Physiological Response to High Temperature and Evaluation of Heat Tolerance of Different Grape Cultivars.

[Objectives] This study was conducted to investigate the differences in the physiological responses of different grape cultivars to high temperature. [Methods] The 19 tested cultivars were selected from the grape germplasm resources pool of Turpan Research Institute of Xinjiang Academy of Agricultural Sciences. Twelve physiological indexes including gas exchange parameters, chlorophyll content, antioxidant enzyme activity and proline content were determined in grape leaves under field conditions during the middle period of local natural high temperature period ( July, daily maximum air temperature > 35 °C). The heat tolerance of different cultivars was evaluated by fuzzy membership function analysis and optimum partitioning clustering of ordered samples. [Results] ① Under natural high temperature conditions in Turpan, the 19 tested grape cultivars responded differently to high temperature. 'Red Globe', 'Fujiminori', 'Beta', 'Hetianhuang ' had strong heat tolerance, while 'Thompson Seedless', 'Hongqi Tezaomeigui', 'Shuijing Wuhe', 'Victoria', 'Yatomi Rosa' and 'Crimson Seedless' had weak heat tolerance. ② Among the 12 physiological indexes, malondialdehyde content and antioxidant enzyme activity were mostly different among various grape cultivars. The grape cultivars with strong heat tolerance, ' Red Globe' and ' Fujiminori', had relatively lower malondialdehyde contents, while 'Beta' and ' Hetianhuang' had relatively higher malondialdehyde contents. But they had higher activity of antioxidant enzymes. ③ The results of fuzzy membership function analysis showed that the cumulative membership value ( AR) of each physiological index was consistent with its apparent heat tolerance performance, suggesting that AR can be a potential index for the evaluation of heat tolerance of grape cultivars. Further cluster analysis classified the tested cultivars as strong, medium and weak. ' Red Globe', 'Fujiminori', 'Beta' and ' Hetianhuang' had strong heat tolerance. [Conclusions] This study provides a reference for grape cultivation under high temperature and stress and breeding of heat-tolerant varieties. [ABSTRACT FROM AUTHOR]