Biological control ginseng grey mold and plant colonization by antagonistic bacteria isolated from rhizospheric soil of Panax ginseng Meyer

Botrytis cinerea Pers.ex Fr. is a common soil borne fungal pathogen that infects economic crops, such as ginseng, worldwide. One ideal strategy for controlling B. cinerea is to develop and use beneficial rhizobacteria. The goal of this study was to assess the potential of rhizospheric bacteria as antifungal agents against ginseng grey mold disease. In this study, 169 bacterial strains isolated from rhizospheric soil of ginseng plants were screened using the K-B paper dispersion method and the Oxford cup plate assay. Subsequently, strain SW-34 was selected as a potential stock for biocontrol due to the broad-spectrum antibiotic activity of the SW-34 fermentation liquor against pathogens. To assess the antifungal efficacy of SW-34 against ginseng grey mold as well as its ginseng growth promotion abilities, pot experiments were performed under plastic greenhouse conditions. The morphology, physiological and biochemical characteristics, 16S rRNA and gyrB gene sequence were assessed to for the taxonomic characterization of strain SW-34. The results showed that, SW-34 (which was identified as Bacillus amyloliquefaciens) exhibited an antagonistic activity against B. cinerea of 85.13% and also provided broad-spectrum antibiotic activity. Inoculation of the SW-34 cell suspension suppressed disease lesions caused by ginseng grey mold with a strong control efficacy of 72.29%, which was significantly higher than that of the Mancozeb 70% WP fungicide treatment (p < 0.05). Moreover, SW-34 exhibited high cell densities in ginseng plants (root, leaf and stem) and promoted ginseng plant growth. Because the B. amyloliquefaciens SW-34 successfully inhibited ginseng grey mold, the results of our study provides a basis for the potential biocontrol of ginseng grey mold caused by B. cinerea.