Evaluation of 137 peach germplasm resources to heat tolerance

【Objective】 This research aim to explore one method to identify the heat tolerance of 137 peach germplasm resources by using the chlorophyll fluorescence parameter（Fv/Fm）. This result would provide theoretical basis for cultivating heat-resistant peach varieties and further research on illustrating the heat-resistant mechanism.【Method】The peach germplasm resources from Hubei Peach resources nursery were used as experimental materials. Under heat water bath stress， the Fv/Fm value of gender leaves of peach annual branches were measured by the portable fluorometer. The critical temperature（T_C）and heat treatment time suitable for peach heat resistance evaluation were determine. On this basis， the heat resistance of 137 peach germplasm resources was evaluated.【Result】In 25-55 ℃ water bath， the Fv/Fm values of three different peach germplasm resources，Fengguang 24-2， Zaoxianhong and Jinhui，were measured. Data analysis showed that T_C for evaluating the heat resistance of peach was 47.0 ℃.At 47.0 ℃， when the treatment time was 50 min， the Fv/Fm values among the three cultivars were significantly different （P<0.05）. Based on the above， the optimal temperature （47.0 ℃）and heat stress treatment time（50 min）were used to determinate the heat tolerance of peach cultivars. Fv/Fm of heat tolerance of 137 peach germplasm resources was between 0.1723 to 0.6968. The peach heat tolerance traits basically followed the normal distribution， it proved that the peach heat-resistant was quantitative trait controlled by multi-genes. The heatresistance of 137 peach germplasm resources was divided into three levels by optimal segmentation： strong， moderate and weak. Among them， 26 cultivars with strong heat resistance（Fv/Fm>0.6）accounted for 19%，94 cultivars with moderate heat resistance（0.6≥Fv/Fm>0.4）accounted for 69%， and 17 cultivars with weak heat resistance（Fv/Fm≤0.4） accounted for 12%.【Conclusion】High temperature has an impact on the photosynthesis of peach leaves， and there are some heat resistance differences among different germplasm resources. Among them，26 strong heatresistance germplasms， such as Fengguang 24-2， 14-101， 04-1-41， Zhongtao 10， Xiazhimeng，Chunxue and Taobadan， can be used as parents to breed heat tolerant peach and used for investigating the peach heat tolerance mechanisms.