Scientists develop soy with better resistance
been developed in order to better protect an industry under
pressure.
The new line, DT97-4290, developed by Agricultural Research Service (ARS) scientists in Mississippi, is a potentially valuable source of resistance to charcoal rot for soybean breeders and producers in areas experiencing yield losses due to the disease.
Charcoal rot, caused by the soilborne fungus Macrophomina phaseolina,is a major yield-limiting disease of the Mid-South and other soybean-producing regions throughout the world. It thrives in the hottest, driest part of the growing season, and unlike most soil fungi, which decline in activity when soils become too warm, it is most active when soil temperatures are as high as 80-95° F.
During the charcoal rot field studies at Stoneville, Mississippi, ARS researchers identified three breeding lines with genetic resistance.
The new line was selected for its adaptation to the clay soils of thelower Mississippi River valley, and for its field resistance to charcoal rot, soybean mosaic virus and stem canker, and moderate resistance to frogeye leafspot. Genetic material of this release will be deposited in the National Plant Germplasm System, where it will be available for soybean researchers and breeders.
The ARS says that no chemical controls currently exist for charcoalrot, and resistance has been hard to identify.
This scientific breakthrough should therefore come as welcome relief to the US industry, which has been badly affected by disease. Last month, American Soybean Association (ASA) president Neal Bredehoeft called for the USDA to ensure there was enough fungicide available to tackle the growing menace of soybean rust.
"Fungicide availability and soybean rust research are two areas of paramount concern to ASA," said Bredehoeft. "ASA is strongly encouraging the USDA to take the steps necessary to protect the future of the $18 billion U.S. soybean industry."
The combined effects of disease have taken their toll. US soybean producers intend to plant 73.9 million acres in 2005 in total, down 2 percent from last year's record-high acreage. Of the 31 soybean producing states, growers in 16 states intend to plant fewer acres this year, with the largest acreage declines in the Dakotas.
However, scientific breakthroughs, such as the most recent ARS release of charcoal rot-resistant soybean strains, should help protect the industry, which faces stiff competition on the international market. And earlier this month, the ARS, in cooperation with Washington State University (WSU), suggested that the herbicide glyphosate could help suppress Asian soybean rust.
"These early findings are promising," said R. James Cook, plant pathologist and interim dean of WSU's College of Agricultural, Human, and Natural Resource Sciences.
"However, further research must be conducted to validate the results under field use conditions. If these results translate to the field, this could provide another tool to soybean producers in combating Asian soy rust."
Glyphosate herbicides are not currently registered or labeled to protect against or control Asian soybean rust and existing residue tolerances may not be adequate for this potential use. As it stands, it is a violation of federal law to use a glyphosate pesticide in a manner inconsistent with its labeling.
But this discovery could help change all this, and there is certainly a great deal of pressure from the soybean sector to find a solution.
