Relationship between Pigment Composition and Peel Color for the Fruit of Chinese Flame Tree

Abstract

Chinese flame tree (Koelreuteria bipinnata var. integrifoliola), a common ornamental tree in southern China, exhibits a variety of fruit colors among individual plants within the same cultivated field. In this study, 44 plants with different fruit colors were selected to investigate the impact of pigment composition on the coloration of fruit peels. The plants were divided into three groups based on the color phenotype of the fruit peel: red, pink, and green. The values of lightness (L*) were negatively correlated with redness (a*) and positively correlated with yellowness (b*). The correlations of chroma (C*) with the other color parameters differed among the three groups. In the pooled pink and red groups, C* was negatively correlated with both L* and b* and positively correlated with a*, whereas the opposite relationships were found in the green group. According to the pigment analysis, anthocyanins, chlorophylls, and carotenoids were detected in the fruit peels. Anthocyanins were found to be the main pigment responsible for the differences in fruit color among the various groups. The highest anthocyanin content of fruit peel was found in the red group, followed by the pink group; the lowest anthocyanin levels appeared in the green group. The major anthocyanin component in the fruit peels was identified as cyanidin 3-O-rutinoside. By classifying fruit peel color and determining pigment composition, this study provides a theoretical basis for further researching genetic control and regulation of anthocyanin biosynthesis genes on pigment accumulation and peel coloration of chinese flame tree.