Exploitation of defense compounds from sheath blight infected rice with Rhizoctonia solani isolates

Rice is a crucial global food staple that provides nourishment for over half the world’s population. Rice crops face numerous biological threats, with sheath blight standing out as one of the most harmful diseases caused by the fungus Rhizoctonia solani Kuhn. and primarily damages leaf sheaths, as irregular, water-soaked lesions that can spread throughout the plant. Ten isolates of R. solani collected from different sources were used for testing their pathogenicity under pot culture experiment from January to April 2025 at SRM College of Agricultural Sciences, Baburayanpettai, Chengalpattu Dist., Tamil Nadu. Infected sheath and leaf samples from each isolate inoculated plants were collected on 30th day of inoculation for analysis of biochemical variation based of pathogenicity. Virulent nature of isolates exhibited variation in lesion size. Sheath blight infection in rice plants respond to various biochemical changes viz., chlorophyll contents, soluble protein, enzyme activities (including peroxidase and polyphenol oxidase), hydrogen peroxide, oxalic acid and superoxide radicles as defense compounds. Virulent isolate inoculated plants (Rs 6) reduced the total chlorophyll content of 1.069 mg/g and increased soluble protein (152.67 mg/g), superoxide radicals (6.60 mmol/g FW) and oxalic acid (47.67 mg/g) contents. Defense enzymes like poly phenol oxidase (237.00 U/g of protein) and peroxidase enzyme (64.65 U/g of leaf sample) decreased in samples of Rs 6 isolate inoculated plants and showed the capacity of virulence.