On a soybean stem, the dark speckles are the sclerotia of the charcoal rot pathogen. (Image courtesy William G. Willis, Kansas State University.)

Researchers Find Resistance to Soybean Fungus

By Jim Core
June 13, 2005

The first soybean line with genetic resistance to charcoal rot has been released by Agricultural Research Service scientists in Mississippi.

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.

The new line, DT97-4290, developed by scientists in the ARS Crop Genetics and Production Research Unit at Stoneville, 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 symptoms usually appear when weather conditions are hot and dry, causing the soybean plant to lose vigor. In more advanced stages, petioles and leaves may turn yellow and wilt, while remaining attached to the plant. No chemical controls currently exist for charcoal rot, and resistance has been hard to identify.

Field studies were conducted at Stoneville to find charcoal rot resistance among 24 selected soybean genotypes. The researchers identified three breeding lines with genetic resistance, according to Bob Paris, the research geneticist who developed the line with Alemu Mengistu, a soybean pathologist.

The new line was selected for its adaptation to the clay soils of the lower 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.

ARS is the U.S. Department of Agriculture's chief scientific research agency.