Genetic Behavior of Some Rice Genotypes under Normal and High Temperature Stress

Thirteen rice genotypes were grown in the two successive rice seasons 2017 and 2018 to assess the presence of variability for desired traits and estimate genetic parameters and correlations for traits under normal and heat stress conditions. Analysis of variance revealed significant differences due to environments, genotypes and their interaction for all studied characteristics in both seasons. The estimates of genotypic (GCV) and phenotypic (PCV) coefficient of variation were highly significant for all studied traits and generally, the PCV values were higher than GCV values, in both seasons. Leaf rolling and sterility percentage increased under heat stress, while days to heading, plant height, number of tillers and number of panicles / plant, 100-grainweight and grain yield/plant decreased under heat stress in comparison to normal condition. As mean performance Giza 179, Giza 178 and Sakha 101 surpassed other genotypes in grain yield and its important attributes, while WAB56-50/Sakha101-1, WAB56-50/Sakha101-2 and IR65907-206-7-8/Gyehwa71 gave the lowest grain yield in both seasons. Giza178 and WAB56-50/Sakha101-1 recorded the lowest values of geometric mean productivity, stress susceptibility index and yield index which refer to those genotypes highly tolerance to heat stress, while Giza 177 and Sakha 101 gave the highest values to be the most heat susceptible genotypes under study. Highly positive and significant phenotypic correlations were observed between yield index and leaf rolling, sterility percentage, geometric mean productivity and stress susceptibility index, otherwise number of tillers/plant, number of panicles/panicle and panicle weight, as yield attributes had highly significant negative correlation with the yield index. From the results we can conclude that, the genotypes can be scored as heat tolerant, based on days to heading, leaf rolling, tillering productivity and spikelets sterility percentage.