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

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.