Abstract
Elevated temperature can decrease the ratio of anthocyanins to soluble solids in red-skinned berries and warming trends in grape production regions have raised concern about color to alcohol balance in wines produced from fruit with altered ratios. In this study, we tested the effectiveness of a foliar reflective film to increase the ratio of anthocyanins to soluble solids in deficit-irrigated Merlot grapevines. Vines were irrigated to provide 90 or 35% of their estimated water demand (DI90 and DI35, respectively) and were either sprayed with a kaolin-based reflective film or left unsprayed in a replicated, split-plot design. Crop load was adjusted in half the number of vines in each subplot in the last three years of the 5-yr study by removing 50% of clusters prior to bloom. The reflective film increased the ratio of anthocyanins to soluble solids under both irrigation amounts and crop loads when soluble solids concentration was between 18 and 24%. The reflective film did not alleviate water-deficit-associated decreases in yield or titratable acidity. The film had no influence on yield per vine; however, it reduced the number of berries per cluster, especially under DI35 irrigation. Under DI90 irrigation, the decrease in berry number per cluster was associated with an increase in berry fresh weight and anthocyanin content per berry. Cluster removal influenced berry composition at harvest only under DI35 irrigation. The ratio of anthocyanins to soluble solids during ripening was higher under DI35 than under DI90 irrigation. Results from this study show that foliar reflective film, in combination with deficit irrigation, can be used to increase the ratio of anthocyanins to soluble solids under arid conditions with high solar radiation.
- ©2015 by the American Society for Enology and Viticulture
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