L., I IDRC-080e ARCHIV MACINTedings of the Fourth Symposium of the 23101 Lational Society for Tropical Root Crops Held at CIAT, Cali, Colombia, 1-7 August 1976 Edited by James Cock, Reginald Maclntyre, and Michael Graham (' N The International Society for Tropical Root Crops in collaboration with Centro Internacional de Agricultura Tropical International Development Research Centre United States Agency for International Development IDRC-080e PROCEEDINGS of the FOURTH SYMPOSIUM of the INTERNATIONAL SOCIETY FOR TROPICAL ROOT CROPS held at CIAT, Cali, Colombia, 1-7 August 1976 Edited by James Cock, Reginald MacIntyre, and Michael Graham '041 20 IV1977 The International Society for Tropical Root Crop in collaboration with Centro Internacional de Agricultura Tropical International Development Research Centre United States Agency for International Development @ 1977 International Development Research Centre Postal Address: Box 8500, Ottawa, Canada K1G 31-19 Head Office: 60 Queen Street, Ottawa Cock, J. MacIntyre, R. Graham, M. International Society for Tropical Root Crops CIAT IDRC USAID IDRC-080e Proceedings of the Fourth Symposium of the International Society for Tropical Root Crops held at CIAT, Cali, Colombia, 1-7 August 1976, Ottawa, IDRC, 1977. 277 pp. / IDRC pub CRDI /. Proceedings of a symposium on / root crop / / plant production / in the / tropical zone /includes / list of participants /, / bibliography/s, and / statistical data /. UDC: 633.4(213) ISBN: 0-88936-115-0 Microfiche Edition $1 CONTENTS Foreword5 Society Council, 1976-79 6 Welcoming addresses 7 Participants 11 Section 1:Origin, dispersal, and evolution 19 Papers by:Léon 20; Plucknett 36; Sadik 40; Martin 44; Mendoza 50; Kobayashi and Miyazaki 53; Degras 58; and Warid et al. 62 Summary of discussions65 Section 2:Basic productivity69 Papers by:Loomis and Rapoport 70; Holmes and Wilson 84; Ferguson and Gumbs 89; Dharmaputra and de Bruijn 94; Nitis and Suarna 98; Obigbesan et al. 104; Ngongi et al. 107; Howeler et al. 113; Rendle and Kang 117; Mohan Kumar et al. 122; Edwards et al. 124; Wahab 131; Umanah 137; Montaldo and Montilla 142; Montilla et al. 143; Wilson et al. 146; Tanaka and Sekioka 150; and Sykes 151 Summary of discussions152 Section 3:Preharvest and postharvest losses155 Papers by:Lozano and Terry 156; Bock et al. 160; Mukiibi 163; Mukiibi 169; Terry 170; Ninan et al. 173; Leu 175; Terry 179; Obigbesan and Matuluko 185; Bellotti and van Schoonhoven 188; Nyiira 193; Yaseen and Bennett 197; Pillai 202; Thompson et al. 203; and Albuquerque 207 Summary of discussions208 Section 4:Utilization211 Papers by:Christiansen and Thompson 212; McCann 215; Chandra and De Boer 221; Valdes Sanchez 226; Phillips 228; Oke 232; Delange et al. 237; Hew and Hutagalung 242; Khajarern and Khajarern 246; Varghese et al. 250; Hutagalung and Tan 255; Gomez et al. 262; Gregory et al. 267; Nartey 270; Nakayama et al. 274; and Jeffers 275 Summary of discussions277 3 Origin, Evolution, and Early Dispersal of Root and Tuber Crops Jorge Léonl Tropical root and tuber crops have been domesticated in SoutheastAsia, west-central Africa, and tropical Latin America (including the high Andes).The crops belong to different families. Species of the one genus (Dioscorea)were domesticated independently in each of the three regions. Species of Colocasia and Xanthosoma(family Araceae) and Pachyrrhizus and Pueraria (family Leguminosae)were domesticated in separate regions. Many of these crops have restricted areas of distribution dueto physiological requirements and are becoming relict crops. Roots and tubers are ancient crops, and even todaysupport groups of people who gather them from wild plants. Poisonous, acrid,or bitter qualities were found in the most important crops by early man, who learned how toremove or destroy these undesirable qualities. Most of the root and tuber crops are polyploids, andmost of them are vegetatively propagated. Fertility traits are therefore of special importance in their evolution under cultivation, but there is no evidence that clonal propagation has ledto sterility. Information on their evolution is extremely scarce as cultural sources, archaeological, linguistic, and historic information is scanty and unevenly distributed. On biologicalsources, compara- tive taxonomy, metaphase cytology, and hybridization have givensome important clues, but there is still very little information available on the evolution of these species. Root and tuber crops dispersed slowly between Southeast Asia andAfrica. After the seventeenth century a very active interchange occurred especially withthe American crops. Since then, there has been a continuous replacement of crop species, especially in Africa. The sweet potato, of American origin, was found in Oceania whenthe Europeans arrived, but no satisfactory explanation of how it got to Polynesia hasever been made. Root and tuber crops are thought to be oftion" with cereals. In vegetative propagation ancient origin, and are often regardedas relicsprimitive farmers apply simple husbandry, but of primitive agriculture. This concept is basedthe same is true when they grow seed crops. On on the important role these crops play in exist-the other hand, some vegetative crops, such as ing primitive societies, and on the rudimentarypotatoes, have reached an advanced stage of husbandry they require, particularly vegetativeproduction and technology, comparable to propagation. These crops are easily adapted inmany other crops. The view persists, however, the less-advanced agricultural systems becausethat vegetative propagation represents a low of their high yields, resistance and earliness,stage of progress, and a distinguished cyto- and in the dietary pattern by their bulk andgeneticistinhisinterpretationofhistory taste qualities. (Darlington 1969), points to "the fatal abun- Since the last century, geographers andan-dance of tropical root crops imported from thropologists have contrasted root and tuberAsia and America" as one of the main factors production, which includesotherclonallyin the decline of Africa. propagated crops such as bananas, breadfruit, The contrastingof agriculturalsystems sugarcane, with seed agriculture. Vegetativebased on the differences between seed and propagation, developed in tropical regions, isclonal propagation is a simplification of a assumed to be a static system, whereas seedproblem that is too complex to be reduced to agriculture is associated with the developmentthe duality of planting materials. of more advanced societies. Geographers and historians are tempted to associate "civiliza- The Basic Materials Roots and tubers are storage organs that are 1Programa de Germoplasma, CATIE, Turrial-developed in many families of plants, probably ba, Costa Rica. as a result of selective pressures in environ- 20 LION: ORIGIN, EVOLUTION, AND DISPERSAL 21 ments with varying amounts of rain. Theon crop evolution comparative taxonomy, storage organs permit the accumulation of nu-cytological analysis especially at metaphase, trients elaborated by the aerial parts of the and experimental hybridization have been plant. By growing underground, they maintain applied to some of the root and tuber crops. the nutrients with minimal loss. Once the tem-However, as a whole, the information avail- porary branches or foilage have dried, newable, with the possible exception of potatoes, shoots develop from the storage organs. Byis very poor and scattered. harvesting roots and tubers before the plants Comparative taxonomy aims to establish the have flowered, man has interrupted this pro-relationships among existing taxa with the cul- cess, and has thus kept the plants in a kind oftivated species. The definition of their taxo- permanent juvenile stage. nomic position permits the identification of Although storage organs may vary in theirputative parents and the delimitation, within phylogeny and structure, the nature of theirthe genus, of the cluster of species more storage tissues is common. These organs areclosely associated with the cultivated taxa. The large masses of parenchyma thatcontaintraditional methods of taxonomy do not work mainly water and starch grains. The paren-well with root and tuber species. Often foliage chyma is intimately connected with the vascu- isdifficultto accommodate in herbarium lar system, which permits easy transport fromsheets; flowers are bulky, fleshy, and frequently and to the storage organs. Frequently, there are absent; root and tubers too difficult to preserve. poisonous, bitter, or acrid substances in theIn some genera, like Xanthosoma, the taxo- storage tissues, which present an obstacle to the nomic status is extremely unsatisfactory; the utilization of roots and tubers. However, theseabundant synonymy in the aroids and yams is, substances are a deterrent to animals and there-in part, a result of studies based on herbarium fore play an important role in the survival ofmaterials. As in other crops, the identification plants growing in natural conditions. Theof a wild population closely related to the cul- quantity of these materials (e.g. raphides ortivated species, raises the question of whether it glucosides)variesconsiderably within theis an ancestor of the cultivated type or a feral or same species, a trait that is mainly determinedweedy form. In Ullucus, an aboriginal species by inherent factors. has been described (Brucher 1962), but this The storage organs may be roots or stems. could be only a wild variety. A hexaploid popu- In roots, such as cassava, the storage tissueslation of Ipomoea