Biocontrol Activity of spp. and spp. Against and Other Cannabis Fungal Pathogens.

Gray mold caused by is one of the most widespread and damaging diseases in cannabis crops worldwide. With challenging restrictions on pesticide use and few effective control measures, biocontrol agents are needed to manage this disease. The aim of this study was to identify bacterial biocontrol agents with wide-spectrum activity against . and other cannabis fungal pathogens. Twelve and strains were first screened with in vitro confrontational assays against 10 culturable cannabis pathogens, namely . , , , , , , , , sp., and sp. Six strains displaying the highest inhibitory activity, namely LBUM279, FZB42, LBUM1082, LBUM979, LBUM223, and Pf-5, were further assessed in planta where all, except LBUM223, significantly controlled gray mold development on cannabis leaves. Notably, LBUM279 and FZB42 reduced disease severity by at least half compared with water-treated plants and prevented lesion development and/or sporulation up to 9 days after pathogen inoculation. Genomes of LBUM279, LBUM1082, and LBUM979 were sequenced de novo and taxonomic affiliations were determined to ensure nonrelatedness with pathogenic strains. Moreover, the genomes were exempt of detrimental genes encoding major toxins and virulence factors that could otherwise pose a biosafety risk when used on crops. Eighteen gene clusters of potential biocontrol interest were also identified. To our knowledge, this is the first reported attempt to control cannabis fungal diseases in planta by direct antagonism with beneficial bacteria.