Gainsville, Florida, USA
August 10, 2010
Saccharin, the artificial sweetener used in diet drinks and other consumer products, has an unexpected sweet agricultural benefit: It helps soybean plants ward off a disease that threatens the entire soybean industry, University of Florida researchers say.
If the sugar substitute performs as well in the field as it did in the lab, it may give farmers a cost-effective weapon in the fight against Asian soybean rust, an invasive fungal disease that appeared in the continental U.S. in 2004 and is now a major grower concern.
The 2009 U.S. soybean crop was valued at $31.8 billion, according to the U.S. Department of Agriculture; Florida’s crop was worth $12.3 million.
The study, presented today at the annual meeting of the American Phytopathological Society in Charlotte, N.C., is one example of scientists’ efforts to harness a phenomenon called systemic acquired resistance, said Pratibha Srivastava, a postdoctoral associate with UF’s Institute of Food and Agricultural Sciences.
Systemic acquired resistance, known as SAR, occurs when a plant receives minor exposure to a pathogen and responds by upping its resistance to that pathogen for weeks or months, said Srivastava, who led the study. Sometimes, SAR boosts resistance to multiple pathogens.
Commercial use of SAR-inducing treatments could reduce the need for fungicides and other products used to battle crop diseases, she said. Benefits could include lower costs for farmers and less environmental impact.
Various chemicals stimulate SAR, including saccharin, which has been shown to work in tobacco, beans, barley and cucumbers, said Srivastava, at UF’s North Florida Research and Education Center in Quincy.
Saccharin is chemically similar to compounds produced by plants, said Jim Marois, a plant pathology professor at the Quincy center. A synthetic compound, it’s used to sweeten soft drinks, candy, toothpaste and medicine.
“Saccharin activates certain genetic reactions that make the plant resistant,” Srivastava said.
Researchers will try to pinpoint which genes are responsible and whether they can be controlled by other means, she said. They also want to develop SAR-strengthened soybeans through conventional plant breeding.
“Part of the purpose of the study was to see if SAR works against Asian soybean rust, and we were happy to see it did,” Marois said. “So even if we don’t end up using saccharin in the future, we could use something else.”
In the study, researchers grew soybean plants in greenhouses and applied a saccharin solution to their roots or leaves. Then each plant was exposed several times to the fungus that causes Asian soybean rust.
Plants that received the saccharin solution on their roots showed better resistance after just one day with treatment. When plants received the solution on their leaves, resistance increased 15 days later.
Compared with control plants, the treated soybeans showed less severe disease symptoms. The saccharin solution had no effect on plant size or growth.
Results from the UF study support the idea that SAR has a place in soybean disease management, though it isn’t likely to completely replace fungicides and other methods, said Ray Hammerschmidt, chairman of Michigan State University’s plant pathology department.
It’s also important to know that saccharin could help reduce the severity of Asian soybean rust on soybean because the disease is a significant threat to U.S. production, Hammerschmidt said.
Although soy is a lesser-known Florida crop, the Quincy center is a hotbed for Asian soybean rust research because the growing season begins earlier in Florida than in major soy producing states further north, said David Wright, an agronomy professor at the center.
“We’ve been the center of activity for Asian soybean rust studies since 2005, as far as research on outdoor plots,” Wright said. “We have the disease early and we have gotten it severely, so there have been some great learning opportunities.”
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