Breeding nutritious sweetpotatoes in Zambia

Dr. Martin Chiona is plant breeder and head of the root and tuber research team at the Zambia Agricultural Research Institute (ZARI). This organization is collaborating with the International Potato Center (CIP) and partners under a three-year project: Sweetpotato Genetic Advances and Innovative Seed Systems (SweetGAINS) to improve nutrition, resilience and incomes through enhanced sweetpotato cultivation. 

Vivian Atakos, CIP’s Regional Communication Specialist for Africa, spoke with Chiona, to understand his role with SweetGAINS and the program’s progress to date.  

Q: What is the contribution of sweetpotatoes to Zambia’s overall agri-food system?  

Chiona: Sweetpotato is one of the crops for which we rarely see statistics being collected in Zambia. However, what you find is that the crop is being sold on the roadside throughout the year. That tells you of the value it has to the food system. During the rainy season, you will still find sweetpotatoes at the market.  Sweetpotato roots and leaves are used for food in Zambia. So, in terms of contribution to the food system, I think it has been undervalued. What we may require in the future is to document this contribution.  

Chiona in one of the trial screenhouses where sweetpotato varieties are grown (photo: ZARI)
Chiona in one of the trial screenhouses where sweetpotato varieties are grown (photo: ZARI)

Q: Does it mean we don’t know exactly how much sweetpotato is produced in Zambia?  

Chiona: It is possible to find some figures, but I don’t think those may be a true representation of quantity in Zambia. Sweetpotato roots are harvested whenever required; people go in, remove the big roots and still leave the plant to continue producing more roots. And for that reason, when data is being collected, they collect data at one point, and they ignore what has already been removed from the plant. So that creates a challenge in terms of quantifying how much is produced. 

Q: Is that what you call piecemeal harvesting? 

Chiona: Yes 

Q: Can you confirm what kind of varieties are grown in Zambia.  

Chiona: Traditionally grown varieties have been white flesh with red skin. Beginning with the breeding programs in the late 80s, there was an introduction of the variety “chingova,” which is white and with a high dry matter content. Working closely with CIP, we then tried to introduce orange-fleshed sweetpotatoes (OFSP). But at that time, they were quite moist; very little dry matter content. They were not preferred. But over time, we have been re-introducing the OFSP slowly, following gains made through breeding varieties with a high matter content. Now, we have about 50-50 white versus OFSP moving towards more of the orange ones. 

Q: Ok. When did you start introducing the improved varieties?  

Chiona: About 1993, that is when we started introducing OFSP. We have seen the acceptance levels rising as we continue to improve the dry matter content of the orange materials. 

Q:. As a sweetpotato breeder in Zambia, what is that one problem you are trying to solve? 

Chiona: In the initial stages, our concentration was on yield because most of the varieties were low yielding — It was about 5 to 6 tonnes per hectare.  We endeavored to increase yield to over 15 tonnes per hectare. Our preoccupation is to ensure the varieties we develop have high dry matter, are high yielding and ensure the leaves can be used for vegetables—an important characteristic for Zambians.  

We later realized, because Zambia had challenges with Vitamin A deficiency (VAD) and through our interaction with CIP, that sweetpotatoes can be a very big contributor to alleviating VAD. As sweetpotato is grown basically by everybody that has a piece of land, even in backyards – we realized OFSP could be part of the solution. So, ZARI got on board and started also considering integrating beta-carotene into varieties being bred. We received OFSP materials from CIP and the South African breeding program.  Through our breeding program, we now have varieties that combine both high dry matter and are orange-fleshed yet also provide families with leaves for vegetables. We have released 10 improved varieties — five are white, and five are orange-fleshed. 

Q: What are the current statistics of VAD in Zambia? 

Chiona: The Zambia Demographic and Housing Survey (ZDHS), 2018 shows the figures are at about 54 % for the under-five’s.  

Q: How is the problem being addressed? 

Chiona: Through food fortification of products like sugar, margarine, and others. There is also an intervention of growing of palm trees. However, we see that the people that desperately need vitamin A cannot afford these products. That is why growing sweetpotatoes seems to be a more sustainable approach, especially for rural dwellers.   

Q: Let’s move to SweetGAINS where we are talking about modernizing breeding operations. What does this all mean? 

Chiona: It entails use of modern tools to drive new genetic variations in our breeding programs. Such tools entail genomic selection, marker assisted selection and others that help us to reduce the time that we spend on developing varieties to each release. So these tools (including use of tissue culture) will help us rapidly multiply the new varieties. Others include the sweetpotato base which we now use to input and analyze our data, and to develop breeding trial designs. This ensures that our period and breeding efficiency is much improved. 

Chiona inspects leaves on sweetpotato plants currently under development for release as new varieties in Zambia.
Chiona inspects leaves on sweetpotato plants currently under development for release as new varieties in Zambia.

Q: What do you mean by efficiency in breeding? 

Chiona: It’s about being able to reduce the time it takes to release a variety. Under conventional breeding, when you are selecting for a particular trait, once you combine traits in a crossing block, you must grow that material to establish whether you are successful or not. It takes a lot of time.  

But with the modern tools, even when it is at the seedling stage, you can get a plant and measure the trait of interest so that at that time you can decide on what to move forward, what to select and what not to select.  

Q: Turning to product profiles. Do you consider product profiles as an example of modernizing breeding? 

Chiona: Yes! Product profiles are part of modernizing breeding traits helping breeders know what traits to focus on.  

What we have been doing is to bring stakeholders at a round table to agree on key traits to breed for. Modern tools that have been made available to us then come into play in helping us deliver according to the stakeholders’ expectations. 

Q: Tell me about a moment when you were proud as a breeder of sweetpotatoes.  

Chiona: In 2018, the traditional chiefs in Luapula province of Zambia gave me an award for contributing to the agricultural sector because of the work we have been doing with sweetpotatoes.  

Q: What is the value of the relationship that CIP has with ZARI? 

Chiona: Most of the knowledge gained in ZARI in terms of sweetpotato breeding agronomy and seed systems has been because of our interaction with CIP. They [CIP] have done a lot of capacity building for our staff. This continues now through SweetGAINS whose focus is on use of modern tools for both phenotyping and genotyping.  

Q: How do we improve our interaction even as we move in the #oneCGIAR direction? 

Chiona:  What I had in mind is now happening. We are implementing the same activities in different countries. For example, we have a target population and environment trial that we are implementing here in Zambia, ongoing in Mozambique and Malawi. That creates an environment where we are doing the same thing and learning from each other. Capacity is being built within our institutions. But I am sure also CIP will be learning from what we do and together we can move the sweetpotato industry forward.