Yam bean: forgotten crop being improved to yield quality food in resource-poor countries

We often write about the biomass and biofuels potential in developing countries. Projections show it is very high over the long term - with some putting Africa's sustainable potential by 2050 at around 400 Exajoules per year, more than the total amount of fossil fuels consumed by the entire world today.

But these opitimistic projections are based on a great variety of assumptions about population trends, demand for food, wood, fiber and feed, about technological advancements and agricultural and biotech breakthroughs. To arrive at the high estimates, one of the assumptions is that food production and the livestock sector's output will become far more efficient. With improved food and feed production (higher yields) and improved feed conversion, more land becomes available for energy crops.

The question is: will these breakthroughs and improvements actually occur? Researchers from the International Potato Center and the Centre Songhai in Porto-Novo (Benin) offer us an example showing that this is indeed the case: they report how a forgotten and underutilized crop is being improved to yield more robust and efficient food production systems, especially suitable for resource-poor countries. Results from their study will be published in the July-August 2007 issue of Crop Science.

The Yam bean (Pachyrhizus genus) is the focus of their efforts. The crop originated where the Andes meets the Amazon and is locally grown in South and Central America, South Asia, East Asia and the Pacific. Yam bean is produced in three species which are called the Amazonian, Mexican and Andean. Interbreeding of the bean has resulted in fertile and stable hybrids. This gives it potential to be reclassified as a single species, provide high quality food production and offer a sustainable cropping system that could find its way in the drier regions of Africa.

Researchers believe they have now discovered a protein-rich starch staple in the yam bean in Peru. They were previously considered a root vegetable due to the high water content; however this ‘Chuin’ type has lower water content. Families living in the area have been producing it as flour. The crop has extremely high seed production, but its seeds contain high concentrations of rotenone. This toxic compound has been used for reducing fish populations and parasitic mites on poultry. Seeds are never consumed since they are mildly toxic to humans and other mammals. If the rotenone was removed from the seeds, they could provide a strong protein source as well as seed oil profitable in the food industry.

Séraphin Zanklan, a scientist at the Centre Songhai in Benin, has investigated the yam bean for its potential to grow and produce food under West African conditions. The study was funded by a scholarship from the German Academic Exchange Service (DAAD). Thirty-four yam genotypes were grown with and without flower removal at one droughty location and one irrigated location:
biomass :: bioenergy :: biofuels :: food production :: genetics :: plant breeding :: underutilized crops :: yam bean :: Africa ::

Of the 33 traits that were measured, nearly all showed large genetic variation. This and the easy spreading of its seeds, make the crops very desirable to breeders.

The study identified genotypes with high storage root production. Flower removal increased storage root production by 50 to 100%. Several yam bean genotypes showed very low reduction in storage root and seed production under drought stressed conditions. As expected, the storage roots did show high protein and starch contents. They have as much as three to five times more protein than potatoes or yams. Most importantly, it was found that storage roots can be processed into ‘yam bean gari.’ This is similar to the current staple of West Africa, ‘cassava gari,’ a granular flour.

The bean could make a significant contribution to the improvement of food support, especially where resources are poor. The research is ongoing at the International Potato Center, which has a mandate for the bean in the frame of Andean Root and Tuber Crops. Further evaluation is needed on the range of yam bean variations under different conditions. More information on where they can be grown, their agronomic potential and genetic diversity is important to determine the types of breeding programs necessary for yam beans.


Picture: Researchers think the small Yam bean has great potential to provide high quality food production and offer a sustainable cropping system that could boost food and biofuel production in Africa. Credit: Wolfgang Gruneberg.

References:
Eurekalert: Yam bean a nearly forgotten crop - Interbreeding may produce quality food source for resource-poor countries - September 15, 2007.