Scientists breed nutritionally rich yam bean

Farmers in Uganda are poised to benefit from a nutritionally superior yam bean with the research now in its final stages thanks to concerted efforts from Makerere University and NARO researchers.

The researchers are keen on ensuring that both the seed and the tuber of the crop is edible as opposed to only consumption of the tuber as is the case currently due to high rotenonen content in the seeds. Researchers are optimistic that the yam bean will contribute significantly to food security because unlike other root tubers, it is rich in protein, carbohydrates, zinc and iron which are nutritionally recommended plus other nutrients on top of improving soil fertility.

The research is being spearheaded by scientists in plant breeding, agronomy and plant genetic resources from Makerere University College of Agricultural and Environmental Sciences (CAES) in collaboration with the International Potato Center (CIP). The scientists have embarked on popularizing the use of yam beans as human food in Eastern and Western Africa. The four year project funded by the Belgium Technical Cooperation also aims at availing of larger seed quantities for three to four varieties with high yields and adaptation to central African conditions.  

Scientists describe the yam bean as an adventure and a challenge because the true seeds of the crop are inedible due to its high rotenone contents. Plant breeder from the Department of Agricultural Production Makerere University, Dr. Phinehas Tukamuhabwa said research in the laboratory and in the farmers’ fields for screening to determine rotenone in the yam bean has been developed with promising results. “We are doing research on how this rotenone can be removed or deactivated from the seeds because once that is done; we are capable of recommending the bean for human and livestock consumption. We are doing this in collaboration with a University in Belgium” Said Dr. Tukamuhabwa.

Laboratory and Farmer field experiments are being conducted in Luwero, Soroti, Namulonge, Kabale- Kachekano and Kabanyolo nearing commercialization. Achievements so far include the inclusion of 31 new accessions to the CIP gene bank, about 60 farmer varieties now maintained at CIP, and well adaptability in central Africa high lands conditions of Rwanda, Burundi, DR Congo where temperatures do not fall below zero and in tall grass savannah agro ecological zone. “We hope by the end of the third year of this project we should be able to tell you which variety is the best but we can say right that there are prospects that farmers will take it as a serious crop and that some of these varieties are adoptable to our conditions “. Dr. Tukamuhabwa said.

He also explained that over 60 varieties of the yam bean were obtained from Peru and are differentiated by seed colours for example white, red, and black while some varieties have soft and hard tubers which are taken to farmers for selection. “What we are doing is adopting a technology by getting varieties got from Peru and, growing them in our own environment to see if they are doing very well and grow them with farmers. We bring different varieties, multiply them and do different experiments with them in different fields. Then when we harvest we get root tubers and develop them into different food types using our graduate student and also get the seed and see how much rotenone is there”.

The breakthrough in the reduction of the poisonous substance in the yam bean will be one of the most celebrated achievements in farming systems in Africa that will enhance food security for the hungry world.

According to Dr. Daniel Adewale from World Agro Forestry Center (ICRAF), African Yam bean is an orphaned crop which is highly nutritious and culturally resonant but undervalued by policy makers. “Little data information exists on how many people consume it. Like many neglected plant species, the African yam bean has also been little researched,” explained. He further indicated that the yam bean’s high nutritional value is a major reason why resources should be directed towards preserving and improving it in order to foster food security. “The tuber is rich in calcium and phosphorus while its’ crude protein content is about 29 percent which is higher than that of cowpeas at 25 percent or the common bean at 16-21 percent,” noted Adewale.