Soybean Rust Still on the Horizon

January 7, 2012 11:25 AM

Looking for a silver lining in 2011 weather patterns? It might be more of a thread than a lining, but soybean rust didn’t like last year’s weather.

Daren Mueller, Iowa State University plant pathologist, observes that the critical steps for rust to get to Iowa simply didn’t happen. "It must survive winters somewhere in the South; build up inoculum [spores where survival occurs]; and there must be movement of these spores to fields further north, with successful infection of the soybeans in those fields," Mueller says.

Soybean rust is a severe fungal disease that causes yield losses of up to 80% in a affected field. South American growers have largely been impacted by the disease, but Southern U.S. growers have also experienced losses since the disease was first discovered in North America in 2004.

During the past few years, droughts, heat and other conditions have kept soybean rust spores from migrating north until late in the growing season. In 2011, Mueller says, there was little to no inoculum to move. Drought in Texas and neighboring states stopped rust before it ever got established.

In 2011, 14 confirmed cases of rust were found in three states and parts of Mexico and Puerto Rico.

Mueller says growers should not be complacent about the disease. "Plant pathologists continue to monitor for soybean rust, especially in Southern states," he says. "Midwest growers have the peace of mind to know they’ll have an advance warning as long as monitoring continues."

Seed companies still have the disease on their radar. Quinn Showalter, commercial trait lead for Syngenta, says that rust tolerance derived from multiple native gene traits could be available from Syngenta as early as 2013 in South America.

"Managing rust will also require the continued use of fungicides for sustainable solutions," Showalter says. "South America is our primary focus, but we do believe the solution will have value in North America."

DuPont and Evogene Ltd. recently announced a multiyear collaboration to develop soybeans with
in-plant resistance to rust. Pioneer Hi-Bred’s pipeline shows first-generation rust resistance in Phase 3 (advanced development), and second-generation soybean rust resistance in Phase 1 (proof of concept). Time lines are always subject to regulatory review.

The companies will jointly generate a genomic database for soybean rust resistance. Pioneer will use proprietary technologies to evaluate genes in transgenic soybeans and might advance leads for development.

Learn more about soybean diseases.

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