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Alliance Between Conifer Trees and Endophytic Fungi Against Insect Defoliators

Summary

Scientists discovered that beneficial fungi living inside white spruce trees help protect the trees from damaging spruce budworm insects. These fungi work in two ways: they produce toxic substances that poison the insects, and they help trees produce protective chemical compounds called terpenes. In greenhouse experiments, trees with more of these beneficial fungi had significantly more protective chemicals in their leaves. This natural partnership between trees and fungi represents millions of years of evolution working together to fight off pests.

Background

Fungal endophytes inhabit plant tissues and can enhance plant defense against herbivores through direct toxic effects or by altering plant secondary metabolism. While endophyte-mediated resistance is well-studied in annual plants, their role in conifer defenses against insect herbivores remains largely unknown.

Objective

To characterize endophytic fungal communities and their effects on white spruce resistance to eastern spruce budworm, and to determine whether fungal endophytes directly inhibit herbivore growth or indirectly enhance plant terpene production through a proposed Plant Partnership Hypothesis.

Results

Fungal endophytes varied among white spruce families and sites, with five dominant genera identified. Bioassays demonstrated that fungal mycelium and volatile compounds reduced budworm fitness and caused up to 100% mortality at higher doses. Inoculation experiments showed that increased fungal abundance corresponded to 33% higher monoterpene and 28% higher sesquiterpene concentrations in seedlings.

Conclusion

Fungal endophytes provide direct and indirect anti-herbivory protection to white spruce against eastern spruce budworm through toxic metabolites and by enhancing terpene production. These findings support a co-evolutionary relationship among fungal endophytes, tree defenses, and insect herbivores, highlighting the ecological importance of plant-microbe partnerships in conifer defense.
  • Published in:Plant, Cell & Environment,
  • Study Type:Experimental Research Study,
  • Source: 10.1111/pce.15503, PMID: 40166909
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