Growth Characteristics and Ginsenosides Production of In Vitro Tissues of American Ginseng, Panax quinquefolius L.

Abstract

American ginseng (Panax quinquefolius L.) is an economically important perennial herb whose root is highly valued in the Orient for its medicinal properties. The root grows into different morphotypes, notably “bulb or round” (BLB), “man-like” (ML), and “straight or stick” (STK), and these roots are valued differently by consumers because they are assumed to have different medicinal qualities. Currently, wild-growing and field-cultivated plants are the major source of ginseng roots available on the market; however, because of declining wild populations and the lengthy time required in field cultivation to produce marketable root size, in vitro propagation has been sought as a potential alternative to supply ginseng's bioactive components (ginsenosides). The objectives of this study were: 1) to evaluate how explants derived from the three root morphotypes (lines), BLB, ML, and STK, responded to in vitro callus induction and growth; 2) to compare ginsenosides profiles and content among stock roots and their callus tissues; and 3) to assess genetic diversity among stock roots. Root explants were cultured on solid Murashige and Skoog medium supplemented with 1.0 mg·L−1 2,4-D and 0.1 mg·L−1 kinetin for 12 weeks. Explants from the three lines exhibited varied callus induction response, growth, and ginsenosides production. Explants from the ML line induced callus faster, were prolific in growth, and accumulated more biomass compared with explants from BLB and STK lines. ML lines (both stock roots and calluses) had significantly higher total ginsenosides content than either BLB or STK lines. There were positive and highly significant correlations between total ginsenosides content of stock roots and callus tissues and callus dry weights. Ginsenosides profiles varied among lines. ML lines exclusively exhibited low Rg1/high Re ginsenosides profiles, whereas BLB and STK lines exhibited mixed Rg1/Re profiles. Random amplified polymorphic DNA (RAPD) analysis of stock roots showed genetic variations within and among lines; however, there was no clear link between DNA bands or band patterns and ginsenoside profiles or content. Overall, these results showed that ginsenoside content of stock roots directly influenced callus induction response and subsequent callus biomass and ginsenoside content. These results provide information that could be useful in selecting suitable stock plants for in vitro production of ginsenosides. Also, because there are no ginseng cultivars, this information would be useful in advancing breeding efforts toward selecting superior cultivars for this species. Chemical names used: 2,4-dichlorophenoxyacetic acid (2,4-D)