Green light for yellow cassava
In December 2011, Nigeria's National Variety Release Committee announced three winning varieties in a 12 year contest between thousands of entrants. The contest, in reality a joint breeding programme of IITA* and Nigeria's National Root Crops Research Institute, had just one goal: to identify high yielding, disease resistant cassava varieties that could help to tackle one of Nigeria's most serious forms of malnutrition.
Vitamin A deficiency, which lowers immunity to disease and causes impaired vision or even blindness, affects almost 20 per cent of pregnant women and nearly one third of children under five in Nigeria. Standard white-fleshed cassava is eaten by more than 70 million Nigerians every day, but contains virtually no beta-carotene, a substance converted by the body into Vitamin A. In contrast, the newly released varieties, which have yellow roots, contain around six micro-grams of beta-carotene per gram, enough to provide up to 25 per cent of daily needs.
Screening, selecting and testing
The breeding work, which has used conventional methods and has been funded for the last eight years by the HarvestPlus programme, screened up to 100,000 cassava seedlings a year for high beta-carotene content and other desirable traits. Hundreds of the most promising plants were then investigated further in multi-locational trials in 13 states, covering Nigeria's major agro-ecologies from rainforest belt to northern guinea savannah. Farmers have been key participants, both in the early stages of selection, in order to ensure that yellow-rooted varieties perform well against the full spectrum of farmer preferences, and in on-farm trials of the most promising candidates.
Measuring the beta-carotene levels in cassava poses its own challenges. The roots deteriorate quickly once harvested, restricting the number of samples that can be tested; this has prompted research into long-term storage strategies. But the breeding process has grown significantly faster over the life of the programme, with greater gene frequency achieved for Vitamin A and improved selection and screening. As a result, while the three new varieties took 12 years from first being crossed to being ready for release, a second group of varieties has reached almost the same point in just six years and contains nearly double the quantity of beta-carotene. Even higher pro-vitamin levels are currently being pursued, with the breeding programme aiming to achieve a target concentration of 15 micrograms per gram by 2015.
Decentralised and demand-driven
Changing the colour of a staple food is normally risky, since it can prejudice adoption by consumers. In the case of cassava, however, local processors often add palm oil to white cassava flour when producing the most popular cassava-based food, gari, giving it a golden hue. As a result, the yellow colour of the new varieties was no deterrent, and was even preferred by some processors. Farmers involved in evaluation trials were also impressed, the new varieties yielding up to 20 tonnes per hectare, comparable with popular white varieties, and having similar starch levels and processing characteristics.
Cassava stems are bulky and quickly lose quality when transported, so multiplying and distributing the new cassava varieties in significant quantities requires a localised approach. The programme is initially focussing on four key states, with ten local governments per state each cultivating a one hectare plot to provide planting material for village level multiplication. By 2013, the plan is to produce enough stems to supply 25,000 households, which will be available at no cost, on condition that recipients supply stems to two other households in the following year.
Providing financial incentives is part of the scaling-up strategy. Private sector companies and NGOs have been enrolled to train farmers in multiplication techniques and encourage young farmers to enter a potentially rewarding business. "It's a win-win situation," says Samson Odedino of Envoy Consultancy Services, which has worked with farmers to establish multiplication plots. "Farmers selling stems will make money, rural people will enjoy better health and everyone will be happy."
For HarvestPlus, which supports conventional crop breeding to address a range of nutritional deficits, the work in Nigeria is a pilot. The programme currently has similar work underway in the Democratic Republic of Congo, but beyond this looks to promote policies and institutional supports that encourage acceptance of biofortification as a strategy and yellow cassava in particular, across many more countries, including Benin, Ghana, Cameroon and Uganda.
* IITA - International Institute of Tropical Agriculture, Ibadan, Nigeria
Date published: January 2012
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