The genus Panax Linnaeus was first described by Carl Linnaeus in 1753 with the typical species P. quinquefolius Linnaeus (1753:1058) and P. trifolius L. (1753:1059) distributed in North America (Linnaeus 1753; Seemann 1868). Currently, this genus includes 16–18 species and varieties worldwide (Wen and Zimmer 1996; Wen 2001; Xiang and Lowry 2007), such as P. pseudoginseng Wall (1829:117) in Nepal; P. ginseng C.A. Mey (1842:524) in North Korea, Northeast China, and Russian Far East; P. japonicus (T. Nees) C.A. Mey (1843:340) in Japan and China; P. bipinnatifidus Seem (1868:54) in Northeast India, Nepal and China; P. stipuleanatus H.T. Tsai and K.M. Feng (1975:44) in China, and P. vietnamensis Ha and Grushv. (1985:519) in Vietnam (Wallich 1829; Fischer and Meyer 1841; Mey 1843; Tsai and Feng 1975; Ha and Grushvitzky 1985).
The appraisal of ginseng origin is now dominant to protect the interests of consumers as well as control the brand name of ginseng species (Ho and Pham 2020; Baeg 2022). In Vietnam, Panax species consisting of P. stipuleanatus H.T. Tsai et K.M. Feng (Tsai and Feng 1975); and P. vietnamensis Ha et Grushv (Ha and Grushvitzky 1985) have been reported. Based on molecular evidence of 18S rRNA, ITS, and matK gene sequences, P. vietnamensis was divided into three varieties including P. vietnamensis var. vietnamsensis, P. vietnamensis var. fuscidiscus, and P. vietnamensis var. langbianensis (Phan et al. 2014; Nong et al. 2016; Pham et al. 2020; Duy et al. 2020). There are differences in the value of these ginsengs on the market. P. vietnamensis var. vietnamensis (Ngoc Linh ginseng) possessed higher economic value than others. Therefore, it is necessary to find a technique to distinguish Ngoc Linh ginseng from others.
Simple sequence repeat (SSR), also called microsatellite, was the frequent molecular marker used in the authentication studies of ginseng species (Kim et al. 2007; Ma et al. 2007). In addition, expressed sequence tag (EST)-SSR markers were utilized to authenticate Panax cultivars by assessing the difference of specific alleles. In previous studies, P. ginseng cultivars could be identified by one or a combination of EST-SSR markers (Cheng-Jun et al. 2008; Kim et al. 2012). However, the analysis process to search for SSR or EST-SSR markers was time-consuming and required a genomic database (Jo et al. 2017).
Another microsatellite, short tandem repeat (STR) marker, has been promising for ginseng authentication. Hon et al. (2003) found nine microsatellites could be applied to differentiate American and Oriental ginsengs through screening STR markers from over 190 ginseng samples, then proposed the applicability of STR marker in the identification of Panax species. After that, Qin et al. (2005) developed a rapid technique for identification of ginseng species based on STR marker. Currently, most Panax species have chloroplast genomes published in GenBank and polymorphic microsatellites were detected frequently in these chloroplast genomes (Kim et al. 2015; Kim et al. 2017; Nguyen et al. 2018). Therefore, it is possible to generate STR markers and check their specificity for each Panax species or variety from chloroplast genomic data.
Recently, Nguyen et al. (2018) used derived cleaved amplified polymorphic sequences (dCAPS) markers to recognize ginseng species. The authors analyzed the chloroplast genomes from seven Panax species and discovered 1,128 single nucleotide polymorphisms (SNPs) in coding gene sequences. Subsequently, eighteen dCAPS markers were designed at the SNP sites and allowed to discriminate these ginsengs from each other (Nguyen et al., 2018). In addition, Nong et al. (2016) identified a new variety of Panax in Vietnam, P. vietnamensis var. langbianensis, based on the nucleotide sequence comparison of three gene regions: ITS1-5.8S-ITS2, 18S rRNA, and matK. Notably, the authors listed the SNP positions of the matK gene, which could be used to design dCAPS markers for distinguishing Panax species and varieties in Vietnam.