Five questions with Dr. Robert Mwanga and Dr. Jan Low


Following our Spotlight Seminar on the Future of Agriculture of Africa, we were delighted to speak to Dr. Robert Mwanga, one of the event’s speakers, as well Sweet Potato Breeder at the International Potato Center and 2016 winner of the World Food Prize, and Dr. Jan Low, co-winner of the 2016 World Food Prize and Principal Scientist and Leader of the Sweetpotato for Profit and Health Initiative, Sweetpotato Action for Security and Health in Africa Project Leader. Dr. Mwanga and Dr. Low discussed some of the key challenges facing African farmers today, as well as providing an overview of their prize-winning work on the biofortification of the orange-fleshed sweet potato.

1) What are the key challenges in African agricultural development?

Robert Mwanga: The challenges are enormous. First of all, there is the threat of drought. When drought comes, it hits the major staples, which include maize, groundnut, and rice. This affects a large proportion of the population. In addition, there are all sorts of pests and diseases, which take a heavy toll on the major crops. Markets are also a problem, as well as the overproduction of crops and ensuing wastage. Furthermore, there is a lack of well-maintained road networks on the continent, which means that it’s difficult to transport crops to highly populated areas. Until Africa overcomes these problems, agricultural development will remain stagnant or very slow.

Jan Low: To add to what Robert said, I believe that agriculture has to be better integrated with other sectors. Furthermore, governments need to prioritise the development of hard infrastructure, and create the conditions that allow greater private sector investment in agriculture. Another challenge is that an ageing population dominates the rural sectors in many African countries. Consequently, we need to engage young people to pursue agriculture and encourage them to stay in rural areas, as opposed to migrating to the cities. We face a number of issues concurrently, as Robert said, but they can be addressed through the right combination of policy and investment. Agriculture has to become a real priority for African countries, not just on paper.

2) Could you please tell us about your work on the bio-fortified orange-fleshed sweet potato?

Robert Mwanga: First of all, 100 million Africans suffer from vitamin A deficiency, which is the leading cause of blindness, and one of the chief causes of death in the region. Sub-Saharan Africa also has a food shortage and spends $US35 billion importing food. The orange-fleshed sweet potato can help address these problems. Sweet potato can be grown two-three times a year where there is steady rain or irrigation. The crop also has high yields and farmers can produce several crops a year. As a result, this helps address the problem of food shortage, especially in areas where cultivatable land is diminishing or where the population is increasing. In addition, sweet potato can also provide large quantities of quality food that is high in vitamin A.

However, it’s also worth noting that a sweet potato variety, which is popular in one country, may not be appropriate for another because of local preferences or that it is not adapted to the area. Apart from creating sweet potato varieties suited to local tastes, there is also a need to disseminate the crop to different countries. In recognition of these problems, the International Potato Center (CIP) and the International Food Policy Research Institute (IFPRI) acquired funding to form the Sweet Potato Action for Security and Health in Africa programme. Working together, we created new varieties, reduced the breeding cycle from eight years to four years, and used a variety of methods to get the crop to different segments of the population. We also used different marketing strategies including radio announcements, songs, and plays to educate the communities and encourage people to accept and eat the orange-fleshed sweet potato.

We also used a ‘divide and conquer’ strategy where breeders in different regions created orange-fleshed sweet potato varieties that were suited to local market preferences and climate. The programme asked breeders in West Africa to create less sweet varieties while their counterparts in east and Central Africa concentrated on breeding for virus resistance. In addition, the breeders in southern Africa concentrated on breeding drought-resistant varieties. In Mozambique, our breeders produced 15 varieties of orange-fleshed sweet potato, and, in east and central Africa, our colleagues increased yields from 4.5 to 10 tons per hectare. We also tackled the problem of vitamin A deficiency.

Jan Low: Robert’s given you the long-term perspective, but let me go back in time and tell a story. I’m a social scientist and agricultural economist, and I first came to the International Potato Center in 1994 as a post-doctoral researcher. At that time, Robert was one of the few breeders in east Africa and there was very little investment in sweet potato as a crop. When we were out doing varietal selection, the breeder we were working with had some orange varieties in the germplasm that they were testing with the farmers.

At that time, the conventional wisdom held that Africans and Asians wouldn’t eat orange sweet potato, an argument that was also put forward in a major book that came out in 1992. The World Vegetable Center, formerly known as the Asian Vegetable Research and Development Center, had introduced orange-fleshed sweet potatoes in Asia, but they had been rejected. In Africa, too, most traditional sweet potato varieties are white fleshed, with neither beta-carotene nor pro-vitamin A, or yellow flesh with very limited amounts. However, when we were doing taste tests in the field, I observed that people actually liked the orange colour a lot, so I questioned this conventional wisdom. Of course, when a theory is published in a book, people tend to believe it.

Not long after, the International Center for Research on Women called for research on women-focused ways to combat micronutrient malnutrition in Africa. I met with colleagues and collaborators from the Kenyan Agricultural Research Institute and said, ‘We have this orange-fleshed sweet potato material in our germplasm bank. Let’s go out and test this hypothesis’.

During that first, small project, we learnt that it wasn’t actually the colour that deterred people from eating these varieties, but rather the texture. In England and the United States of America, people love sweet potato varieties with a low dry-matter content. This makes them easy to mash and means that they taste great when roasted. However, in sub-Saharan Africa, particularly in Uganda, Robert’s home country, people love high dry-matter varieties that are very mealy. Sweet potato is actually a bread substitute for breakfast so preferred varieties have a dry matter content of 30-32%.

As a result, we recognised that we needed to breed orange-fleshed sweet potato varieties with higher dry matter content to win the support of the adults. During that first project, we also learnt that the children prefer and love the low dry matter content.Our philosophy is to use the orange-fleshed sweet potato varieties that we have while we’re breeding for better. Due to the hard work of the breeders on the team, we now have high dry matter flesh varieties that adult Africans love to eat.

The bio-fortified OFSP varieties have emerged from a process of questioning conventional wisdom and theories. We learnt that, if there is a food product that can boost nutrition where it’s most needed, we should exploit it. We can make the most of the OFSP through conventional breeding.

3) How can the orange-fleshed sweet potato help enhance food security in Africa?

Jan Low: The orange-fleshed sweet potato can really help enhance food security in Africa. First of all, sweet potato is such a flexible crop, as it can be grown in almost every agro-ecology except for the desert. In addition, it has flexible planting and harvesting times. For example, if farmers plant maize two weeks late, they can lose 50% of their yields. However, sweet potato crops will provide adequate yields even if they are not planted at the optimum time. As a result, farmers often prioritise more sensitive crops such as maize and plant sweet potato afterwards. Sweet potato can also be stored very easily. Depending on the dry season, farmers can often store it in the ground.

We’ve also been breeding for early maturing sweet potato varieties that are ready in three-five months, rather than the six-eight month process for traditional varieties. This is really helpful because climate change has made rains really unpredictable so our varieties can fit in.

Sweet potato’s other great advantage is that all parts of the plant can be used. Humans can eat the roots as well as the leaves, which have a very high protein content, and are loaded with lutein, which, again, is important for eyesight. People can also give the vines and leaves for their livestock to eat. It really is a crop that can fit in to most food systems in sub-Sarahan Africa.

In sum, there are few crops in the world, which can be used so widely, and contain such a range of vitamins and minerals. Sweet potato contains energy, vitamins and minerals, which make it the ideal food security crop.

Robert Mwanga: Sweet potato produces high yields in a short time, which means that it can be used in a huge range of products. If the processing industry is developed further, sweet potato can help provide food at times when there is a shortage of other crops. We also have not yet fully exploited its nutritional benefits. We have increased its vitamin A content to combat vitamin A deficiency, but sweet potato also has folic acid and anticarcinogenic agents (anthocyanins), which prevent cancer. It is also loaded with minerals such as potassium, magnesium, and calcium. The crop provides quality food, which can help combat malnutrition.

4) What are your future research projects?

 Robert Mwanga: We have asked breeders to breed fast and smart to deal with climate change. Basically, there is always a new problem to deal with. New outbreaks of disease, and pests all affect food, and this means there is a constant need for new models and techniques.

Jan Low: By 2020, we expect, and we’re well on our way to developing, an orange-fleshed sweet potato variety that is also biofortified in iron. In our conventional breeding in Mozambique, we have been selecting for increased iron and zinc content in every generation. By 2020, I think that we will be able to achieve this goal for iron, but not for zinc.

If we are serious about breaking into urban markets, we have to be able to store the fresh foods efficiently so we have focused a lot of our efforts on post-harvest management. Our team is working to create storage facilities that can run on solar power. This is because electricity is expensive and unreliable in east Africa and inappropriate to use for storing sweet potato. We are also doing a lot of research on how to make steamed and mashed orange-fleshed sweet potato puree that can be stored in vacuum pack containers without refrigeration. Again, this is because urban consumers prefer a more convenient form of the product.

Furthermore, we recognise that roots and tubers often drop out of urban systems because they’re bulky and costly to transport. We are working on a breakthrough product that can help substitute a large percentage of wheat flour in baked products because Africa spends US$5.5 billion per year on importing wheat.

At the CIP, our emphasis is on creating markets for farmers, particularly smallholder farmers, because any class of farmer can grow sweet potato. Accordingly, we’re very committed to help develop value chains that help small farmers, not just the large farmers. That requires more work and more training, but we have found that small farmers can be even more productive in terms of pre-unit area use than larger farmers. What they need are the opportunities, business training and skills to work in associations so they can aggregate their product and reach these emerging markets.

5) What advice would you give to young Africans who are hoping to pursue a career in agricultural research?

Robert Mwanga: Last year, Dr. Jan Low, Dr. Maria Andrade and I won the 2016 World Food Prize for our work on the biofortified orange-fleshed sweet potato. I hope that our win will encourage young scientists and people to see agriculture as a higher-status job. It shows that one can be successful in agriculture, but, of course, recognition takes a long time. I would tell young Africans who want to pursue agricultural research to persist and not to give up. Solving major world problems is a massive challenge, but also a road to success.

Jan Low: A lot of young scientists have come up to me and said, ‘I’m going to get the World Food Prize’. I think that it is a great stimulus to see Robert and Maria (Andrade), in particular, gain this recognition. To me, our win encourages young people to challenge conventional wisdom, and follow their heart if they have an idea that they believe in.

It took us 10 years in the wilderness before people gave us the real initial funding we needed to do our proof of concept. This was not an overnight achievement. It required the policy environment evolving to consider our efforts to integrate agriculture and nutrition. To any young Africans who want to pursue a career in agricultural research, I would say, ‘Stick to your beliefs, question conventional wisdom, and have fun’.

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