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Scientists Gear Up to Counter Soybean Rust Disease

A showdown is simmering. In one corner are Agricultural Research Service (ARS) scientists and collaborating researchers. In the other is a fungal rust disease whose 2001 arrival in South America has cast a menacing shadow over U.S. soybeans.

At stake is a nearly 2.9-billion-acre legume crop whose protein, oil and derivatives are used in everything from baby formula and salad dressing to biodiesel and printing ink. The rust fungus hasn’t appeared on the U.S. mainland yet, but ARS researchers Reid Frederick, Morris Bonde and Glen Hartman aren’t wasting any time. Frederick and Bonde, for example, have already developed a molecular method to rapidly detect the rust fungus based on specific DNA sequences that are unique to it.

Since 2000, all three ARS researchers have worked with scientists abroad to learn as much as they can about their fungal foe’s basic biology, genetic variability, life cycle and pathogenicity. The so-called Asian rust strain--the more aggressive of two known forms- -has spread to Africa and South America, notes Hartman, at ARS’ Soybean/Maize Germplasm, Pathology and Genetics Research Laboratory at Urbana, Ill.

Hartman, Frederick and Bonde also will spearhead a project supported by the United Soybean Board to coordinate field tests at rust “hot-spot” regions in China, Thailand, Zimbabwe, South Africa, Brazil and Paraguay. There, they’ll search for the best sources of soybean resistance to the rust fungus. Inside a biocontainment facility operated by ARS’ Foreign Disease-Weed Science Research Unit at Fort Detrick, Md., they’ll also expose domestic and exotic soybean lines to multiple races of the fungus to determine which offer the broadest range of disease resistance. And in fungicide trials, they’ll examine the chemicals’ effectiveness and potential phytotoxicity to soybean plants.

Meanwhile, Iowa State University collaborator X.B. Yang is using computer modeling to simulate rust disease outbreaks on U.S. soybean-growing regions based on climate, wind patterns and other criteria. By one simulation, the fungus’ establishment causes soy crop losses of up to 40 percent.

ARS is the U.S. Department of Agriculture’s principal scientific research agency.