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Kenya inching closer to disease-free GMO cassava

Lilian Ziro, a farmer in Tezo, Kilifi, prepares cassava meal. PHOTO | COURTESY
Lilian Ziro, a farmer in Tezo, Kilifi, prepares cassava meal. PHOTO | COURTESY 

Cassava farmers are about five years away from accessing disease-resistant genetically modified varieties, currently being tested in specific locations around the country.

Kenya Agricultural and Livestock Research Organisation (Kalro) scientists are developing a transgenic variety that is resistant to the Cassava Mosaic Virus and the Cassava Brown Streak Disease the two diseases that have in recent years destroyed the crop causing farmers massive losses and threatening food security in rural Kenya.

“Currently, we have close to 200,000 hectares under cassava in Kenya, most of which (60 per cent) is in western Kenya. Close to 30 per cent of the crop is at the coast and the rest in the central region,” said Simon Gichuki, a senior principal research officer at Kalro who is also the coordinator of the crop biotechnology programme that is conducting the GMO cassava research.

Dr Gichuki said both diseases, especially the cassava mosaic, have been destroying the crop for a very long time, making the intervention critical.

“We have never been able to control it. The brown streak has also been there but not as big a problem. But in recent years, the two have become an epidemic, posing a big threat to cassava farming,” he added.

The Cassava Mosaic disease attacks the leaves of the plant, causing them to wither, bend and discolour, while also making the cassava root bumpy, leaving only a small percentage edible.

For millions of Kenyan farmers, the Cassava Mosaic disease became a real problem in the mid-1990s when it started spreading like wildfire, causing up to 80 per cent yield losses.

Since then, research focused mostly on breeding for resistant cassava mosaic varieties. Not only did it take 10 years or more to breed the resistant varieties but it also emerged that ultimately, the resistance was not 100 per cent.

More damage

It was later in 2009 when scientists realised that Cassava Brown Streak Disease was causing much more damage than the Cassava Mosaic disease and that it needed urgent intervention because there was no cure for it.

Brown streak disease shows barely any symptoms on the leaves, but when the roots are dug out, there will be brown spotting on the cassava, which makes it completely inedible, results in 100 per cent yield loss.

“The problem is, we’ve no conventional breeding methods to control these diseases. That’s why we decided to look for biotechnological solutions,” said Dr Gichuki.

Since 2009, the Kalro team has conducted numerous tests, under the Virus Resistant and Nutritionally Enhanced Cassava for Africa (VIRCA PLUS) Project.

Today, there are three test sites in Kenya, Kandara in Kiambu County, Mtwapa in Kilifi and Alupe in Busia.

The first phase of the project involved proving that it was possible to develop a genetically modified resistant variety.

Resistance genes

In the second phase, the scientists focused on taking disease resistant genes and inserting them in cassava varieties of farmers’ preference, without necessarily having to create a whole new variety.

The project is now in the third and final phase of seeking regulatory approval.

“In this phase, we are now just trying to make sure that the plants we have developed are safe for humans, safe for the environment and animal feeds.

"So here we will be testing the composition, taste and all kinds of tests to make sure that it is safe,” Dr Gichuki said.

Last year, the team got approval from the National Biosafety Authority to carry out confined field trials and the three test sites were chosen to represent each cassava growing region.

The GMO cassava research is not only being conducted in Kenya but also in neighbouring Uganda, because just like Kenya, Uganda has suffered massive cassava losses caused by the two diseases.

Cassava Brown Streak Disease particularly started along the East African coast, having spread from Mozambique, Tanzania and then Kenya. From the Kenyan coast, it spread inland, crossing the border into Uganda, Burundi, Rwanda and the Democratic Republic of Congo.

Whiteflies on a cassava leaf, which spread two diseases that affect the crop. PHOTO | ZEYNAB WANDATI |NMG

Whiteflies on a cassava leaf, which spread two diseases that affect the crop. PHOTO | ZEYNAB WANDATI |NMG

Staple foods

Cassava was introduced in Uganda in the mid-1800s and is currently one of the most important staple foods in the country.

The crop is grown with a mixture of legumes and cereals in plots of land that average two-five hectares. Until the mid-1990s, Uganda produced a surplus of cassava.

But in 1988, there was a severe Cassava Mosaic Virus outbreak that threatened production in many parts of the county.

By 1994, Uganda’s surplus production had dropped from about 1¼ million tonnes to less than 700,000 tonnes. Production has, however, been increasing since 2010 as the country finds ways of managing the diseases.

Today, production stands at more than four million tonnes annually, 60 per cent of which comes from northern Uganda.

But with the emergence of Brown Streak disease, Uganda’s cassava production is under threat once again, with annual losses estimated at $22.4 million.

The scientists say it was, therefore, important that a test site is located at the Coast, because not only is the prevalence of the disease much higher, but also there are more strains of the brown streak disease along the Kenyan coast than there are anywhere else.

“This research is important to us because, for the first time in the world, biotechnology is being used to improve cassava varieties,” said Dr Theresia Munga, a cassava breeder based at the Kalro, Mtwapa Centre.

“With conventional breeding, it would take us a minimum of 10 years to breed for resistance, but even then, it wouldn’t be 100 per cent. But with genetic modification, we are able to achieve results in less than five years,” she added.

These diseases are spread along with the infected vegetative planting material and also by small white insects called the whiteflies.

Breeding for resistance to Cassava Mosaic Disease and Cassava Brown Streak Disease was initiated in 1937 in Amani, Tanzania and due to insufficient levels of resistance in cultivated cassava, a strategy to incorporate resistance from wild species was adopted.
'Farmer varieties'

Several of these inter-specific hybrids have been incorporated into farming systems in the region and are now considered as ‘farmer varieties’ such as ‘Kaleso’ in Kenya and ‘Namikonga’ in Tanzania.

To date, these two farmer varieties form an important gene pool for resistance breeding.

With cassava being the most important food for the coastal communities after maize, thousands of locals have welcomed the idea of resistant varieties, because it means more money in their pockets.

“I don’t know much about GMOs or what it really means, but if it will save my cassava, then I will happily plant it,” Lilian Ziro says.

“I have a cassava variety on my farm that was developed through research. It is called ‘Tajirika Sasa’. This cassava is not GMO but it has shown strong resistance to cassava mosaic disease, and that is good for us farmers.

"I have one and a half acre under the Tajirika variety and when I harvested last year, I earned Sh600,000,” says Dhahabu Charo, a cassava farmer in Kilifi, adding that before she got the new variety, the indigenous seed she had planted on the same piece of land gave her just Sh25,000.

Charo and Ziro both belong to same self-help group in Tezo, Kilifi, which was started in 2013 to help cassava farmers in Tezo grow their yields through good agricultural practices and adoption of certified seed.

Dhahabu now grows seed cassava, which she sells to Kalro and the county government as well as individual farmers.

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