Identification of Suitable Barcodes for Specifically Detecting Adulterants of Turnip (Brassica rapa) and Radish (Raphanus sativus) in Maca (Lepidium meyenii)

Maca (Lepidium meyenii Walp.), an edible medicinal plant and popular dietary supplement, is native to South America in the Andes mountains of Peru. However, maca is frequently adulterated due to its high nutritional and medicinal value, which compromises its safety and effectiveness. In the present study, maca and its two adulterants, Brassica rapa (turnip) and Raphanus sativus (radish), were identified by one nuclear barcode (ITS) and four chloroplast barcodes (matK, psbA-trnH, rbcL, and trnL-trnF). All five DNA barcodes were perfectly identified in maca, turnip, and radish. Out of the five tested barcodes, trnL-trnF could be regarded as the ideal barcode for detecting turnip/radish adulteration in maca as it generated different sequence length among these three species, it was further validated by mixing turnip/radish into maca at various proportions, and trnL-trnF efficiently and sensitively detected adulteration even at a very low level (0.5% of adulteration).