Influence of Ginsenosides on the Pathogenicity of Ilyonectria spp.

Commercial cultivation of American ginseng (Panax quinquefolius L.) suffers from ginseng replant disease (GRD) when planted in a former ginseng garden. GRD typically manifests as a severe root rot due to the fungus Ilyonectria mors-panacis (A.A. Hildebr.) A. Cabral & Crous. Ginsenosides released to the soil by ginseng are thought to contribute to GRD mainly through the alteration of soil microbial communities. However, ginsenosides do not persist in ginseng garden soil post-harvest, suggesting that they are not direct contributors during GRD. Instead, ginsenosides can alter the virulence of Ilyonectria spp., specifically I. rufa A. Cabral & Crous, toward ginseng roots when pre-exposed to ginsenosides in vitro. Although I. rufa infection has not been previously implicated in GRD, a similar mechanism may occur in I. mors-panacis, thereby suggesting that ginsenosides may contribute to establishing the GRD state. Additionally, while various Ilyonectria isolates were able to metabolise select ginsenosides, this did not correlate with virulence.