Papiliotrema terrestris PT22AV VOCs contribute to soil suppressiveness against soil-borne fungal pathogens

Soil-borne fungal diseases are difficult to manage in intensive horticulture, and the microbial processes underlying disease-suppressive soils remain incompletely understood. Here, we investigate the ability of the yeast Papiliotrema terrestris PT22AV to control Fusarium oxysporum, Rhizoctonia solani , and Sclerotinia minor , as well as its mechanisms of action. PT22AV persisted in bulk soil, colonized the rhizosphere, and induced long-lasting, soil-dependent restructuring of resident microbial communities. Its antifungal activity was mediated primarily by volatile compounds whose production was linked to branched-chain amino acid catabolism through the Ehrlich pathway. Consistently, a gap1 Δ mutant impaired in amino acid transport showed reduced volatile-mediated inhibition in the presence of L-leucine and L-valine. These findings provide a first step towards defining the contribution of soil-associated yeasts to disease suppressiveness and establish PT22AV as a model for investigating metabolically regulated, volatile-driven biocontrol at the soil–root interface.