Breeding trials and clonal propagation of selected species: achieving genetic gain
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.