Phenotypic and Molecular Identification of Stable Rice (Oryza sativa L.) Lines Resistant to Blast (Magnaporthe oryzae)

Abstract

Rice blast, caused by Magnaporthe oryzae, is a major constraint to rice production and requires the identification of resistant breeding material through reliable screening approaches. The present study evaluated stable rice breeding lines for leaf blast resistance by integrating phenotypic screening under Uniform Blast Nursery conditions with molecular marker analysis. Thirty-six stable F6 breeding lines, along with Tetep as the resistant check and TN-1 as the susceptible check, were evaluated during Rabi 2025 at the Regional Agricultural Research Station, Polasa, Jagtial, Telangana. Disease reactions were recorded using the IRRI Standard Evaluation System (2013) for rice, and molecular confirmation was conducted using the Pi54MAS functional marker linked to Pi54 and the SSR marker RM527 linked to Pi2. The susceptible check confirmed the adequacy of disease pressure during field screening. Field screening identified nineteen breeding lines with resistant, moderately resistant or highly resistant reactions. Four lines, JGL-55531, JGL-55507, JGL-55508 and JGL-55510, showed highly resistant reactions with a disease score of 0, while JGL-55509 showed a resistant reaction with a score of 1. Molecular analysis detected the Pi54 resistance allele in five lines and the Pi2-associated allele in thirty lines. Four lines, JGL-55531, JGL-55507, JGL-55508 and JGL-55510, carried both Pi54 and Pi2. The correspondence between field reaction and marker data indicated that combined phenotypic and marker-assisted screening was useful for identifying blast-resistant breeding lines in the tested material. The resistant lines identified in this study may serve as useful genetic resources for further evaluation and incorporation into rice improvement programmes focused on blast resistance.