Quantitative Indices for Drought Tolerance in Rice: Leveraging Genetic Resources for Climate-Resilient Breeding

Climate change-induced drought is a major threat to global rice production, underscoring the urgent need for drought-resilient cultivars. This study aimed to identify drought-tolerant, high-yielding rice genotypes using quantitative yield-based indices and multivariate analyses. Eighty-two diverse genotypes were evaluated over three seasons (2020-2022) under two moisture regimes (normal irrigation and terminal drought stress), constituting six environments in total. Data were analyzed using ANOVA, correlation, GGE biplot, and principal component analysis. Results revealed significant genotype, environment, and genotype-by-environment interaction effects, highlighting substantial genetic diversity. Mean grain yield under normal irrigation was 4428 kg/ha, which declined to 2676 kg/ha under terminal drought stress, a reduction of 39.58%, primarily due to a 26.85% decrease in filled grains per panicle. Genotypes M1, Sela-Zodras, and Shiroudi were consistently identified as superior, demonstrating high yield under both normal and stress conditions, coupled with outstanding STI, GMP, and MP values. Correlation and PCA analyses confirmed high collinearity among STI, GMP, MP, and Yield Index, establishing their reliability for simultaneous selection of high yield potential and drought tolerance. GGE biplot analysis further validated M1 as an ideal genotype with superior yield and stability. We recommend STI, GMP, and MP as the most effective indices for drought tolerance screening. The elite genotypes M1, Sela-Zodras, and Shiroudi represent valuable genetic resources. They are recommended for further multi-location testing under terminal drought conditions and, pending validation, for potential direct cultivation in drought-prone areas or as donor parents in breeding programs to enhance climate resilience in rice.