Age trends of heritabilities and genotype-by-environment interactions for growth traits and wood density from clonal trials of Eucalyptus grandis HILL ex MAIDEN

Obtaining accurate and precise genetic parameter estimates is fundamental to determining breeding strategies, and for choosing genotypes for commercial propagation. Results for survival and growth from seven clonal genetic tests of Eucalyptus grandis in Colombia supported the a priori contention of sub-dividing them into three different environments for deployment and possibly breeding purposes. The genotype-by-environment interactions (GxE) for growth traits were moderate at six years of age in the target environment (5 sites representative of 95% of the E. grandis planting area for the clonal program). Therefore, it is recommended to breed and select for clones that perform well across the range of sites within the target environment. The clonal rankings for growth traits at the two extreme sites differed markedly between these two distinct environments, and between each extreme environment and the five sites in the target environment. Thus, the extreme environments require separate clonal test locations and deployment populations. Broad sense heritabilities for survival, individual tree volume and mean annual increment (MAI) tended to increase over time for the three environments, but the trends for height were quite different among environments. The broad sense heritabilities for mean wood density declined with age, but GxE interaction for wood density was low indicating that clonal rankings were stable among the five sites within the target environment. The estimation of genetic gains by two methods, predicted clonal values and the classical formula, gave similar results and showed great potential for increasing productivity in the target environment through selection of the top clones.