Partnership for yam bean
While many of Africa's staple foods - maize, cassava, potatoes, Asian rice - have been introduced from other parts of the world, the idea of introducing yet another new food crop appears a daunting challenge. But over the last decade, a partnership of crop breeders and researchers from South America, Europe and Central and West Africa have been testing the potential of American yam bean (Pachyrhizus spp.) to thrive in African farms and be accepted by consumers. Three species of yam bean have been tested across multiple locations in four Central African countries - Uganda, Rwanda, Burundi and DR Congo - and Benin and Ghana in West Africa. In each case, the storage root of the plant is the main object of interest.
Yam bean, which is native to Central and South America, is a leguminous plant related to soybean. But unlike soybean, Pachyrhizus seeds contain toxins and are not edible. The large storage roots are edible, and are significantly richer in protein, iron and zinc, than those of cassava, sweet potato or yam. The roots of three yam bean species, originating in Mexico (P. erosus), the Andes (P. ahipa), and the Amazon (P. tuberosus) have a relatively high water content, a beany taste and a texture similar to apple. They are generally eaten peeled and raw as a refreshing field snack by farmers who grow them. But in 1993, scientists from the Royal Veterinary and Agricultural University (KVL) in Denmark became aware of certain P. tuberosus types which have high levels of dry matter in their tubers. These cultivars, mainly developed by the Peruvian Amazon Shipibo community and known to them as Chuin, are used to make flour and masato - a drink usually made from cassava.
Testing yam bean potential in Africa
Work to test the potential of yam bean for West and Central Africa on a broader scale began with collaboration between researchers at the University of Abomey-Calavi in Benin and the International Potato Center (CIP) in Peru. Thirty three low dry matter yam bean types were tested in two locations to assess their performance and response to agronomic practices in wet and dry conditions. They were also tested for their suitability to make gari, a widely eaten staple in West Africa normally made from cassava flour. But while these low-dry matter types were found capable of making a nutritious and palatable gari, they all had a very low conversion rate of about five per cent, an uneconomically small amount of gari produced for each kilo of roots processed. Tests on the high dry matter Chuin types in Peru, however, revealed a conversion rate of around 19 per cent, similar to that of cassava.
More recent field trials in Benin have identified two low dry matter varieties that yield well on-farm (up to 30 tonnes/ha) and have now been recommended for some areas of the country by Benin's national agricultural research institute (INRAB). INRAB has also tested different food products made from these varieties, including yoghurt, juice, flour, chips and alcohol, with the processed roots potentially making a lower-cost alternative to palm wine. Use of the roots in animal feed, for giant snails, nursery fish and grasscutters (large rodents valued for their meat), is also showing valuable potential. Another project partner, the Danish NGO, BØRNEfonden, is currently working with 23 village communities to assess whether, and how, these varieties can be adopted more widely.
In 2012, work also began in Benin to test the potential for gari making under African conditions using the high dry matter Chuin types. This has only been possible thanks to a special permit by the Peruvian authorities; in late 2011, they agreed to CIP exporting Chuin plant material from its genebank in Lima, for testing in West and Central Africa. These types are now being multiplied, with results from the gari-making experiments due by April 2013.
Capacity building through collaboration
In Central Africa, CIP's Peruvian and Ugandan offices have been working in partnership with Makerere University in Uganda, and with agricultural research institutes in Rwanda (Rwanda Agricultural Board), Burundi (lnstitut des Sciences Agronomiques du Burundi) and DR Congo (Institut National pour I'Étude et la Recherche Agronomiques). Multi-environment on station trials have tested around 30 yam bean types in areas at high, mid and low altitude and with varying amounts of rainfall. In each country, a number of top performing types have been recommended for dissemination in specific zones. In Uganda, two farming communities have been involved in field testing, and in the development of porridge and other food products in which yam bean can be combined with other staples.
Capacity building for yam bean research in Central Africa has also been a key project focus. Three BSc, seven MSc and two PhD students are being supported to study through Makerere University, their work encompassing field trials and the development of nutritionally balanced foods in the four participating countries. According to Phinehas Tukamuhabwa of Makarere University, the multidisciplinary yam bean project has built linkages and confidence between CIP and the participating research institutes. Through their partnership, the institutes have gained access to new crop germplasm, capacity building in infrastructure and personnel, and networking at regional and global levels. Wolfgang Gruneberg of CIP-Peru agrees, citing the project as a good example of south-south exchange and partnership, and of the trend for CGIAR centres to conduct research with and through partner institutes rather than on their own.
Note: The project is funded by the Government of Belgium, Federal Public Service Foreign Affairs, Directorate General for Development Cooperation - D2.2 (Inclusive growth-agriculture)
Date published: January 2013
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