Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Biology

Supervisor

Mark A. Bernards

Abstract

American ginseng (Panax quinquefolius L.) produces natural products called ginsenosides. The biggest challenge Ontario commercial ginseng farmers face is ginseng replant disease. To understand the function of ginseng root exudates, ginsenoside accumulation and persistence over time were investigated. Currently, no reliable ginsenoside specific extraction method, characterizing the changes in soil chemistry exists. Ginsenoside extraction protocol optimization was required to determine how ginsenoside composition changed over time. Overall, protocol optimization resulted in a 30% increase in yield of ginsenosides compared to previous extraction protocols. In the ginseng gardens, ginsenoside accumulation occurs slowly and did not reach significantly measurable amounts until the end of the second growing season. Until that time, only trace amounts of ginsenosides were detected, but with no pattern of persistence. High levels of variation existed within sites, reflecting the non- uniform distribution of ginsenosides within garden soils. Future sample collection will solidify pattern seen in these fields.

Summary for Lay Audience

American ginseng (Panax quinquefolius L.) is cultivated for the pharmacological and medicinal properties deriving from the compounds, called ginsenosides, that it produces. The commercial ginseng industry in Ontario produces a substantial revenue worth hundreds of millions of dollars, solely on the P. quinquefolius species. The biggest challenge Ontario commercial ginseng growers face is ginseng replant disease (GRD), such that growers cannot successfully produce ginseng in the same garden after an initial crop. The disease is largely attributed to various pathogens; however, it is understood that GRD not only involves pathogens, but a combination of several abiotic and biotic factors that aren’t well studied. It is becoming apparent that the exudates from ginseng plants, including ginsenosides, and plant residues may play a role in this complex disease system. The objective of this project was to track ginsenoside accumulation and persistence in both newly planted and recently harvested ginseng gardens. To be able to characterize changes in soil chemistry, such as the accumulation and persistence of ginsenosides, a reliable method of detection must be employed. However, there was no consistent ginsenoside specific extraction method standard. Therefore, to accurately survey the soil for changes in ginsenoside composition, ginsenoside extraction protocol optimization and subsequent validation was required. Overall, improvements to the protocol were established, validated and applied to ginseng garden soils. Using the optimized protocol, ginsenoside levels were measured in newly planted gardens, and found to accumulate to significant levels (relative to the control) after two years of cultivation. Trace amounts of ginsenosides were detected in the harvested gardens, but showed no pattern of persistence in either of two sites monitored. Within site variation in ginsenoside content was evident, which was likely due to the non-uniform distribution of these compounds in the soil. Further collection and analysis of soils collected during the third and fourth growing seasons will allow for a more detailed analysis of pattern and trends described here. Ultimately, this project represents one piece of a puzzle that will add to our understanding of whether changes and composition in ginsenoside levels in newly planted and recently harvested ginseng gardens contribute to GRD.

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