There is an urgent need for novel products that lower the dependence on agrochemicals. Biological control organisms (BCOs) and priming are two approaches to boost plant innate immunity against biotic stressors. Popular priming compounds include pectin- and chitosan-derived oligosaccharides, OGs and COS, and recently levan-derived oligosaccharides (LOS) have also been shown to protect an array of plants against grey mold. We hypothesize that LOS can be released from levan accumulating BCOs through the action of endo-levanases from beneficial levan-degrading BCOs, possibly assisted by plant 6-FEHs. Next, LOS may function as prebiotics and/or signals in cross kingdom communication between beneficial microbes, plants and plant pathogens. Here, LOS producing BCOs from the lettuce and barley rhizospheres will be isolated and combined with levans, LOS, COS and OGs in the context of seed(ling) priming, considering systemic protection at the leaf level against grey mold (lettuce) and Fusarium Head Blight (barley). Promising endo-levanases and plant 6-FEHs will be fully characterized and selected to develop CRISPR knockout lines that will be compared to their wild-type counterparts under biotic stress. This will increase our mechanistic insights in the role of these enzymes in LOS production. This research will provide powerful tools to develop innovative formulations for plant protection based on combinations of levans, levan degrading BCOs and different protective oligosaccharides.