Vol. 9, Issue 7, Part U (2025)

Bacterial leaf blight (BB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is a major biotic constraint to rice productivity particularly in irrigated and lowland ecosystems. In this study, 50 F₆ advanced breeding lines derived from a cross between RNR 15048 and MTU1010 NIL (Xa21) were evaluated for BB resistance under field conditions using a virulent local Xoo isolate. The disease severity was assessed based on lesion length following IRRI Standard Evaluation System (2013). Out of the 50 advanced breeding lines screened, 28 exhibited high resistance, 13 showed moderate resistance and 9 were moderately susceptible. The checks-ISM, TN 1, RNR 15048 and MTU1010 NIL confirmed the virulence and accuracy of the screening. The study highlights the effectiveness of incorporating the major resistance gene Xa21, demonstrating its potential utility in breeding programs aimed at developing BLB-resistant rice cultivars for Telangana and similar agro-ecologies.