Genetic parameters for growth and wood mechanical properties in Eucalyptus cloeziana F. Muell.

Genetic parameters for wood mechanical properties and their correlations with growth traits are not well established in the important tree genus Eucalyptus L'H,r. Based on a progeny trial of 115 open-pollinated families of Eucalyptus cloeziana F. Muell., this study estimated the heritability and trait-trait correlations for growth, including height (H), diameter at breast height (D) and volume (V), and wood mechanical traits, including basic density (BD), green density (GD), modulus of elasticity (MOE), modulus of rupture (MOR) and parallel-to-grain compressive strength (sigma c). Narrow-sense heritability (h (i) (2) ) ranged from 0.04 to 0.35 for growth across ages 0.5-9.5 years and from 0.06 to 0.24 for wood mechanical properties at age 9.5, indicating low to moderate magnitude of additive genetic control of these traits. Phenotypic (r (p) ) and additive genetic (r (g) ) correlations at the final age of 9.5 years were consistently significantly positive between growth traits and mostly significantly positive between wood mechanical traits, while r (p) and r (g) were small and adversely significant, respectively, between the two types of traits, posing a challenge for concomitant improvement of growth and wood traits. In addition, r (p) and r (g) coefficients between age 9.5 and earlier years for each of the growth traits H, D and V were all positively significant (except for H (2.5)) and had a generally increasing trend with age, suggesting the possibility of early selection.