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 fungus Ilyonectria mors-panacis. Ginsenosides
released to the soil by ginseng are thought to contribute to GRD but, to be effective,
ginsenosides need to be present in the soil. Using soils collected from commercial
ginseng gardens, I show that ginsenosides accumulate for the first three and a half years
of cultivation but decline in the fourth year. They are largely gone within one-year post-
harvest, suggesting that they are not direct contributors during GRD. Instead, I revealed
that Ilyonectria spp., specifically I. rufa, increase in virulence on ginseng roots when pre-
exposed to ginsenosides in vitro, suggesting ginsenosides may contribute to establishing
the GRD state. Additionally, while various Ilyonectria isolates were able to metabolize
select ginsenosides, this did not correlate with virulence.
