Biocontrol of Sheath Blight (Rhizoctonia solani Kühn) in Rice (Oryza sativa l.) by Native Trichoderma Isolates

Rice sheath blight caused by Rhizoctonia solani Khn is one of the major diseases occurring in all rice growing areas of Nepal.Management of this pathogen is difficult due to its broad host range and high survival ability under various environmental conditions.This present study aims to evaluate native Trichoderma isolates for eco-friendly management of the disease.Thirty Trichoderma isolates from the soils of rice fields of different parts of Nepal terai, and three Rhizoctonia solani isolates from sheath blight-infected rice plants grown in the terai region were isolated.The R. solani isolates were tested for pathogenicity in rice cv.Sona Mansuli and selected a virulent one for further use.The Trichoderma isolates were evaluated for antagonism against R. solani by dual culture technique.Of the 30 isolates, RN-1, RN-5, RN-4, RN-10, and RN-12 significantly inhibited the mycelial growth of R. solani, thus selected for an in-vivo experiment in a screenhouse.The experiment included four rice varieties recommended for Nepal terai (Sabitri, Bahuguni 2, Sworna Sub-1, and Sona Mansuli), seed and seedling treatments by the selected five Trichoderma isolates following challenge inoculation with R. solani, and assessment of disease reduction and plant growth.All five selected Trichoderma isolates (based on dual culture results) significantly reduced the relative lesion height of sheath blight in treated rice plants as compare to untreated control.Highest reduction of the disease was obtained with the isolate RN-1 in all four rice varieties.The Trichoderma isolates also significantly enhanced the growth of rice plants.Plants treated with the isolates RN-10 and RN-1 had significantly highest plant height, maximum flag leaf length, number of tillers, and root length.The present results clearly showed that native Trichodermas have potential in controlling sheath blight disease and enhance growth of rice plants. HIGHLIGHtSm Native Trichodermas are found effective against Rhizoctonia solani that causes sheath blight disease in rice.m Trichodermas exerted plant growth promoting effects on rice (cv Sona Mansuli, Sabitri, Sworna Sub-1 and Bahuguni-2).m Native Trichodermas can be utilized as an important component in the integrated crop management of rice.