High concentrations of antagonistic bacterial strains from diseased sanqi ginseng rhizosphere suppressed Fusarium root rot

Sanqi ginseng Fusarium root rot caused by Fusarium oxysporum, is a serious soil-borne disease that threatens the sustainable development of the sanqi ginseng industry. This study determined the distinct soil bacterial communities from healthy and diseased plant rhizospheres. The ability of beneficial bacteria isolated from the diseased plant rhizosphere with different inoculation concentrations to control Fusarium root rot was investigated. The evenness and Shannon diversity indexes of bacteria in the diseased plant rhizosphere soil were significantly lower than those in the healthy plant rhizosphere soil because the bacterial communities were enriched in the Bacteroidetes and Proteobacteria phyla. The relative abundances of some genera such as Chryseobacterium, Flavobacterium, Stenotrophomonas, and Lysobacter were significantly larger in the diseased plant rhizosphere than in the healthy plant rhizosphere. Two strains, Bacillus sp. KW6 and Lysobacter sp. KW8, isolated from the diseased plant rhizosphere soil exhibited strong antagonistic activity against F. oxysporum, producing chitinase, cellulase, and beta-1,3-glucanase. Bacillus sp. KW6 with an inoculation concentration of 10(8) colony-forming units/g of soil exhibited the largest suppression in the control of sanqi ginseng root rot. The disease incidence of this treatment was only 38.89%, which was 59% lower than that of the control. Sanqi ginseng fresh weight increased with increasing inoculation concentration in treatments applied with antagonistic strains. The amounts of pathogen in stems and roots from treatments inoculated with antagonistic strains were significantly lower than the control.