Ginsenosides as host resistance factors in American ginseng (Panax quinquefolius)

American ginseng (Panax quinquefolius L.) produces a number of saponins (ginsenosides). The ability of saponins from cultivated American ginseng to inhibit fungal growth in vitro was evaluated. Fungi exhibited a range of sensitivity to ginsenosides extracted from roots collected in two growing seasons. Important root pathogens (Cylindro carpon destructans, Fusarium solani, and Fusarium oxysporum) were unaffected by these phytochemicals at a concentration of 1 mg·mL–1, whereas the growth of Alternaria panax and nonpathogenic Trichoderma spp. was inhibited. The same trend emerged when a range of ginsenoside concentrations was used on a subset of fungi. Hyphal growth of C. destructans was unaffected up to a level of ginsenosides approaching that found in roots (i.e., ~ 3% dry weight). The growth of F. solani was significantly less than that of the control at saponin concentrations of 0.1 to 3.0% (w/v), but was relatively unaffected in comparison to growth of Trichoderma hamatum and A. panax.