Impact of apple microbiota on Pichia anomala strain K, a biocontrol yeast against apple major postharvest diseases

The yeast Pichia anomala strain K is a Biological Control Agent (BCA) against two postharvest apple pathogens (Penicillium spp. and Botrytis cinerea). Progress has been made during the past two decades to understand the modes of action of the strain K through various studies (microbiology, enzymatic, genomic, transcriptomic and proteomic). Nevertheless, BCAs commercial application has been hampered by low or non-reliable efficacies in comparison to fungicide treatments (Droby et al., 2016) as it is the case of the strain K. Massart et al. (2015) identified new alternatives to improve BCA efficacy using microbiota. Once applied on the fruit surface, a BCA will face a complex microbiota where ecological interactions such as parasitism, mutualism and commensalism occur, thus affecting its efficacy. In this study, we evaluate the potential of apple microbiota to influence the efficacy of the strain K. Apple fruit samples of seventeen varieties grown in four disease management practices have been collected and their epiphytic microbiota harvested to create a bank of apple microbiota to be screened. Biological assays on apple fruits have been carried out by co-inoculating each apple microbiota with the strain K and B. cinerea. The results of the preliminary assays revealed that the apple microbiota can either raise, drop or have no effect on the efficacy of the strain K. Study is ongoing to identify ecological strains/species or groups of taxa which are benefic to the strain K efficacy.