Genetic parameters of the physical and chemical wood properties of cool temperate eucalypts

This thesis comprises quantitative genetic studies of chemical and physical wood properties of the two main temperate plantation eucalypts in Australia, Eucalyptus globulus and E. nitens. The use of near-infrared spectroscopy models allowed the large-scale assessment of pulp yield and other wood chemical traits, including cellulose, lignin, extractives content, and lignin composition (syringyUguaiacyl ratio [S/G]), to compare with more readily assessed growth and density traits. The study of a fertiliser trial involving E. nitens clones showed that pulp yield was mainly affected by genetics. A large study was undertaken using a field trial of open-pollinated families collected from across the geographic range of E. globulus. This showed that wood properties were generally under medium to strong genetic control. There were significant differences between the geographic subraces of E. globulus, and narrow-sense heritability within subraces ranged from 0.15 to 0.51 across all traits, consistent with other studies of forest trees. A study of age trends in genetic parameters not only revealed the dynamic nature of heritability estimates but provided evidence of a changing genetic correlation between growth and density with age. Several discrepancies in the magnitude and direction of genetic correlations between traits were found compared to those reported in the literature, which were mostly smaller in sample size. Pulp yield increased with increasing latitude of provenance, suggesting that the economic worth of southern Tasmanian subraces for a lcraft pulpwood breeding objective had previously been underestimated. Pulp yield was shown to be highly positively correlated with cellulose and negatively correlated with lignin content. Lignin composition (S/G ratio) was highly positively correlated with pulp yield and also showed a clear latitudinal cline across the geographic range of E. globulus