Phenotypic Evaluation of Advanced Breeding Lines for Introgression of Blast Resistance Genes in Rice (Oryza sativa L.)

Rice blast, caused by Magnaporthe oryzae, remains a major fungal disease affecting rice productivity worldwide, and the development of resistant cultivars is an economical and environmentally sustainable approach for its management. The present investigation evaluated fifty advanced breeding lines derived from the cross MTU1010 NIL × Akshayadhan NIL for resistance to blast under Uniform Blast Nursery (UBN) conditions during Rabi 2020–21 at the Regional Agricultural Research Station (RARS), Jagtial, Telangana, India. Phenotypic screening was performed using the virulent local isolate SPI-40 of M. oryzae, and disease reactions were recorded according to the Standard Evaluation System (SES) scale. The breeding lines showed clear variation in response to blast infection under the imposed disease pressure. Of the fifty lines evaluated, thirty-six exhibited resistant reactions with a disease score of 3, thirteen showed moderately resistant reactions with a disease score of 5, and one line, VSR-49, was susceptible with a score of 7. The susceptible parent MTU1010 NIL and the susceptible check TN1 recorded highly susceptible reactions, each with a score of 9. In contrast, the resistant parent Akshayadhan NIL and the resistant check NLR34449 expressed resistant responses, with scores of 3 and 1, respectively. The high frequency of resistant lines indicates successful recovery of blast-resistant breeding material in the MTU1010 genetic background. The results also support the usefulness of UBN-based phenotypic screening for identifying promising lines under controlled disease pressure. These resistant lines may be useful genetic resources for further varietal evaluation, marker-assisted selection and breeding programmes aimed at developing blast-resistant rice cultivars for blast-endemic regions.