Gene Discovery Could Help Breeders Reduce Head Scab in Wheat

PEORIA, Ill., July 10--U.S. Department of Agriculture scientists have discovered a useful chink in the genetic armor of the fungus behind head scab disease that causes billions of dollars in crop losses annually.

Anne E. Desjardins, Robert H. Proctor, Susan P. McCormick and Thomas M. Hohn of USDA's Agricultural Research Service pinpointed and deleted the genetic codes for an enzyme that the fungus needs to produce the toxin trichothecene. The research team is based at the ARS National Center for Agricultural Utilization Research here.

The head scab fungus--Fusarium graminearum--uses trichothecene to infect and weaken cereal crops such as wheat and barley. Head scab disease cuts crop yields and leaves the plants vulnerable to other diseases and insect damage. The disease gets its name from the scab-like marks it leaves on the infected plant.

Hohn, a microbiologist, says studying the genetic makeup of the fungus is a different approach in fighting cereal crop diseases.

"The work we have done characterizes the disease from the fungal perspective and demonstrates how the toxin affects the virulence of the disease," he noted. "This new information could have a great impact on wheat breeding strategies and development of disease-resistant crop varieties."

In field tests, wheat plants were infected with a form of F. graminearum from which the enzyme gene had been deleted. "The wheat plants still developed some disease," says Hohn. "But we saw less damage and yield losses."

Head scab disease has baffled plant breeders and growers alike because it severely infects crops one year, then disappears for a year or two before reappearing. Its sporadic nature has caused head scab disease to receive less attention from researchers than more frequently seen crop diseases. But severe head scab outbreaks over the last four years have devastated crops in some regions of the country and emphasized the need for effective control strategies.

Scientific contact: Thomas Hohn, Mycotoxin Research, ARS National Center for Agricultural Utilization Research, 1815 N. University St., Peoria, IL 61604, phone (309) 681-6380, fax (309) 681-6665, [email protected].