Application of abscisic acid at veraison improves red pigmentation and accumulation of dietary antioxidants in red table grapes cv. Red Globe at harvest

Abstract

Poor red pigmentation in the berries of red table grapes has been a serious challenge to viticulture industry around the globe. During 2016 and 2017, the effects of spray applications of 100–400 mg L−1abscisic acid (ABA), alone or in combination with 125 or 250 ppm Ethrel® (Eth) applied at veraison, on color development, firmness and accumulation of dietary antioxidants in ‘Red Globe’ grape-berries, grown under the suboptimal conditions of Saudi Arabia, were investigated. At physiological maturity, the berries harvested from the grapevines treated with two spray applications of 200 mg L−1 ABA combined with 125 ppm of Eth at veraison, applied one week apart, exhibited significantly higher levels of total anthocyanins, phenolic and flavonoid contents in the skin compared to those harvested from the untreated (control) vines. At veraison, a brief exposure of grape-berries to ethylene seems to be required to initiate the process of anthocyanin biosynthesis. The firmness of the ABA-treated berries was slightly higher than those treated with Eth alone. In conclusion, two spray applications of ABA @ 200 mg L−1, combined with the substandard dose (125 ppm) of Eth at veraison, one week apart, substantially enhanced red pigmentation and increased the accumulation of dietary antioxidants in ‘Red Globe’ grape-berries grown under the non-conductive climatic conditions for anthocyanin biosynthesis. However, alternative management strategies need to be developed to maintain/improve the quality of grapes including berry firmness at commercial harvest and during storage.