Researcher Hunts for Genes to Make Corn Resistant to Aflatoxin

Linda F. Benedict, Bogren, Richard C.

A big hurdle to increased corn production in Louisiana is aflatoxin, a byproduct of a fungal infection that generally occurs in drought-stressed corn. And Steve Moore, a researcher at the LSU AgCenter’s Dean Lee Research Station near Alexandria, is trying to find a remedy.

The toxin is produced by a fungus called Aspergillus flavus, Moore said. But not all strains of the fungus produce aflatoxin, and aflatoxin becomes a problem only when the environmental conditions are right.

“Aflatoxin is considered the most potent natural carcinogen in existence,” Moore said. That’s why the U.S. Food and Drug Administration prohibits infected corn in interstate transportation when the aflatoxin level exceeds a mere 20 parts per billion.

Although most corn grown in Louisiana is destined as feed for livestock, the toxin is particularly harmful to cattle and horses as well as people.

“Heat affects the activity of the fungus, and drought stresses the plant,” Moore said. “Any stress on a corn plant generally makes it more susceptible to aflatoxin contamination.”

Moore has embarked on a research program to develop corn hybrids resistant to aflatoxin-producing strains of Aspergillus flavus. He is focusing on breeding genetic resistance into corn hybrids.

“There are about a half-dozen public breeding lines that show some resistance,” Moore said. But he’s doubtful current resistance levels are adequate to protect a corn crop when environmental conditions are favorable.

In 1998, for example, widespread drought and high temperatures led to millions of dollars in crop losses with 70 percent or more of the Louisiana corn crop infected.

Moore proposes to find resistant genes and introduce them into commercially valuable corn hybrids. He’s starting by screening 800 of the approximately 50,000 breeding lines of corn throughout the world.

“We’re already putting what we have in commercial hybrids,” Moore said. “But I believe that more resistance is likely needed.”

Moore said he’s looking for genetic resistance that’s carried by only a few dominant genes so they can be more easily introduced into commercial breeding lines.

In addition to searching for effective genes to resist aflatoxin, Moore also is looking at other strains of Aspergillus flavus that don’t produce aflatoxin.

“The strains of Aspergillus flavus that don’t produce aflatoxin are called atoxigenic,” Moore said. “We’re looking at different strains to find atoxigenic strains that can out-compete the others.

“If we can help farmers identify resistant varieties, we can help them improve their productivity,” Moore said. “It can be worth it to give up some yield, if necessary, to protect against an outbreak of aflatoxin.”

Rick Bogren

4/5/2005 1:15:04 AM
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