Bridging the genetic and genotypic gain gap for Eucalyptus: the critical role of inbreeding and dominance effects in breeding strategies

Understanding the mating system of Eucalyptus species is necessary to accurately estimate genetic parameters and improve breeding programs. Eucalyptus species often exhibit mixed mating systems, leading to complex relationships among progenies. Traditional tree breeding programs that assume a half-sibling relationship for open-pollinated (OP) trials may overestimate genetic gains by neglecting the effects of inbreeding and dominance. This study focuses on Eucalyptus pellita, a species with a mixed mating system, to quantify the impact of selfing and dominance on breeding strategies. We simulated OP trial growth data for 100 randomly selected families in a randomized complete block design, using published data for diameter at breast height (DBH). Our analysis indicated that marker-based models, particularly those incorporating dominance effects, provide more accurate genetic parameter estimates and higher predicted genetic gains than pedigree-based models. Furthermore, we identified significant genetic and genotypic gain gaps when traditional models were used, underscoring the need to consider non-additive genetic effects in breeding programs. These findings highlight the importance of using marker-based approaches to enhance genetic improvement and achieve sustainable forestry.