African Yam Bean (Sphenostylis Stenocarpa) tubers for nutritional security

Abstract

African yam bean (AYB) is an “orphan” crop in Africa, despite its nutritional benefits and potentials as a food security crop. It produces two valuable products, edible seeds and tubers. The tubers which are consumed in most parts of East and Central Africa have not been given much attention in West Africa. This study also evaluated 40 AYB accessions for tuberization and investigated the proximate, mineral and anti-nutritional composition of tubers of some AYB accessions harvested in the 2011/2012 cropping season. Tuberization occurred in 42.5 % of accessions investigated. Accession TSs 140 produced the highest number of tubers (6 tubers/plant) while AYB1 had the least (1 tuber). Three different tuber shapes were identified; ovate, spindle and irregular, with the spindle shape being the most dominant. Tuberization was more pronounced in 2012 with less rainfall (185.74mm) and sunshine hour (4.9 hr), compared to the 2011 season. The tubers were low in moisture content (10.3%) while crude protein content ranged from 15.05 % (AYB 57) to 15.86 % (TSs 107); and the carbohydrate content ranged from 67.34 % (AYB 45) to 67.96 % (TSs 140). Magnesium and potassium were prominent in AYB tubers evaluated (1.67gkg-1 and 10.09gkg-1). Antinutrients were generally less in the tubers compared to the seeds. Accessions TSs 107 and TSs 140 had the least anti-nutrients in harvested tubers and had high amounts of protein (15.9% and 15.4%) and carbohydrate (68.7% and 67.9%) respectively. The tubers of AYB could therefore be incorporated into animal feeds and serve as an alternative staple food for man.