Genetic variability, heritability and genetic advance in Iranian local rice genotypes for yield, and some agronomic traits

Rice (Oryza sativa L.) is a cornerstone of global food security, providing 20 % of the world's dietary energy and serving as a staple for half the global population. In Iran, rice supports food supply and economic stability, yet faces challenges like disease susceptibility and low yields. This study evaluated the genetic diversity and heritability of agronomic traits in 26 Iranian rice genotypes to inform breeding strategies for enhanced yield and adaptability. Conducted during the 2021–2023 years at the Rice Research Institute of Iran in Guilan Province, the experiment employed a Randomized Complete Block Design with three replications. Traits assessed included grain yield, plant height, panicle number, thousand-grain weight, grain dimensions, awn length, and days to maturity. Analysis of variance revealed significant genetic variation (p < 0.01) across all traits. Grain yield ranged from 3.00 to 4.00 t ha−1, with high-yielding genotypes like Ali Kazemi and Hashemi identified. Broad-sense heritability was high (0.886–0.974), indicating strong genetic control, particularly for grain shape (H2 = 0.974) and awn length (H2 = 0.997). Genotypic and phenotypic coefficients of variation were closely aligned, suggesting minimal environmental influence, with genetic advance as a percentage of the mean highest for awn length (206.93 %) and grain shape (32.71 %). Correlation analysis showed positive associations between grain yield and grain width (r = 0.29), while path analysis highlighted thousand-grain weight (0.226, p = 0.015) and productive tillers (0.190, p = 0.041) as key yield contributors. Hierarchical clustering grouped genotypes into four distinct clusters, reflecting diverse genetic profiles. These findings underscore the potential for targeted selection and hybridization to develop high-yielding, adaptable rice cultivars, enhancing Iran's rice production and global food security.