By Kathleen Berger, Executive Producer for Science & Technology
When there’s a threat to human welfare, it’s met with a strong response. Scientists at the Donald Danforth Plant Science Center in St. Louis are on the front lines fighting for the future of the global food system. They are combatting a disease that threatens cassava, one of the world’s key crops.
“It’s a source of starch for millions of people but it’s primarily grown and eaten by people in the tropics,” said Becky Bart, PhD, Associate Faculty Member and Principal Investigator at the Donald Danforth Plant Science Center.
Cassava research in the Becky Bart Lab at Danforth is uniting scientists across the globe, as farmers in Africa, India, and Southeast Asia suffer huge yield losses due to cassava mosaic disease (CMD).
“This is a DNA geminivirus pathogen of cassava that infects the cassava plant. It’s transmitted by little white fly insects,” said Bart.
“It’s a DNA virus which will get into the plant cell, it hijacks the plant’s DNA replication system in the plant cells and then uses that for itself. And then it will replicate very, very quickly. It can be really devastating,” explained Nigel Taylor, PhD, Associate Member and Dorothy J. King Distinguished Investigator at the Donald Danforth Plant Science Center. “You could lose 50 or more percent of the yield.”
Taylor has been studying cassava for 30 years. He’s concerned about the future of the crops, farmers, and the world food supply.
Crops infected with cassava mosaic disease don’t fully develop the storage roots that are used for food. The starchy root crop is rich in carbohydrates. It’s one of the most important staple foods in the world feeding nearly one billion people.
“Cassava mosaic disease – it does not yet exist in Latin America. If it gets to Latin America, it will be a huge problem because none of the varieties grown in South America and the Caribbean have resistance to cassava mosaic disease.”
But research in the Becky Bart Lab at Danforth now has the world a step closer to the possibility of planting disease resistant crops. Bart is principal investigator and the international research team had a breakthrough this year. It’s a discovery that reveals a mutation responsible for disease resistance to CMD found in certain species of cassava.
“Our discovery is the gene in cassava that protects it from this virus,” said Bart. “There’s a lot of different varieties of cassava out there. Some don’t have this specific gene and are therefore susceptible to the pathogen. If they have this certain variation, this mutation in this gene, then they are resistant to this disease. Just genetic resistance.”
“The gene we found this mutation in, it’s called DNA polymerase,” said Kerri Gilbert, Research Associate at the Donald Danforth Plant Science Center. “It’s a really interesting protein because it’s part of a complex that replicates all the DNA inside of our cells.”
Thanks to technology and collaborations around the world, Gilbert used big data analytics for the discovery.
“Folks around the world have been working on the problem of cassava plants and this virus for a long time. They generated a lot of data,” explained Gilbert. “I was able to access this publicly available data, sequencing data, disease data, and look to see which plants are resistant and maybe, do they have the same mutation? And we did!”
The work sheds light on how to maintain resistance to secure yields in the future, including breeding strategies.
“You may have one cassava plant that’s really productive but happens to be susceptible to this disease. You can cross that variety of cassava with a variety of cassava that has the resistance and get new varieties of cassava that combine those two traits,” said Bart.
The discovery offers hope for other major crops experiencing attacks by this family of closely related viruses.
“Geminiviruses, like the one that causes cassava mosaic disease, are very common. They infect lots of different crops- cotton, tomato, grape, etc.,” said Bart. “In many of those cases, there are no known disease resistance control strategies. What we are interested in doing now, is figuring out whether we can take our discovery from cassava and recreate it in some of these other plants to generate a novel source of resistance.”
“This discovery could be made to operate in some of the most important crops in the world,” said Taylor. “To improve the livelihoods of hundreds of millions of people.”
