Genetic and demographic patterns in American ginseng (Panax quinquefolius L.) populations from western North Carolina

Background/Question/Methods

Wild American ginseng (Panax quinquefolius L.), native to Eastern United States, has been harvested and exported to Asia for over 200 years for use as a stimulant in Eastern medicinal preparations.  Because the biologically active compounds, ginsenosides, are most concentrated in the roots, collection for export requires the removal of the entire plant.  Aggressive harvesting and non-compliance with harvesting guidelines has caused P. quinquefolius to be listed as a CITES Appendix II species since 1973. Studies examining the genetic diversity at allozyme loci have shown loss of genetic diversity, outbreeding, and genetic structure in unprotected populations. We used newly published microsatellite primers to assess genetic relatedness among American ginseng individuals from five Western North Carolina populations with different levels of harvesting protection.  Leaflets from 158 individuals were collected, total genomic DNA was extracted, and samples were PCR-amplified with four different primer sets.   Genetic data were analyzed using GenAlEx and were then correlated with demographic variables including plant size and reproductive status.

Results/Conclusions

Allelic diversity varied significantly among populations (P < 0.001), as did the percent of microsatellite loci that showed within-population polymorphisms (P < 0.001).  More private alleles were found in the two isolated populations than in the three that experienced poaching (P < 0.001).  All five populations deviated significantly from Hardy-Weinberg equilibrium (P = 0.010), as expected.   AMOVA results showed that 85% of the molecular variance was found within populations,  and Nei’s statistics revealed that genetic distances were not related entirely to geography.  Although plant size differed among populations (P = 0.007), reproductive status did not, and neither variable was correlated with any measure of genetic diversity.  Ongoing work is sampling additional populations and is correlating genetic data with analyses of ginsenoside content, with the long-term goal of attributing patterns of ginsenoside production to specific genotypes.