Age trends in genetic parameters for growth and quality traits in Abies alba

Genetic parameters for growth, stem straightness, survival, wood density and percentage of late wood were estimated in a progeny test of European silver fir (Abies alba Mill.) established in Romania in 1980. The experiment was conducted on 95 families collected from 10 natural stands and five provenance regions, and trait measurements were taken 6-34 years after planting. The family effect was highly significant for 14 traits and significant for one trait. The additive genetic variance increased with age for all the studied traits, and family heritability was higher than individual heritability. Stem diameter, volume per tree, wood density and late wood were the traits with the highest heritability. The trend of individual and half-sib family heritability estimates decreased between 6 and 15 years of age for height and between 6 and 10 years for diameter, while both height and diameter heritabilities were stable at older ages. High age-age genetic correlations were observed, though genetic correlations between growth and wood density were weak. Selection at age 6-10 could increase genetic gain in volume in mature silver fir trees. Selection based on family breeding values combined with within-family selection is recommended to maximize genetic gain in breeding activities in silver fir.