Effects of Population and Age on Ginsenoside Content of American Ginseng (Panax quinquefolium L.)

American ginseng (Panax quinquefolium) is valued in traditional Asian medicine, and its use in Western countries has increased in recent years. The value of artificially-cultivated ginseng is much lower than that of woods-cultivated or wildcollected ginseng, but populations of the latter are threatened throughout its range. Our goal is to identify what factors influence the concentration of the pharmacologically active ginsenosides. Age-related increase in ginsenosides have been reported by several authors but variation among wild populations has not been considered. Ginsenoside analysis via HPLC was performed on roots collected from 8 different NY State populations. Statistical analysis of the effects of population and age on ginsenoside content indicated that there was a significant effect of both on ginsenoside Rc, a significant interaction between population and age for ginsenosides Rb1 and Rb2, and a significant three way interaction between population, age and root fresh weight for Re. Ginsenosides Rb1 and Rb2 increased with age for some populations, but not for other populations. We conclude that the prevailing generalization that ginsenosides increase with root age cannot be applied to wild North American ginseng without taking into consideration population differences. The effects of population on ginsenoside content is likely to be related not only to environmental differences among collection sites but also genetic differences since there was considerable (several fold) variation in the content of ginsenosides within single populations. It is likely therefore that selection and cloning of individual roots for higher ginsenoside content could be a useful strategy for improvement of this medicinal crop. These results also suggest that populations could be selected based on their sensitivity to age and fresh weight-related increase in ginsenosides concentration. INTRODUCTION Ginseng is a valuable medicinal herb that is used widely in traditional Asian medicine, and its use in Western countries is increasing. The value of this herb root-crop varies depending on several factors including whether it is cultivated or wild-collected, what production system is used to grow it under cultivation, and the age of the plant. Roots collected from the wild are worth approximately $600 per pound dry weight, whereas woods cultivated ginseng is worth approximately 1/3 than amount, and intensively (artificial shade) cultivated ginseng is worth 10% or less as much as wildcollected ginseng. Although wild ginseng is becoming increasingly scarce, it is still collected in substantial quantities throughout most of its range in eastern North America. There are competing claims that roots collected from or grown in one region are of higher quality than roots collected from another region. Because criteria for determining quality and economic value are largely subjective it is difficult to assess the validity of such Proc. XXVI IHC – Future for Medicinal and Aromatic Plants Eds. L.E. Craker et al. Acta Hort. 629, ISHS 2004 Publication supported by Can. Int. Dev. Agency (CIDA) 162 claims. Furthermore, lack of objective quality criteria complicates the goal of long term deliberate genetic improvement of the crop through breeding or clonal selection. Although the medicinal properties of American Ginseng are thought to be associated, at least in part, with a group of triterpene saponins known as ginsenosides, the ginsenoside content is not taken into consideration in assessing quality, i.e. there is no clear relationship between the price of ginseng and its ginsenoside content. Instead, root morphology (shape), and to some extent root age, are the primary determinants of quality and price. Although there is no direct determination of ginsenoside content in assessing quality and price, the fact that older roots are considered more valuable (per unit weight), does relate indirectly to ginsenoside content since there are several reports that ginsenoside content increases with age (Court, Reynolds, and Hendel, 1996; Jackson, Dini, Lavandier, Rupasinghe, and Proctor, 2001; Jackson, Rupasinghe, and Schooley, In Review for this volume; Soldati and Tanaka, 1984). Although genetic effects of ginsenoside content can be inferred from studies which have compared different cultivated populations (Jackson, Dini, Lavandier, Rupasinghe, and Proctor, 2001; Jackson, Rupasinghe, and Schooley, In Review for this volume; Li, et al. 1996), little is known about the extent of genetic influence on ginsenoside content among wild populations. This could be valuable information in future breeding and/or clonal selection programs. Hence the objectives of this study was to compare ginsenoside content of several wild American ginseng populations from New York state and determine the extent to which genetic difference contribute to observe variation in ginsenosides among populations. This report will present the results from the first year of an ongoing three year study. MATERIALS AND METHODS Collection and Planting of Wild American Ginseng Populations In the Fall of 2000, wild ginseng roots were collected from 8 different hardwood forested sites, within a contiguous five county region in south-central New York (Fig. 1). These included 3 populations from Chenango county, 2 populations from Deleware county, 1 population from Broome county, 1 population from Otsego county, and 1 population from Schoharie county. Approximately 150 plants were collected from each site, and each set is referred to as a population below. After collection, root age was estimated by counting annual bud scars (nodes) along the rhizome. Plants ranged in age because it was not feasible to predetermine root age before digging the plant, nor would it have been feasible to collect from the wild populations sufficient numbers of equal or closely-aged plants for the experiment. Most plants ranged in age from 3 to 12 years old, except one plant from population 1 was one year old, one plant from each of populations 1 and 3 was two years old, one plant from population 5 was 16 years old, and one plant from population 1 was 30 years old. Six to 15 plants, depending on population, were collected from each population for analysis of ginsenoside at the start of the experiment (Time0), and approximately 40 of the remaining plants of each of the 8 populations were planted at each of three experimental woods garden sites (same 8 populations at each of 3 sites). These included Cornell University’s Arnot Teaching and Research Forest near Van Etten, NY; Phetteplace Raw Furs near Norwich, NY and Sylvan Botanicals near Cooperstown, NY. The latter two experimental ginseng plantings were managed by cooperating ginseng growers, Bruce Phetteplace, and Scott Harris, respectively. A “woods cultivation” management system was used at each site, i.e. natural forest shade and minimal inputs other than bed preparation which consisted of rototilling and the addition of leaf mulch from local hardwoods (maple, oak, etc.). Ginsenoside Analysis At Time0 (Fall, 2000) the number of replicate plants used for ginsenoside analysis, ranged from 6 to 15, depending on population. Subsequently, at the end of the first