Successful biocontrol of Pichia spp. strains against Botrytis cinerea infection in apple fruit: unraveling protection mechanisms from proteomic insights

Botrytis cinerea causes major crop losses, especially under postharvest conditions. We have found that Pichia fermentans Pf-31 and Pichia terricola Pt-36 are two promising yeast strains that are able to efficiently control B. cinerea infection in apples. This effect is most pronounced when the yeasts are applied as live cells, although dead cells or culture filtrates also show some degree of control. Both strains arrest spore germination, inhibit mycelial growth, strongly attach to hyphae and promote their own proliferation in the fruit when B. cinerea is present, probably due to preferential colonization of apple wounds. Indeed, this metabolism enhancement was corroborated by a proteomic analysis, which revealed the differentially accumulated yeast proteins that contribute towards this antagonistic behavior. Besides the boost in proteins involved in energetic metabolism, other changes in proteins related to cell envelope composition are implicated in the biocontrol abilities of both strains, and this might be to facilitate hyphal adhesion or biofilm formation. The results of this study are of great value because they promote a deep understanding of the proteins that undergo changes during yeast antagonistic interactions, but also because they provide new insights into the proteomes of non-Saccharomyces yeasts, which have not been previously described.