Forty rice genotypes including 23 introgression lines (IL) derived from BC2F6 of Swarna × O nivara and KMR3 × O rufipogon and 3 mutants of N22 were evaluated for heat tolerance at germination, seedling and early vegetative stage of development under different temperature treatments. Swarna × O. nivara ILs 166-2, 175-2, 3-1K, KMR3 × O. rufipogon ILs 377-13, 50, 117, 13-7 and three IET hybrids 21528, 20907 and 20114 showed higher percent germination, mean shoot and root length, dry weight, chlorophyll, carotenoids and leaf senescence index compared to the tolerant check Nagina 22 at high temperature. At 40°C, two deep water rice varieties, Jalmagna and Madhukar and IL117 showed highest values for the first four traits. The two N22 mutants NH686 and NH787 had the least shoot and root length at 40°C. The effect of heat on carotenoid content was highly significant (p<0.05). Highly significant variations were observed between the genotypes for all other traits
