Arsenal from Science Helps the Soybean Combat Two Powerful Fungal Enemies

Farmers have powerful new weapons against fungal pathogens that destroy soybeans, thanks to scientists at the Agricultural Research Service. New soybean lines and a better understanding of the disease process promise to reduce crop losses to fungal disease.

Phytophthora sojae causes one of soybeans' most serious diseases--Phytophthora root rot, that can cut yields up to 25 percent. Sudden death syndrome, (SDS), another soybean disease, is caused by a toxin-producing form of the fungus Fusarium solani.

After 30 years of research, ARS plant pathologist Scott Abney has become an expert on the genetics and virulence of both fungal pathogens. At ARS' Crop Production and Pest Control Research Unit, West Lafayette, Ind., Abney studies the interaction between host plants and fungal parasites to identify the plants' inherent disease resistance.

Details of Abney's research are described in the October issue of Agricultural Research magazine. The story can also be seen on the World Wide Web at:

http://www.ars.usda.gov/is/AR/archive/oct97/soil1097.htm

The data collected by Abney and his colleague, geneticist James R. Wilcox, has resulted in 14 new soybean varieties with improved resistance to fungal diseases. All 14 were released to commercial breeders.

Abney's work on the Phytophthora fungus focuses on soybean "Rps" genes. These genes trigger production of an antifungal compound, phytoalexin, that protects the plant from the fungus. Abney also discovered seven new Phytophthora races and identified two additional Rps genes breeders can use.

In other research, Abney confirmed that F. solani causes SDS and revealed new, complex host-parasite interactions. He also observed that highly virulent isolates of the fungus produce a rare Nectria sexual stage--a discovery that could lead to better strategies for reducing fungus infection.

Scientific contact: T. Scott Abney, ARS Crop Production and Pest Control Research Unit, West Lafayette, Ind., phone (765) 494-9859, fax 494-0363, [email protected].