December 09, 2003

SIUC Country Column

by K.C. Jaehnig

CARBONDALE, Ill. -- A newly emerging fungal disease hit soybean fields in the Midwest's north-central states hard this growing season.

"It was the worst year ever for charcoal rot in Iowa," said Jason P. Bond, a plant pathologist at Southern Illinois University Carbondale. "It was also among the worst for Missouri, Kansas and Illinois.

"In Illinois, it's becoming widespread, getting into the major production areas of our state. The yield-loss estimates I have seen are roughly three times what was lost last year, and it's pretty much the same in Missouri."

Plant pathologists and soybean breeders from seven states met at SIUC Nov. 20-21 to compare notes on this year's outbreaks of charcoal rot and frogeye leaf spot, another fungus that attacks soybeans. The scientists have joined forces in a three-year effort aimed at managing the diseases in their region. Their ultimate aim: genetic control of both. A grant from the North Central Soybean Research Program is paying for the work.

Farmers in Iowa suffered a charcoal rot "epidemic," while Kansans experienced only moderately high to severe levels, Bond said.

Frogeye leaf spot, on the other hand, while present throughout the region, showed up late and, in most cases, did little damage. Illinois, however, was a different story.

"We generally didn't see it above Interstate 64, with the exception of Lawrence and Calhoun counties," Bond said.

"But in the southern counties, it was moderate to severe. In a few low-lying fields or fields near rivers, we saw some fields losing 50 to 70 percent of yields."

As for the project's overall progress so far, members have:

 

  • Developed greenhouse and field procedures to screen for resistance to both diseases as well as a field symptom rating scale for frogeye leaf spot;

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  • Screened more than 450 commercial soybean varieties and 150 public germplasm lines, finding 87 and 46 respectively that appeared to have some resistance to frogeye leaf spot;

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  • Identified two soybean lines with field tolerance to charcoal rot and collected information over the course of the growing season that, when fully analyzed, may point to other resistant lines;

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  • Made some initial crosses of leaf spot-resistant parents to produce new lines, which they will test in the field in the coming growing season;

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  • Begun collecting samples of the pathogens that cause both diseases, which will allow the scientists to sort them into different races or pathotypes and to assess the virulence of each such group;

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  • Posted information about charcoal rot on the Plant Health Initiative Web site, http://www.planthealth.info(look for it under the soybean plant health topics link).

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"There are pictures, management tips, and e-mail links to some of the project members, and the information is always available," Bond said of the Web site.