Dormancy in yams

The tubers of yam, principally those of Dioscorea rotundata (white Guinea y am) and D. alata (water or greater yam), are important staple foods and sou rces of carbohydrate in West Africa. Yams are grown in diverse environments - from the high-rainfall forest zone on the coast to the seasonally arid s avannas of West Africa, that is in situations in which the duration and the timing of the onset of the growing season vary appreciably. Dormancy in bo th underground and aerial tubers of the Dioscoreaceae is an important adapt ive mechanism that helps to maintain organoleptic quality during storage an d also ensures that tubers germinate at the start of the growing season. Pl ant breeders are especially keen to manipulate the duration of the dormant period in order to synchronize growth periods and, therefore, to produce mo re than one generation per year. The control of tuber dormancy, however, is poorly understood. This review examines critically those factors that affe ct tuber initiation, dormancy and sprouting, and makes recommendations for future priorities in research.