GENETIC-PARAMETERS AND GAINS EXPECTED FROM SELECTION FOR DRY-WEIGHT IN EUCALYPTUS-GLOBULUS SSP GLOBULUS IN PORTUGAL

Genetic and phenotypic parameters of growth and wood density were calculated for two open-pollinated progeny trials of Tasmanian Blue Gum (Eucalyptus globulus ssp. globulus) in Portugal. These parameters are used to develop selection indices and predict genetic responses for different strategies. Mean individual heritabilities (averaged across the two trials) of height and wood density were high (h2 = 0.34 +/- 0.10 and 0.65 +/- 0.12, respectively) and those of sectional area and dry weight were intermediate (h2 = 0.18 +/- 0.06 and 0.21 +/- 0.11). Mean genetic correlations (across trials) were strongly positive (0.94 +/- 0.05 to 0.99 +/- 0.03) between dry weight and height or sectional area, and moderate (0.17 +/- 0.20) between dry weight and wood density. Sectional area and height were slightly negatively correlated (-0.08 +/- 0.25 to -0.09 +/- 0.17) with density. Selection indices constructed to maximize genetic gain in dry weight gave results which clearly favored indirect selection on height. A genetic gain of around 47% in dry weight may be expected from second-generation selection of 1 tree in 200 for E. globulus in Portugal. Marginal deterioration can occur in wood density unless family means for either dry weight or density are included in the index with height. A strong response in wood density from index selection requires a substantial sacrifice of gains in dry weight.