Scientists from the International Potato Centre (CIP) and the Agricultural and Rural Management Training Institute (ARMTI), Ilorin, Kwara State are breeding and helping to disseminate vitamin A-rich sweet potatoes tolerant to drought. The largest producers of sweet potato in Africa are Malawi, Nigeria, and Tanzania, with the area under cultivation equal to East and West Africa.
CIP said Africa is the most affected by the triple burden of malnutrition. Thirty African countries suffer undernutrition,micronutrient malnutrition, and the increasing problem of overweight. Collaborating this, the Food and Agriculture Organisation (FAO) added that the quantity of undernourished people in sub-Saharan Africa (SSA) rose 23 per cent, from 181 million in 2010 to almost 222 million in 2016.
Also, SSA had the highest prevalence of inadequate intake of vitamin A and second highest for iron, zinc, niacin, vitamin B12, and calcium.
FAO said the economic cost of undernutrition was staggering – estimated to cost up to 11 per cent of the Gross Domestic Product (GDP) in Africa.
Sweet potatoes are rich in vitamins
Emphasis in the past two decades has been on enhancing three major micronutrients (vitamin A, iron (Fe), and zinc (Zn)) in staple food crops. Just 125g of biofortified orange-fleshed Sweet potato (OFSP) meets a young child’s daily vitamin A needs.
Experts said flesh-types are good sources of vitamins C, K, E, and several B vitamins, and the mineral magnesium and that sweet potato roots are also a good source of dietary fibre, stimulating feelings of fullness.
Sweet potatoes-breeding programs
Sweet potato breeders in Africa had the opportunity through the Sweet potato Action for Security and Health in Africa (SASHA) project, funded by the Bill & Melinda Gates Foundation (BMGF), and others supporting national breeding, funded by the Alliance for a Green Revolution in Africa (AGRA), to organise breeding programmes based on improved methods and protocols. Three sub-regional sweet potato support platforms (SSPs) were established in SSA with emphasis on population improvement providing 14 national breeding programmes with improved true-seed populations and better parental material for key traits, whereas national agricultural research institute (NARI) breeding programmes emphasised cultivar development. As a result, decentralised breeding was achieved along with allowing each national partner to keep independence and autonomy. The breeding programme in Mozambique became the lead population and cultivar development programme for drought tolerance, with 234,962 seeds from this programme shared with 18 NARIs partners in Southern Africa, East and Central Africa, West Africa, Brazil, and Southeast Asia from 2010 through 2019. This effort had as desired strategic objectives improved efficiency of breeding methods, increased recombination and number of parents, accelerated breeding and better allocation of resources, more controlled cross breeding, and concomitant stepwise reduction of polycross breeding.
The Executive Director of ARMTI, Dr Olufemi Oladunni, believes the introduction and dissemination of nutritious, drought tolerant OFSP in SSA requires improved understanding of the commodity value chain challenges, constraints, and opportunities.
Some of the value chain challenges, according to him, included lack of access to ample and quality planting material at the beginning of the rains; post-harvest losses; low farm gate price during the peak harvest seasons and poorly developed marketing system.
Despite its tolerance to poor soil fertility, sweet potato responds to improved nutrient management. In Nigeria, experts found that sweet potato yields were nearly doubled (from seven–10 to 14–17 tonne/hectare (ha) by applying moderate rates of NPK fertiliser and poultry manure, while yields increased by only 50 per cent with application of high rates of either NPK or manure .
ARMTI has been involved in exposing farmers to greater awareness of the benefits of improved nutrient management on sweet potato, possibly through demonstrations. However, where sweet potato is a secondary crop, farmers may just prioritise investments in fertiliser on other crops in their farming system.
Sweet potato varieties
National Coordinator, Sweet potato Programme and senior agronomist at CIP, Dr. Jude Njoku said two OFSP varieties were introduced into the country, but in Osun State, Mothers’ delight variety, is cultivated.The variety is believed to be very high in beta-carotene. Its dry matter is low,soft and sweet.
But despite its benefits and as alternative to other root crops, its cultivation is still limited to few states, a development that has raised concerns among advocates.
Despite the closeness of other Southwest states to Osun, none has keyed into the opportunity of cultivating this crop.
One of the factors responsible for this, according to farmers, is the challenge of getting access to quality planting materials.
Aside its value to scale up the school feeding programme with nutritional value at a very low cost, it was learnt that bakery offers opportunities for OFSP farmers; also the local markets, which serve as an important alternative for mopping up excess production.
Meanwhile, breeders at CIP in several locations (Mozambique, Ghana, Uganda) and at Uganda’s National Crops Resources Research Institute, started to breed OFSP with higher dry matter, making some use of rare orange-fleshed landraces discovered in African farmers’ fields. In addition to high dry matter, however, they also needed to breed for resistance to viral diseases and to various growing conditions, such as drought, in different countries. As more countries saw the potential of OFSP, new varieties had to be bred and selected to perform well in their particular conditions. At the same time, effective “seed” systems had to be put in place.
Like other roots and tubers, sweet potato is propagated, meaning that cuttings from vines are its “seed”. “Seed systems for OFSP in particular in general in Africa are informal and local,” says an expert, Graham Thiele.
By mid-2019, the effort known as the Sweet potato for Profit and Health Initiative had 11 organisations and five donors reaching more than six million households in 15 countries. The research will continue to address emerging bottlenecks, and Jan Low, a Principal Scientist at CIP, Low Thiele stressed: “There is no one-size-fits-all model for the diverse and complex conditions found in SSA.”
OFSP is probably the most successful biofortification initiative to date, as recognised with the award of the World Food Prize in 2016 to three CIP scientists (Jan Low, Maria Andrade, and Robert Mwanga) and Howarth Bouis of HarvestPlus.
While people still may not say that they crave vitamin A, as a result of the project, many are getting the micronutrients they need and more will share the benefits in the future of climate-resilient OFSP.
