TROPICAL YAMS 

 AND THEIR POTENTIAL 



Part 6. Minor Cultivated 

 Dioscorea Species 



By Franklin W. Martin and LuciEN Degras^ 



INTRODUCTION 



The Edible Species of Dioscorea 



Of the 600 species of yams {Dioscorea), probably all have been 

 tested as food plants. Some are harmless and useful, and some are 

 poisonous and have been rejected or used only medicinally. Techniques 

 have been developed to detoxify a few of the poisonous species. Few 

 genera have yielded more edible species than Dioscorea, and 12 species 

 of yams are fairly well known for their edible tubers. Other species are 

 important sources of steroidal and alkaloidal drugs. 



Five or six species of yams {D. alata L., D. rotundata (L.) Poir with 

 D. cayenensis Lam., D. esculenta (Lour.) Burk., D. bulbifera L., and 

 D. trifida L.) can be considered the principal yams of the Tropics and 

 probably account for 95 percent or more of the yams eaten in the Trop- 

 ics. In the Temperate Zone, two species, D. opposita Thunb. and D. 

 japonica Thunb. , are grown but are little known outside of the Orient. In 

 addition to these species, about 40 or 50 species are collected from the 

 wild or cultivated as crop plants. Some of the least valuable of these are 

 disappearing, and introduced substitutes are being emphasized. The 

 edible yams mentioned in the literature are listed in table 1. The text by 

 Coursey (9)^ and Tanaka's Cyclopedia (20) are the principal sources of 

 the species names and geographical origins given in the table. 



{Coyi tinued on page 6 . ) 



1 Horticulturist, Mayagiiez Institute of Tropical Agriculture, Science and Education 

 Administration, U.S. Department of Agriculture, Mayagiiez, P.R. 00708, and plant 

 geneticist, Station d'Amelioration des Plantes, Institut National de la Recherche 

 Agronomique, Domaine Duclos, Petit-Bourg, Guadeloupe. 



^Italic numbers in parentheses refer to items in "Literature Cited," p. 22. 



1 



