Characterization and antifungal properties against Botrytis cinerea of bacteria isolated from hemp seed oil

Botrytis cinerea is a pathogen infecting Cannabis sativa L. plants, causing economic losses, and can develop resistance to chemical fungicides, the use of which is restricted in cannabis production. Thus, developing biocontrol methods is imperative. Seven bacterial strains were isolated from hemp seed oil, characterized, and examined for the potential to control a B. cinerea isolate from cannabis. Three isolates, Bacillus mojavensis HOB3, Paenibacillus sp. HOB6 and Bacillus subtilis HOB7 exhibited significant inhibition of B. cinerea. These isolates were further evaluated for their biosurfactant activity using two liquid media, Lysogeny Broth (LB) and hydrocarbon-amended Bushnell and Haas (BH). The oil-spreading and drop-collapse assays revealed growth-medium-dependent variation in surface activity associated with biosurfactant presence. The BH cell-free extract (BH-CFE) of B. subtilis HOB7 showed the highest estimated biosurfactant presence and antifungal activity against B. cinerea, but both activities were absent when using the LB cell-free extract (LB-CFE) of B. subtilis HOB7. Thus, a potential relationship between antifungal activity and biosurfactant production was suggested. Genome mining of the strains identified gene clusters encoding compounds with antifungal activity, including the biosurfactants polymyxin B, fusaricidin B, fengycin, and surfactin. To our knowledge, this is the first report of the isolation of hemp seed oil bacteria with potential biocontrol properties against fungal phytopathogens