Effect of environmental factors on skin pigmentation and taste in three apple cultivars

To assess the effects of both development and environment on apple fruit quality, skin color and flavor/taste characteristics were compared between shaded (bagged) and sun-exposed (without bagging) apple fruit. Field experiments were conducted during the middle-to-late fruit development, using three cultivars (non-red 'Golden Delicious', pale-red 'Cripps Pink', and deep-red 'Qinguan') at 830.9 m altitude, and two cultivars ('Qinguan' and 'Golden Delicious') at three different altitudes (519.8, 830.9, and 1072.5 m). The chromaticity values L*, C*, and h degrees differed between non-red and both red cultivars over time. Sun-exposed fruits contained more chlorophyll and carotenoids than shaded fruits. Trace amounts of anthocyanin accumulated in the skin of sun-exposed 'Golden Delicious', while shading prevented anthocyanin accumulation in red cultivars. The sugar contents of all three tested cultivars increased over time, while the organic acid contents decreased. Shading reduced the sugar and organic acid contents but did not affect their variation trends over time. The growing environments affected both the h degrees values and pigment contents of 'Qinguan', and the maximum fructose and sucrose proportions and the minimum glucose proportion were detected at the lowest altitude. Although red peel color, sugars, and organic acid proportion were determined via genetic cues under natural conditions, the growing environment is centrally important for these traits. Both the temperature and light of the planting region influenced each other and impacted the contents of sugars and organic acids in the tested apple fruit.