2019 ASHS Annual Conference

Vineyard variability is present due to the variable physical environments, and it is limiting the berry and wine chemical composition and hence wine quality from being uniform and optimal. Ecophysical variability affecting grape and wine flavonoid composition was characterized in a Cabernet Sauvignon (Vitis vinefera L.) vineyard in Sonoma County, California for two consecutive seasons. Based on calculated stem water potential (Ѱstem) integrals, the research site was separated into two distinct zones: severely (Zone 1) and moderately (Zone 2) stressed zones. Berry primary metabolites, including total soluble solids (TSS), titratable acidity (TA), pH, berry weights were measured throughout the whole season. Also, secondary metabolites of final wine were characterized with reversed-phase HPLC. TSS separated between the two zones in the first week of September in both years. When Zone 2 reached 26 °Brix in 2016 and 24 °Brix in 2017, Zone 1 reached 30 °Brix and 27 °Brix respectively, fruits were harvested and vinified separately. All anthocyanin and flavonol derivatives were higher in Zone 2 in 2016. Proanthocyanidin subunits were also higher in Zone 2 in 2016. However, there was no difference in any flavonoid compound in 2017. In 2017, the harvest was about 2 weeks earlier than 2016, the differences in flavonoid concentration was not affected greatly enough by Ѱstem even though TSS was separated. Water stress exacerbated the anthocyanin degradation when harvesting relatively later in 2016. This study provides fundamental knowledge to coalesce vineyard variability in wine flavonoid composition based on plant water status by conducting differential harvest at an earlier time.Keywords: grapevine, anthocyanins, flavonoids, water stress, spatial variability, viticulture, wine