Abstract: Downy mildew is one of the most destructive grapevine diseases and resistance inducers could be promising alternatives to chemical fungicides. We previously showed that Trichoderma harzianum T39 induced resistance against downy mildew in grapevine. Our aims were to select novel beneficial microorganisms with improved ability to induce resistance and to finely characterize their mechanism of action against downy mildew. In particular, the strain T. atroviride SC1 (SC1) induced local and systemic resistance in grapevine. It showed also direct activity against Plasmopara viticola sporangia in vitro. SC1 could be a valuable biocontrol agent against downy mildew. However, the identification of key cellular processes is required to further develop robust resistance inducers.