Clonal variation and selection for growth and branch traits in young Tectona grandis plantations

Objective This study aims to investigate the genetic variation and correlation of the growth and branch traits of teak clones, and to comprehensively evaluate and select teak clones with rapid growth and excellent branch types.

Method We investigated the growth and branch traits of 19 teak clones at 5-year old located in the Pingxiang City of Guangxi, and conducted repeatability estimation and phenotype correlation analysis. The comprehensive score of each clone was calculated through principal component analysis.

Result There were significant differences (P<0.001) in tree height (H), diameter at breast height (DBH), and individual volume (V) among the teak clones, with coefficients of variation ranging from 28.2% to 38.8%, and repeatability ranging from 0.821 to 0.863. There were significant differences (P<0.001) in average branch angle (Ang), branch base diameter (BD), and branch length (BL) among different clones, with coefficients of variation ranging from 16.3% to 57.9%, and repeatablity ranging from 0.497 to 0.817. There were significant correlations (P<0.01 or P<0.05) between growth and branch traits. Using the principal component scores and a selection rate of 15%, three excellent teak clones (7765, 6601, 7703) were selected, with their comprehensive scores exceeding the control. Their average values for H, DBH and V were 5.68 m, 6.20 cm and 11.52 dm³ respectively, representing increases of 10.65%, 15.39% and 31.51% compared to the corresponding averages. After selection, the real gains in H, DBH and V were 9.07%, 10.69% and 30.20% respectively.

Conclusion The growth and branch traits of 5-year-old teak clones exhibit rich genetic variation and high potential for improvement. The growth and branch traits are moderately to strongly controlled by genetic factors. Through comprehensive evaluation of the 5-year-old teak clones, three teak clones with rapid growth and excellent branch characteristics were selected. These clones can serve as high-quality genetic materials for teak clones and can be promoted in the southwest region of Guangxi.