DNA Barcoding Reveals Limited Accuracy of Identifications Based on Folk Taxonomy

Abstract

BackgroundThe trade of plant roots as traditional medicine is an important source of income for many people around the world. Destructive harvesting practices threaten the existence of some plant species. Harvesters of medicinal roots identify the collected species according to their own folk taxonomies, but once the dried or powdered roots enter the chain of commercialization, accurate identification becomes more challenging.MethodologyA survey of morphological diversity among four root products traded in the medina of Marrakech was conducted. Fifty-one root samples were selected for molecular identification using DNA barcoding using three markers, trnH-psbA, rpoC1, and ITS. Sequences were searched using BLAST against a tailored reference database of Moroccan medicinal plants and their closest relatives submitted to NCBI GenBank.Principal FindingsCombining psbA-trnH, rpoC1, and ITS allowed the majority of the market samples to be identified to species level. Few of the species level barcoding identifications matched the scientific names given in the literature, including the most authoritative and widely cited pharmacopeia.Conclusions/SignificanceThe four root complexes selected from the medicinal plant products traded in Marrakech all comprise more than one species, but not those previously asserted. The findings have major implications for the monitoring of trade in endangered plant species as morphology-based species identifications alone may not be accurate. As a result, trade in certain species may be overestimated, whereas the commercialization of other species may not be recorded at all.

Unidentifiable by morphology: DNA barcoding of plant material in local markets in Iran

“…Alternatively, the traditional products may consist of different species than those mentioned in the pharmacopoeia. Similar research in Morocco also showed a high level of substitution and suggested that, in addition to the options above, gradual substitution over time of one species for another could explain the discrepancy [9,22]. Some examples of cases where DNA barcoding showed samples to be completely different from the putative species in this study are “Marzeh” and “Maryam goli.” The vernacular name “Marzeh” refers to either Satureja laxiflora C.Koch or S .…”

DNA Barcoding and Pharmacovigilance of Herbal Medicines

“…Species delimitation based on molecular data is being developed but requires many accessions as well as many loci [58]. The most reliable approach to DNA barcoding of plants is the creation of high-quality specific sequence reference databases for the identification of targeted species [31,37,59]. Such databases should include reference to a specific taxonomic voucher that has been determined by a professional taxonomist.…”

The relevance of pharmacognosy in pharmacological research on herbal medicinal products

“…Microscopic identification can be applied to whole, fragmented, or powdered material, and it can be helpful in cases where plant species are undistinguishable merely based on their macroscopic characteristics [30]. These methods are very time-and cost-efficient; therefore, they are very widely applied for authentication purposes of traditional herbs [129,130]. Also, herbal pharmacopeia monographs usually contain a detailed description of macroscopic and microscopic drug characteristics, allowing a first assessment of identity and, in some cases, the identification of common adulterants [30,131].…”