A. Colin Matheson

Genetics of wood stiffness and its component traits in Pinus radiata

The potential for breeding Pinus radiata D. Don to improve wood stiffness (modulus of elasticity, MoE) was examined by obtaining pith-to-bark cores from trees at breast height in two independent ge...

Estimation of Pinus radiata D. Don clear wood properties by near-infrared spectroscopy

The use of calibrated near-infrared (NIR) spectroscopy for predicting of a range of solid wood properties is described. The methods developed are applicable to large-scale nondestructive forest resource assessment and to tree breeding and silviculture programs. A series ofPinus radiata D. Don (radiata pine) samples were characterized in terms of density, longitudinal modulus of elasticity (EL), and microfibril angle (MFA). NIR spectra were obtained from the radial/longitudinal face of each sample and used to generate calibrations for the measured physical properties. The relations between laboratory-determined data and NIR fitted data were good in all cases, with coefficients of determination (R2) ranging from 0.68 for 100/MFA to 0.94 for densitystrip. A good relation (R2 = 0.83) was also obtained forEL estimated using data collected by SilviScan-2. The finding suggests that an NIR instrument could be calibrated to estimate theEL of increment cores based on SilviScan data. In view of the rapidly expanding range of applications for this technique, it is concluded that appropriately calibrated NIR spectroscopy could form the basis of a testing instrument capable of predicting a range of properties from a single spectrum obtained from the product or from the raw material.

Achievements in forest tree improvement in Australia and New Zealand: 8. Successful introduction and breeding of radiata pine in Australia.

Summary Radiata pine (Pinus radiata) was originally known as Pinus insignis or ‘remarkable pine’, an apt name for a tree which has had such a dramatic impact on the world timber scene. It is a native conifer of California, USA, and was first introduced into Australia around 1857 for ornamental plantings. There were two major sources of original importation, one through Ferdinand von Mueller to Victoria and South Australia in the 1860s, and the second through New Zealand seed merchants. Forty-year-old trees were clearfelled for sawing in 1908 in Victoria. The fast early growth of radiata pine in Mount Gambier and north of Adelaide in the 1870s and 80s prompted the state forest services of South Australia, Victoria and New South Wales to advocate planting of the remarkable pine as an exotic conifer to compensate for the relative paucity of indigenous softwood in Australia. There was some plantation development in the 1920s and 1930s, but planting almost stopped during World War II. Large-scale planting of radiata pine started again only in the late 1950s. Up to the late 1960s, unimproved seeds used to establish plantations in Australia were at first from early ornamental plantings, then from small plantations and later, in part, imported from New Zealand. Initial research and breeding were undertaken by the Forestry and Timber Bureau (at Canberra and Mt Gambier) and the Queensland Forestry Department — both studied reproductive biology, selected superior trees and established progeny tests in the early 1950s. Following the Seventh British Commonwealth Forestry Conference in Australia and New Zealand in 1957, the other five state forest services and two private companies initiated genetic improvement work in the late 1950s. After establishment of the first grafted seed orchard in 1957, a total of 145 ha of seed orchard was established by 1968. Large-scale plantings using improved seeds started in the early 1970s. Many clones were received from NZ before the 1970s, and a range-wide seed collection was made in the five native stands in California in 1978. In 1983, the Southern Tree Breeding Association (STBA) was formed to coordinate the national breeding program of radiata pine, and it now serves about half of Australias radiata pine estate. The other half is controlled by Forests New South Wales (FNSW) and the Western Australian Forest Products Commission (FPC). Radiata pine has been bred for three generations since the 1950s, with realised genetic gain up to 33% for volume from the first generation and more than 10% gain predicted from the second generation. The focus of the third-generation breeding in STBA has shifted to wood quality traits with: • integration of quantitative genetics, molecular genetics and wood science • development of economic breeding objectives • application of best linear unbiased prediction (BLUP) and a Web-based interactive database for customised delivery of breeding values. During 50 years of breeding radiata pine in southern Australia, several changes in strategic directions have been developed and implemented. Options for such flexibility must be maintained. To further increase genetic gain, infusion of new genetic material from the range-wide collections, increased recombination rate and selection intensity, purging of inbreeding depression, deployment by clonal forestry, and development of strategies dealing with adverse genetic correlation between wood volume and quality traits will be critical.

General and specific combining ability from partial diallels of radiata pine: implications for utility of SCA in breeding and deployment populations

Variances for general combining ability (GCA) and specific combining ability (SCA) and the relationship between mid-parental GCA and SCA effects were estimated for tree diameter (DBH) from a series of 20 sets of 6×6 half-diallel mating experiments in radiata pine, planted at ten sites across Australia. Significant SCA variance for DBH was almost equal to GCA variance for the combined analysis of all ten sites. The importance of SCA variance varied among sites, from non-significant to SCA variance accounting for all genetic variation among full-sib families. Significant SCA × site interaction was detected among the ten sites. A significant and positive correlation between mid-parental breeding values and best linear unbiased predictions of the SCA effects was observed. About a quarter of extra genetic gain is achievable through use of SCA variance if selection is based on the best breeding values. To fully exploit genetic gain from SCA variance in a deployment population, positive assortative matings are required for the best parents. It is estimated that the additional deployment gain of 46.0% for ten sites combined, or 52.9% for four sites combined that had significant GCA as well as SCA effects, were achievable relative to gain from GCA only, if all SCA variance within this breeding population was exploited. For a breeding population, selection for breeding values may be sufficient due to positive correlations between breeding values and SCA values. For a deployment population to capture more SCA genetic gain, it is preferable to make more pair-wise mating for parents with higher breeding values.

Marker-based adjustment of the additive relationship matrix for estimation of genetic parameters - an example using Eucalyptus cladocalyx

The effects of adjusting additive (numerator) relationship matrices (A) for inbreeding estimates taken from molecular markers were investigated using a small, model population of Eucalyptus cladocalyx. A number of individual-tree, mixed-models were compared, incorporating estimates of population- and family-level selfing and ancestral inbreeding applied either as average values to the entire population or as variable estimates for subpopulation and family groups. The consequences of ignoring inbreeding were inflated additive genetic variance estimates and underestimation of residual variance, with resulting inflation of heritability. We found models that correct for differential inbreeding at the subpopulation level give similar results to more complex ones including family-level estimates. Our analysis indicates that the commonly applied coefficient of relationship for first-generation eucalypt progeny of ρ = 1/2.5 appears to be quite suitable for correcting variance component and heritability estimates. However, if inbreeding is not specifically corrected for by adjustment of A, some minor rank changes of individual breeding values can occur, especially where levels of inbreeding vary among families, and some suboptimal selections and loss of genetic gain may ensue.

Conserving the Pines of Guadalupe and Cedros Islands, Mexico: An International Collaboration

Monterey pine (Pinus radiata D. Don) is an enigmatic species. Native to only Mexico and USA, it is restricted to three populations along the central coast of California and one on each of two Mexican islands off Baja California— Guadalupe and Cedros Islands. Commercially, it is grown in exotic plantations worldwide on over 4 million hectares with high economic value, yet there is little value in its countries of origin. Overall, the species has lost perhaps 50% of its natural habitat and is threatened by various human-related influences. The two insular pine populations are well differentiated genetically and have different ecological associations both from each other and the mainland populations Although Guadalupe Island has protected status under the Mexican Ministry of the Environment and Natural Resources (SEMARNAT), the pine population may be headed towards extinction because of grazing pressure from introduced goats. On neither island are the pines protected from current threats or do they have dedicated funding or a specific conservation plan. Effective longterm conservation of the pines requires a consistent, institutionalized strategy and dedicated funding. International interest in the insular pine populations can contribute to their conservation through research, providing information to support conservation plans and public education materials, providing the technical justification and a proposal to include the island populations of Monterey pine on the threatened and endangered species list in Mexico, maintaining a backup seed collection for restoration, publicizing the value and vulnerability of these populations, and providing funds, as possible. A multinational expedition to both islands in 2001 to collect seeds and information for conservation purposes is an example of the feasibility and value of international collaboration in protecting the Mexican island pines.

Genetic parameter estimates informed by a marker-based pedigree: A case study with Eucalyptus cladocalyx in southern Australia

Analysis of stem diameter, height and axis persistence (AP) in a first-generation Eucalyptus cladocalyx breeding population comprising 137 wild and land-race families planted at 11 sites in southern Australia revealed significant genetic variation among subpopulations and among families within subpopulations. Alternative analyses were carried out using individual-tree mixed models that (i) assumed the trees within families were half-siblings (HS) and (ii) used molecular marker-based information to account for highly heterogeneous relatedness and inbreeding depression among families resulting from mixed mating (MM). For certain site and trait combinations, the HS models would not converge, as estimates of additive variance exceeded the total phenotypic variance, demonstrating the fundamental unsuitability of the HS assumption for this breeding population. Where HS models converged, moderate to very high heritability estimates resulted for growth traits. The MM assumption resulted in re-ranking of individual-tree breeding values and markedly lower estimates of narrow-sense heritability for all trait-site combinations. In some cases, however, heritability remained moderate to high, probably reflecting unquantified dominance variance in some highly inbred subpopulations. Genotype-by-environment interaction was significant overall due to reactivity of genotypes on a few sites, with type-B correlations between pairs of sites ranging from 0.06 to 0.99. Generally, families from the Australian land race were found to perform particularly well for both growth and AP traits. Some wild families were found to be vigorous, despite significant inbreeding. The study has demonstrated that traditional models assuming non-relatedness and/or homogeneous inbreeding in first-generation eucalypt breeding populations can be significantly improved upon by flexible mixed models that integrate marker-based data.

Effect of genotype-by-spacing interaction on radiata pine wood density

Summary Effects of spacing, family and spacing-by-family interaction on corewood and outerwood density, and annual latewood percentage from cambial age 2 to 21 years in radiata pine (Pinus radiata D.Don) were studied using 55 families planted at three spacings (1 × 1, 1 × 2 and 2 × 3 m). Significant family effects were observed for corewood and outerwood density, and latewood percentage, but spacing effects were significant only for outerwood density and latewood percentage. There was significant spacing-by-family interaction on corewood density (rB = 0.62). Closer spacing increased latewood percentage in both corewood and outerwood and reduced corewood proportion but it did not increase wood density in corewood significantly. It was also observed that closer spacing had no effect on outerwood length, but increased wood density in outerwood significantly. Closer spacing increased heritability for wood density (1.11 ± 0.27 vs 0.46 ± 0.15) and increased juvenile–mature genetic correlations for wood density while increasing the negative genetic correlations between diameter at breast height (DBH) and corewood density. There were positive genetic correlations between latewood percentage and density in both corewood and outerwood. The significant genotype-by-spacing interaction for corewood density may be used to increase wood density of corewood through breeding.