Assessment of rice genotypes for susceptibility to sheath blight disease caused by Rhizoctonia solani AG1-IA

Rice crop endures several biotic stresses among which sheath blight is one of the devastating diseases. This disease is caused by necrotrophic fungus Rhizoctonia solani AG1 IA that reduces 20 to 40% yield. Forty two diverse rice germplasms were evaluated against sheath blight under artificial epiphytotic condition in the field of National Wheat Research Program Bhairahawa, Nepal during the year 2019. Four disease variables viz. PDLI (Percent diseased leaf incidence), PDTI (Percent diseased tiller incidence), PRCHI (Percent relative collar height infection), and AUDPC (Area under disease progress curve) were considered for evaluation of germplasms. Out of forty two genotypes Sabitri, GSR 310 and Hardinath-3 were found moderately resistant with mean AUDPC values 217.99, 252.78 and 214.67 per day respectively. Furthermore IR 15D 110, Pant-1, NR 2152-23-1-2-1-1-1-1 and IR 82635-B-B-114-3 were found moderately susceptible with mean AUDPC values 438.48, 445.55, 421.81 and 437.59 respectively. Moderately resistant genotypes viz. Sabitri, GSR 310 and Hardinath-3 had PDLI range 30.98-31.67, PDTI range 10.56-15 and PRCHI range 9.01-28.64 whereas moderately susceptible genotypes IR 15D 110, Pant-1, NR 2152-23-1-2-1-1-1-1 and IR 82635-B-B-114-3 had PDLI range 31.25-51.29, PDTI range 25.82-38.75 and PRCHI range 22.18-45.8. Disease variables PDLI, PDTI and PRCHI were positively and significantly correlated with AUDPC with correlation coefficient value 0.75, 0.65 and 0.62 respectively. Moderately resistant rice genotypes found in this study could be evaluated for yield potential and its stability across different geographical region of Nepal and could be a good alternative against sheath blight diseases for Nepalese farmers.