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New R&D Agreement Aims at Natural Controls for Plant Fungi

By Sarah Tarshis
August 16, 1999

Zosteric acid, a natural product made by a common seagrass, may lead to a nontoxic way to protect strawberries and other crops from fungal diseases. Scientists at the Agricultural Research Service--USDA’s chief scientific arm--are exploring the acid as an environmentally safe alternative to chemical fungicides.

Zosteric acid is found in eelgrass (Zostera marina L.) that grows in many saltwater bays and harbors. Under a new Cooperative Research and Development Agreement, ARS and PhycoGen, Inc., Portland, Me., will evaluate zosteric acid against fungi that cause fruit and crown rot of strawberries.

Fungal pathogens rely on spores to infect a plant or fruit, but spores must first attach to a leaf or fruit surface and then germinate to cause infection. Unlike chemical fungicides, zosteric acid doesn’t kill fungi; rather, it may act as a shield, preventing spores from attaching. This mode of action would be environmentally safe and would sidestep the risk of fungi developing chemical resistance.

David Wedge of ARS’ Natural Products Utilization Research Lab in Oxford, Miss., will conduct laboratory studies with strawberries and blueberries, and Barbara Smith with ARS in Poplarville, Miss., will also conduct greenhouse studies. Kenneth Curry of the University of Southern Mississippi will work with the ARS team to examine zosteric acid's antifungal features. Randall Alberte of PhycoGen will conduct lab studies on strawberries.

Most research to develop fungicides is done by industry and focuses on major crops. But the ARS research will benefit small farmers who often grow so-called “minor crops.” While grown on relatively few acres, minor crops are worth about $31 billion annually to U.S. growers and are economically vital to many rural communities and family farms.

PhycoGen, which manufactures zosteric acid, will also cooperate with ARS to develop a product to protect stored seeds from fungi. The company is also exploring the acid as a marine antifouling agent for boat hulls and other applications.

Scientific contact: David Wedge, ARS Natural Products Utilization Research Unit, National Center for Natural Product Research, University, MS, phone (601) 232-1137, fax (601) 232-1035,