GENETIC GAIN FROM BREEDING <em>ACACIA</em> <em>AURICULIFORMIS</em> IN VIETNAM

Abstract

Hai, P. H., Harwood, C., Kha, L. D., Pinyopusarerk, K. & Th inh, H. H. 2008. Genetic gain from breeding Acacia auriculiformis in Vietnam. Seedlots of Acacia auriculiformis collected from a seedling seed orchard (SSO) and an unpedigreed seed production area (SPA) in northern and central Vietnam were compared with a natural-provenance control and a commercial seedlot from Vietnam. Trials were established on lowland sites in central, north-central and northern Vietnam. Four years after planting, overall survival was good to excellent (83–91%). The SSO and SPA seedlots exhibited significantly (p < 0.001) greater height, diameter at breast height (dbh) and stem volume per hectare than the natural provenance controls, which in turn significantly outperformed the local commercial seed source. Conical stem volume in m³ ha^-1 at age four years averaged across the three trials was 27.7 for a select SSO seedlot, 23.0 for a select SPA seedlot, 22.3 for a routine SSO seedlot, 19.2 for the natural provenance control and 12.1 for the commercial seedlot. The SSO and SPA seedlots had significantly (p < 0.001) straighter stems and reduced incidence of stem forking than the natural provenance control, which was in turn superior to the commercial seedlot. Relative performance of the seedlots at the three trial sites was very similar, indicating seedlot-by-environment interaction was of no practical significance. Selected clones of A. auriculiformis included in one trial ranked second in height and diameter growth to the select SSO seedlot and displayed the best stem straightness and axis persistence. The increased dbh values of the SSO and SPA seedlots relative to the natural provenance control were consistent with predictions based on genetic parameters derived from the SSO and selection intensities.