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<p>Myrtle rust caused by <i>Austropuccinia psidii</i> is an important disease of Myrtaceae species in tropical and subtropical regions of the world. The pathogen is of concern to the forest plantation industry in Brazil which is primarily based on introduced eucalypts from Australia. <i>A. psidii</i> has multiple biotypes, including a native Brazilian biotype, that causes damage to <i>Eucalyptus</i> spp. and <i>Syzygium jambos</i>, and a pandemic biotype. As an invader, the pandemic biotype affects numerous Myrtaceae hosts in countries around the world, including those in Australia. Although the pandemic biotype of&#xa0;<i>A. psidii</i> has had little impact on eucalypt plantations in Australia to date, this may change if the Brazilian or other biotypes/races invade, or if there is genetic change in the pandemic biotype in Australia. In Australian seedling inoculation studies, families from range-wide native stand seed collections of Australia’s main plantation eucalypt, <i>Eucalyptus globulus</i>, have shown considerable genetic variation in resistance to the pandemic biotype of <i>A. psidii</i>. In a seedling inoculation study undertaken in Brazil with a subset of these families, we similarly show significant genetic variation in host resistance to the common Brazilian race of <i>A. psidii</i> (race 1) at the family and population levels. The disease severity in the Brazilian and Australian studies was significantly correlated at the family level, ranging between 0.49 and 0.57, due mainly to genetic-based covariation in the immune response. Overall, the <i>E. globulus</i> families exhibited less resistance to the Brazilian than the pandemic biotype, but it is unclear whether this is due to greater pathogen virulence or different inoculation and growing conditions. Regardless, there is genetic variation in <i>E. globulus&#xa0;</i>susceptibility to both <i>A. psidii</i> biotypes, which would allow genetic improvement. Further, despite variation in the relative susceptibility of some families to the different biotypes, selection of <i>E. globulus</i> for reduced susceptibility to one biotype is expected to make positive gains in resistance to the other, and some families exhibited relatively ‘stable resistance’ with low susceptibility to both biotypes.</p>

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Resistance of open-pollinated families of Eucalyptus globulus to two biotypes of Austropuccinia psidii

  • 期刊论文

  • 发表日期：

    2025年6月25日

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  • Rosiane F. Almeida,
  • João Vitor P. V. Ferreira,
  • Rafael F. Alfenas,
  • Brad M. Potts,
  • Jules S. Freeman,
  • Federico R. Fernández,
  • Acelino C. Alfenas

摘要

Myrtle rust caused by Austropuccinia psidii is an important disease of Myrtaceae species in tropical and subtropical regions of the world. The pathogen is of concern to the forest plantation industry in Brazil which is primarily based on introduced eucalypts from Australia. A. psidii has multiple biotypes, including a native Brazilian biotype, that causes damage to Eucalyptus spp. and Syzygium jambos, and a pandemic biotype. As an invader, the pandemic biotype affects numerous Myrtaceae hosts in countries around the world, including those in Australia. Although the pandemic biotype of A. psidii has had little impact on eucalypt plantations in Australia to date, this may change if the Brazilian or other biotypes/races invade, or if there is genetic change in the pandemic biotype in Australia. In Australian seedling inoculation studies, families from range-wide native stand seed collections of Australia’s main plantation eucalypt, Eucalyptus globulus, have shown considerable genetic variation in resistance to the pandemic biotype of A. psidii. In a seedling inoculation study undertaken in Brazil with a subset of these families, we similarly show significant genetic variation in host resistance to the common Brazilian race of A. psidii (race 1) at the family and population levels. The disease severity in the Brazilian and Australian studies was significantly correlated at the family level, ranging between 0.49 and 0.57, due mainly to genetic-based covariation in the immune response. Overall, the E. globulus families exhibited less resistance to the Brazilian than the pandemic biotype, but it is unclear whether this is due to greater pathogen virulence or different inoculation and growing conditions. Regardless, there is genetic variation in E. globulus susceptibility to both A. psidii biotypes, which would allow genetic improvement. Further, despite variation in the relative susceptibility of some families to the different biotypes, selection of E. globulus for reduced susceptibility to one biotype is expected to make positive gains in resistance to the other, and some families exhibited relatively ‘stable resistance’ with low susceptibility to both biotypes.