Marker-based pedigree reconstruction reveals limited diversity within commercial Eucalyptus benthamii breeding populations in Brazil

Eucalyptus benthamii is an economically important but increasingly endangered tree species in its natural range in Australia. Recent germplasm introductions from natural stands used to develop breeding populations might thus represent relevant repositories of diversity for reforestation purposes. We used microsatellite markers to reconstruct the pedigrees and estimate diversity parameters for breeding populations of two Brazilian forest-based companies. The analysis, together with evidence from historical germplasm export data from the Australian Tree Seed Centre, revealed that genetic diversity within the two breeding populations is modest. Status number, i.e., the effective number of unrelated individuals in the two breeding populations, was estimated to be in the range 8.5 – 22.0 per population based on marker-based co-ancestry estimates. This is likely a result of the narrow genetic base of the initial introductions and subsequent directional selection and breeding. As further selection and breeding will likely lower the status number, genetic infusion of new, unrelated selections will be required to manage the breeding programme in the future.