As botanist Nigel Taylor moves through a greenhouse kept to 90 degrees Fahrenheit and 80 percent humidity, he checks the stems of young, potted cassava plants.
“You can see it there, OK?” Taylor said, pulling one forward. “We’re getting lesions on the stem, this plant’s quite badly infected.”
Call it manioc, tapioca or cassava — this starchy, tropical tuber feeds millions of people around the world. In many parts of East and Central Africa, farmers are experiencing declining yields of cassava due to brown streak virus, a plant disease that can render a crop inedible.
For the past decade, scientists at the Donald Danforth Plant Science Center in Creve Coeur have led a project that tries another tack: genetically modifying cassava plants for disease resistance.
It aims to contain the virus, which is transmitted by a common pest called a whitefly and was previously confined to coastal areas in East Africa. But it’s now affecting farmers in at least eight countries in the Great Lakes region, including Uganda, Kenya and Tanzania.
Traditional breeding methods have been slow to help cassava crops develop resistance to brown streak, partially because the plant can reproduce without seeds. Often, farmers simply cut a section of stalk and replant it in the ground, growing a plant that is genetically identical to its parent.
The plant in Taylor’s hands is surely doomed, he says. But except for occasional streaks on a cassava plant’s woody stem, symptoms of brown streak virus can be difficult to detect until the roots are harvested and sliced open — a full nine months or more after planting.
“It can have a very devastating effect on the farmers, who have put in so much and invested in it,” said Catherine Taracha, who directs crop biotechnology for the Kenya Agricultural and Livestock Research Organization. “They’ll not have enough food and they’ll not have any income.”
In East Africa, cassava is frequently grown by subsistence farmers, who use the crop for food as well as income. Three million tons are grown every year in Uganda alone, according to the country’s agricultural census.
“It’s resistant to drought and it does very well in marginal lands,” said Taracha who is completing a six month fellowship at the Danforth center. “And the whole plant is useful. From the leaves to the stems to the roots.”
The cassava plant grows into a woody shrub about 10 feet tall and the leaves can be stewed and eaten or fed to livestock. The stems are used as firewood. Roots can be boiled and mashed, dried and ground, or distilled into ethanol. There is one catch: if prepared incorrectly, cassava can produce cyanide.
The Danforth Center’s project is called VIRCA: Virus Resistant Cassava for Africa. The project is going through field trials by agricultural authorities in Uganda and Kenya, and preliminary results have been promising. But researchers do not expect to complete regulatory approvals which would allow them to donate clean plant cuttings to farmers for at least another four years.
In a lab at the Danforth Center, Taylor, VIRCA’s principal investigator, pulls out a Petri dish full of what looks like clumps of minced garlic.
“This is actually a mass of several hundred thousand individual cells. Each one of them is what’s called embryogenic and has the potential to regenerate and make a new plant,” Taylor explains.
In the lab, scientists then introduce the genes that can help a fully grown cassava plant fight off disease. Then, they’re regenerated into ‘micro plants,’ which are multiplied into the plants used in field trials. Although Monsanto's genetically modified corn and soybeans have been criticized for requiring more and more herbicide use as weeds develop resistance to Roundup, the VIRCA plants do not require additional products to resist the brown streak virus.
When the plants are three inches tall, they are packed onto a plane and sent for field tests at agricultural research institutes in Uganda and Kenya. Eventually, Taylor expects all steps of VIRCA production to be completed in those countries as well.
“It’s a numbers game. You have to produce a lot of plants, you do a lot of work, you then select for the ones that are performing best,” Taylor said.
Genetic modification, after all, is an expensive way to manipulate plants. Proteins and processes used during development are often registered as intellectual property, and researchers must pay royalties or receive permission to use them for humanitarian purposes. Major donors to VIRCA are the Bill and Melinda Gates Foundation, the U.S. Agency for International Development and the charitable arm of Monsanto.
Ugandans are debating whether genetically modified crops should be permitted at all. The country’s Parliament tabled a bill to approve genetically modified crops earlier this year after local opposition. According to local news reports, critics believe the bill is in the interest of multinational companies like Monsanto, not Ugandan farmers. Others raise concerns that genetically modified food is unsafe to eat, although researchers argue that the plants go through rigorous testing during the regulatory process.
Barbara Ntambirweki, a university professor in Kampala who works with the Advocates Coalition for Development and Environment, falls in the middle. She believes that Uganda should pass a bill to allow genetically modified crops, but thinks that the latest version does not regulate them closely enough.
“For example, in the bill, there’s no labeling of GMO’s. We think is very important, that the public should be given opportunity to choose products that are free of GMO’s,” Ntambirweki said.
As the Uganda government mulls the decision, a handful of genetically modified crops are getting closer to fruition, including bananas, cotton and corn. Each comes with promises of disease resistance, bio-fortification or drought tolerance. But is genetic modification the best way to improve farmer's yields in East Africa?
This piece is part of a series reported by St. Louis Public Radio health reporter Durrie Bouscaren, who is visiting Uganda for a fellowship with the International Women’s Media Foundation, which is funded by the Howard G. Buffett Foundation. (The HGBF is also a donor to the VIRCA project). Bouscaren's reporting will focus on Uganda's debate over genetically modified crops, as well as projects that were initially developed in St. Louis for use in East Africa.
Follow Durrie on Twitter: @durrieB.