Abstract
Certain species within the genus Panax L. (Araliaceae) contain pharmacological precious ginsenosides, also known as ginseng saponins. Species containing these compounds are of high commercial value and are thus of particular urgency for conservation. However, within this genus, identifying the particular species that contain these compounds by morphological means is challenging. DNA barcoding is one method that is considered promising for species level identification. However, in an evolutionarily complex genus such as Panax, commonly used DNA barcodes such as nrITS, matK, psbA-trnH, rbcL do not provide species-level resolution. A recent in silico study proposed a set of novel chloroplast markers, trnQ-rps16, trnS-trnG, petB, and trnE-trnT for species level identification within Panax. In the current study, the discriminatory efficiency of these molecular markers is assessed and validated using 91 reference barcoding sequences and 38 complete chloroplast genomes for seven species, one unidentified species and one sub-species of Panax, and two outgroup species of Aralia L. along with empirical data of Panax taxa present in Vietnam via both distance-based and tree-based methods. The obtained results show that trnQ-rps16 can classify with species level resolution every clade tested here, including the highly valuable Panaxvietnamensis Ha et Grushv. We thus propose that this molecular marker to be used for identification of the species within Panax to support both its conservation and commercial trade.
Highlights
The genus Panax L. is well-known in culinary and medicinal traditions in many countries including China, Korea, Japan, and Vietnam
Two sister species P. bipinnatifidus and P. stipuleanatus were separated into two distant clades based on the combined dataset of six markers by Zuo et al (2011)
P. vietnamensis was reported to belong to the same clade as Panax japonicus var. major (Burkill) C.Y.Wu et Feng, Panax pseudoginseng subsp. himalaicus H.Hara based on 18S rRNA and matK (Komatsu et al 2001), and to be closely related to Panax zingiberensis C.Y.Wu et Feng and Panax wangianus S.C.Sun based on ITS2 (Ali et al 2012), P. notoginseng based on ITS, matK, rbcL, psbA-trnH, and 18S rRNA (Le et al 2017), as well as P. japonicus based on in silico data of four potential markers (Manzanilla et al 2018)
Summary
The genus Panax L. is well-known in culinary and medicinal traditions in many countries including China, Korea, Japan, and Vietnam. Known as ginseng saponins with strong antioxidant, antidiabetic, antitumor, and neuroprotective activities (Jung et al 2017; Patel and Rauf 2017) Due to their high commercial demand, many species within Panax have been over-harvested and are at risk of extinction (Case et al 2007; McGraw et al 2013; Manzanilla et al 2018). In Vietnam, there are three species of Panax including Panax vietnamensis Ha et Grushv., Panax stipuleanatus H.T.Tsai et K.M.Feng, and Panax bipinnatifidus Seem., all recorded and classified as endangered. Of these species P. vietnamensis is endemic to Vietnam and is considered to have the highest medical potential and is the most commercially valuable (Nguyen 2005; Nguyen et al 2007).
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