Identification of Elite Rice (Oryza sativa L.) Lines with Durable Bacterial Blight Resistance through Phenotypic and Molecular Approaches

Abstract

Bacterial leaf blight, caused by Xanthomonas oryzae pv. oryzae, is an important disease of rice that can substantially reduce crop performance under favourable disease conditions. The present study was conducted to identify elite rice lines resistant to bacterial leaf blight using phenotypic evaluation supported by molecular marker analysis. Thirty elite rice lines, together with the resistant check Improved Samba Mahsuri and the susceptible check TN-1, were evaluated under field conditions at the Regional Agricultural Research Station, Warangal, during Kharif, 2025. Artificial inoculation was performed using the leaf-clipping method, and disease reaction was recorded 15 days after inoculation according to the IRRI Standard Evaluation System. Molecular screening was performed using the pTa248 marker linked to the Xa21 resistance gene and the xa13 promoter marker linked to the xa13 resistance gene. Phenotypic screening showed that three lines, WG-GP-375, WG-GP-377 and WG-GP-378, exhibited a highly resistant reaction, while WG-GP-376 showed a resistant reaction. Eight lines were moderately susceptible, fifteen were susceptible and three were highly susceptible. Molecular analysis detected the Xa21 resistance allele in all four phenotypically resistant lines, whereas the xa13 resistance allele was detected in WG-GP-375, WG-GP-377 and WG-GP-378. The combined phenotypic and molecular assessment identified WG-GP-375, WG-GP-376, WG-GP-377 and WG-GP-378 as useful sources of bacterial leaf blight resistance. These lines may be considered for further validation and use in rice breeding programmes aimed at improving resistance to bacterial leaf blight.