Inbreeding Depression in Two Field Trials of Young Pinus sylvestris (L.)

Inbreeding depression after selfing was estimated in two field trials of Pinus sylvestris, age 11 and 14 years, respectively, by comparing stem volume and height after selfing and outcrossing. For the majority of trees, inbreeding caused a statistically significant reduction in stem volume. The average inbreeding depression for stem volume was 46% and 66% for the two trials, respectively, with a large variation among trees. For one of the trials, the inbreeding depression for height remained at a constant level between age 6 to 14 years, while the inbreeding depression increased between age 6 to 11 years for the other trial. Inbreeding depression was not found to be correlated with the GCA for stem volume of the individual trees. The relative phenotypic within-family variance was found to be higher in progenies after selfing as compared to outcrossing.