Biocontrol Efficacies of Bacillus Species Against Cylindrocarpon destructans Causing Ginseng Root Rot

Abstract

Two antifungal bacteria were selected from forest soils during the screening of microorganisms antagonistic to Cylindrocarpon destructans, a cause of ginseng root rot. The antifungal bacteria were identified as Bacillus subtilis (I4) and B. amyloliquefaciens (yD16) based on physiological and cultural characteristics, the Biolog program, and 16S rRNA gene sequencing analyses. Antagonistic activity of both bacterial isolates to C. destructans increased with increasing temperature. More rapid starch hydrolytic activity of the bacteria was seen on starch agar at higher temperatures than at lower temperatures, and in the higher density inoculum treatment than in the lower density inoculum treatment. The bacterial isolates failed to colonize ginseng root the root tissues inoculated with the bacteria alone at an inoculum density of 1 × 10 6 cfu/ml, but succeeded in colonizing the root tissues co-inoculated with the bacteria and C. destructans. Scanning electron microscopy showed that the pathogen was damaged by the low-density inoculum treatment with the bacterial isolates as much as by the high-density inoculum treatment. Both bacterial isolates were more effective in reducing root rot when they were treated at a concentration of 1 × 10 6 cfu/ ml than at 1 × 10 8 cfu/ml. Also, only the former treatment induced prominent wound periderm formation, related to structural defense against pathogen infection. The results suggest that the bacterial antagonists may have high potential as biocontrol agents against ginseng root rot at relatively low-inoculum concentrations.

Characterization of Bacillus mojavensis KJS-3 for the Promotion of Plant Growth

“…Many studies have demonstrated PGPEs to be effective biocontrol agents for plant protection in vitro and in vivo and field application of suspensions of Bacillus spp. in the growth season of plants more over resulted in significantly reduced disease incidence [1,9,14,19]. PGPEs are rhizosphere bacteria that can enhance plant growth in a wide variety of applications such as microbial pesticides, microbial fertilizers, and animal feed additives.…”

Biological control of Colletotrichum panacicola on Panax ginseng by Bacillus subtilis HK-CSM-1

“…Members of the genus Bacillus are known to suppress various plant diseases, such as anthracnose in red peppers [3] , mangos and wax apples [4] , as well as root rot in ginseng caused by Fusarium cf. incarnatum and Cylindrocarpon destructans [5,6] . Furthermore, Bacillus subtilis has been reported to be relatively benign to humans and several B. subtilis strains are listed by the Organic Materials Review Institute [7] .…”

Chlamydospore Induction from Conidia of Cylindrocarpon destructans Isolated from Ginseng in Korea

“…However, this method is expensive for soil-borne disease, and the effects of chemicals diminish over time as it takes at least 4 years before ginseng is harvested. Alternatively, a biological strategy has been widely performed; several Bacillus strains were shown to have a highly antagonistic effect against C. destructans [ 8 ]. However, in most tests aimed at confirming the efficacies of such biological agents, only the inhibition levels of mycelial growth have been measured, and not inhibition of chlamydospore germination.…”