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Commercial teas highlight plant DNA barcode identiﬁcation successes and obstacles Mark Y. Stoeckle, Catherine C. Gamble, Rohan Kirpekar, Grace Young, Selena Ahmed, and Damon P. Little*
Commercial Teas Highlight Plant DNA Barcode Identification Successes and Obstacles SUBJECT AREAS: BIOINFORMATICSEARTH AND ENVIRONMENTAL SCIENCES Mark Y. Stoeckle1, Catherine C. Gamble2, Rohan Kirpekar2, Grace Young2, Selena Ahmed3 PLANT SCIENCES & Damon P. Little4 BIODIVERSITY 1 Program for the Human Environment, The Rockefeller University, New York, NY 10065, USA, 2Trinity School, New York, NY 10024, USA, 3Department of Biology, Tufts University, Medford, MA 02115, USA, 4Lewis B. and Dorothy Cullman Program for Received Molecular Systematics, The New York Botanical Garden, Bronx, New York, NY 10458, USA. 25 May 2011 Accepted Appearance does not easily identify the dried plant fragments used to prepare teas to species. Here we test 6 July 2011 recovery of standard DNA barcodes for land plants from a large array of commercial tea products and Published analyze their performance in identifying tea constituents using existing databases. Most (90%) of 146 tea 21 July 2011 products yielded rbcL or matK barcodes using a standard protocol. Matching DNA identifications to listed ingredients was limited by incomplete databases for the two markers, shared or nearly identical barcodes among some species, and lack of standard common names for plant species. About 1/3 of herbal teas generated DNA identifications not found on labels. Broad scale adoption of plant DNA barcoding may Correspondence and require algorithms that place search results in context of standard plant names and character-based keys for requests for materials distinguishing closely-related species. Demonstrating the importance of accessible plant barcoding, our findings indicate unlisted ingredients are common in herbal teas. should be addressed to M.Y.S.
samples•146 products: •33 manufacturers •17 countries of origin •73 Camellia sinensis (tea) products •73 ‘herbal’ products •44 listed a single plant ingredient •29 listed 2–10 different plants •82 plant common names on labels •Herbs of Commerce (2nd Edition)
barcoding techniques•morphologically homogenous samples (86%) •one DNA extraction•morphologically heterogeneous samples (14%) •divided into morphologically homogeneous material •average 3, range 2–8 •DNA extracted separately•Qiagen DNeasy96 plant kit with added protease K•matK: 3F/1R•rbcL: F1/R634
‘portable’ laboratory•10 specimens reanalyzed •processed by Catherine, Rohan, and Grace•Qiagen DNeasy plant mini kit•rbcL: F1/R634•commercial sequencing facility (Macrogen)
label incompatibility•4% of Camellia sinensis (tea) products•35% of ‘herbal’ products
product: K24 ginger root, natural ﬂavors, linden, lemon label: peel, blackberry leaves, lemongrass, citric acid non–label annual bluegrass (Poa annua) DNA: K24 rbcL is an exact match to Poa annua (annual bluegrass), family Poaceae. Listedinterpretation: ingredient lemongrass (Citropogon citratus) is also in Poaceae. K24 rbcL has lower identity to C. citratus (94.0%; GQ436383).
product: MRa6 label: ginger, chicory non–label stevia (Stevia rebaudiana) DNA: MRa6 rbcL is an exact match to Stevia rebaudiana, family Asteraceae, tribe Eupatorieae. Listed ingredient chicoryinterpretation: (Cichorium intybus) is also in family Asteraceae, but in a different tribe, Cichoreae. MRa6 rbcL has lower identity to C. intybus (97.4%; L13652).