Effect of Sunlight Exclusion at Different Phenological Stages on Anthocyanin Accumulation in Red Grape Clusters

Abstract

The influence of sunlight exclusion from grape clusters at different phenological stages on berry composition, especially anthocyanin accumulation in berry skin, was investigated. Sunlight was excluded from clusters at three different stages: fruit set to about 1 week preveraison, about 1 week preveraison to about 1 week postveraison, and about 1 week postveraison to maturity for the red grape cv. Jingxiu (Vitis vinifera L.) over two seasons and three cultivation conditions (in the field in 2011 and in the greenhouse and rain shelter in 2012). Sunlight exclusion at the different stages did not consistently affect berry weight, soluble solids content, or titratable acidity at maturity. However, sunlight exclusion from fruit set to 1 week preveraison consistently significantly increased anthocyanin content both at 1 week postveraison and at maturity, compared to the clusters exposed to sunlight throughout fruit development (control). Clusters with sunlight excluded from 1 week preveraison to 1 week postveraison accumulated less anthocyanins than control clusters at 1 week postveraison, while re-exposure to sunlight resulted in recovery of anthocyanin synthesis to a similar total content to control clusters at maturity. The absence of sunlight from 1 week postveraison to maturity did not significantly affect anthocyanin content compared to the control. The increase of anthocyanin content by sunlight exclusion from fruit set to 1 week preveraison might have a practical application for production of more anthocyanins in red grape berry skin.