Index selection for growth and construction wood properties in Pinus elliottii open-pollinated families in southern China

The initial introduction of Pinus elliottii (PEE) to China occurred in the 1930s, and the planting of this conifer species has now attained close to 3 million ha in the subtropical zone of southern China. A large-scale genetic improvement program for PEE was implemented in southern China to produce fast-growing trees with high wood quality to address the severe shortage of timber production over the last two decades. In this paper, selection for stem volume, basic wood density (DEN) and modulus of elasticity (MOE) was based on the Smith–Hazel index, and a total of approximately 2 000 individual trees from 158 PEE open-pollinated families were selected at 22 years of age. The DEN and MOE for each tree were determined by non-destructive evaluation techniques using the Pilodyn and Hitman Director ST300® acoustic velocity device. The heritabilities and genetic and phenotypic correlations for the traits that were measured were estimated using the residual maximum likelihood approach in the flexible mixed modelling program ASReml-R. The results showed that the heritability estimates for the wood properties were between 0.292 and 0.309, and the heritabilities of the growth traits ranged from 0.129 to 0.216. The genetic correlation between the DEN_P and acoustic velocity (V?) with MOE_P was 0.45 and 0.95, respectively. An indirect selection based on V was observed to be highly effective for determination of MOE. It indicated that V can be integrated into tree improvement programs as a useful index of MOE by ranking candidate families or individuals within the selection population. The genetic correlations between the growth traits and wood properties were not significant. By contrast, the phenotypic correlations between them were significantly positive, but the correlation coefficients were very low. The appropriate selection index (I₄), which placed 10 times as much weight on DEN and MOE as the equal emphsis method, was determined as the appropriate selection index.