MICHIGAN STATE (US)—Researchers have developed two new lines of pest-resistant soybeans that promise healthier harvests for growers.

“Sparta—the Soybean Aphid Shield” is the new trade name for genetics developed by Dechun Wang, associate professor of crop and soil science at Michigan State University.

Some 2,000 strains of soybeans were tested against aphids to isolate four with different resistant genes. From those Wang developed germplasm—seeds to breed into varieties suited to Michigan’s shorter growing season.

“The final goal,” Wang says, “would be to have one variety that has all those resistant genes,” maximizing protection against different biotypes of aphids and perhaps other pests such as the Japanese beetle.

Soybean aphids suck plant sap and secrete sticky honeydew that promotes sooty black mold, and when they sprout wings can transmit plant viruses widely. Fifteen generations of aphid can live on a soybean plant in the summer, with eggs overwintering on nearby buckthorn.

“In the field, we will inoculate a plant with just two aphids, and the entire plant will be totally covered by aphids in a few weeks,” Wang says. “It takes aphids just five days to produce more babies, and aphids are born pregnant, so the regeneration cycle is incredibly fast.”

Soybean has been cultivated in Asia for thousands of years, but in America only since 1904. It is chiefly processed here into animal feed and vegetable oil.

Tiny soybean aphids, also native to Asia, were first identified in Wisconsin in 2000, but quickly cut a wide swath until beaten back mostly with chemical pesticides.

Unchecked, aphids can lay waste to half the output of a field, and one application of insecticide might add 10 percent to the cost of production—and kill beneficial insects as well.

“That really has been our only answer until this new host plant material,” says Keith Reinholt, field operations director for the Michigan Soybean Promotion Committee.

“With one exception, all the major soybean genetics companies have licensed his (Wang’s) germplasm because the level of resistance to soybean aphids is very high,” says James Kells, chairman of the Department of Crop and Soil Sciences.

In addition to funding by growers, Wang’s research is supported by the Michigan Agricultural Experiment Station and the Michigan Soybean Promotion Committee.

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