Genetic relationships between wood quality traits and diameter growth of juvenile core wood in Sitka spruce

The trend towards shorter rotations in planted conifer stands has resulted in a reduction in the proportion of mature wood relative to juvenile core wood, raising concerns that the mechanical performance of sawn battens will be affected. The potential to improve the wood quality of the juvenile core of Sitka spruce (Picea sitchensis (Bong.) Carr.) without compromising growth rate was investigated. Rapid and inexpensive indirect methods of assessing wood properties on standing trees using a Pilodyn gun and acoustic velocity were compared with direct measurement made on wood samples cut from the juvenile core. Strong genetic correlations were observed between Pilodyn gun values and direct measures of density (-0.76), and between acoustic velocity and direct measure of MOE (0.73). The genetic correlation between the square of acoustic velocity and microfibril angle was also strong (-0.84). These results suggest that indirect assessments of wood properties within the juvenile core wood are sufficiently reliable for these techniques to be used in the Sitka spruce breeding programme. Although a strong negative genetic correlation between DBH (diameter at 1.3 m from the tree base) and density was noted (-0.79), there is sufficient variation within the breeding population to select specific families with both good growth rate and high modulus of elasticy wood.