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Microbes Protect Potatoes from Storage Rot

By Ben Hardin
September 30, 1998

A bacterium patented by the Agricultural Research Service to reduce Fusarium dry rot in stored potatoes has proven 50 percent more effective than a synthetic chemical now used to control rot in commercial storage bins. The chemical, thiabendazole (TBZ), is the only federally registered fungicide for potatoes destined for human consumption.

Scientists with ARS, the University of Idaho and United Agri Products, Inc., of Greeley, Colo., conducted research on potentially protective bacteria under a cooperative research and development agreement (CRADA). They tested the bacteria on potatoes stored in bins for four to eight months at four North Dakota and Idaho sites.

The most outstanding bacterium tested, Enterobactercloacae strain S11:T:07, reduced dry rot an average of 21 percent in contrast to 14 percent by TBZ. Researchers noted a 17 percent drop in dry rot when the S11:T:07 strain was applied to potatoes infected with TBZ-resistant strains of the fungus Fusariumsambucinum in an earlier pilot study. When TBZ was applied instead, dry rot increased 7 percent.

ARS scientists at the National Center for Agricultural Utilization Research, Peoria, Ill., are researching improved formulations of S11:T:07, one of 18 beneficial bacteria they've patented as dry rot inhibitors. The scientists have shown the microbe can be produced in a liquid culture system compatible with industrial fermentation practices.

Dry rot fungi plague the potato industry worldwide, causing a dark tissue discoloration on the potato that eventually forms a dry, crumbly rot. Annual losses in stored potatoes in the United States are estimated at more than $100 million.

ARS is seeking to license the 18 patented bacteria or form cooperative research agreements with private firms to develop biocontrol products based on the beneficial microbes. The agency is the lead scientific wing of the U.S. Department of Agriculture.

Scientific contacts: David A. Schisler and Patricia J. Slininger, USDA-ARS National Center for Agricultural Utilization Research, 1815 N. University Street, Peoria, IL 61604, (309) 681-6567, fax (309) 681-6427,,