Age-age correlations for tracheid length and wood density in Pinus sylvestris

The existence of strong genetic correlations between traits at an early age and at an adult age should shorten the generation turnover of tree breedin g populations and render forest tree breeding more effective. Genetic age-a ge correlations for tracheid length and wood density were estimated in Scot s pine (Pinus sylvestris L.) and the efficiency of early selection for thes e traits was evaluated. Increment cores of 10-mm diameter were collected fr om trees of 106 full-sib families in a progeny trial located in southeaster n Sweden and consisting of controlled matings between 30 parent trees. The additive genetic age-age correlations were consistently close to unity for all traits and ages studied. The additive genetic variance differed signifi cantly from zero for all traits. The dominance variance was zero for trache id length and small and insignificant for wood density. The heritabilities varied between 0.3 and 0.5. The genetic gain per year for both tracheid len gth and wood density was largest if selection was carried out at tree age 1 1, the lowest age studied, indicating that early tests for these traits wil l be efficient.