A DNA Barcode-Based RPA Assay (BAR-RPA) for Rapid Identification of the Dry Root of Ficus hirta (Wuzhimaotao)

Background: Wuzhimaotao (the dry root of Ficus hirta) is used as both medicine and food ingredient by the locals in areas around Nanling Mountains of China. Due to its very similar external morphologies with Duanchangcao (the root of Gelsemium elegans, which contains gelsemine that is extremely neurotoxic) and the associated growth of these two plants, incidents of food poisoning and even death frequently occur, resulting from the misuse of Duanchangcao as Wuzhimaotao. The aim of this study is to develop a fast, even, on-spot approach to identification of Wuzhimaotao. Methods: We used DNA barcode-based recombinase polymerase amplification (BAR-RPA) with species–specific primers targeting the internal transcribed spacer (ITS) region of the rDNA of F. hirta. BAR-RPA reaction time and temperature were optimized and the specificity and sensitivity of BAR-RPA species–specific primers were assessed. Results: This technique showed a high specificity and sensitivity to amplify the genomic DNA of F. hirta and allowed for rapid amplification (within 15 min) of the ITS region under a constant and mild temperature range of 37–42 °C without using thermocyclers. Conclusions: The BAR-RPA assay with a fast DNA extraction protocol provides a simple, energy-saving, and rapid method for identification of Wuzhimaotao in both laboratory and field settings.