Phenological and physiological responses of hybrid rice under different high-temperature at seedling stage

Background The projected increase in global temperature is expected to negatively impact food production in many regions. Rice exposure to heat stress can limit plant growth in different stages, especially at the seedling stage. In this experiment, two Indica parental lines N22 (heat tolerant) and BIM (heat sensitive) along with their F 2 hybrid were elucidated under different high temperatures (28 °C, 35 °C, and 42 °C) at the seedling stage. Results The results indicated that the F 2 hybrid inherited the heat tolerance rate from the male heat-tolerant N22 parent. Based on phenological and physiological attributes, the F 2 hybrid exhibited excessive-performance as compared to its BIM parent under different high-temperature conditions. Specifically, absorbing the ample available water through the long-rooted system enabled rice seedlings to carry out high transpirational cooling. Furthermore, there was a strong relationship ( r = 0.89, p < 0.01) between root length and transpiration rate under 42 °C. The temperature 35–42 °C caused a significant reduction in seedlings’ growth, chlorophyll content, and survival rate (18–20%), while the relative heat injury percentage and leaf temperature increased in heat-sensitive BIM parent as compared to F 2 hybrid. Conclusion This study suggests that the breeding of heat-tolerant hybrid rice plays an important role in the production of a resilient rice plant through heat-tolerant seedlings at the initial vegetative growth stage.