Steven H. Moore | 4/19/2005 10:28:59 PM
ALEXANDRIA – "It’s the No. 1 corn production problem in the South," Dr. Steve Moore says of aflatoxin.
A product of hot, dry field conditions, aflatoxin is a byproduct of a fungal infection that generally occurs in drought-stressed corn. And 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 says. 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 says. That’s why the U.S. Food and Drug Administration prohibits interstate transportation of infected corn when the aflatoxin level exceeds a mere 20 parts per billion.
While most corn grown in Louisiana is destined as feed for livestock, experts point out 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 says. "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 A. flavus. His current work is focusing on breeding genetic resistance into corn hybrids.
"Currently, there are about a half-dozen public breeding lines that show some resistance," Moore says. But he’s doubtful current resistance levels are adequate to protect a corn crop when environmental conditions are favorable for development of the fungus.
In 1998, for example, widespread drought and high temperatures led to millions of dollars in crop losses when 70 percent or more of the Louisiana corn crop was infected.
Moore proposes to find resistant genes and introduce them into commercially valuable corn hybrids. He’s starting to evaluate some of the approximately 50,000 breeding lines of corn that exist throughout the world – beginning with material from hot, dry climates such as Texas, Mexico and Africa.
"We’re already putting what we have in commercial hybrids," Moore says. "But I believe that more resistance is likely needed."
The researcher is in the process of screening about 800 corn lines and may evaluate more in subsequent years.
Moore says 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.
"We’re looking for effective dominant genes," he says.
In addition to searching for effective genes to resist aflatoxin, Moore is also looking at other strains of A. flavus that don’t produce aflatoxin.
"The strains of Aspergillus flavus that don’t produce aflatoxin are called atoxigenic," Moore says. "We’re looking at different strains to find atoxigenic strains that can outcompete the others."
While Moore continues to look for improved genetic resistance and atoxigenic strains of A. flavus, he’s continuing his evaluation of corn hybrids currently on the market.
"If we can help farmers identify varieties that are more resistant to A. flavus, we can help them improve their productivity," Moore says. "It can be worth it to give up some yield, if necessary, in order to protect against an outbreak of aflatoxin."