a.-y/ TROPICAL YAMS AND THEIR POTENTIAL Part 2. Dioscorea bulbifera <r> Agriculture Handbook No. 466: ^-^ fTl ^C3 --i r '^ Agricultural Research Service UNITED STATES DEPARTMENT OF AGRICULTURE in cooperation with U.S. Agency for International Development This publication reports research involving pes- ticides. It does not contain recommendations for their use, nor does it imply that the uses discussed here have been registered. All uses of pesticides must be registered by appropriate State and/or Federal agencies before they can be recommended. M4 " ¿ùêfé4aéùaaS44fy « s, IIMITKIII «f tllKtllllil CAUTION: Pesticides can be injurious to humans, domestic animals, beneficial insects, de- sirable plants, and fish or other wildlife—if they are not handled or applied properly. Use all pesti- cides selectively and carefully. Follow recom- mended practices for the disposal of surplus pesti- cides and pesticide containers. Washington, D.C. Issued October 1974 For sale fay the Superintendent of Documents, U.S. Government Printing Office Washington, D.C, 20402 - Price 40 cents Stock Number 0100-03349 The feeding of future generations requires a knowledge of the individual crop plants of the world and their potentials. Crops can be recommended for use in particular regions only on the basis of potential yield, the costs of production, the food and feed value of the crop, and the way the crop can be processed or otherwise used. For most of the major food crops of the world, a body of information is already available. However, tropical roots and tubers, which are widely used as staple foods, have been largely neglected. Only in recent years has an awareness been growing of the potential of these crops to supply large amounts of food in relatively small amounts of space. Yams are the second most important tropical root, or tuber, crop. The annual production, perhaps 25 million tons, places them second in importance to cassava. But yams are better food than cassava, and while they are usually thought to be more difficult to grow, under some conditions yams out- produce cassava. Yams fill an important role in the diet of many areas of the Tropics—a role that can increase in im- portance. That role and its potential are not, however, well understood. The yam is not a single species. Perhaps 60 species have edible tubers; of these about 10 species can be considered crop plants. The literature concerning these species is widespread but fragmentary. This is the second in a series of Agriculture Handbooks dealing with the major species of yams. It is part of a research effort cosponsored by the Agricultural Research Service of the U. S. Department of Agriculture and the U. S. Agency for International Development to introduce, evaluate, and distribute better yam varieties. Also in 'Tropical Yams and Their PotentiaF* series— Part 1. Dioscorea esculenta, USD A Agriculture Handbook No. 457. CONTENTS Page Preface ..- .- iii Introduction - .- 1 History and origin 1 Geographic distribution —- — 1 Botany 2 Classification -. 2 Morphology 2 Cytology 10 Varieties 12 Culture 13 Environmental requirements 13 Land preparation and planting 14 Fertilization -.. — 14 Staking 15 Pests and diseases --. 15 Harvesting 15 Culinary characteristics .- 15 Composition 16 Poisonous or obnoxious contents 18 Folk medicine 19 Potential uses . 19 Literature cited 19 IV TROPICAL YAMS AND THEIR POTENTIAL Part 2. Dioscorea hulhifera By FRANKLIN W. MARTIN, plant geneticist^ Federal Experiment Station^ Southern Region, Agricultural Research Service, JJ. S, Department of Agriculture, Mayaguez, P,R, INTRODUCTION and Africa. The African varieties are so distinct from the Asian that One of the most common and their distribution must have taken widespread yams of the Tropics is place in prehistoric times. Perhaps Dioscorea hulhifera L., the air- the species had two centers of di- potato yam, so called because it is versity, one in Indochina, Malaya, grown chiefly for its edible aerial or Indonesia, and the other in Af- tubers. Known in both Asia and rica. Although Coursey (4)^ Africa for centuries, it has been speaks only of the former center, widely distributed through the ac- two closely related species in East tivities of man and has gone wild Africa, D, asteriscus Burk. and D, in many tropical regions. The spe- paleata Burk., suggest an African cies is best known in India, where center of diversity also. Burkill there are superior edible varieties, (1) agrees with this hypothesis but it is also common in West Af- and suggests that the wide diver- rica. D. hulhifera probably is only sity of African varieties is due to a poor fourth or fifth in worldwide the hand of man. Certainly the production of yams, for it is sur- range of variation in West Africa passed by D. alata L., the Asian is sufficient to indicate independ- greater yam; D. rotundata Poir. ent evolution of Asian and African and possibly D. cayenensis Lam., forms. Furthermore, a major dif- the West African yams; and D. es- ference of shape is usually suffi- culenta (Lour.) Burk., the Asian cient to distinguish Asian from lesser yam. Although not one of African types. Whereas the former the best yams, some varieties pro- are more or less spherical, the lat- duce large numbers of aerial tu- ter are angular. bers over long periods of time, making them especially suited to Geographic Distribution the home garden. In addition, some Probably D, hulhifera can be also produce underground tubers. found in every hot, humid, tropical The better varieties are not well region. Burkill (1) speaks of D, distributed, but merit introduction hulhifera as having extended to and trial. the most remote islands of the Pacific. Wild forms, usually bitter History and Origin D. hulhifera is the only edible 1 Italic numbers in parentheses refer yam species native to both Asia to items in "Literature Cited," p. 19. AGRICULTURE HANDBOOK 466, U.S. DEPT, OF AGRICULTURE and often poisonous, are the most esculenta (Lour.) Burk.], airpo- common. The more ennobled vari- tato yam, air potato, aerial yam, eties usually do not survive in the bulbil-bearing yam, and, in Span- wild for long periods. ish, ñame de gunda (bulbil-bear- D, bulbifera is not native to the ing yam). Western Hemisphere. Neverthe- D. bulbifera belongs to the sec- less, it is so widespread that it is tion Opsophyton, an Old World noted in most floras of the tropical section, with two other African countries of Central and South species, D. asteriscus Burk. and D. America. Because it is common, it paleata Burk., which are neither has frequently been given colorful edible nor commercially valuable. names 5ueh as mata gallina (kills In common with other yams, the hens). The more desirable forms airpotato yam belongs to the fam- of Z). bulbifera are not widely dis- ily Dioscoreaceae, of which Dio- tributed in the Western Hemi- scorea is the principal genus. The sphere, and the species is not an family is usually classified among important food anywhere within the monocotyledons, although this region. some evidence of a second cotyle- don has been found (7). The fam- ily is characterized by rhizomes, BOTANY usually reduced to a nodeless struc- Classification ture. The male and female flowers, D. bulbifera L., because of its usually on separate plants, are wide distribution, has many syn- small and often inconspicuous. The onyms. The African forms have inferior ovary becomes quite been distinguished as D, latifolia prominent after fertilization. The Benth,, a name not regarded floral pattern is based on sets of with favor now. Other synonyms three. include D, anthropophagorum A. Chev., D. hoff a Cordemog, JD. hof- Morphology ika Jumelle & Perrier de la Bathie, D. bulbifera is a glabrous vine D. longepetiolata Baudon, D. op- that climbs by twining to heights positif olia Campbell, Z>. perrieri R. of 12 meters or more (fig. 1). The Knuth, D, sylvestris de Wild., D, stems range from thin (1-milli- violácea Baudon, and Helmia bul- meter diameter) to thick (8-milli- bifera Kunth. The name D. sativa meter diameter) and twist to the Thumb, is also sometimes seen in left in twining. The leaves, often the literature, specifically with re- quite large, are alternate and usu- spect to the edible Asian varieties. ally orbicular, but with well-devel- This name has also been applied to oped acuminate tails. They are other species, but it is botanically cordate at the base. Details of the invalid. Among the common names sinus between the lobes, of the are potato yam [used also for D, tail, and of the degree of rugosity, TROPICAL YAMS AND THEIR POTENTIAL, PART 2 PN—3671 FIGURE 1.—Mature D. bulbifera vines climbing bamboo poles for support. folding, cupping, and reflexing of surface of the tuber itself in some, the leaf are varietal traits making but not all, varieties. identification possible (fig. 2). The small flowers are frequent- The leaves are usually glabrous, ly seen during summer. They are but in some varieties they are cov- sessile and appressed to the ped- ered with a bluish bloom. Another uncle in long racemes produced in trait useful for identification is the axils of the leaves (fig. 4). The the resistance of the leaf to leaf- male and female flowers superfi- spot disease, common in all yam- cially appear alike, but the female growing regions. The petiole, is easily recognized from its in- which is enlarged at the base, has ferior ovary. The perianth ranges earlike projections that often en- from green to white to slightly circle the stem (fig. 3). pink. The flowers produce a pleas- Only small seedlings have true ant odor, which attracts bees and roots, and these are short-lived. other insects. The principal adventitious roots The seed capsules are trilocular, arise from the crown, the region 2 to 5 centimeters long, and rise of the stem immediately above the vertically from the racemes (fig.