Genetic variation and parental performance under inbreeding for growth in Eucalyptus globulus

We aimed to better understand the genetic architecture of growth in E. globulus undergoing inbreeding by comparing families from selfing (SELF), open pollination (OP) and unrelated polymix crossing (POL) of common parents. Stem diameter at breast height (DBH) was assessed at 4, 6 and 10 years after planting in a field trial. The OP heritability was overestimated at an early age relative to the POL heritability. No significant correlations were found between the SELF and POL parental effects, indicating substantial non-additive genetic variation under inbreeding. The OP family effects were better correlated with the SELF than the POL population, and only at age 10 years, after substantial mortality of inbred progeny has occurred, was the positive correlation between OP and POL families significantly different from zero. The estimated dominance variance arising from inbreeding was nearly 10-fold greater than the dominance variance associated with random mating and the additive variance, and appeared to be a major contributor to the variation in inbreeding depression amongst selfed families.