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<p>In breeding programs, where the selection for desirable traits is prioritised, the maintenance of genetic diversity is important for long-term breeding sustainability. <i>Eucalyptus nitens</i> is the primary plantation eucalypt in Tasmania (Australia), playing a key role in the forestry industry. To investigate the impact of 50 years of breeding and selection on genetic diversity and population structure, the present study analysed a subset of both the base breeding population (G1) sampled from across the natural range of <i>E. nitens</i>, and advanced breeding generations (G2 &amp; G3), using 4,730 SNPs genotyped in 1,272 trees. The base population exhibited stable expected heterozygosity (<i>H</i><sub>e</sub> = 0.13) across its five races. The relationships between these races analysed using STRUCTURE and PCA analyses revealed two principal genetic clusters: one comprising the Northern New South Wales (N_NSW) and another encompassing the Central Victorian races with the Southern NSW race intermediate between both. Overall genetic differentiation among races was moderate (<i>F</i><sub>ST</sub> = 0.08) and mainly driven by the divergence of N_NSW from the Central Victorian races. Advanced generations showed no evidence of a genetic bottleneck, retaining the genetic diversity of the base population, as evidenced by stable <i>H</i><sub>e</sub> and allelic richness, alongside increased observed heterozygosity (<i>H</i><sub>o</sub>) and a decrease in the inbreeding coefficient. Infusion of NSW selections, intended to improve disease resistance, is reflected in genetic affinities of advanced generations, which show evidence of increasing inter-race hybridisation. These findings argue that even with a predominantly open-pollinated breeding strategy, genetic diversity and inbreeding can be effectively managed in eucalypt breeding program.</p>

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Evaluation of genetic diversity across multiple generations of a Eucalyptus nitens breeding population

  • 期刊论文

  • 发表日期：

    2025年12月29日

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  • Nana Y. Sarpong,
  • Kelsey R. Joyce,
  • René E. Vaillancourt,
  • Brad M. Potts,
  • Rebecca C. Jones

摘要

In breeding programs, where the selection for desirable traits is prioritised, the maintenance of genetic diversity is important for long-term breeding sustainability. Eucalyptus nitens is the primary plantation eucalypt in Tasmania (Australia), playing a key role in the forestry industry. To investigate the impact of 50 years of breeding and selection on genetic diversity and population structure, the present study analysed a subset of both the base breeding population (G1) sampled from across the natural range of E. nitens, and advanced breeding generations (G2 & G3), using 4,730 SNPs genotyped in 1,272 trees. The base population exhibited stable expected heterozygosity (He = 0.13) across its five races. The relationships between these races analysed using STRUCTURE and PCA analyses revealed two principal genetic clusters: one comprising the Northern New South Wales (N_NSW) and another encompassing the Central Victorian races with the Southern NSW race intermediate between both. Overall genetic differentiation among races was moderate (FST = 0.08) and mainly driven by the divergence of N_NSW from the Central Victorian races. Advanced generations showed no evidence of a genetic bottleneck, retaining the genetic diversity of the base population, as evidenced by stable He and allelic richness, alongside increased observed heterozygosity (Ho) and a decrease in the inbreeding coefficient. Infusion of NSW selections, intended to improve disease resistance, is reflected in genetic affinities of advanced generations, which show evidence of increasing inter-race hybridisation. These findings argue that even with a predominantly open-pollinated breeding strategy, genetic diversity and inbreeding can be effectively managed in eucalypt breeding program.