Metabolites derived from fungi and bacteria suppress in vitro growth of Gnomoniopsis smithogilvyi, a major threat to the global chestnut industry

Introduction Chestnut rot caused by the fungus Gnomoniopsis smithogilvyi is a disease present in the world's major chestnut growing regions. The disease is considered a significant threat to the global production of nuts from the sweet chestnut (Castanea sativa). Conventional fungicides provide some control, but little is known about the potential of biological control agents (BCAs) as alternatives to manage the disease. Objective Evaluate whether formulated BCAs and their secreted metabolites inhibit the in vitro growth of G. smithogilvyi. Methods The antifungal potential of BCAs was assessed against the pathogen through an inverted plate assay for volatile compounds (VOCs), a diffusion assay for non-volatile compounds (nVOCs) and in dual culture. Methanolic extracts of nVOCs from the solid medium were further evaluated for their effect on conidia germination and were screened through an LC-MS-based approach for antifungal metabolites. Results Isolates of Trichoderma spp., derived from the BCAs, significantly suppressed the pathogen through the production of VOCs and nVOCs. The BCA from which Bacillus subtilis was isolated was more effective in growth inhibition through the production of nVOCs. The LC-MS based metabolomics on the nVOCs derived from the BCAs showed the presence of several antifungal compounds. Conclusion The results show that G. smithogilvyi can be effectively controlled by the BCAs tested and that their use may provide a more ecological alternative for managing chestnut rot. The in vitro analysis should now be expanded to the field to assess the effectiveness of these alternatives for chestnut rot management.

Automated summary

This study evaluated the antifungal potential of biological control agents (BCAs) and their secreted metabolites against G. smithogilvyi. The results showed that BCAs significantly suppressed the pathogen's growth through the production of volatile and non-volatile compounds. Metabolomics analysis also revealed the presence of antifungal compounds in the BCAs. These findings suggest that BCAs could be an ecological alternative for managing chestnut rot, but further field studies are needed to assess their effectiveness.