The antifungal potential Debaryomyces hansenii against durum wheat pathogen Fusarium graminearum

Durum wheat is highly susceptible to Fusarium head blight (FHB) caused by the fungal pathogen Fusarium graminearum. Wheat can be protected with the use of environmentally-friendly and sustainable methods involving biological control agents (BCAs) such as yeasts. However, the mechanism underlying the antagonistic effects of yeasts on plant pathogens has not been fully elucidated. Therefore, the aim of this study was to expand the existing knowledge about the mechanisms of action of a Debaryomyces hansenii biopreparation through transcriptome profiling in F. graminearum cells using RNA sequencing (RNA-seq). The changes in the F. graminearum transcriptome resulting from biotic stress induced by the application of D. hansenii cells to durum wheat spikes, and abiotic stress induced by the application of a cell-free supernatant were compared and comprehensively analyzed. Each stressor elicited a completely different transcriptomic response, and differentially expressed genes (DEGs) encoding metabolic pathways essential for pathogen development associated with carbohydrate and amino acid metabolism, pathogenicity factors, effectors, and secondary metabolites. Numerous transporter genes were also identified, which indicates that fungi exhibit complex responses to biotic and abiotic stresses. The study demonstrated that F. graminearum uses various strategies to overcome the biotic stress associated with BCAs, including the upregulation of the brefeldin A resistance gene (FGSG_02870), which encodes an antifungal compound that inhibits the growth of BCA cells. The present findings provide novel insights into the interactions between pathogens and BCAs with specific mechanisms of action at the transcriptome level, thus helping to explain the relative ineffectiveness of BCAs under certain conditions.