Biological characteristics ofBacillus amyloliquefaciensAK-0 and suppression of ginseng root rot caused byCylindrocarpon destructans

The effect of Bacillus amyloliquefaciens AK-0 (AK-0) on ginseng root rot disease caused by Cylindrocarpon destructans was investigated.From 190 ginseng rhizosphere bacteria, AK-0 was selected for further analysis; its morphological characteristics were investigated by microscopy. AK-0 was identified as B. amyloliquefaciens using the Biolog system, 16S rRNA gene sequence analysis and examination of morphological and biochemical characteristics. Bacterial population and media optimization were estimated by the bacterial growth curve. The number of AK-0 cells was relatively higher in brain-heart infusion (BHI) medium than in other media. The potential antifungal effect of AK-0 culture filtrate on the in vitro conidial germination of C. destructans and root rot development on root discs and 4-year-old ginseng roots were assessed. Polymerase chain reaction (PCR) analysis of antibiotic biosynthesis gene expression suggested that the release of antibiotic compounds is involved in the antifungal effect of AK-0 and the suppression of ginseng root rot.These results indicate that the CF of AK-0 has antifungal effects on fungal pathogens of ginseng, resulting in the suppression of root rot disease caused by C. destructans.AK-0 is a potential source of novel bioactive metabolites. AK-0 CF exhibited antifungal effects against C. destructans on ginseng roots. PCR analysis indicated that the AK-0 harbours genes involved in the biosynthesis of antimicrobial compounds.