Improving biological control using microbiota: the case of apple for postharvest diseases

The use of Biological Control Agents (BCA) in commercial application has been hampered by low or non-reliable efficacies in comparison to fungicide treatments (Droby et al., 2016). To address this concern, Massart et al. (2015) identified new alternatives to improve BCA efficacy using epiphytic microbial communities (microbiota) by the selection of helper strains and prebiotics of biocontrol. Helper strains are microorganisms that effectively enhance BCAs activities whereas prebiotics of biocontrol are molecules that modulate the microbiota composition to favor the biocontrol agent. The yeast Pichia anomala strain K is a BCA against apple two postharvest pathogens (Penicillium spp. and Botrytis cinerea). Progress have 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) and its ecological niche. However, the efficacy of strain K needs to be stabilized and improved. A good alternative is to focus on the interaction between strain K and the apple microbiota because once applied on the fruit surface, the strain K will face a complex microbiota where ecological interactions such as parasitism, mutualism and commensalism occur, thus affecting its efficacy and stability. In this study, we investigated the potential of apple microbiota to improve the efficacy of strain K against B. cinerea. Apple fruit samples were collected and their microbiota harvested to generate a diverse microbiota bank to be screened. The microbiota bank is made up of seventeen varieties grown in four disease management practices. Biological assays on wounded apple fruits have been carried out by co-inoculating each apple microbiota with the strain K and B. cinerea. The results of the biological assays revealed that the apple microbiota can either raise till 100%, drop or have no effect on the efficacy of strain K. Thanks to next generation sequencing that makes the microbiota profiling possible, studies are ongoing to identify ecological strains/species or groups of taxa which are benefic to the strain K efficacy.