OPTIMUM AGE FOR SELECTION IN PINUS-RADIATA USING BASAL AREA UNDER BARK FOR AGE-AGE CORRELATIONS

Age-related changes in the inheritance of stem diameter in radiata pin e were studied using discs cut at 1.3 m above ground in trees from a p rogeny test. Measurements of cross-sectional area enclosed within annu al growth rings yielded annual estimates of basal area. The progeny te st was a diallel cross which enabled estimation of genetic parameters such as heritability and genetic correlations between measurements at different ages. The greatest gain per generation would have been obtai ned through selection at age 14, but gain per year was greatest at age 10. Additive genetic variance generally increased with time, but non- additive variance was a maximum at age 4, declining to negligible leve ls by age 9. Age-age correlations generally improved the closer the 2 ages involved were. However, these correlations were not linearly rela ted to the logarithm of the age ratio.