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In a race to prevent hunger, Danforth researchers use CRISPR to gene-edit cassava

Michael Okello arranges his cassava harvest, untouched by viruses.
File photo | Durrie Bouscaren | St. Louis Public Radio
At his home in northern Uganda, Michael Okello arranges his cassava harvest, untouched by viruses, in 2016.

To prove that a new-gene editing technology could be used to alter the cassava plant, scientists in the St. Louis suburbs zeroed in on a gene used to process chlorophyll. Before long, they had petri dishes full of seedlings that were white as chalk.

The plan is to use CRISPR — a cheaper, faster way to genetically modify crops — to grow cassava plants that are resistant to common plant viruses threatening food supplies in East Africa. But regulatory agencies have yet to finalize how they will treat the new crops.

“It’s only really been available for use in plants for three, four years,” said principal investigator Nigel Taylor, of the Donald Danforth Plant Science Center in Creve Coeur. “Right now, it’s an experimental tool.”

Taylor has spent more than a decade developing strains of cassava that are resistant to brown streak disease and mosaic virus through older genetic engineering methods. Both viruses are spread by whiteflies, a common pest, and can wipe out an entire crop before a farmer knows that a field is contaminated. Crop researchers in East Africa have also developed strains of cassava that are traditionally bred to build resistance to the viruses, but they are not as effective as their GM counterparts. 

In conjunction with scientists in Uganda and Kenya, Taylor’s team is conducting field trials of genetically modified strains that are resistant to the viruses. Earlier this month, Uganda’s parliament passed a long-awaited bill to allow genetically modified crops to be grown commercially.

For researchers, CRISPR presents the alluring possibility of getting gene-edited crops to market more quickly and efficiently. When previous generations of plant scientists spent decades and huge sums of cash to genetically modify a crop, the energy was spent on corn, soy and other commodity crops. To an extent, CRISPR levels the playing field for academics, students, or NGO’s that study crops used by subsistence farmers.

“Investments are being made in the orphan crops now,” Taylor said. “We’re almost six months behind or a year behind the corn and the soybeans. And that’s a huge change from 20 years ago.”

Other scientists have raised concerns that CRISPR could have unintended consequences, such as disrupting local economies or altering plants in unexpected ways.  

“The application of CRISPR-Cas9 technique involves risks since it may produce off target mutations, which can be deleterious,” wrote Chilean bioethics researcher Eduardo Rodriguez in an ethics review of CRISPR published in the Journal of Clinical Research & Bioethics. “Efforts have been made to reduce off target mutations, but further improvement is needed." 

But regulatory agencies in the United States and abroad have yet to determine how plants developed with CRISPR methods will be handled.   

“If the regulatory rules on CRISPR… edited plants are less than GMO’s, I think yes, we can deploy faster. If it’s the same, then it will be the same timelines,” Taylor said. “As we get better at this, the price is going to come down, and the cost of doing it is going to come down.”

Follow Durrie on Twitter:@durrieB

Correction: A previous version of this story misidentified the molecule chlorophyll, and Danforth's involvement in traditionally bred cassava trials. That version also made reference to a process that Danforth's researchers are not using.