Economic loss due to cold weather events is a major constraint to winegrape (Vitis vinifera) production and wine-related industries where extreme and/or fluctuating winter temperatures induce injury and require remedial retraining and replanting increases production costs and lowers yield and fruit quality. The purpose of this study was to determine whether a foliar application of abscisic acid (ABA) could increase the freezing tolerance (FT) of field-grown, ‘Chardonnay’ winegrape and whether its effectiveness can be influenced by the phenological timing of the application. Mature ‘Chardonnay’ grapevines were treated with a foliar application of ABA at a concentration of 500 mg·L−1 at vine phenological stages corresponding to 50% véraison, postvéraison, and postharvest. Results from field trial sites located in four distinct winegrape production regions in the United States (Idaho and Ohio) and Canada (British Columbia and Ontario) showed that foliar application of ABA increased bud FT, primarily during autumn cold acclimation. Foliar ABA application had no consistent influence on bud FT in midwinter or during spring deacclimation, or on percent budburst in spring. Vine phenological stage at the time of ABA foliar application influenced ABA effectiveness, although results were inconsistent among locations. At most locations, applications made at véraison or postvéraison were more effective than applications made postharvest. No phytotoxic response or adverse changes in yield or berry composition were detected in response to ABA application. The consistent increase in bud FT during autumn cold acclimation observed at all trial locations in this study indicates that foliar ABA, applied at véraison or postvéraison, can reduce the risk of economic loss due to cold injury in production regions with frequent early autumn cold weather events.

The effects of abscisic acid (ABA) form, concentration, and application timing on bud cold hardiness, phenology, and fruiting performance of Merlot grapevines (Vitis vinifera) were evaluated in a three-year field trial with site locations in British Columbia and Ontario, Canada, and in Washington and Idaho, United States. Solutions containing natural S-ABA (ABA N ) and a purported long-lived ABA analogue 8'-acetylene ABA (ABA A ) at differing concentrations were applied to the vine canopy at veraison or post-harvest. Postharvest foliar applications of ABA N at concentrations greater than or equal to 5000 ppm tended to advance leaf abscission and increase autumn bud cold hardiness. Postharvest foliar applications of ABA A at 1000 ppm tended to delay budbreak in the spring following application and increase spring bud cold hardiness. Fruit yield and basic composition were affected little by the ABA treatments. Bud hardiness was enhanced by ABA N mostly in autumn and by ABA A mostly in the spring, indicating that the suitability of ABA forms for reducing bud damage would depend on when injurious cold events are more likely.

Alkyl-methoxypyrazines are an important class of odor-active molecules that contribute green, ‘unripe’ characters to wine and are considered undesirable in most wine styles. They are naturally occurring grape metabolites in many cultivars, but can also be derived from some Coccinellidae species when these ‘ladybugs’ are inadvertently introduced into the must during harvesting operations. The projected impacts of climate change are discussed, and we conclude that these include an altered alkyl-methoxypyrazine composition in grapes and wines in many wine regions. Thus, a careful consideration of how to manage them in both the vineyard and winery is important and timely. This review brings together the relevant literatures on viticultural and oenological interventions aimed at mitigating alkyl-methoxypyrazine loads, and makes recommendations on their management with an aim to maintaining wine quality under a changing and challenging climate.