Thursday, July 31, 2014
   
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UNL research seeks ways to block rice blast

Study may help fight disease in wheat.

University of Nebraska-Lincoln research is looking for ways to control the fungus that causes rice blast disease, which can cause yield losses of 10 to 30 percent a year, and annually destroys enough rice to feed 60 million people.

The research could have broader implications in the United States as a similar fungus causes disease in wheat, said Richard Wilson, UNL plant pathologist who’s leading the effort.

Wilson’s research was featured in a journal article in the Proceedings of the National Academy of Sciences.

Rice blast disease is caused by the fungus Magnaporthe oryzae, whose spores land initially on the plant’s leaves before forcing their way through the surface into the tissue beneath. There, in a nutrition-rich environment, the fungus colonizes and spreads rapidly, deriving nutrition from living tissue while evading or suppressing the plant’s natural defense system.

Efforts to fight the disease through breeding resistant varieties of rice have had some short-term benefit, but Magnaporthe oryzae has adapted effectively to overcome those efforts.

Wilson’s research, which he began at the University of Exeter in England and has continued at UNL, focuses on understanding the regulatory mechanisms that allow the fungus to develop so effectively and rapidly.

Wilson and his colleagues have discovered there’s a genetic switch that regulates plant infection by signaling to the fungus it’s in a nutrition-rich environment. “That’s the trigger for it to establish disease,” he said.

This genetic switch “is a target we can try to manipulate so it’s always in the off position,” Wilson added. “We don’t know those processes yet.”

But the research won’t stop with understanding the genetic trigger’s activation process, the Institute of Agriculture and Natural Resources scientist said. It will search for other parts of the process, controlled by the switch, that also could be targeted to control the disease.

The more steps in the fungus’s infection process scientists can understand and target, Wilson said, the more effective fungicides ultimately can be developed.

This phase of the research is likely to take two or three years. Then, collaborations with other scientists will lead to developing fungicides to attack the fungus.

Although rice is most widely grown in countries other than the United States, the U.S. is the world’s third largest rice exporter; rice is the sixth most valuable crop grown in the U.S., and an outbreak of rice blast is currently under way in Arkansas. A related disease also has been found in wheat in Brazil, said Wilson, who’s been assisted by graduate student Cristian Quispe.

Wheat blast is considered an emerging disease that some day could make its way to North America. If that occurred, the research into rice likely would be applicable to wheat, Wilson said, giving a head start in the fight against wheat blast.

This research is funded by IANR’s Agricultural Research Division and a grant from the National Science Foundation Nebraska EPScoR.

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