST PATHOGEN INTERACTION STUDIES OF Rhizoctonia solani KUHN. CAUSING SHEATH BLIGHT IN RICE
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Date
2022-12-23
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University of Agricultural Sciences, Bangalore
Abstract
Rice is the staple food crop for more than half of the world's population with 90 percent production and consumption from Asia. Sheath blight caused by Rhizoctonia solani is one of the most economically significant rice diseases worldwide with no cultivated resistant variety reported till date. Out of 512 landraces/ genotypes screened, twenty-nine were identified as resistant against sheath blight during Kharif 2021. Association studies of morphological traits with sheath blight resistance revealed traits i.e. plant height, flag leaf length, stem thickness, stem breaking resistance, leaves and sheath thickness were positively linked while tiller number was a negative character. The resistant genotype (Tetep) had recorded latent period of five days with 17.41 per cent relative lesion height whereas susceptible genotype (Jyoti) had three days with 68.30 per cent relative lesion height. In detached leaf assay maximum mean sclerotia production of 4.33 was recorded after ten days in Jyoti while it was minimum of 0.33 in Tetep. Scanning electron micrographs showed varied hyphal growth of R. solani on the surface of Tetep and Jyoti genotypes. A vigorous growth and more number of infection structures observed on the surface of Jyoti while sparser growth with lesser number on Tetep. An abundant cuticular wax deposition was observed in Tetep which act as barrier to pathogen’s establishment. Biochemical profiling revealed a higher induction of defense related enzymes viz., polyphenol oxidase, peroxidase, superoxide dismutase, phenylalanine ammonia lyase and chitinase in resistant genotypes (Tetep, Zenith and KMP220) than the susceptible genotypes (Jyoti, Swarna).