The effect of temperature on grapevine phenological intervals: Sensitivity of budburst to flowering

Advancement of grapevine phenological stages due to climate change has been well documented. There is less information regarding which phenological intervals in the grapevine growth cycle are most affected by temperature and thus drive this advancement. This study focused on investigating the relationship between temperature and the phenological interval lengths between budburst, flowering, veraison (onset of grape ripening) and maturity, to identify the interval most influenced by temperature change. Historical data from four climatically different vineyards in Victoria, Australia were used that included 15 cultivars and covered 7 years, 2012–2018, to investigate trends in the intervals between phenological stages. The interval between budburst and flowering shortened significantly more than the subsequent intervals between flowering and veraison and between veraison and maturity, as related to average daily springtime temperature (max). We found the best relationships between temperature and interval length were for the budburst to flowering interval, and for the relationship between the average daily maximum temperature during this interval and interval length. We found this relationship was best described by a curvilinear rather than linear function, which also varied between cultivars. These findings indicated that with increasing spring maximum temperatures, the rate of decrease in length of the interval between budburst and flowering will slow and plateau. The study showed the importance of the budburst to flowering interval to the length of the grapevine growth cycle and indicates that there is cultivar diversity of response to temperature. This knowledge helps our ability to understand and predict phenological timing and assists development of our adaptation strategies to climate change.