Objective Young elite families of Cornus hongkongensis were tested, in order to reveal the genetic variation of the growth and form-quality traits of C. hongkongensis families from different seed sources, and provide a theoretical basis for the exploration and utilization of C. hongkongensis germplasm resources.

Method 3-year-old C. hongkongensis elite families from different seed sources were used to study the genetic variation of growth and form-quality traits among the seed sources and the families from the same seed source. In addition, the correlation between traits was studied, the principal component analysis and cluster analysis were performed based on 9 traits. The experimental forest was established in 2016 at Longquan of Zhejiang Province.

Result Significant differences were observed in traits of C. hongkongensis families among the seed sources and the families from the same seed source. Among them, the traits with the largest and smallest coefficient of variation were maxi-branch length (38.78%) and tree height (21.53%), respectively. The variation coefficient of growth traits range was between 21.53% and 26.66%, and the variation coefficient of growth traits was generally lower than that of form-quality traits. The variation of traits within the families from the same seed source (26.61%) was greater than the variation among seed sources (18.86%). The C. hongkongensis family with higher height, larger basal diameter and crown width had more branches and thicker branches. The more branches, the larger the branching angle and the smaller the crown width, the higher the straightness of the trunk. The 9 traits were integrated into 3 principal components, and their cumulative contribution rate could reach 82.636%. Tree height, maxi-branch length and stem straightness were the main distinguishing traits of growth and form-quality traits respectively. The 92 C. hongkongensis families tested were grouped into two categories. Type Ⅰ includes 56 families, which from 6 seed sources, i.e. Guangfeng of Jiangxi, Shangyou of Jiangxi, Longnan of Jiangxi, Datian of Fujian, Wuping of Fujian and Xingshan of Hubei. Type Ⅱ includes 36 families, which from 5 seed sources, i.e. Longquan of Zhejiang, Nanyue of Hu’nan, Yuanzhou of Jiangxi, Fenyi of Jiangxi and Yanping of Fujian.

Conclusion There are significant variation of the traits of C. hongkongensis among the seed sources and families from same seed sources. Tree height, crown width and maxi-branch length, stem straightness, etc., are the major variation factors. Fast-growing families have the characteristics of more branches and thicker branches. The families tested are divided into two categories. The families included in Type Ⅰ are most from the seed sources in the southern geographically, with the main characteristics of tall form, compact plant-type, thick branches and fast-growing. The families included in Type Ⅱ are most from the seed sources in the northern geographically, with the main characteristics of spreading branches, high straightness of stem and slow-growing.