Genetic characterization, ginsenoside analysis and micropropagation of American ginseng (Panax quinquefolius L.)

American ginseng (Panax quinquefolius L.), is an economically important medicinal plant native to eastern deciduous forests of North America. Like many other medicinal plants worldwide, P. quinquefolius is mainly collected from the wild. And because of its growing demand, abundance of wild populations is threatened with over harvesting. In West Virginia, P. quinquefolius is available both in cultivation and in the wild. Even though P. quinquefolius occurs in all 55 counties in West Virginia, patterns of its harvesting and cultivation vary across the state. As described in chapter 2, the genetic diversity and population structure of P. quinquefolius under two levels of wild harvesting and cultivation intensity in West Virginia was examined using RAPD analysis. It was observed that harvesting pressure decreased genetic diversity whereas cultivation intensity increased genetic diversity. Unlike other medicinal plants that are mostly harvested for their leaf materials, P. quinquefolius is harvested for its root material. The root of P. quinquefolius is unique because it has a tendency to branch into different morphotypes, and this variation in root shapes influences the perceived quality and hence value of P. quinquefolius roots in the market. In chapter 3, the profiles and contents of ginsenosides (bioactive constituents of ginseng) among the three common root morphotypes encountered in P. quinquefolius were assessed using HPLC, and a simple economic analysis was conducted to determine if sorting roots to respective morphotypes before selling can leverage returns for the grower. It was found that roots of "man-like" (ML) morphotypes had more total ginsenosides content than those of "bulb or round" (BLB) or "straight or stick" (STK) morphotypes. ML roots exhibited low Rg1/high Re profile whereas roots of BLB and STK morphotypes exhibited both low Rg1/high Re, and high Rg1/low Re profiles. Economic analysis showed that sorting roots to respective morphotypes at the farm level before selling can increase returns even with a modest price mark up for high quality roots (ML) only on condition that the strategy does not result in a price mark down on the other root morphotypes. Given the slow growing nature of ginseng, in vitro culture has been suggested as a quick alternative way of producing ginseng's bioactive components. In chapter 4, in vitro response and resulting ginsenosides content of explants from the three root morphotypes (ginseng lines) was evaluated. It was found that callus induction response, callus biomass, ginsenoside profiles and total ginsenosides content varied among lines. Correlations between total ginsenosides content of stock plants and callus biomass or total ginsenosides content of callus were positive and highly significant. RADP analysis revealed some genetic differences among root morphotypes. Based on molecular distances of their RAPD profiles, BLB and STK roots grouped into the same cluster and separate from ML roots. However, a specific link between a particular DNA band or banding pattern of roots and a given ginsenosides profile or abundance was not apparent. Overall, these findings will have important implications to the conservation, grading and breeding of P. quinquefolius and in vitro production of ginsenosides.