Initiative Takes Aim at Fungal Crop Disease Culprit

The fungus Sclerotinia sclerotiorum—which affects sunflower, soybean, canola and dry edible bean crops—forms a hard, protective casing, called sclerotia, in order to survive unfavorable soil conditions. This reduces the effectiveness of fungicide treatments, crop rotation and other measures of control.

But these seemingly impenetrable sclerotia are no match for Coniothyrium minitrans, a mycoparasite that penetrates the fungus' casings to feed. A mycoparasite is a parasitic fungus whose host is another fungus. Now, thanks to the National Sclerotinia Initiative (NSI), a multiorganizational effort led by the Agricultural Research Service (ARS), C. minitrans could prove a useful ally to growers in their fight against S. sclerotiorum.

Studies by scientists at North Dakota State University—one of many NSI participants—show that the mycoparasite can diminish the severity of Sclerotinia infection by destroying the sclerotia before the fungus germinates.

But no single control is likely to become the "magic bullet" against S. sclerotiorum, which attacks more than 400 species of plants. That's why NSI scientists are exploring other strategies as well, notes Bill Kemp. He administers the initiative as director of the ARS Red River Valley Agricultural Research Center at Fargo, N.D.

Since 2002, NSI scientists have conducted their research with four objectives in mind: develop new, disease-resistant varieties; learn more about S. sclerotiorum's growth and biology; decipher its genomic secrets and disease epidemiology; and develop new diagnostic tools and disease management strategies to better protect vulnerable crops.

Sclerotinia outbreaks cost about $242 million annually in yield losses and diminished quality. Important inroads made to minimize the damage include:

• Risk-assessment maps and indices that farmers can use to take preventive action in edible dry beans and canola;
• Fungicide evaluations for Sclerotinia head rot control in sunflower; and
• New screening methods that speed the identification and development of Sclerotinia-resistant varieties.

Read more about the research in the October 2007 issue of Agricultural Research magazine.

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