CHARACTERIZATION AND DOMESTICATION POTENTIAL OF WILD YAM IN KENYA

Abstract

Over four million people in Kenya, are faced with severe hunger and malnutrition caused by frequent drought. Wild yam (Dioscorea spp.) has been used as famine food by many communities. There is potential for domestication of the drought tolerant wild yam to improve food and nutritional security in various communities. This study investigated on the wild yams in selected parts of Kenya, with the objective of identifying the more productive and nutritious accessions that can be used for food and prevent malnutrition. Thirty one wild yam accessions were collected from selected localities in seven Counties which included Kombosang (KB1), Moigutwo (MB1), Kasaka (KB2a and KB2b), Mormorio (MB2a and MB2b), Bossei (BBa, BBb and BBc), Kapkwang (KB3a, KB3as, KB3b and KB3c) and Katimok Forest (KB4a and KB4b), Kolol (KEa, KEb and KEc), Turesia (TE, TEs1 and TEs2), Kapseret Forest (KUa, KUb and KUc), Chepsangor (CNa), South Nandi Forest (SNa and SNb), Nyakomisaro Stream (NK), Lugusi (LKa) and Kaya Tsolokero (KKa and KKb). Three cultivated yam accessions; Mathia (MN), Mogoi (MT) and St Mary’s, Kitale (ST) were also collected and used as control. The accessions were locally and botanically identified. Their response to domestication was assessed in the net-house and field experiments. Internode and vine lengths, number of leaves per plant, number and fresh weight of tubers and bulbils per plant were assessed. The tubers were analysed for nutrient and secondary metabolite composition. The data obtained were analysed statistically and the differences of means were adopted as significant at P≤0.05. The wild yam accessions comprised four species, D. schimperiana Kunth. (KB1, MB1, MB2, KB3a, KE1, TE, KUa, CNa, NK and LKa), D. bulbifera var. bulbifera (KB4a, KEc, KUb, BB and KKb) and D. quartiniana var. quartiniana (KB2, KB3b, KEb and KUc) and D. dumetorum L. (KKa). The cultivated accessions were D. bulbifera var. anthropophagorum (ST) and Dioscorea alata L. (MT and MN). Wild D. schimperiana Kunth., D. bulbifera and D. dumetorum were used for famine food. Dioscorea quartiniana tubers were considered non-edible. Dioscorea schimperiana and D. quartiniana were used to treat various ailments. All the wild yam accessions produced significantly heavier tubers than the cultivated accessions in the net house. In the field, KEa, MB1 and MB2 produced significantly heavier tubers per plant compared to the control (MB2C) while the cultivated type (MN) did not form tubers. Whereas MB1, KEa, TE, KUb and CNa formed bulbils in the net-house plants, only KEa produced bulbils in the field. The wild yam tubers contained high levels of proteins, lipids and carbohydrates. The tubers also had the highest levels of K compared to the other mineral elements. Generally, the tubers had high levels of P, Na, K, Ca, Mg, Fe and Zn that were comparable to the cultivated types. The wild yam tubers also had high quantities of alkaloids, flavonoids, saponins and tannins that were similar to those of cultivated type (MN), but were within the allowable limits for consumption. The results show that diverse wild yam species exist in various geographical locations in Kenya. Kenyan wild yams have high potential for domestication outside their natural environments. Edible and non-edible yam tubers contained high amounts of nutrients and secondary metabolites. Dioscorea schimperiana and D. bulbifera could be incorporated to food crop systems. Dioscorea schimperiana, D. quartiniana and D. bulbifera accessions could have medicinal value because of their high secondary metabolites.