African Centre for Crop Improvement

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African Centre for Crop Improvement

“Training African Breeders on African Crops, in Africa”


High hopes for South African cassava project

The African Centre for Crop Improvement is poised to become a key player in a move to kick-start large-scale cassava production in South Africa.

Although cassava is not widely produced or consumed here, it is Africa’s number one root crop, and in many sub-Saharan countries, it’s crucial for keeping starvation at bay during the annual late-summer ‘Hunger Gap’.
Dubbed the “Rambo root”, several studies have indicated that cassava is the only crop likely to benefit from climate change because it is drought and heat tolerant. It also tolerates locusts and marginal soils, has low fertilizer requirements and the long-term storability of its roots below ground means it can be kept until needed.
Apart from being an important food security crop, cassava is also widely used as an industrial starch, and a global beer manufacturer is currently investigating the feasibility of using it in its African factories.
Prof Mark Laing
ACCI director, Professor Mark Laing, says discussions around investigating the feasibility of industrial-scale cassava production started a decade ago, but the project only got going in earnest three years ago.
The ACCI is well placed to contribute, with at least nine of its PhD graduates having worked on breeding improved varieties of cassava since the centre started training plant breeders in 2002. Several of these improved varieties have been released in their home countries.
A National Working Group (NWG) has now been formed with three units heading up research: the ACCI, the Agricultural Research Centre (ARC) and the University of the Free State.
Laing says a challenge for the project is producing the quantity of planting material needed. “How to do you go from one perfect cassava plant to 10 million in the shortest time possible? It’s a big technical challenge, but we’ve worked out how to do it.”
He explains that, starting three years ago as a feasibility study, the ACCI undertook to produce 200 000 seedlings from relatively 10 parent plants and showed that it can be done. “It takes three generations to get enough seedlings and these have all been planted out in trials in Limpopo, Mpumalanga and KZN for the ARC to assess their potential,” says Laing.

One drawback is that the study was done using unproven and unknown varieties, accumulated by the ACCI from student work over the years, so the focus now needs to be on breeding improved varieties that have been measured in terms of desired traits.

“The NWG has been tasked with putting forward a project proposal before the end of June to evaluate and start breeding cassava varieties that meet South Africa’s needs,” says Laing. Evaluations will be done in KwaZulu-Natal by the ACCI and in Mpumalanga by the ARC.
“We have a pathway of what needs to be done. First, we need cultivars to give to farmers. The goal is to have good varieties and good agronomic packages available to them within five years,” says Laing.
“It’s relatively quick to breed new varieties – about four years. You only need one perfect individual, which you then use to propagate cuttings. But we will want a number of good parents so the farmers are not vulnerable to new diseases.”
The ACCI already has some cassava germplasm, and can access more if needed, and Laing says the breeding programme will involve growing a wide range of germplasm for South African conditions. Parent material will be sought that have good traits of disease resistance, high yields, cold tolerance and earliness, which is especially important.
One of the barriers to growing cassava in South Africa in the past was that old varieties took 18 months to grow and the crop couldn’t survive through winter. ACCI students have since bred seven-month varieties, making the crop feasible here. A seven-month variety also means that farmers can harvest a crop every year.
“Once good parents have been identified, we will make crosses, plant that seed out and then look for outstanding progeny plants. We can then develop clones for doing economic trials, where we test the best progeny on a larger scale and can get a better idea of yields and performance.”
“We will actively engage with farmers, select the best of the parent material and then they can get started.”
After that, Laing says the DTI will need to get involved in setting up the industry in terms of the economics and establishing factories to process industrial starch.
He’s also applying his mind to the agricultural engineering side. “Harvesting, peeling and processing all need to be considered. How do you dig up cassava tubers? They can be big, almost a metre long and 10kg in weight, and how do you peel them? Then you also have to deal with a waste stream that’s full of cyanide compounds, which is found in cassava. How do you process that?”
The NWG has agreed that two streams of breeding will need to take place — for industrial and edible cassava.
The requirements for industrial cassava are low protein and high cyanide content, so that animals don’t eat the crop while it’s growing. This cassava will go to the factory to be converted into starch or beer.
Desirable traits for edible cassava are high levels of protein and the micronutrients, pro-Vitamin A, zinc and iron, as well as low levels of cyanide and a longer shelf life.
Laing says most of the ideas for the project have been worked out and the final budget is being drawn up. If the proposal is accepted, the ACCI will receive funding to do breeding and agronomic studies that could involve four to five PhD students working on it for a five to ten-year period.
He’s upbeat about the potential of the project.
“Cassava production could be a very good industry for South Africa. We have outstanding infrastructure here, such as roads, railways and capital, compared to our competition. And farmers need more crop diversity because crops like sugar are not doing well.”
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