Assessment of Genetic Variability and Trait Associations in Advanced Rice Lines

Abstract

Rice (Oryza sativa L.) is one of the world’s most important cereal crops, serving as a staple food and a key component of food and livelihood security across Asia. However, rice productivity has stagnated in several regions due to multiple biotic and abiotic stresses, variable climate and a narrow genetic base in modern cultivars. To sustain productivity and enhance yield potential, understanding genetic parameters and interrelationships among yield components is essential for effective selection and crop improvement. The present study was carried out at the Agricultural Research Station, Ragolu, Andhra Pradesh, during the Kharif 2024 season to assess the genetic variability, heritability and associations among yield-related traits in 22 advanced rice breeding lines in RCBD. Significant variability was observed among genotypes for all traits, indicating sufficient genetic diversity within the experimental material. The close relationship between genotypic and phenotypic variation suggested limited environmental influence on trait expression. High h2 (>60%) combined with high GAM (>20%) for major yield components revealed that additive gene action was predominant, implying that direct selection would be effective for improving these traits. Correlation analysis showed that grain yield was positively associated with several yield-contributing characters such as filled grains per panicle, plant height, test weight and ear bearing tillers, suggesting that simultaneous improvement in these traits could enhance yield. Path coefficient analysis further confirmed that filled grains per panicle, test weight and plant height exerted strong direct effects on yield (0.30-0.99), whereas unfilled grains had negative effects. The study revealed wide genetic divergence, highlighting FGP and TW as key traits for selection, offering valuable opportunities for selection and breeding of high-yielding, resilient rice cultivars suited to diverse environments.