Marker-assisted confirmation and BLB reaction profiling of donor and recipient parents in a multi-gene introgression program

Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae is a major constraint to rice productivity, necessitating the deployment of durable resistance genes. The present study evaluated donor and recipient parents for introgression of BLB resistance genes xa5, xa13 and Xa21 into the susceptible but widely cultivated rice varieties Mahamaya and Swarna. Phenotypic screening using a virulent Raipur isolate revealed high susceptibility in Mahamaya (SES score 9) and Swarna (score 7), whereas donor parents Improved Samba Mahsuri and DRR Dhan-62 exhibited strong resistance (SES score 1). Molecular validation using seven gene-specific and linked markers showed clear polymorphism between donors and recipients for most loci, with resistant alleles consistently amplified in donor genotypes. Markers RM31, xa13/xa13pro, pTA248 and RM21 were highly informative for allele discrimination. Combined phenotypic and molecular analyses confirmed the suitability of these parental combinations for pyramiding multiple BLB resistance genes through marker-assisted breeding.