The aim of tree breeding is to improve the genetic quality of trees by improving specific tree characteristics called 'traits', for example, growth rate and wood density.

These characteristics are an expression of the genetic code, and the environment in which trees are grown. Tree breeding is most successful for traits that are strongly 'heritable', that is, traits that are strongly determined by their genetic code.

tree breeding in new zealand

Early Tree Breeding in New Zealand

Breeding to improve radiata pine has been undertaken in New Zealand since 1950 using classical plant and animal breeding principles and practices. Initially the emphasis was on selecting excellent trees (called plus-trees) from the early plantations, testing them in a range of environments, and encouraging grafts of these plus-trees to cross in seed orchards to produce seed for new plantations.

These plus-trees provided a foundation for the current breeding population which has advanced two to three generations. Offspring from the ongoing crossing programme were initially tested as seedlings in Backward Selection breeding trials too.

RPBC Breeding Trials and Breeding Values

Each tree in a breeding trial has a unique genetic identity and code name. The physical characteristics of each tree that is being genetically improved are measured and data are used to estimate Breeding Values (EBVs), which are used to rank selections against one another. RPBC uses improved field trial designs to reduce the time taken to select, test, and confirm superior trees and get them into commercial seed orchards.

RPBC's breeding programme does not involve any genetic engineering.

Each candidate tree (selection) is tested, using cloning, in multiple trials across multiple site types and multiple years. The selections are replicated by using vegetative cuttings for trials. The estimated breeding values for any selection may change as a result of new trial measurements being included in the breeding trial data base and annual analyses. Breeding value accuracy increases as the number of measurements for each selection increases. Hence both EBVs and GF Plus™ values can vary slightly from year to year; more so where there is little data. GF Plus™ values are not calculated until the breeding value accuracies are considered reasonably stable.

Risks associated with poor breeding practices

If done badly, tree breeding can lead to genetic 'loss' rather than genetic gain. For example, if radiata pine trees self-pollinates (self-cross), the resulting seedlings could be compromised due to inbreeding. Secondary to the genetic improvement goals, tree breeders manage the tree crossing programme to avoid inbreeding, as well as to maintain genetic diversity in plantations.

Also, breeding for improvement in some traits can lead to deterioration in other traits. For example, growth rate and wood density are negatively related. This means that selection for very fast growing trees may also lower wood density values. When both characteristics are required, breeders have to manage tree selection and breeding to provide top selections with improvement for a range of traits.


Estimated Breeding Values (EBVs) are produced annually for six traits:

  • Diameter growth
  • Stem straightness
  • Branching habit
  • Dothistroma resistance
  • Wood density
  • Corewood stiffness

EBV's are estimated for all genotypes in the breeding orchard, breeding trials and conservation archives. The EBV dataset also includes genotypes that are ancestors to current genotypes. Ancestor genotypes may no longer be physically available but their EBV data are used in EBV analyses.

Breeding values are not available yet for all traits for all genotypes in breeding trials. The EBV dataset increases as more trials, trees and traits are measured. For each genotype with a trait EBV there is also a value for Accuracy and the related GF Plus™ value. Breeding values for corewood stiffness have not yet been converted to GF Plus™ values.

our germplasm

Our germplasm is produced through our breeding programme, past and present, and is characterised by breeding values.

The germplasm includes all the genotypes; and is represented as:

  • trees in the breeding orchard
  • the conservation archives
  • shareholder seed orchards
  • the breeding trials.

RPBC germplasm also includes:

  • pollen, cones and seeds produced in the breeding and seed orchards, and
  • seedlings and clonal vegetative cuttings grown for breeding trials
  • Scions (for grafting) and pollen taken from any trees in orchards, archives, or trials are also RPBC germplasm.

Shareholders are entitled to collect scions for propagation and sale. RPBC owns the genetic information contained in all forms of RPBC germplasm.

breeding strategy

RPBC is breeding elite germplasm managed on a 'rolling front' to deliver optimal gain in several traits that enhance profitability in radiata pine plantations.

The genetically improved traits are:

  • diameter growth
  • wood density
  • corewood stiffness
  • resistance to Dothistroma needle blight
  • stem straightness and
  • branch habitat

RPBC is in the process of integrating its multiple, trait-based breeding strategy into a single, breeding objective expressed in terms of Net Present Value. The needs of individual growers with regard to combinations of traits will be accommodated through their choice of specific genotypes to deploy in forest operations. RPBC manages its breeding programme for elite germplasm on a ‘rolling front’, or forward selection basis, to deliver optimal gain in several traits that enhance profitability in radiata pine plantations.

RPBC is also focused on shortening the breeding cycle for faster delivery of genetic gain in new germplasm to the market. Germplasm from the breeding orchard is tested through regional testing of vegetatively cloned germplasm in breeding trials.

Our long-term aspiration is to deliver maximum genetic gain to the Australasian forest industry via well-characterised germplasm, as fast as possible, and at least cost. Overall, we want to improve forest growers’ profitability by increasing the rate of annual genetic gain in a cost-effective way.

Further details of the breeding and deployment strategy are available here

breeding trials

Germplasm from the breeding programme is tested in annual breeding trials in New Zealand and Australia (New South Wales and Tasmania), hosted by RPBC shareholders - click on a map for more details of trial locations.

Breeding trials provide estimates of the genetic worth of germplasm in the breeding programme and trees in commercial seed orchards. New breeding trials are established each year. At any point in time there are approximately 50 breeding trials actively growing toward the measurement phase of their life cycle. There are more than 100 trials supporting breeding value calculations and other breeding related research. Breeding trials are measured when the trees reach an average height of 10 metres, and before the trial host schedules the surrounding stand for silvicultural treatment.

For further information about breeding trials contact us at

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breeding orchard

The RPBC breeding orchard is located on Purchas Road in Amberley, New Zealand. It is six hectares in size, on a former alluvial plain of the Waipara River where the soils are generally shallow sandy loams. The average rainfall is 600mm per year with few frosts.

The breeding orchard contains trees that are vegetatively cloned replicates (ramets) of each genotype selected for the crossing programme. These trees are managed for seed production through specific, control-pollinated (CP) crosses. Seed from the crossing programme is germinated, and multiple, genetically identical cuttings from each of these seedling (vegetative clones) offspring are planted in the annual breeding trials.

conservation archives

RPBC maintains five conservation archives in New Zealand. They are located in Southland, the East Coast, North Canterbury, Nelson and Rotorua.

Conservation archives contain a broader set of selected trees than those in the breeding orchard to ensure that a large gene pool is available to reconstruct the breeding orchard in the event of losses, to supply pollen, and supply scions for shareholders and members to graft and plant in seed orchards.

New seed orchards established and owned by both New Zealand and Australian shareholders provide additional sources of germplasm further reducing the risk of loss of these unique resources.

Conservation archives have a limited lifetime of about 15 years so new archives are required both as replacements and to hold the continuous flow of new genotypes arising from the breeding programme.