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<p>Rapid ‘ōhiʻa death (ROD), caused by fungal pathogens <i>Ceratocystis lukuohia</i> and <i>Ceratocystis huliohia</i>, is devastating ʻōhiʻa (<i>Metrosideros polymorpha</i>), the keystone forest tree species of Hawaiʻi. Ceratocystidaceae fungi produce fruity volatile organic compounds (VOCs) and sticky sexual spores, suggesting they are adapted for insect dispersal. In this study, we explored chemical signaling of the causal agents of the ROD disease complex and how those VOCs mediate ambrosia beetle (Coleoptera: Curculiondiae: Scolytidae)-plant interactions. Four species of ambrosia beetles (<i>Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus</i>, and <i>Xyleborus perforans</i>) are direct vectors of the ROD pathogens in addition to spreading the fungi indirectly through contaminated frass. To further understand the extent to which semiochemicals mediate relationships between agents of the ROD pathosystem, we identified fungal VOCs both <i>in vitro</i> and <i>in vivo</i>. We then tested behavioral responses of the ROD-associated ambrosia beetles to the odor of the fungi using still-air olfactometer assays. Similar fruity and banana-like fusel alcohols and acetates were produced by <i>C. lukuohia</i> and <i>C. huliohia</i> in culture and when colonizing ‘ōhiʻa seedlings, which could be detected one-day post-inoculation, nine days before symptom onset. <i>X. affinis</i> was attracted to both <i>C. lukuohia</i> and <i>C. huliohia</i>, while <i>X. ferrugineus</i> positively responded to <i>C. lukuohia</i> and <i>X. perforans</i> to <i>C. huliohia</i>. These findings suggest a semiochemical association and potential support for the hypothesis of coevolutionary history between <i>Ceratocystis</i> fungi and insects.</p>

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The In Vitro and In Vivo Fungal Volatile Organic Compounds Associated with Rapid ʻŌhiʻa Death and the Response of Xyleborine Ambrosia Beetles to those Compounds

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年5月27日

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  • Kylle Roy,
  • Eva Brill,
  • Dan Mikros,
  • Kelsey Tobin,
  • Jennifer Juzwik,
  • Brandon Mcnellis,
  • Douglass Jacobs,
  • Lisa Keith,
  • Dong H. Cha,
  • Matthew Ginzel

摘要

Rapid ‘ōhiʻa death (ROD), caused by fungal pathogens Ceratocystis lukuohia and Ceratocystis huliohia, is devastating ʻōhiʻa (Metrosideros polymorpha), the keystone forest tree species of Hawaiʻi. Ceratocystidaceae fungi produce fruity volatile organic compounds (VOCs) and sticky sexual spores, suggesting they are adapted for insect dispersal. In this study, we explored chemical signaling of the causal agents of the ROD disease complex and how those VOCs mediate ambrosia beetle (Coleoptera: Curculiondiae: Scolytidae)-plant interactions. Four species of ambrosia beetles (Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, and Xyleborus perforans) are direct vectors of the ROD pathogens in addition to spreading the fungi indirectly through contaminated frass. To further understand the extent to which semiochemicals mediate relationships between agents of the ROD pathosystem, we identified fungal VOCs both in vitro and in vivo. We then tested behavioral responses of the ROD-associated ambrosia beetles to the odor of the fungi using still-air olfactometer assays. Similar fruity and banana-like fusel alcohols and acetates were produced by C. lukuohia and C. huliohia in culture and when colonizing ‘ōhiʻa seedlings, which could be detected one-day post-inoculation, nine days before symptom onset. X. affinis was attracted to both C. lukuohia and C. huliohia, while X. ferrugineus positively responded to C. lukuohia and X. perforans to C. huliohia. These findings suggest a semiochemical association and potential support for the hypothesis of coevolutionary history between Ceratocystis fungi and insects.