Genetic variation in growth and wood-quality traits ofCorymbia citriodorasubsp.variegataacross three sites in south-east Queensland, Australia

Abstract

Ten growth or wood-quality traits were assessed in three nearby Corymbia citriodora subsp. variegata (CCV) open-pollinated family-within-provenance trials (18 provenances represented by a total of 374 families) to provide information for the development of a breeding program targeting both pulp and solid-wood products. Growth traits (diameter at breast high over bark [DBH], height and conical volume) were assessed at 3 and 7 years of age. Wood-quality traits (density [DEN], Kraft pulp yield [KPY], modulus of elasticity [MoE] and microfibril angle [MfA]) were predicted using near-infrared spectroscopy on wood samples collected from these trials when aged between 10 and 12 years. The high average KPY, DEN and MoE, and low average MfA observed indicates CCV is very suitable for both pulp and timber products. All traits were under moderate to strong genetic control. In acrosstrials analyses, high (>0.4) heritability estimates were observed for height, DEN, MoE and MfA, while moderate heritability estimates (0.24 to 0.34) were observed for DBH, volume and KPY. Most traits showed very low levels of genotype × site interaction. Estimated age-age genetic correlations for growth traits were strong at both the family (0.97) and provenance (0.99) levels. Relationships among traits (additive genetic correlation estimates) were favourable, with strong and positive estimates between growth traits (0.84 to 0.98), moderate and positive values between growth and wood-quality traits (0.32 to 0.68), moderate and positive between KPY and MoE (0.64), and high and positive between DEN and MoE (0. 82). However, negative (but favourable) correlations were detected betweenMfA and all other evaluated traits (−0.31 to −0.96). The genetic correlation between the same trait expressed on two different sites, at family level, ranged from 0.24 to 0.42 for growth traits, and from 0.29 to 0.53 for wood traits. Therefore simultaneous genetic improvement of growth and wood property traits in CCV for the target environment in south-east Queensland should be possible, given the moderate to high estimates of heritability and favourable correlations amongst all traits studied, unless genotype × site interactions are greater than was evident.

Are tree breeders properly predicting genetic gain? A case study involving Corymbia species

“…Theĥ 2 a estimates, related to the component of inheritance that is effectively transmitted to the next generation (Falconer and Mackay 1996;Bernardo 2010), were classified as moderate (0:15\ĥ 2 a 0:50) to high (0:50\ĥ 2 a ) (Resende 2002) for all the traits evaluated (Table 3) with estimates for CCV higher than those for CCC. Hung et al (2016) observed estimates ofĥ 2 a for CCV at age 3 years of 0.34 ± 0.03 and 0.42 ± 0.04 for DBH and H, respectively, which was similar to what we found in CCC and lower than what we observed for the same species. Though Hung et al (2016) postulated that their results may be biased due to the use of one-third rather than 1/2.5 for the coefficient of relationship among families and the heavy thinning in some trials, their assumption is similar to our assumption of 1/3.3.…”

“…Hung et al (2016) observed estimates ofĥ 2 a for CCV at age 3 years of 0.34 ± 0.03 and 0.42 ± 0.04 for DBH and H, respectively, which was similar to what we found in CCC and lower than what we observed for the same species. Though Hung et al (2016) postulated that their results may be biased due to the use of one-third rather than 1/2.5 for the coefficient of relationship among families and the heavy thinning in some trials, their assumption is similar to our assumption of 1/3.3. Moreover, is probable that our own estimates of additive variance are inflated, due to (1) confounding of genotype-byenvironment interaction (GxE) variance with additive variance, due to the single-site trials that do not allow estimation of GxE and (2) lack of pedigree ns = not significant; * = significant to 5% of error probability; ** = significant to 1% of error probability information including provenance of ancestral origin information for the families.…”

Genetic variation of microfibril angle and its relationship with solid wood and pulpwood traits in two progeny trials of Eucalyptus nitens in Tasmania

“…Table4). This genetic relationship is consistent with studies in other species (C. citriodora rg = −0.96 ± 0.01,Hung et al (2016)), confirming MFA as a major contributor to wood stiffness along with wood density. While wood density and MFA appear to be genetically independent (Table4), both are highly significantly correlated with MOE, consistent with their independent contributions to wood stiffness.…”

“…A few studies have reported genetic correlations between MFA and KPY. For example Hung et al (2016) similarly reported a moderate to strong negative genetic correlation at the family (−0.77 ± 0.05) and provenance (−0.93 ± 0.04) levels in Corymbia citriodora. As MFA is negatively correlated with wood stiffness, the present finding is also consistent with a significant positive genetic correlation between KPY and wood stiffness related traits (i.e.…”

Variation in wood properties of 26-year-old Handroantus impetiginosus cultivated in Luiz Antônio, SP

“…The fact that the basic density and the microfibril angle do not differ significantly between the sources may be an indication that these properties may be less controlled by genetic and environmental factors than the volumetric shrinkage. However, heritability estimates for wood density and MFA are considered more moderate (Hung et al 2016).…”