Dormancy in Grapevine Cultivars Across Various Pruning Treatments in the Mediterranean Region of Israel

Background and Aims: Dormancy in grapevines (Vitis vinifera) is a critical adaptive strategy that enables vines to survive harsh winter conditions and is influenced by physiological and environmental factors. This study aimed to investigate the progression of endodormancy across different pruning dates and cultivars and to identify the key meteorological and agrotechnical factors influencing dormancy depth. Methods and Results: Seven cultivars (Cabernet Sauvignon, Carignan, Chardonnay, Merlot, Petit Verdot, Shiraz and Tempranillo) were subjected to four pruning dates (e.g., sampling treatments: December, January, early February and late February) over 4 years (2021–2024). Single-node cuttings from each treatment were placed under controlled growth conditions (14-h light, 23°C) for dormancy assessment. Dormancy levels reduced with time and subsequent pruning treatments, with cultivar-specific variations. Tempranillo and Petit Verdot displayed deeper dormancy, while Chardonnay and Carignan exhibited an earlier dormancy release. Shiraz showed the least variation across dates, and Merlot had minimal seasonal fluctuations. A random forest model incorporating temporal and meteorological features identified temperatures > 25°C, vapour pressure deficit (VPD) and chill units (CU) as the most influential meteorological factors for dormancy fluctuations, with relative contributions of 10.7%, 9.7% and 7.9%, respectively. Warm winter conditions in 2024 were associated with shallower dormancy (< 25%), particularly in Tempranillo and Petit Verdot during December, followed by an unusual deeper dormancy state (> 95%) during January in several cultivars. Conclusions: Variable dormancy depth was observed across different cultivars and seasons. Meteorological factors, particularly temperature, VPD and CU, influence the dormancy depth, with clear cultivar-specific differences. Significance of the Study: This study provides insights into cultivar-specific dormancy depth with the relative influence of meteorological factors.