Abstract:

【Objective】 In order to understand the mechanism of coloring of red Chinese sand pears, the relationships between pigments biosynthesis and related enzymes activities as well as the contents of soluble sugars were studied in genetically different red Chinese sand pear cultivars. 【Method】 Two red Chinese sand pear cultivars ‘Meirensu’ and ‘Yunhongli No.1’ were used to investigate the changes in the concentrations of anthocyanin, chlorophyll, carotenoid, flavonoid, total phenolics, and the activities of PAL and UFGT in fruit peel as well as the contents of soluble sugars in fruit flesh during the period of fruit development. The total anthocyanin was estimated by a pH differential method. The concentrations of chlorophyll, carotenoid, flavonoid and total phenolics were determined by colorimetric assay. The activity of PAL was measured by a colorimetric assay, but the activity of UFGT was assayed by HPLC. The concentration and composition of soluble sugars were detected using HPLC. 【Result】 Although the trends of physiological changes were similar in two cultivars, the concentration of anthocyanin in ‘Yunhongli No.1’ was higher than in ‘Meirensu’ at the maturation stage of fruit. At the early stage of fruit development, the concentrations of chlorophyll, carotenoid, flavonoid and total phenolics all increased, but the concentration of anthocyanin was too small to detect. From the beginning of 13 weeks after anthesis, anthocyanin accumulated rapidly with degrading chlorophyll and reached the highest content when fruit harvested. The activities of PAL and UFGT were high when anthocyanin began to biosynthesize in fruit peel. With the accumulation of anthocyanin, the activity of PAL decreased, but the activity of UFGT remained at a high level later. During the fruit development, the content of total soluble sugars increased gradually and the accumulation of sucrose was in parallel with the increase of anthocyanin. 【Conclusion】 Fruit coloration in red Chinese sand pear is accompanied by fruit maturation. Chlorophyll degradation and anthocyanin accumulation made the fruit skin red. Anthocyanin biosynthesis might be induced by PAL, while anthocyanin accumulation is closely related to UFGT activity. Anthocyanin biosynthesis is determined primarily by genotypes and the potential of anthocyanin synthesis is higher in Yunhongli No. 1 than in Meirensu. The accumulation of anthocyanin is in parallel with the changes of total soluble sugar.

Key words: red Chinese sand pear, anthocyanin, coloring