A Pipeline to Investigate Fungal-Fungal Interactions: Trichoderma Isolates against Plant-Associated Fungi

Featured Application Nucleation dynamic assay is a concrete strategy to identify microbial behaviours-in particular, interactions of Trichoderma fungi with other members of soil microflora. Soil fungi play essential roles in ecosystems, forming complex interaction networks with bacteria, yeasts, other fungi, or plants. In the framework of biocontrol strategies, Trichoderma-based fungicides are at the forefront of research as an alternative to synthetic ones. However, the impact of introducing new microbial strain(s) on the soil microbiome of a habitat is not well-explored. Aiming to identify a quantitative method to explore the complex fungal interactions, we isolated twelve fungi from three Italian vineyards and identified three strains of the Trichoderma genus in addition to nine more plant-associated fungi of different genera. Investigating in dual nucleation assay fungal-fungal interactions, we recognised two types of interaction: neutral or antagonistic. All three Trichoderma strains displayed a slight inhibitory behaviour against themselves. Trichoderma strains showed a mutually intermingling growth with Aspergillus aculeatus and Rhizopus arrhizus but antagonistic behaviour against the plant pathogens Alternaria sp., Fusarium ramigenum, and Botrytis caroliniana. Yet, in some cases, antagonistic behaviour by Trichoderma fungi was also observed against plant-promoting fungi (e.g., Aspergillus piperis and Penicillium oxalicum). Our study highlights the importance of studying the interactions between fungi, aiming to clarify better the impact of fungal-based biological fungicides in the soil communities, and offers a pipeline for further applications.

Automated summary

The nucleation dynamic assay is used to identify microbial behaviors, such as the interactions between Trichoderma fungi and other members of soil microflora. Trichoderma-based fungicides are being researched as an alternative to synthetic ones, but the impact on the soil microbiome is not well-studied. In this study, twelve fungi were isolated from Italian vineyards, including three Trichoderma strains and nine other plant-associated fungi. Through a dual nucleation assay, it was observed that Trichoderma strains exhibited both neutral and antagonistic interactions with different fungi, including plant pathogens. The findings emphasize the importance of studying fungal interactions to understand the impact of fungal-based biological fungicides on soil communities.