Genetics of wood stiffness and its component traits in Pinus radiata

The potential for breeding Pinus radiata D. Don to improve wood stiffness (modulus of elasticity, MoE) was examined by obtaining pith-to-bark cores from trees at breast height in two independent genetic trials. The effectiveness of early selection for stiffness and indirect selection on the component traits, microfibril angle (MfA) and wood density, was determined as well as the age-related changes in the genetic variation of these traits. The first trial comprised 50 open-pollinated families in the central North Island, New Zealand. The second trial comprised 20 control-pollinated families in New South Wales, Australia. The genetic control of MfA, density, and MoE was found to be high in the corewood and moderate in the outerwood. Estimated genetic correlations suggested that early selection for most traits would be successful but could be carried out slightly earlier at the New Zealand site than at the Australian site. To maximize gain in the corewood, selection for MoE and MfA would be most effective around rings 4-8. There were no adverse correlations between MoE and MfA or density, implying that selection for MoE would also improve MfA and density.