Effects of abscisic acid and shading treatments on the levels of anthocyanin and resveratrol in skin of Kyoho grape berry

Effects of abscisic acid and shading treatments on the levels of anthocyanin and resveratrol, a phytoalexin of grapes, in the skins of Kyoho grape berry were investigated. Treatments with abscisic acid (1000ppm) and shading in which clusters were covered with aluminum films were conducted at veraison. Anthocyanin was extracted from berry skin with 1% HCl-methanol and measured by the absorbancy of the extract at 530nm. Resveratrol extracted from berry skins were derivatized to trimethylsilyl esters and analysed by capillary gas chromatography. Although anthocyanin levels in berry skins increased during maturation of grape berry, resveratrol levels were almost constant. The application of abscisic acid stimulated the accumulation of anthocyanins in the berry skin. Anthocyanin accumulation in berry skins was inhibited by shading treatment. At maturity, anthocyanin level in the berry skins treated with abscisic acid was 170% of the control, whereas that in the berry skins shaded was 56% of the control. The application of abscisic acid increased concentration of resveratrol in the berry skin; resveratrol levels in the berry skins treated with abscisic acid was 1.2 folds of that in the control at maturity. No obvious differences were observed in concentration of resveratrol in the berry skins between shading treatment and the control. It appears that abscisic acid stimulates the accumulation of not only anthocyanins but also resveratrol in grape berry skins, and that shading treatment has no effect on the resveratrol levels in grape berry skins.