Abstract
Sixteen rice genotypes were planted under normal and high temperature during 2018 and 2019 seasons to understand the mechanisms that make plants tolerant or susceptible to heat stress and methods which may lead to generate new varieties with sustainable yield production. The combined analysis showed significant differences at the level of probability 0.05 and 0.01 among years for all characters except, chlorophyll content and leaf rolling which would indicate wide differences among the weather of both years. Environment's variance was significant at the level of probability 0.01 over all characteristics. The significant differences at the level of probability 0.01 were recorded among genotypes and G x E interaction variances for all characteristics. The highest values of panicles number plant(-1) were obtained from 'Giza 178' and 'Hybrid 2', however, the highest values of 100-grain weight were recorded with 'Giza 179' and 'Egyptian Yasmine'. The minimum values of sterility% were recorded with 'Sakha 107' and 'IET1444'. Concerning the cultivars performance across two environments, the cultivars 'Giza 178', 'Giza 179', 'Sakha 107' and 'IET 1444' gave the best desirable values over natural and heat stress so, those cultivars are considered to play a vital role in breeding program to enhance heat stresses tolerance accompanied with high yield potential.