Yeast-Fusarium interactions and mycotoxin modulation in the phyllosphere.

Yeasts are prevalent members of the phyllosphere microbiome, but fundamental knowledge of the chemical basis of their interactions with other members of the phyllosphere microbiota remains largely elusive. Our previous study revealed that wheat flag leaves harbor taxonomically diverse populations of yeasts with various traits important for successful colonization and survival in the harsh phyllosphere environment. In this study, we investigated interactions between two specific yeast genera, Aureobasidium and Metschnikowia, and the mycotoxigenic fungus Fusarium graminearum, causal agent of Fusarium head blight (FHB). Using multiple experimental approaches, we demonstrate that phyllosphere yeasts effectively colonize wheat leaves and heads, markedly reducing FHB incidence when established before pathogen arrival. Based on metabolomic data, we further show that Aureobasidium and Metschnikowia isolates can degrade the Fusarium mycotoxin deoxynivalenol (DON) and DON-inducing plant compounds produced during or in response to FHB. Our findings highlight the ecology of phyllosphere yeasts and the chemical basis of their multipartite interactions with a mycotoxigenic fungus and the host plant.