Phenotypic traits diversity analysis of some Chinese bayberry germplasm resources

【Objective】Chinese bayberry (Myrica rubra Sieb. et Zucc.) is a subtropical evergreen fruit tree of the Myrica genus in Myricaceae family , bearing delicious, berry-like fruits. The fruit ripens in June and early July in the main production areas of China (i.e., Zhejiang and Jiangsu provinces), and its colors and appealing flavor are very attractive to the domestic and foreign consumers. The genus Myrica Linn. contains more than 50 species, of which six are found in China, including M. rubra, M. esculenta, M. nana, M. adenophora, M. integrifolia and M. arboresceus, respectively. According to relevant survey statistics, there are more than 300 Chinese bayberry cultivars in China. Diversity analysis of the phenotypic characters is a basic method for the evaluation of germplasm resources. However, there have been few reports on the identification of phenotypic traits of Chinese bayberry. In this study, the phenotypic traits diversity of 95 Chinese bayberry germplasm resources were analyzed in order to provide theoretical foundation for breeding and further utilization of the different bayberry resources. 【Methods】In current study, 95 accessions of the Chinese bayberry germplasm resources were uesd as test materials, among them, 93 belongs to M. rubra, one to M. esculenta and one to M. nana × M. rubrahybrid. A total of 44 phenotypic traits (i.e., 20 descriptive indexes and 24 quantitative indexes) were investigated. The descriptive indexes including the fruit, stone, leaf and inflorescence traits were recorded by description and observation method. The quantitative indexes including the fruit, stone, leaf and inflorescence traits were analyzed by correlation analysis, cluster analysis and principal component analysis. The correlation analysis and principal component analysis were analyzed using SPSS26.0 software, while the cluster analysis was performed using MEGA X software.【Results】The genetic variation in phenotypic traits of 95 accessions of the Chinese bayberry germplasms was abundant. The ShannonWiener index H and Simpson index D of the 20 descriptive traits ranged from 0.512 5 to 1.515 3 and 0.271 9 to 0.766 0, respectively. The higher diversity indexes were observed in the fruit color (H: 1.447 7, D: 0.728 8), stone fur color (H: 1.224 0, D: 0.662 2), and stone color (H: 1.515 3, D: 0.766 0), indicating relatively rich genetic diversity in these traits. The mean value of variation coefficient of the 24 quantitative traits was 19.03%, and the highest variation coefficient was observed in the fruit color index b* value (63.99%). The correlation analysis between quantitative traits showed that 72 pairs of correlation coefficients were extremely significant (p＜0.01), and 23 pairs of correlation coefficients were significant (p＜0.05). The principal component analysis indicated that the cumulative contribution rate of the 8 main principal components was 81.827%, which mainly reflected factors of the fruit size, fruit color, fruit sugar content and acid content. The germplasms were divided into five main groups by the cluster analysis at the Euclidean distance of 20. The Group Ⅰ contained only 1 germplasm, namely Maoyangmei, which had the smallest single fruit weight, the smallest fruit vertical diameter, the lowest soluble solids content, the smallest solid- acid ratio and the thinnest leaf thickness among 95 germplasms, suggesting it could be used as a special germplasm resource. The Group Ⅱ included 4 germplasms, which mainly charactered by the large fruit shape and fruit weight. The Group Ⅲ contained 3 germplasms. The Group Ⅳ had 8 germplasms, which was mainly characterized by the white bayberry germplasms. The Group Ⅴ included 79 germplasms.【Conclusion】The 95 accessions of the Chinese bayberry germplasm resources were rich in genetic variation and high in diversity of phenotypic traits. The single fruit weight, fruit appearance color index, sugar content and acid content could be used as most important indicators for comprehensive evaluation of Chinese bayberry quality. The 95 accessions of the Chinese bayberry germplasm resources could be divided into 5 groups, among them, the group Ⅱ could be used for breeding larger fruit and higher quality variety, and the group Ⅳ could be used for breeding white bayberry variety.