Impact of Drought Stress Timing and Intensity on Physiological Performance and Wine Quality in Two White Grapevine Cultivars Planted in a Mountain Vineyard

In response to a warming and drying climate, viticulture at higher elevations could be a viable adaptation strategy for the wine industry. Nevertheless, our knowledge about the optimal water management in mountain vineyards remains limited. This study evaluated the effect of drought stress on two grapevine cultivars (Sauvignon Blanc and Chardonnay) under irrigated and rainfed conditions. The research took place in the mountainous region of South Tyrol in northern Italy. Soil‐water status, several plant‐based physiological stress indicators, yield components, berry quality, and wine sensory attributes were monitored across two growing seasons. Drought stress varied in timing and intensity. In 2021, a 10‐day drought occurred during berry set, while in 2022, a more severe drought coincided with veraison and was combined with a 9‐day heatwave. Reduced soil‐water availability caused growth inhibition and impaired photosynthetic activity, particularly in 2022. Conversely, the mild to moderate water deficit during berry set caused a greater reduction in berry size and weight, and consequently in yield, than the more severe water deficit at veraison. As for berry quality traits, drought stress affected berry soluble solids accumulation, but not pH or titratable acidity. Furthermore, sensory analysis revealed distinct differences across vintages and cultivars. Wines from rainfed vines displayed enhanced hedonistic attributes (e.g., complexity, fullness, and length), particularly when the stress occurred early during the season. Generally, despite comparable stress exposure, Sauvignon Blanc vines were more drought‐sensitive, showing greater growth inhibition, decreased photosynthetic activity, substantial yield loss, and altered wine sensory profiles. Chardonnay, conversely, seemed more resilient to drought conditions, showing no discernible differences between rainfed and irrigated wines. In conclusion, this study reveals varying levels of drought tolerance between the two cultivars across two seasons. These findings may help develop cultivar‐specific irrigation schedules for mountain vineyards, enhancing water conservation, preserving yields, and ultimately achieving the desired wine quality.