Identification of Yams – A Comparative Study of the Tubers of Four Species of Dioscorea L. (Dioscoreaceae) by Microscopy and HPTLC
The genus Dioscorea L. (Dioscoreaceae) s.l. consists of about 630 species distributed in the tropical and warmer parts of the world . The starchy tubers ('yams') are economically important for their edible and medicinal uses. The present work provides a comparative anatomy and HPTLC analysis of the tubers of four species of Dioscorea, namely D. balcanica, D. bulbifera, D. cayennensis subsp. rotundata and D. villosa. The rootstock in D. balcanica and D. villosa is rhizomatous, whereas, it is tuberous in the other two species. The present study showed that the anatomical characteristics such as features of periderm; presence or absence of sclereids, crystals of calcium oxalate and mucilage ducts; and features of starch grains are – in conjunction with HPTLC – useful in distinguishing these species . Detailed anatomical descriptions illustrated with light and SEM images, and comparative HPTLC analysis, are provided.
Fig. 1: Anatomy and micromorphology of yams (Dioscorea spp.). (a-d: light microscopy; e-f: scanning electron microscopy). a & b- D. balcanica tuber in TS showing a portion of tuber (a) and vascular bundle (b); c- starch granules in D. bulbifera; d & e- TS of D. cayennensis subsp. rotundata tuber showing sclereids in the periderm (d) and a bundle of raphide crystals in cortex; f- TS of D. villosa tuber showing starch granules in the parenchyma cells of ground tissue. Scale bars: a = 200 µm; b & d = 50 µm; c = 25 µm; e = 10 µm; f = 20 µm.
Acknowledgements: This research was supported by Grant Number P50AT006268 from the National Center for Complementary and Alternative Medicines (NCCAM), the Office of Dietary Supplements (ODS) and the National Cancer Institute (NCI). Additional funding was also provided by the United States Food and Drug Administration (FDA) grant entitled “Science Based Authentication of Dietary Supplements” Number 5U01FD004246. References:  Mabberley DJ (2008) Mabberley's Plant-book: A Portable Dictionary of Plants, their Classifications, and Uses. Cambridge University Press, Cambridge.  Chakrabarti K, Datta PC (1977) Quart J Crude Drug Res, 15: 67 – 76.