Effects of Different Light Qualities on Color Development and Anthocyanin Metabolism of Peach Skin during Postharvest Storage

The objective of this work was to study the effects of different light treatments on the color development of peach skin during postharvest storage and to explore the regulatory mechanism of light on anthocyanin metabolism. Peach fruits, cv. Zhongtao 9, were subjected to different lights (red, green, blue and white) for 12 h and darkness for another 12 h at (22 ± 1) ℃, while those kept in darkness for 24 h were considered as a control. The variations in fruit skin color, anthocyanin content and enzymatic activities involved in the anthocyanin metabolic pathway, as well as the expression levels of the structural genes of anthocyanin biosynthesis and related transcription factors after light treatment were measured. The results showed that the color development of peach skin was not affected by red and green light, but was weakly promoted by white light and significantly induced by blue light. The anthocyanin content in blue light-treated peach skin was 27.26 mg/kg, which was 4.48 and 10.34 times as high as that in the white light treatment and control groups on the sixth day after harvest, respectively. Under blue light treatment, the enzymatic activities of the anthocyanin biosynthesis pathway and the expression levels of structural genes and transcription factors were significantly higher than those in the control and other light treatment groups at most of the time points tested (P < 0.05). The expression levels of the structural genes PAL, CHS, F3H, DFR, ANS and UFGT and the transcription factor MYB10.1 showed significantly positive correlation with the color parameters and anthocyanin content of peach skin. Collectively, this study indicated that blue light treatment promoted the synthesis and accumulation of anthocyanins in peach skin by up-regulating the anthocyanin synthesis pathway, which will deepen the understanding of the regulatory mechanism of anthocyanin metabolism by light in plants and provide a theoretical basis for the development of postharvest technologies to improve peach skin color.