Differential antagonism of individual isolates and mixtures of yeasts against Fusarium and Trichoderma

Abstract: The soil microbiome comprises a plethora of tritagonists that can influence the antagonist-pathogen-plant interaction in many ways. Instead of screening for the strongest antagonist, we sought to identify yeasts that differentially suppress soilborne pathogens of the genus Fusarium and beneficial fungi of the genus Trichoderma in order to improve the biological control of fungal pathogens. We quantified the antagonistic/agonistic activity of 40 yeast isolates against two Fusarium and three Trichoderma isolates, respectively. This screen identified a broad range of antagonistic activities and a positive correlation between the antagonism of yeasts against Fusarium and Trichoderma. Combining the six yeasts with the least effect on Trichoderma did not change the response against Trichoderma, but the mixture suppressed Fusarium more strongly than any of the six yeasts did when tested alone. This proof-of-concept experiment indicated that combinations of yeasts may exhibit altered, improved activities for the biological control of soilborne fungal pathogens as compared to single isolates. Mixtures of weakly antagonistic, inactive, or even agonistic microorganisms may thus provide a novel strategy for the biological control of the soilborne pathogen Fusarium.