Soybean pathogens build up quickly in a tight rotation like corn and soybeans. That’s led seed companies like Pioneer Hi-Bred to incorporate a wide array of defensive traits.

“A bean will be in the market seven to eight years,” says Paul Stephens, Pioneer senior research director for soybean product development. “You have to have a product that will cover different

diseases in different years. One year, it might be white mold, the next year, it might be a different disease.”

Sudden Death Syndrome

In 2010 in Iowa, that “different disease” was Sudden Death Syndrome (SDS).

SDS is a difficult disease for which to develop resistant varieties, since multiple genes are involved. Diseases like Brown Stem Rot, in which a single gene conferred resistance, was not as difficult to breed into a single line, he says.

“We have grown in our ability to prevent SDS,” says Stephens. He says 80% of Pioneer soybean varieties for 2011 have a ranking of 6 (1 on this scale is highly susceptible, 9 is highly resistant). In states like Illinois, a Pioneer sales representative will not typically position a product in a field unless it has a 6 SDS rating or above, he says. 

Phytophthora root rot

Genes that resist phytophthora root rot are getting tired.

“The old phytophthora genes not as good as they used to be,” says Stephens. The corn-soybean monoculture and pathogen race shifting are breaking down the resistance, says Stephens. To boost resistance, Pioneer breeders are improving resistance by grouping phytophthora-resistant genes together to develop multiple-gene resistance.

White mold