Genetic improvement of RNR 15048 for blast resistance by using UBN phenotypic screening method

Rice blast, caused by Magnaporthe oryzae, remains one of the most severe biotic stresses, leading to major yield losses. Breeding for host resistance is the most sustainable and eco-friendly approach to mitigate these losses. RNR 15048 (Telangana Sona), a popular cultivar known for its desirable grain quality and low glycemic index, lacks durable resistance to blast. To enhance its resistance profile, a breeding program was undertaken at Institute of Rice Research, ARI, Rajendranagar, Hyderabad. Subsequently, Pi54, a major blast resistance gene, was introgressed into RNR 15048 through marker-assisted pedigree breeding using MTU1010 NILs as donors. Fifty F7 progenies were phenotypically screened for blast resistance during Rabi 2024-25 under UBN conditions for identification of improved lines. Advanced breeding lines were evaluated in a Uniform Blast Nursery (UBN) using SES (0-9 scale). Susceptible (TN1) and resistant (NLR 34449) checks validated the screening. Of these 50 advanced breeding lines, 21 showed resistant reaction with a disease reaction score of 3, while 6 lines were moderately resistant with a disease reaction score of 5 and other 23 lines showed Highly resistant reaction with a disease reaction score of 1. While Susceptible check TN1 showed highly susceptible reaction with a disease reaction score of 9 and resistant (NLR 34449) check is one.