2) Dr. Tamir Caras

Heat waves, increasing in frequency and duration due to climate change, profoundly affect grapevine physiology, particularly sugar accumulation and transport. Cultivars differ in their tolerance to heat stress and can be categorized into three strategies: resistant, maintaining transpiration and metabolic activity; resilient, exhibiting transient stomatal closure with subsequent recovery; and sensitive, showing metabolic cessation with limited recovery. This study evaluated cultivar responses to extreme heat events in 2022 and 2023, quantified recovery rates, and tested the use of UAV thermal imagery as a tool for detecting heat stress. Six grapevine cultivars were monitored in a research plot in the Negev, Israel. UAV flights were conducted at 08:00, 12:00, and 16:00 on days following heat waves, alongside ground-based measurements of leaf temperature, water-use efficiency (WUE), and metabolomic profiles. Data analysis focused on diurnal canopy temperature trends, correlations between UAV thermal data and ground observations, and classification of cultivars according to heat-response strategies. Results revealed distinct cultivar responses: Syrah exhibited resistance by sustaining photosynthesis throughout the day. Petit Sirah, Pinot Noir, and Tempranillo displayed resilience, recovering after midday stress. In contrast, Petit Verdot and Sangiovese were sensitive, failing to regain full activity. UAV thermal imagery correlated strongly with ground-based measurements (R2 = 0.82), confirming its effectiveness as a semi-automated phenotyping tool for monitoring heat stress and recovery for climate change adaptation. These findings highlight the potential of thermal remote sensing to complement physiological and metabolic metrics, providing an efficient approach for screening cultivar resilience and guiding vineyard management under intensifying climate stress.