Genetic control of traits influencing sawn timber properties of plantation-grown Eucalyptus urophylla

Background: Eucalyptus urophylla S.T.Blake is a major plantation species in tropical and subtropical regions, mainly grown for pulpwood. Increasing interest in solid wood applications has highlighted the need to improve wood properties through genetic selection. Methods: A subset of 200 trees representing 50 open-pollinated families from three seed sources in an eight-year-old progeny trial in northern Vietnam was sampled. Wood basic density, tangential, radial and longitudinal shrinkage, coefficient of anisotropy, and log end-splitting index (LESI) were assessed. Results: Wood basic density showed high heritability (h² = 0.90 ± 0.24). Tangential and radial shrinkage exhibited moderate heritability estimates (0.43 ± 0.22 and 0.34 ± 0.21, respectively), while longitudinal shrinkage showed no genetic variation. The coefficient of anisotropy and LESI also showed moderate heritability estimates (0.32 ± 0.21 and 0.31 ± 0.21). Genetic correlations between growth and wood traits were weak and non-significant, but a strong negative genetic correlation was observed between wood density and coefficient of anisotropy (–0.89 ± 0.37). Conclusions: Substantial additive genetic variation exists for key wood properties in E. urophylla, indicating good potential for genetic improvement. Selection for higher wood density is expected to reduce anisotropy without compromising growth. These results support the integration of wood quality traits into breeding objectives to enhance solid wood recovery from plantation-grown E. urophylla.