Genetic Parameters, Multivariate Analysis and Tolerance Indices of Rice Genotypes under Normal and Drought Stress Environments

In order to evaluate genetic parameters and drought tolerance indices using multivariate analysis, seventeen genotypes of rice were evaluated under normal and drought conditions. The combined analysis of variance indicated highly significant effects of genotype on all studied traits under normal and drought conditions. Most studied genotypes were better than the grand mean during normal and drought conditions. Drought stress reduced the studied traits while other was tolerant to drought, suggesting genetic variability in these genotypes for drought tolerance. The environmental and genetic variances and heritability showed highly significant for all studied traits under normal and drought conditions. The maximum values of genetic variance were found for all studied traits followed by the environmental and genotypes × season variances at normal and drought conditions. High heritability coupled with high genetic advance as percent of the mean was observed for most studied traits under normal and drought conditions. The differences between phenotypic coefficients of variation (PCV%) were higher than the values of genotypic coefficients of variation (GCV%) for all studied traits under normal and drought conditions. The moderate to low values of GCV% and PCV% were recorded for studied characteristics during drought condition. The values of the relative coefficient of variation were higher than the unity for all studied traits at normal and drought conditions. Hence, these genetic parameters can be used as direct selection criteria for rice improvement under drought stress conditions. The first two PCs with eigen values >1 contributed 99.74% of the variability amongst genotypes. PC1 accounted for about 73.25% of the variation in drought tolerance indices and PC2 for 26.49%. According to tolerance indices, correlation and principle component analysis, indices including STI, MP, GMP, YI and HM under Yp and Ys as well as YI, YSI and DI under Ys could properly distinguish drought tolerant rice genotypes with high yield performance. Therefore, these indices were considered as a better predictor of Ys and Yp than TOL and SSI. The former other indices were independent of SSI and TOL. Screening drought tolerant genotypes using mean performances, drought tolerance indices and multivariate analysis, discriminated genotypes G3, G16, G7 and G2 as the most drought tolerant (Group A) and we recommend them for using in a breeding program for high yielding of rice under normal and drought conditions in Egypt.