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Alliance Between Conifer Trees and Endophytic Fungi Against Insect Defoliators

Summary

This study discovered that special fungi living inside white spruce trees help protect the trees from damaging insects called budworms. These fungi produce toxic substances and smelly compounds that kill or repel the budworms. When researchers increased the amount of these beneficial fungi in young spruce trees, the trees produced higher levels of protective chemicals called terpenes. This research shows that the relationship between spruce trees, fungi, and insects has evolved together over time, with fungi playing a crucial role in keeping trees healthy.

Background

Fungal endophytes inhabit plant tissues and can enhance plant defense against herbivores through direct toxicity or indirect metabolic effects. However, their role in conifer defenses against insect herbivores remains largely unknown. This study investigates the tripartite interactions between white spruce, endophytic fungi, and the eastern spruce budworm.

Objective

To characterize endophytic fungal communities and terpene concentrations in white spruce families, determine direct effects of fungal endophytes on budworms, and examine whether changes in fungal communities alter terpene concentrations in seedlings. The study tests the Plant Partnership Hypothesis regarding co-evolutionary relationships among fungi, tree defenses, and insect herbivores.

Results

Analysis identified 45 endophytic fungal genera with significant variation among families and sites. Fungal endophytes produced toxic metabolites and volatile compounds that reduced budworm fitness or caused 100% mortality at higher doses. Inoculation experiments demonstrated that increased fungal abundance corresponded with 28-33% increases in monoterpene and sesquiterpene concentrations in seedlings, with positive linear relationships between fungal abundance and terpene production.

Conclusion

Endophytic fungi provide both direct anti-herbivory protection through toxicity and indirect protection by enhancing terpene production in white spruce foliage. Results support the Plant Partnership Hypothesis, demonstrating a co-evolutionary relationship among fungal endophytes, tree chemical defenses, and insect herbivores. These findings highlight the ecological significance of fungal endophytes in conifer defense mechanisms.
  • Published in:Plant, Cell & Environment,
  • Study Type:Experimental Study,
  • Source: PMID: 40166909
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