Molecular characterization and phenotypic selection for blast resistance and yield enhancement in rice (Oryza sativa L.)

Gurjari, a widely cultivated high-yielding potential variety popular among the farmers of Gujarat, is highly susceptible to the blast disease. To improve its blast resistance, GNR-9 and Tetep, which carry major broad-spectrum resistance genes, were used as donors in a marker-assisted breeding program, combined with phenotypic selection for key agro-morphological traits. Foreground selection in F3 generation confirmed the presence of blast resistance genes Pikh/Pi54, Pitp(t) and Pita-2/Pi67 in 36 of 178 breeding lines. These 36 lines, along with 4 checks, were further evaluated in a Randomized Block Design (RBD) during Kharif 2022 for variability, correlation, Principal Component Analysis (PCA) and Multi-Trait Genotype-Ideotype Distance Index (MGIDI) for selecting the best lines and molecular screening of blast resistance. Analysis of variance revealed significant variation for all 13 traits, with moderate GCV for plant height, productive tillers, 100-grain weight, grain yield, straw yield and harvest index. Grain yield showed positive correlations with panicle length, grains per panicle, 100-grain weight, straw yield and harvest index. PCA explained 82.13 % of total variation across traits, while MGIDI identified four high-performing lines; 22KSMF4-8, 22KSMF4-5, 22KSMF4-6 and 22KSMF4-14. Molecular screening of F₄ progenies identified nine F₄ derivatives carrying three blast resistance genes, with two (Gurjari × GNR-9) exhibiting superior grain yield and quality over Gurjari, making them promising candidates for developing high-yielding, blast-resistant varieties.