Accumulation of anthocyanins and quercetin glycosides in ‘Gala’ and ‘Royal Gala’ apple fruit skin with UV-B–Visible irradiation: modifying effects of fruit maturity, fruit side, and temperature

Abstract

We measured the accumulation of the anthocyanins and quercetin glycosides, after irradiation with UV-B–Visible light, in the skin of apple fruit ( Malus domestica Borkh.), ‘Gala’ and ‘Royal Gala’, at two temperatures, 10 and 20°C for five harvests up to 2 weeks after the start of the commercial harvest. The response to irradiation was compared between sides of the fruit that were outer facing (exposed) and inner facing (shaded) when on the tree. The tree-shaded side of the fruit had a much greater potential to accumulate anthocyanins and quercetin glycosides than the tree-exposed side. This potential of the detached fruit to accumulate anthocyanin in the skin with UV-B–Visible radiation was decreased by fruit maturity at the last harvest. Lower temperature of 10°C prevented the accumulation of anthocyanins and quercetin glycosides compared with 20°C during irradiation with UV-B–Visible light. ‘Royal Gala’, the red sport of ‘Gala’, accumulated anthocyanins, but not quercetin glycosides, to higher concentrations than ‘Gala’. The results show that maturity, the fruit skin’s previous exposure to light and temperature are major modifying factors in the accumulation of anthocyanins by ‘Gala’ and its sport ‘Royal Gala’.