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The evaluation of photosynthetic characteristics of plants is important for the success rate of germplasm introduction. To select grape varieties with higher adaptability and trait performance, this experiment is aimed at evaluating and comparing the photosynthetic indices, chlorophyll fluorescence parameters, photosynthetic pigment content, and leaf characteristics of five Chinese hybrid varieties. The results showed that under high light intensity stress, the leaf growth of ‘Ruidu Cuixia’ was most affected and its specific leaf weight was the lowest, while ‘Jing Hongbao’ had the highest chlorophyll content. The maximum net photosynthetic rate (Pnmax), maximum light quantum yield (Fv/Fm), and apparent quantum efficiency (AQE) were different among varieties. It was reported that the ‘Ruidu Zaohong’ variety had the highest Pnmax. ‘Ruidu Wuheyi’ was found to have the highest Fv/Fm, while the highest AQE was recorded for ‘Ruidu Cuixia’, with intercellular CO2 concentration (Ci) and stomatal conductance (gs) at 292.56 μmol·mol−1, 766.56 mmol·m−2·s−1, and 66.8 μmol·m−2·s−1, respectively. The indices of ABS/CSm, TRo/CSm, and DIo/CSm were significantly different among varieties, and these indices of ‘Ruidu Zaohong’ were the highest. Pn was positively correlated with Ci and Tr, gs were positively correlated with Fv and TRo/CSm. The specific leaf area was negatively correlated with Fv/Fm and ΦDIo. The results of the principal component analysis and TOPSIS comprehensive evaluation showed that ‘Jing Hongbao’ and ‘Ruidu Cuixia’ performed best. Overall, the measurement of the photosynthetic characteristics of the plants during the growing period provided valuable data for the varietal introduction strategies. The better photosynthetic performance of ‘Jing Hongbao’ and ‘Ruidu Cuixia’ indicates more adaptability to the long day, high light intensity, and the high-temperature climate of Xinjiang.

Temperature is one of the most important environmental factors affecting grape season growth and geographical distribution. With global warming and the increasing occurrence of extreme high-temperature weather, the impact of high temperatures on grape production has intensified. Therefore, identifying the molecular regulatory networks and key genes involved in grape heat tolerance is crucial for improving the resistance of grapes and promoting sustainable development in grape production. In this study, we observed the phenotypes and cellular structures of four grape varieties, namely, Thompson Seedless (TS), Brilliant Seedless (BS), Jumeigui (JMG), and Shine Muscat (SM), in the naturally high-temperature environment of Turpan. Heat tolerance evaluations were conducted. RNA-seq was performed on 36 samples of the four varieties under three temperature conditions (28°C, 35°C, and 42°C). Through differential expression analysis revealed the fewest differentially expressed genes (DEGs) between the heat-tolerant materials BS and JMG, and the DEGs common to 1890 were identified among the four varieties. The number of differentially expressed genes within the materials was similar, with a total of 3767 common DEGs identified among the four varieties. KEGG enrichment analysis revealed that fatty acid metabolism, starch and sucrose metabolism, plant hormone signal transduction, the MAPK signaling pathway, and plant-pathogen interactions were enriched in both between different temperatures of the same material, and between different materials of the same temperature. We also conducted statistical and expression pattern analyses of differentially expressed transcription factors. Based on Weighted correlation network analysis (WGCNA), four specific modules highly correlated with grape heat tolerance were identified by constructing coexpression networks. By calculating the connectivity of genes within the modules and expression analysis, six candidate genes (VIT_04s0044g01430, VIT_17s0000g09190, VIT_01s0011g01350, VIT_01s0011g03330, VIT_04s0008g05610, and VIT_16s0022g00540) related to heat tolerance were discovered. These findings provide a theoretical foundation for further understanding the molecular mechanisms of grape heat tolerance and offer new gene resources for studying heat tolerance in grapes. [ABSTRACT FROM AUTHOR]

[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]

Global climate warming will significantly impact grapevine growth and development, and thus grape and wine industries worldwide. Heat-tolerant germplasms are very valuable for grapevine breeding programs. In this study, we assessed the thermotolerance of 247 wild grape accessions by chlorophyll fluorescence parameter (Fv/Fm) under critical high temperature according to Xu et al. in 2016,2017, and 2018. The results showed that 36 grape accessions showed strong heat tolerance. Therefore, these accessions can be used as parents for breeding heat-tolerant grape cultivars. [ABSTRACT FROM AUTHOR]