Effects of Developmental Stages, Light, and an Auxin Polar Transport Inhibitor on the Skin and Flesh Pigmentation of Red-fleshed Peach Fruit

A red-fleshed peach (Prunus persica L. Batsch ‘Tenshin Suimitsuto’; ‘Tianjinshuimi’ in Chinese) was used to study the mechanisms of skin and flesh pigmentation. Anthocyanin accumulation was detected at the pre-endocarp-hardening and maturation stages in skin, while it appeared from maturation stage in flesh. The flesh at harvest stage contained approximately 1.1 mg·g−1 FW of anthocyanin. In contrast, flavonoid and phenolic compounds were found in all stages. The final phenolics concentration was 1.6 mg·g−1 FW. To study the effects of light, fruits were on-tree bagged in double-layered paper bags. The total anthocyanin content in the skin was significantly lowered by bagging, but not in the flesh. This suggested that flesh tissue pigmentation was less sensitive to light intensity than that of skin tissue, and thus, anthocyanin accumulation in flesh occurred even under low light conditions. Dark treatments, such as triple-layered paper bagging, significantly reduced anthocyanin and phenolic concentrations in the skin and flesh. A combined treatment of darkness and an auxin polar transport inhibitor, 2,3,5-triiodobenzoic acid (TIBA), had no effect on anthocyanin concentration in skin and flesh. However, total flavonoids in the skin was increased by TIBA treatments under darkness. Factors affecting anthocyanin accumulation in the flesh tissue are discussed.