Abstract
<title>Abstract</title> <p> <bold>Background</bold> . Climate change increasingly threatens viticulture, with Mediterranean wine regions expected to face more frequent and intense heatwaves. Identifying grapevine varieties with superior heat resilience is therefore critical for sustainable production in arid and semi-arid environments. <bold>Methods</bold> . We applied an integrative phenotyping framework combining leaf physiology, metabolomics, targeted gene expression profiling, and UAV-based thermal imaging to characterize heatwave responses in six <italic>Vitis vinifera</italic> varieties over three growing seasons (2022–2024). <bold>Results</bold> . Marked varietal differences were observed across physiological, thermal, and molecular levels. Syrah maintained higher stomatal conductance (0.6 mol m⁻² s⁻¹) and net CO₂ assimilation rates (27 μmol m⁻² s⁻¹) under heat stress, compared to more sensitive varieties such as Tempranillo. This was accompanied by cooler canopy temperatures captured by UAV thermal imaging, validating its utility for rapid field-scale phenotyping. While interannual variations reflected local climatic fluctuations during each heatwave event, tolerant varieties consistently maintained higher quantum yields and electron transport capacities across all years. Metabolite profiling revealed that amino acids, sugars, and polyols served as major components of heat adaptation, with distinct metabolic shifts discriminating between temporal stress responses. Targeted gene-expression profiling identified variety-specific regulation of heat-shock protein and sugar transport pathways, highlighting <italic>HT4</italic> as a potential regulator of thermotolerance. Furthermore, correlation-network analysis revealed that resilient varieties exhibited tighter coordination between molecular and physiological responses. <bold>Conclusion</bold> . Together, these findings reveal substantial varietal diversity in grapevine heat-response strategies. Integrating UAV-based phenotyping with broad molecular profiling can provide a scalable framework for screening climate-resilient cultivars and guiding adaptation strategies in future viticulture. </p>