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Natural fungicide may help Arkansas rice producers

Rice blast, the most important fungal disease of rice plants worldwide, and other diseases may some day be controlled by a natural fungicide produced by a specially fed bacterium collected from a central Illinois hog farm.

Blast can be a serious problem for Arkansas rice producers, who produce more than 40 percent of the nation's rice.

The U.S. Department of Agriculture has applied for a patent on the bioconversion process developed by Agricultural Research Service scientists at the National Center for Agricultural Utilization Research (NCAUR), Peoria, Ill. ARS is USDA's chief scientific research agency.

“In Arkansas, one of the main weaknesses in our high-yielding rice varieties is the lack of blast resistance,” said Brad Koen, rice verification coordinator with the Cooperative Extension Service, University of Arkansas.

He said if the fungicide developed by USDA researchers was affordable and could reduce the risk of blast, it would be a great benefit to Arkansas rice farmers.

Researchers found the bacterium, a strain of Pseudomonas aeruginosa, in hog manure. The strain converts ricinoleic acid to a new fungicidal compound, called simply TOD. Ricinoleic acid is a major component of imported castor oil, but someday it may be economically made from oil of genetically modified oilseeds such as U.S.-produced soybeans. Castor beans are produced primarily in India.

Scientific collaborators of a major chemical company sprayed rice plants with a diluted solution of TOD and inoculated the plants 24 hours later with Pyricularia grisea, the fungus that causes rice blast. Five days after the inoculations, sprayed plants had only about 29 percent as much fungal growth as unsprayed plants.

Now the scientists are researching ways to scale up production of TOD for further experiments on blast and other fungi and insect pests of crops and stored products. Laboratory tests, using the dilute solutions, so far have also shown inhibition of fungi that cause rice sheath blight and peach blossom blight.

Lamar James is an Extension communications specialist with the University of Arkansas.

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