Genetic analysis of Eucalyptus globulus diameter, straightness, branch size, and forking in Western Australia

Eucalyptus globulus Labill. is increasingly considered for supply of solid-wood products such as sawlogs, yet genetic studies of solid-wood traits have been lacking. We estimated genetic parameters of growth and form traits that affect log value in full-sib families from two advanced-generation breeding populations on eight sites in Western Australia. Mean single-site heritability was 0.11 +/- 0.01 for diameter at breast height (DBH), 0.28 +/- 0.05 for stem straightness, 0.09 +/- 0.02 for branch thickness, and 0.05 +/- 0.02 for forking incidence. Dominance effects were significant (p < 0.05) at four sites for DBH and branch thickness and at three sites (one population) for straightness. Mean intersite additive genetic correlations were 0.76 +/- 0.06 for DBH (n = 7), 0.75 +/- 0.11 for stem straightness (n = 7), and 0.58 +/- 0.07 for branch thickness (n = 4). Mean intersite dominance genetic correlations were 0.90 +/- 0.04 for DBH (n = 7), 0.26 +/- 0.27 (n = 4) for straightness, and 0.68 +/- 0.11 for branch thickness (n = 3). Additive genetic correlations between DBH and straightness ranged from 0.71 +/- 0.23 to 0.33 +/- 0.19 with an average of -0.18 +/- 0.12 (n = 8). Genetic correlations between DBH and branch thickness were mostly weak although straightness was generally associated with thinner branches (mean additive correlation 0.44 +/- 0.15, n = 6). We conclude that prospects appear favourable for improving the solid-wood value of E. globulus by selection and breeding.