Genetic Parameters of Wood, Fibre, Stem Quality and Growth Traits in a Clone Test with Betula pendula

Genetic parameters of wood, fibre, stem quality and growth traits were estimated for an 11-yr-old birch (Betula pendula Roth) clone test in southern Sweden. Growth, wood and fibre properties were found to be under strong genetic control, with broad sense heritabilities varying between 0.43 and 0.73. Heritabilities for stem traits were low, except for number of branches. The genotypic coefficients of variation of the wood and fibre properties were quite low (3.5-6.2%). There was a significant, negative genotypic correlation between diameter and wood density (r_G=−0.53). However, the reduction in density was very modest when diameter was used as the selection criterion. There was no benefit in using density as an extra selection trait together with volume when the objective was to maximize dry matter production. Multiple trait selection is proposed for optimization of growth and wood density. Genotypic correlations between growth rate and fibre traits were weak.