Evaluation of Photosynthetic Performance and Adaptability of Grape Varieties in Arid Regions

Photosynthetic characteristics are critical for grape growth and development. Drought conditions in arid regions significantly affect these characteristics. To identify grape varieties better suited for cultivation in arid environments, this study evaluated the leaf phenotypes and photosynthetic characteristics of 27 table grape varieties in Hotan Prefecture, China. Results revealed significant variations in leaf phenotypes and chlorophyll content (SPAD) among varieties under Hotan’s drought conditions. ‘Kyoho’ exhibited the largest leaf area (254.34 cm2), while ‘Munage’ had the smallest (112.43 cm2), and ‘Manaizi’ showed the highest chlorophyll content (SPAD = 44.21). ‘Munage’ and ‘Flame Seedless’ recorded the highest net photosynthetic rates (PNmax = 16.24 and 16.23 μmol·m−2·s−1, respectively), while ‘Thompson Seedless’ had the lowest respiratory loss (RD = 1.15 μmol·m−2·s−1) and light compensation point (Ic = 22.41 μmol·m−2·s−1), with a highly significant positive correlation between RD and Ic. ‘Crimson Seedless’ exhibited the highest light saturation point (Isat = 2745.15 μmol·m−2·s−1). Chlorophyll fluorescence analysis indicated that ‘Autumn Black’ had the highest PSII photochemical yield (Fv/Fm = 0.84), while ‘Zicuiwuhe’ showed high energy transfer indices (PIabs = 1.78, PItotal = 1.66) and electron transfer efficiency (φEo = 0.39). PIabs was significantly correlated with Fv/Fm, Fv/Fo, and energy flux parameters. ‘Molixiang’ demonstrated superior energy utilization, with the highest light absorption (ABS/CSm = 2440.8) and electron transfer flux (ETo/CSm = 874) and the lowest energy dissipation (DIo/CSm = 455.8), supported by a negative correlation between energy dissipation (DIo/CSm) and photochemical efficiency (φEo). Principal component analysis revealed that ‘Molixiang’ had the highest comprehensive photosynthetic adaptability score (0.97), followed by ‘Zicuiwuhe’ (0.79) and ‘Hetianhong’ (0.73), under Hotan’s drought stress conditions. These findings provide valuable insights for selecting and breeding grape varieties adapted to arid environments and climate change.