The objective of this study was to evaluate the ability of several indices to identify drought resistant genotypes of rice under normal and stress conditions in Egypt. Thirteen drought tolerance indices including stress susceptibility index (SSI), tolerance index (TOL), mean productivity index (MP), geometric mean productivity (GMP), stress tolerance index (STI), yield index (YI), yield stability index (YSI), drought resistance Index (DI), yield reduction ratio (YR) , abiotic tolerance index (ATI), stress susceptibility percentage index (SSPI), harmonic mean (HARM) and golden mean (GOL) were calculated based on grain yield under normal (Yp) and stress (Ys) conditions. Combined analysis of variance for grain yield showed highly significant differences among Irrigations regimes (I), genotypes (G) and G × I interaction. Highly significant differences among genotypes were obtained for grain yields (Yp and Ys) and all drought tolerance indices. A high broad sense heritability (h2) and genetic advance as percent of mean (GAM%) estimates were observed for Yp, Ys and all studied indices. Moderate to high GCV% and PCV% were observed for Ys and all drought tolerance indices except Yp, MP and GMP indices. According to correlation and multivariate analysis, MP, GMP, STI, HARM and YI drought tolerance indices can be used as parameter in breeding programs to increase grain yield under normal and stress conditions, and SSI, TOL, YSI, DI, YR, ATI, SSPI and GOL under stress conditions. During screening drought tolerant genotypes using mean performances, drought tolerance indices and multivariate analysis, the genotypes G3, G16, G7 and G2 (Group A) in normal and stress conditions as well as the genotypes G14, G12 and G13 in stress conditions were the most drought tolerant genotypes. Based on ranking method, the genotypes G16, G13, G12 and G2 (Group A) appeared as the most droughts tolerant. Therefore they are recommended to be used as parents in hybridization programs for improvement of drought tolerance for other cultivars rice in Egypt. Also, MP, GMP, STI, HARM and YI seem to be useful yield-based drought tolerance indices to be employing in plant breeding programs for rice in Egypt.
Keywords: Comparison – Genetic parameters – multivariate analysis – drought tolerance indices – rice