DES MOINES, Iowa – Cassava brown streak disease can keep a cassava farmer awake at night. It can lead to complete crop loss, is difficult to detect and resistant varieties of the crop are proving to be not-so-resistant.
Symptoms are hard for inexperienced farmers to recognize, and it’s often mistaken for the more familiar cassava mosaic disease. They can appear in a young plant, only to disappear and reappear as the plant ages. In a handful of varieties, it can’t be detected at all until the tuber is pulled from the ground, revealing the disease’s namesake brown streak through the cassava root. For a crop that takes eight to twelve months to mature, the loss of production can be significant. To make matters worse, it’s spreading.
“It’s an epidemic in eastern Africa, and by all accounts, this is going to get to West Africa, and it’s going to hit Nigeria,” said Nigel Taylor, interim director of the Institute for International Crop Improvement at the Donald Danforth Plant Science Center located in St. Louis, Missouri. “Nigeria is the largest cassava-producing country in the world. There will be a food security issue when it gets there.”
Nigel and other researchers are working to stay ahead of cassava brown streak using a new technology: Clustered Regularly Interspaced Short Palindromic Repeat, or CRISPR. CRISPR allows geneticists to identify a specific genetic sequence within an organism’s DNA, bind an enzyme to that sequence and cut it off, effectively shutting off the expression of the genes in the targeted sequence. CRISPR has already lead to immense advancements in the medical field, including preventing HIV infections and more rapid identification of bacterial and viral infections.
CRISPR technology has edited two genes in cassava, disabling the virus’s ability to replicate and infect the plant. Scientists plan to edit the remaining five genes that influence the disease in the coming months. CRISPR can do more for crops than prevent disease. Researchers are also using the technology to bring a green revolution to teff by editing genes to make the plant shorter, which would allow for the more efficient production of the plant’s protein and mineral-rich seed.
These advancements are especially useful in plants like teff and cassava because they are orphan crops, vital to the developing regions they are grown in, such as Nigeria and Ethiopia but not a significant portion of global markets. Research has largely focused on global cash crops like corn, wheat and rice. While these grains saw vast improvements in productivity due first to seed breeding during the Green Revolution and later because of genetic modification, very few advancements have been made in cassava and teff production. In West Africa, cassava is a staple food. It’s cheaper, hardier and easier to grow than maize. Making a better cassava could improve the livelihoods of the small-holder farmers that have been thus far left out of revolutionary agricultural technologies.
So what stands in CRISPR’s way?
“Public opinion is largely unformed, and it’s largely uninformed about CRISPR,” said Kevin Pixley, director of the Genetics Resources Program of the International Maize and Wheat Improvement Center.
Regulations about the technology are still developing, even in countries that have already produced volumes of CRISPR research, such as the United States. How the risks and benefits of CRISPR are communicated to the public and to the farmers that would eventually use CRISPR-modified crops will be crucial to the formation of these regulations. Panelists at a Borlaug Dialogue discussion of CRISPR emphasized the importance of keeping African researchers and farmers in the know about developments in this technology.
“If any advance in beneficial technology does not reach smallholder farmers, then we risk really increasing that technology lag and decreasing the competitiveness of smallholder farmers and further then advancing the poverty cycle that we’re all working to alleviate,” Pixley said.