Broad- and narrow-sense heritabilities in a South African cloned open-pollinated Eucalyptus grandis breeding population

Genetic variances and heritabilities of a 66-month old cloned Eucalyptus grandis breeding population of families, derived from open-pollinated selections, were estimated. The genetic variance for the growth traits was largely additive genetic variance, whereas the proportion of non-additive genetic variance was notably higher for stem form and disease tolerance. A notably larger proportion of non-additive variance was observed for the growth traits and stem form among the F2 families. This is probably due to the reduction in additive variance through selection for general combining ability for these traits in the previous generations. No selection for disease took place in earlier generations and the proportion of non-additive genetic variance for this trait remains approximately the same for families of different generations.Southern Hemisphere Forestry Journal 2007, 69(2): 81–9