Master of Science
Ginseng Replant Disease (GRD) is a syndrome in which ginseng cannot be cultivated in soil previously used to grow ginseng. Since GRD can persist for decades, it severely impacts the Ontario ginseng industry. To better understand the origin of GRD, the impact of ginseng cultivation on the soil microbiome was investigated in bulk soil of three newly planted ginseng gardens in Ontario, from seeding through two years of cultivation. While specific trends in species richness, diversity and composition were unclear, PERMANOVA analyses confirmed that they changed over time. Known GRD-related pathogens, including Ilyonectria mors-panacis and Fusarium oxysporum, were detected in ginseng garden soils. An increase in the relative pathogen load in the soil of ginseng gardens may be a primary driver of the development of GRD but could also serve in the development of a diagnostic tool to identify risk of GRD in soils of unknown ginseng cultivation history.
Summary for Lay Audience
Ginseng is a plant farmed in Ontario for its roots, which are used in traditional Chinese medicine, vitamins, food, and drinks for its health benefits. Ginseng Replant Disease (GRD) is a disease that causes ginseng to grow poorly in soil that has previously been used to grow ginseng. GRD causes fewer, and smaller, roots to grow and increases the amount of root rot. GRD can last for decades and has greatly decreased the amount of land still available for ginseng farming in Ontario, which threatens the Canadian ginseng industry. While the exact cause of GRD is unclear, previous research has identified fungal pathogens that are present in most GRD-diseased gardens. Studies in Asia have found a decrease in the number and abundance of bacterial species and an increase in the number and abundance of fungal species in GRD soil. In this project, I sequenced fungal DNA found in ginseng garden soil from three newly planted ginseng gardens from seeding through two years of growth. The number and identity of microorganisms in soil influences the health of the soil, which then affects the health of the plants. By sampling four times a year, a more precise study of the changes in the fungi present in ginseng garden soil was achieved.
While I found that there are changes in fungal composition occurring in the soil, the changes were not large and were difficult to precisely define. I propose the two-year duration of ginseng cultivation in the study gardens was not long enough to influence the soil microbes. However, ginseng pathogens were found in my samples in low abundance which means there is an opportunity for these pathogens to increase in abundance over time, and potentially cause GRD symptoms in these gardens after harvest.
Lambert, Megan E., "Dynamics of the Soil Microbiome in Ginseng Gardens" (2021). Electronic Thesis and Dissertation Repository. 8066.