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Deciphering the complex interactions between the apple microbiota and a biocontrol agent against post-harvest diseases (Pichia anomala strain K)

Sebastien Massart: University of Liège (ULg) - Gembloux Agro-BioTech

<div>The yeast<em> Pichia anomala</em> strain K is a Biological Control Agent (BCA) against two postharvest apple pathogens (<em>Penicillium </em>spp<em>.</em> and <em>Botrytis cinerea).</em> Progress has been made during the past two decades to understand the modes of action of the strain K through microbiology, enzymatic, genomic, transcriptomic and proteomic studies. Nevertheless, BCAs commercial application has been hampered by low or non-reliable efficacies in comparison to fungicide treatments (Droby et al., 2016). 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 characterized at large scale the microbiota residing at the surface of apple and evaluate its potential 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 biobank of apple microbiota. Gene centered high throughput sequencing allowed to decipher the bacterial and fungal populations of the microbiota. Biological assays on apple fruits have been carried out by co-inoculating the apple microbiotas with the strain K and <em>B. cinerea</em>. 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 traits or strains/species which are benefic to the strain K efficacy.</div>