Farm Forestry New ZealandGenetic structure and diversity in the NZDFI Eucalyptus bosistoana and E. argophloia breeding populations
By Clemens Altaner on behalf of Seoljong Kim, June 2023.
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Executive summary
This report on SWP Work Plan WP126 is of preliminary nature. It is an unexamined thesis chapter from Seoljong Kim’s PhD thesis, developed at the University of Canterbury under the supervision of Pieter Pelser, Luis Apiolaza, Tammy Steeves and Clemens Altaner. The thesis is scheduled to be submitted in August 2023, shortly after the SWP programme has finished. Once successfully defended, the PhD thesis will be publicly available online through the University of Canterbury’s library (likely by the end of 2023).
Abstract
Eucalyptus bosistoana is a key breeding species of the NZDFI, which aims to establish forestry plantations of ground-durable, high-value timber hardwoods in warmer dry environments of New Zealand’s east coast regions. Seeds of plants collected in 2008-2012 from trees identified as E. bosistoana in Australia, and of E. argophloia, a reputedly closely related species of secondary interest and to NZDFI, were grown in breeding trials in New Zealand. To inform the NZDFI breeding program, leaf samples of 221 breeding families of both species were genotyped using a Eucalyptus 72kSNP Axiom array to
- identify patterns of genetic structure among E. bosistoana populations;
- assess the genetic diversity of populations of E. bosistoana and E. argophloia; and
- determine the taxonomic identity of breeding families that are morphologically deviating from other E. bosistoana families or that were grown from seed collected outside the known distribution area of E. bosistoana.
The findings are best understood by studying Figure 12.
Despite the initial suspicion on the morphologically deviating plants that might be hybrids between E. argophloia and E. bosistoana, genetic structure study showed that plants of E. argophloia within the NZDFI breeding trials were apparently different from E. bosistoana identified individuals. Some populations of E. bosistoana labelled individuals within the breeding programme were instead identified as E. melliodora.
Although our samples originated from a wide geographic range of localities in Australia, STRUCTURE analysis suggests only weak genetic structure among E. bosistoana collection sites. However, isolation by distance among the collecting sites was statistically significant. Additionally, evidence of hybridization between E. bosistoana and E. melliodora was found in some populations.
The level of genetic diversity was similar among the species, while E. argophloia showed higher level of inbreeding.
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