Genetic limitations in the exploitation of base populations of Eucalyptus globulus ssp. globulus

Large base population collections of Eucalypus globulus ssp. globulus from native stands in Australia are currently being exploited for breeding in many countries. Constraints to the accurate estimation of genetic parameters and prediction of breeding values from these OP (open-pollinated) progenies are addressed. E. globulus ssp. globules exhibits marked inbreeding depression for growth and the relative level of non-additive genetic variance appears high. Narrow-sense heritabilities for two-year growth estimated from OPs are highly inflated compared to controlled cross estimates from the same base parents. The correspondence between parental breeding value predictions for two-year growth from outcrossed versus OP progeny was poor. Site by genotype interactions also appear to be underestimated from OP progenies. possibly due to confounding environmentally sensitive, additive gene effects ('soft' effects) with the deleterious effects of inbreeding and non-additive genetic effects which are expressed relatively independent of the environment ('hard' effects).