Determination of Drought Tolerance Indices as Selection Criteria of Rice Genotypes under Water Deficit Conditions in Egypt

The development of rice genotypes with impressive tolerance to abiotic stress is one of the primary objectives of rice breeding programs. The current study was carried out to assess the capability of different indices to identify rice genotypes that are drought-tolerant under Egyptian conditions during the two growing seasons 2018 and 2019. Thirteen drought tolerance indices were calculated using the grain yield of twenty rice genotypes. According to the combined analysis of variance for grain yield, there were highly significant differences between genotypes (G), irrigation regimes (I), and their interactions. All drought tolerance indices, as well as grain yields under non-stress and stress conditions (Yp and Ys), exhibited significant variations among genotypes. For Yp, Ys, and all indices assessed, estimates of broad sense heritability (h2) and genetic advance as a percentage of mean (GAM%) were high. Using mean performances, drought tolerance indices, and multivariate analysis, the genotypes Giza 179, Sakha 104, IET 1444, and GZ 6296-12-1-2-1 were superior genotypes under both stress and non-stress conditions, as were the genotypes Sakha 107, IRAT 170, IR 68552-55-3-2, WAB 56-104, IRGA 318-11-6-2-6, and NERICA -4 under stress conditions. Hence, it was suggested that they can be utilized as parents in hybridization programs that aim to improve the drought tolerance of other rice genotypes in Egypt. Furthermore, mean productivity index (MP), geometric mean productivity (GMP), stress tolerance index (STI), harmonic mean (HM), and yield index (YI) were the tolerance indices that can be classified as better predictors of drought tolerance considering the yield potentials of the genotypes.