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CHAPTER ONE

INTRODUCTION

1.1   Background of the Study

Yam (Dioscorea spp) are generally classified under the genus Dioscorea, family Dioscoreaceae, and order Dioscoreales. They are the most important food crops in West Africa, except for cereals (Okonkwo, 1985). Yams are the second most important tuber crop in the whole world after cassava, in terms of production (11TA, 2013). They also form an important food source in other tropical countries including East Africa, the Caribbean, South America, India and South East Asia(Okonkwo,1985). Average yam consumption per capita per day is highest in Benin (364 kcal), followed by Cote d’lvoire (342 kcal), Ghana (296 kcal) and Nigeria (258 kcal) (11TA, 2009). Yam may be barbecued, roasted, fried in oil, grilled, boiled, baked, smoke, pounded into paste (fufu) or grated and made into a dessert. It may be cooked or fried with rice, beans, plantain, sweet potato, lamb, chicken and butter nut as squash soup (Umar et al., 2016). It can be boiled, roasted and eaten with oil, vegetable or sauce (11TA, 2004; Timothy and Bassey, 2009). The tubers may be peeled and sliced into tiny pieces and dried to very low moisture contents and milled into yam flour and flakes (Udoh et al., 2005). The tubers may be peeled and prepared into porridge and cooked with traditional spices and served for the sick and aged as appetizer. Yam prices have been increasing in recent years due to strong demand for the crop in Africa and even in Europe and the United State of America where rapidly growing West African migrants’ communities still have big appetite for their traditional preferred staple. Nigeria exported US S27.7 million worth of yam to the United States of America in 2011 (Babatunde, 2012) and it is expected that much foreign exchange through yam trade would be realized in future.

Nigeria is the highest world producer of yam with more than 45.004 million metric tonnes (mmt) annually with Ghana (7.119 mmt), Cote d’lvoire (5.808 mmt), Benin republic (3.220mmt), Ethopia (1.448mmt), Togo (0.786mmt) and Cameroon (0.579mmt) (FAO, 2014), following that order. Yam contributes more than 200 dietary calories per day for over 60 million people in Nigeria (Nweke et al., 1991). In many yam producing areas in Nigeria “yam is food and food is yam”. It is the only crop which is usually celebrated during and after harvest, called yam festival (Ugwu, 1996). Yams are also important as sources of pharmaceutical compounds like saponins and sapogenins, which are precursors of cortisone and steroidal hormones (Okonkwo, 1985).The most important species of Dioscorea include Dioscorea  rotundata, D. cayenensis, D. dumetorum, D. esculenta, D. Bulbifera, D. trifida, D. opposita, D. japonica, and D. hispida. The genus is further divided into 5 sections within which the species are grouped. The section Enantiophyllum comprises the most economically useful species (D. rotundata, D. alata, D. cayenensis, D, opposite and D. Japonica) and are distinguished by the fact that their vines twine in a clockwise direction. The section, Lasiophyton consists of D. dumetorum and D. hispida: Opsophyton, of D. bulbifera; Combilium, of D. esculenta, and Macrogynodium, of D. trifida. All the species in these latter four sections have vines twine anti-clockwise. Dioscorea rotundata Poir (common names: white yame; guinea yam) is the most widely grown and eaten yam species in Nigeria and indeed, West Africa, and it is the most important in the whole world. Germplasm collection and breeding work on yams, especially on the all- important D. rotundata is going on at the National Root Crops Research Institute, Umudike, and the International Institute of Tropical Agriculture (11TA), Ibadan both in Nigeria and the United States Department of Agriculture (USDA) in Puerto Rico and Universities in Nigeria and throughout West Africa (Okonkwo, 1985).

1.2   Statement of the Problem

The pattern of yam production in Benue State, Nigeria is characterized by many problems such as: problem of continuous decline in the yield of yams since the past decade. This is characterized by reduction in land area used for planting yams in favour of cassava production. There is continuous decline in yam production in comparison with cassava production in Benue State. The factors responsible for these includes low fertility of soil due to overuse of land, pest infection and lack of incentives to the farmers (Shehu et al, 2010).