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Fungal alkaloids mediate defense against bruchid beetles in field populations of an arborescent ipomoea

Summary

Researchers discovered that some morning glory trees produce toxic alkaloids with help from fungi living inside them. These alkaloids, especially a compound called swainsonine, protect the tree’s seeds from beetle pests. Trees with more protective fungi had fewer damaged seeds. This shows that plants and fungi can work together as a team to defend against insects.

Background

Convolvulaceae species harbor heritable fungal endophytes that produce alkaloids translocated to plant reproductive tissues. Evidence for the distribution and ecological role of these fungal alkaloids in various host species and growth forms remains incomplete. This study investigates fungal endophytes and alkaloid quantities in leaves and seeds of the arborescent morning glory Ipomoea murucoides.

Objective

The study aimed to identify fungal symbionts of arborescent Ipomoea murucoides, quantify alkaloid concentrations in leaves and seeds, and evaluate herbivory damage from bruchid beetles in field populations. The researchers sought to determine if fungal-derived swainsonine provides defensive benefits against seed predators.

Results

Two fungal taxa were identified: Ceramothyrium (Chaetothyriales) in 23 trees and Truncatella (Xylariales) in 9 trees. Seeds had significantly higher swainsonine concentrations than leaves. Trees harboring Ceramothyrium exhibited higher seed swainsonine levels and less bruchid damage compared to Truncatella-colonized trees. Five sesquiterpenes were detected in glandular trichomes of both fungal types.

Conclusion

Fungal alkaloids, particularly swainsonine, provide demonstrable defense against bruchid beetles in field populations of Ipomoea murucoides. The host plant appears to allocate defensive chemicals from leaves to seeds, protecting them from seed predators. Ipomoea species offers a valuable research system for studying vertical and horizontal fungal symbiont transmission.
  • Published in:Journal of Chemical Ecology,
  • Study Type:Field Study,
  • Source: 10.1007/s10886-025-01578-2, PMID: 39994115
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