Biophysical Basis and Principal Component Analysis of Morphological Traits Conferring Resistance to Yellow Stem Borer, Scirpophaga incertulas (Walker) in land races of Rice

The investigations on evaluation of 252 landraces rice were undertaken in natural field conditions during Summer 2024, aiming to identify biophysical traits conferring resistance to yellow stem borer (YSB), Scirpophaga incertulas . Genotypes were comprehensively assessed for key morphological and anatomical features, such as plant height, leaf length, width and angle, leaf blade pubescence, stem diameter, number of tillers, peduncle length, and panicle length at various crop stages. Infestation was documented through levels of dead heart, white ear formation, and egg mass deposition at 30, 50, and 90 days after transplanting. The evaluation revealed that resistant rice genotypes consistently exhibited greater plant height, longer and narrower leaves, more erect leaf angles, thinner stems, and higher leaf trichome density, while susceptible types displayed broader leaves, wider leaf angles, thicker stems, and lower pubescence. Third leaf length, flag leaf angle, and tiller number were crucial for resistance in early growth, while flag leaf width and third leaf length dominated in mid-stage, and stem diameter with upper leaf pubescence were critical at the reproductive stage. Integrating these traits into breeding and selection strategies offers a sustainable approach for developing rice varieties with enhanced yellow stem borer resistance, supporting stable yields and reducing dependency on chemical control in important rice-growing regions.