Screening of rice (Oryza sativa L.) germplasm of North-Eastern India for early vegetative stage heat tolerance

A total of 600 rice germplasm from the North-Eastern hills of India were evaluated for their tolerance to high temperature. Seeds of each genotype (pre-soaked overnight) were germinated in plastic cups at three different temperatures i.e., 40°C, 45°C and 50°C. A total of 78 genotypes showed more than 80% germination at 40°C, while only 27 genotypes showed 60% or more germination at 45°C. After heat treatment of the latter 27 genotypes at 40°C and 45°C at the seedling stage, 18 genotypes successfully recovered from the 40°C treatment, while only 9 recovered after exposure to 45°C. These 9 genotypes were found to contain 30–60% relative water content under 22 days of drought stress.