The genetic architecture of a Eucalyptus globulus full-sib breeding population in Australia

Genetic parameters were estimated for diameter at breast height (DBH), height and core basic density(CBD) from ten second-generation control-pollinated Eucalyptus globulus progeny trials in Australia.Using multi-site analysis we aimed, firstly, to determine a suitable linear model to fit to the data and,secondly, to determine the relative importance of additive and non-additive genetic effects. A model withheterogeneous additive and error variances was used for all traits. The individual site heritabilitiesaveraged 0.12 for DBH, 0.11 for height and 0.44 for CBD. Over all sites, the ratios of SCA (specificcombining ability) and subrace to additive genetic variance for DBH (0.25 and 0.5) and height (0.30 and0.25) were significantly greater than zero, but not for CBD (0.08 and 1.00). Inter-site additive geneticcorrelations were 0.71 for DBH, 0.72 for height and 1.07 for CBD, and all were not significantly differentfrom 1. This study suggests that, for early growth, levels of dominance are comparable to additive geneticeffects in this breeding population and there are significant genetic differences between subraces. Incontrast, for CBD most genetic variation was additive and significant differences between subraces couldnot be detected with the small sample.