Breeding trials of selected species

Base breeding populations of our selected species have been established on 13 contrasting trial sites across NZ’s eastern drylands regions. These trials are the foundation of our tree improvement programme.

Large breeding populations ensure that a broad range of genetic diversity is captured from which to select multiple traits for improvement.

NZDFI’s selected species on which to focus genetic improvement are:

  • E argophloia              Western white gum
  • E bosistoana              Coast grey box
  • E globoidea                White stringybark
  • E quadrangulata         White-topped box gum
  • E tricarpa                     Red iron bark

Trial sites – location and establishment

Between 2009 and 2012 NZDFI established base breeding populations of these species across ten sites. In 2016, a further three breeding trials were established. Over 70,000 trees have been planted to ensure that broad-based selection of elite trees is possible. The key species are:

  • E. bosistoana             192 families, 32,100 seedlings
  • E. globoidea               161 families, 26,640 seedlings
  • E. quadrangulata      104 families, 15,576 seedlings

We also plan to research and develop inter-specific hybrids - hence the more limited plantings of E. argophloia and E. tricarpa.

The 13 different sites cover the range of abiotic (cold, drought, soils etc) and biotic (pests, diseases) stress factors likely to be found in NZ’s eastern drylands. This range of sites will allow analysis of the stability of superior genotypes under contrasting environmental conditions by identifying the relative contributions of genetic and environmental effects.

Breeding population design

Each site is planted in separate blocks of each species. The individually labelled trees for each family are laid out in a randomised design. Trees are planted at 2315 stems per hectare (1.8m x 2.4m). Each species is replicated at three different sites.

This design ensures control of environmental variation at site level, and enables between- and within-family selection. Permanent sample plots (PSP’s) have been established for measuring productivity and developing growth models.

Before thinning - 6-year old E quadrangulata breeding trial at the Atkinson trial site

Before thinning - 6-year old E quadrangulata breeding trial at the Atkinson trial site

Thinned E quadrangulata breeding trial, Alexander trial site

Thinned E quadrangulata breeding trial, Alexander trial site

Early assessment of individual traits

In 2014 the first of a series of assessments, thinning and wood sampling operations commenced in the fastest growing sites, and these continued in 2015/16. Data analysis following these assessments is guiding the selection of plus trees at these sites.  Plus tree selections are being grafted by Proseed NZ for deployment in seed orchards while they also research vegetative propagation of NZDFI species in their new propagation facility at Amberley supported by University of Canterbury.The assessment of wood quality traits in young trees has also started with a focus on early heartwood and growth stresses.

This early work will underpin our understanding of the genetic architecture (degree of genetic control and association between traits) for each species so that estimates of genetic superiority can be made for our genetically improved trees.