Eighty six full-sib Corymbia F 1 hybrid families (crosses between C. torelliana and four spotted gum taxa: C. citriodora subsp. variegata, C. citriodora subsp. citriodora, C. henryi and C. maculata), were planted in six trials across six disparate sites in south-eastern Queensland to evaluate their productivity and determine their potential utility for plantation forestry. In each trial, the best-growing 20 % of hybrid families grew significantly faster (P = 0.05) than open-pollinated seedlots of the parent species Corymbia citriodora subsp. variegata, ranging from 107 % to 181% and 127 % to 287 % of the height and diameter respectively. Relative performance of hybrid families growing on more than one site displayed consistency in ranking for growth across sites and analysis showed low genotype-by-environment interaction.Heritability estimates based on female and male parents across two sites at age six years for height and diameter at breast height, were high (0.62 ± 0.28 to 0.64 ± 0.35 and 0.31 ± 0.21 to 0.69 ± 0.37 respectively), and low to moderate (0.03 ± 0.04 to 0.33 ± 0.22) for stem straightness, branch size, incidence of ramicorns, and frost and disease resistance traits at ages one to three years. The proportion of dominance variance for height and diameter had reduced to zero by age six years.Based on these promising results, further breeding and pilot-scale family forestry and clonal forestry deployment is being undertaken. These results have also provided insights regarding the choice of a future hybrid breeding strategy.

The fungal pathogen Quambalaria pitereka can cause significant damage to spotted gum (Corymbia sp.) plantations in Australia. A series of seven progeny trials, involving seed from a range-wide collection from 527 individuals within 25 native populations of Corymbia citriodora sub-species variegata, were assessed for height growth and damage from Quambalaria around 1 year after planting. Infection at this young age has been found to detrimentally impact growth, form, and wood quality for many years. Genetic variance was found to be significant at both the provenance and family level. However, selection of families within provenances should lead to greater levels of genetic gain than what can be realized from selecting among provenances as estimates of additive genetic variance were consistently greater than estimates of variance among populations. Strong relationships between height and Quambalaria shoot blight (QSB) damage assessments in these trials were evidenced by very high genetic correlations between the traits; therefore, selection for any of these traits could be used to identify more productive and QSB-tolerant populations. While both provenances and families were found to interact with the trial environments at a similar level across traits, genetic correlations indicated that rankings for growth were be less stable than rankings for QSB tolerance across environments. Genetic parameter estimates derived from general and generalized linear models were very similar and either analytical method could be used to evaluate fungal damage.

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10Evaluation of a series of spotted gum (Corymbia citirodora) progeny trials, 11 established in the subtropical region of Queensland, Australia, was undertaken to 12 provide information for the development of advanced generation breeding 13 populations suitable for pulp production. Measurements of growth at two ages were 14 combined with assessments of wood density and pulp yield from a selected sample 15 of provenances to provide comparisons between provenances, to generate genetic 16 parameter estimates and to predict genetic gain potential. While growth at this age 17 was moderate relative to other eucalypts the near infrared predictions of average 18 wood density of 756 kg/m 3 and pulp yield of 55% indicate the species has 19 considerable potential as a pulpwood crop. A pulp productivity breeding objective 20 was used to identify production populations using a range of selection trait 21 weightings to determine potential genetic gain for pulp productivity. Genetic 22 parameters indicated: 1) levels of genetic control were moderate for all traits and 23 higher for wood property traits, 2) genetic improvements could be achieved by 24 selection among and within provenances with greater levels of improvement 25 available from selection within populations, 3) genotype by environment interactions 26 were negligible, 4) genetic correlations between traits were favourable, and 5) 27 selection of volume production alone would maximise improvements in pulp 28 productivity. 29

& Key message Eucalyptus pellita demonstrated good growth and wood quality traits in this study, with young plantation grown timber being suitable for both solid and pulp wood products. All traits examined were under moderate levels of genetic control with little genotype by environment interaction when grown on two contrasting sites in Vietnam. & Context Eucalyptus pellita currently has a significant role in reforestation in the tropics. Research to support expanded of use of this species is needed: particularly, research to better understand the genetic control of key traits will facilitate the development of genetically improved planting stock. & Aims This study aimed to provide estimates of the heritability of diameter at breast height over bark, wood basic density, Kraft pulp yield, modulus of elasticity and microfibril angle, and the genetic correlations among these traits, and understand the importance of genotype by environment interactions in Vietnam. & Methods Data for diameter and wood properties were collected from two 10-year-old, open-pollinated progeny trials of Handling Editor: Jean-Michel Leban Contributions by co-authors Tran Duy Hung: conception and design of project (50 %), statistical analysis (80 %), wrote the paper (60 %). Jeremy Brawner, Mark Dieters: conception and design of project (50 %), statistical analysis (20 %), wrote and edited paper (20 %).

Summary• Wood is an important biological resource which contributes to nutrient and hydrology cycles through ecosystems, and provides structural support at the plant level. Thousands of genes are involved in wood development, yet their effects on phenotype are not well understood. We have exploited the low genomic linkage disequilibrium (LD) and abundant phenotypic variation of forest trees to explore allelic diversity underlying wood traits in an association study.• Candidate gene allelic diversity was modelled against quantitative variation to identify SNPs influencing wood properties, growth and disease resistance across three populations of Corymbia citriodora subsp. variegata, a forest tree of eastern Australia.• Nine single nucleotide polymorphism (SNP) associations from six genes were identified in a discovery population (833 individuals). Associations were subsequently tested in two smaller populations (130-160 individuals), 'validating' our findings in three cases for actin 7 (ACT7) and COP1 interacting protein 7 (CIP7).• The results imply a functional role for these genes in mediating wood chemical composition and growth, respectively. A flip in the effect of ACT7 on pulp yield between populations suggests gene by environment interactions are at play. Existing evidence of gene function lends strength to the observed associations, and in the case of CIP7 supports a role in cortical photosynthesis.

Different methods for predicting clonal values were explored for diameter growth (diameter at breast height (DBH)) in a radiata pine clonal forestry program: (1) clones were analyzed with a full model in which the total genetic variation was partitioned into additive, dominance, and epistasis (Clone Only-Full Model); (2) clones were analyzed together with seedling base population data (Clone Plus Seedling (CPS)), and (3) clones were analyzed with a reduced model in which the only genetic term was the total genetic variance (Clone Only-Reduced Model). DBH was assessed at age 5 for clones and between ages 4 to 13 at the seedling trials. Significant additive, dominance, and epistatic genetic effects were estimated for DBH using the CPS model. Nonadditive genetic effects for DBH were 87% as large as additive genetic effects. Narrow-sense ( b h 2 ) and broad-sense ( b H 2 ) heritability estimates for DBH using the CPS model were 0.14 ± 0.01 and 0.26 ± 0.01, respectively. Accuracy of predicted clonal values increased 4% by combining the clone and seedling data over using clonal data alone, resulting in greater confidence in the predicted genetic performance of clones. Our results indicate that exploiting nonadditive genetic effects in clonal varieties will generate greater gains than that typically obtainable from conventional family-based forestry of radiata pine. The predicted genetic gain for DBH from deployment of the top 5% of clones was 24.0%-an improvement of more than 100% over family forestry at the same selection intensity. We conclude that it is best practice to predict clonal values by incorporating seedling base population data in the clonal analysis.

Eucalypts are both a proven but largely unexplored source of woody biomass for biofuel production. Few of the some 900 species have been evaluated for cropping, yet among them are the most productive and versatile biomass species in the world, grown in over 90 countries, with species found to suit most tropical and temperate climates. The biology, science and technology underlying the breeding and growing of eucalypts and their potential for biofuel production are reviewed. How eucalypts meet sustainability and economic criteria for biofuel feedstocks, and the advantages of woody feedstocks broadly, are considered. Relevant aspects of eucalypt taxonomy, evolution, natural distribution, human dispersal, composition, domestication and biotechnology of the groups' potential as a biofuel feedstock resource are reviewed. Two case studies are outlined, illustrating species identification, domestication and harvesting processes where eucalypts are prospective biofuel feedstocks. Eucalypts are strong contenders as a universal woody biomass feedstock for biofuel.