Delaying grapevine budbreak to prevent spring freeze damage impacts Lemberger wine flavour compounds under variable weather conditions

Delaying grapevine budbreak through viticultural management practices is a promising method to prevent spring freeze damage for small vineyards. However, in cool-climate regions, delaying budbreak can potentially delay fruit development and maturation, negatively impacting wine quality. In this three-year study, 2017–2019, we evaluated the impacts of delaying budbreak on wine volatile and nonvolatile composition for Vitis vinifera c.v. Lemberger at a cool-climate site, and we related treatment impacts on wine composition to consumer perception. We also assessed if treatment impacts were similar across vintages, or if seasonal weather conditions were more important for wine composition than delaying budbreak. We evaluated four treatments each year: a control (C) (no delayed budbreak strategy applied), a vegetable oil-based adjuvant (Amigo®) applied at either 8 % or 10 % (v/v) concentration during dormancy (A8, A10), and late pruning conducted shortly after budbreak (1–4 leaves unfolded) of apical buds (LP).  Delays in budbreak between treatments and C vines ranged from 5 days (A8, 2017) to 23 days (LP, 2017) across the 3 years. Furthermore, berry colour change, one of the parameters used to assess véraison, started later in LP vines than in C vines each year. Within each vintage, we found that delayed budbreak treatments, especially LP, had lower concentrations of several volatile compounds than C wines. Furthermore, LP wines tended to have higher monomeric anthocyanins relative to C wines, ranging from 18 % (2019) to 36 % higher (2018). Results from consumer discrimination testing broadly reflected differences in wine chemical composition: consumers perceived LP wines as different from C or A8, depending on the year, and all treatments were different in 2019. However, we found that vintage impacted wine composition more than the delayed budbreak treatments. Of the 49 volatile and nonvolatile compounds detected every year, about half showed significant vintage effects, while only three were consistently different by treatment. Together, our results suggest that delaying grapevine budbreak at a cool-climate site can impact wine chemical composition and perception, especially if phenological delays are still present around véraison; however, seasonal weather conditions remain a more important driver of wine chemical composition than relatively small changes in phenological development.