Identification and evaluation for heat tolerance at the flowering stage in different rice genotypes

【Objective】In order to provide theoretical basis and technical reference for the identification and evaluation of the heat tolerance during the flowering stage and the selection of varieties to cope with high temperature and heat injury, rice varieties with high heat tolerance and high yield at flowering stage were selected in this study.【Method】In this study, the heat tolerance of 100 different rice genotypes at the flowering stage was evaluated by simulating high temperature(38℃ for 6 hours per day for 3 d) in a phytotron, using Y Liangyou 1 as the control variety and the relative heat tolerance index as the evaluation index, and also combining with the yield level.【Result】The results showed that there were great differences in spikelet fertility among different rice cultivars under heat stress at the flowering stage, demonstrating that they had different heat tolerance. Under high temperature stress, the spikelet fertility ranged from 3.6% to 64.3%, while the relative spikelet fertility ranged from 9.5% to 80.0%. The heat tolerance of different cultivars was classified according to the relative heat tolerance index, and the number of rice varieties with heat tolerance grade of 1(highly tolerant), 3(tolerant), 5(moderately tolerant), 7(susceptible) and 9(highly susceptible) were 4, 13, 42, 26 and 15, respectively. Cluster analysis was used to divide 100 rice genotypes into six types with different heat tolerance and yield levels. Among them, the first type was popularized in heat injury prone areas with high safety and productivity. Relative spikelet fertility was the main factor for the classification of different rice genotypes, followed by the yield. According to the two-dimensional quadrant distribution characteristics between relative spikelet fertility and yield, some varieties with good comprehensive traits, including strong heat tolerance and high yield level, were further screened out.【Conclusion】Through the identification and evaluation of heat tolerance of 100 different rice genotypes during the flowering time, seven varieties with high heat tolerance and high yield level are selected, such as Teyou 837, Yunguang 14, Q You 8, Guodao 7, Y Liangyou 865, Shanyou 63 and Huanghuazhan. These varieties can be planted in the high temperature prone areas.