Characterization of Iranian rice genetic resources for key grain quality traits

Grain quality traits are crucial for rice (Oryza sativa L.) breeding, as they significantly influence consumer preferences and market value. This study evaluated 48 diverse rice genotypes, including a strong representation of Iranian landraces that constitute unique and valuable genetic resources at risk of erosion, as well as some improved varieties and imported lines, for seven grain quality traits: amylose content, gelatinization temperature, grain length, grain width, cooked grain length, grain shape, and grain elongation during the 2023–2024 growing seasons. The studied rice genotypes showed substantial variation in quality-related traits. All traits demonstrated significant genotypic variation, with high broad-sense heritability (H² ≥ 0.968) and notable genetic advance (up to 49.37% for gelatinization temperature), indicating strong potential for genetic improvement. Correlation analyses showed strong positive relationships among grain length, grain shape, and cooked grain length, but negative associations with grain width and grain elongation, indicating breeding trade-offs. Path analysis highlighted grain length as a primary driver of cooked grain length and identified gelatinization temperature and grain shape as key influences on amylose content. Hierarchical clustering and principal component analysis identified four genotype clusters, with standout performers like Gohar (excelling in grain length) and Gharib Siah Reyhani (high elongation) suitable for breeding programmes. These results not only provide a robust framework for multi-trait selection and the development of high-quality varieties tailored to Iranian and global markets, but also underscore the conservation value and uniqueness of Iranian landraces as representative genetic resources for future rice improvement and food security.