Resistance to copper in Lysobacter capsici AZ78: a starting point for the development of a new sustainable management of Plasmopara viticola?

Little is known about the biology of members of the bacterial genus Lysobacter although it encompasses species with high potential in plant protection. In this work, we investigated on biological features of L. capsici AZ78 a strain capable to control of Plasmopara viticola, the causal agent of grapevine downy mildew. Interestingly, it has been assessed that AZ78 resists copper ions and its resistance to this metal is probably due to the presence of genes coding for copper oxidase (copA) and copper exporting PIB-type ATPases (ctpA). Resistance to copper allowed L. capsici AZ78 to be combined with a low-dose of a copper-based fungicide, leading to more effective control of grapevine downy mildew. Furthermore, L. capsici AZ78 persists in the phyllosphere of grapevine plants and tolerates environmental stresses such as starvation, freezing, mild heat shock and UV light irradiation. These biological traits suggest that L. capsici AZ78 could be a suitable candidate for developing a new biofungicide to be used in combination with copper to control grapevine downy mildew.