Relations among pigments, color and phenolic concentrations in the peel of two Gala apple strains according to canopy position and light environment

Pigments, total phenolic and total flavonoids concentration are important factors determining color and internal apple quality. Their concentrations are influenced by the cultivar strain and fruit position within the canopy. The aim of this study was to determine coloring patterns in two Gala apple strains (‘Baigent’ and ‘Galaxy’) and their relationship to the concentrations of pigments, phenolic and flavonoids, in fruit from different positions of the tree and therefore light conditions. During two growing seasons fruit from five different locations within the canopy were picked at commercial harvest and the peel of exposed and shaded side were removed after determining color parameters (CieLa*b*). The concentration of pigments, total phenolic (TPC), and total flavonoids (TFC) in fruit peels was determined. Also the photosynthetically active radiation (PAR) was measured at each canopy position where the fruit were harvested. With the exceptions of anthocyanins (in both season), and chlorophyll b, and carotenoids (in the second season) no differences were found between the strains. In the first season, anthocyanin concentration on the exposed side of ‘Baigent’ fruit increase asymptotically up to 100 μg cm−2 with PAR, whereas ‘Galaxy’ increase linearly but the maximum value was <80 μg cm−2. The hue angle (h) and lightness (L) decreased exponentially (R2 = 0.93) and linearly (R2 > 0.80), respectively, with increased anthocyanins in the apple peel, independent of the season, strain, fruit side or canopy position. Chromaticity was positively related with anthocyanins and negatively with chlorophyll a (R2 = 0.74). There was a positive association between anthocyanin concentrations and the chlorophyll b chlorophyll a−1 ratio (R2 = 0.45). The concentrations of total flavonoids and phenolic of the two strains were similar in the first season, 0.34 and 0.81 mg cm−2, whereas in the second season those were 86 and 56% higher in ‘Baigent’ than ‘Galaxy’, respectively. Under environmental conditions that do not favor color development, the PAR within the canopy explained more than 50% of the variability of total phenolic and flavonoids concentration, although this association was not evident under favorable environmental conditions to red color development.

► Anthocyanin is the main pigment defining CieLab parameters in apple Gala.
► Baigent presents higher PAR sensibility for anthocyanin synthesis than Galaxy.
► Chlorophyll b/a ratio was associated with anthocyanin concentration.
► Flavonoids differences in Gala strains could be change with season conditions.