Apr. 5, 2005 URBANA -- Miscarriages and infants born with neural tube defects are just two of the possible risks for pregnant women who consume corn that has been contaminated by the mycotoxin fumonisin produced by species of Fusarium which cause Fusarium ear and kernel rot of corn. Women who take vitamins containing folic acid when they are pregnant are more protected from the effects, but women in many countries may not be.
"In the United States, food grade corn is tested at the grain elevators for mycotoxins, including fumonisin," said Martin Bohn, maize breeder and geneticist at the University of Illinois. "If the mycotoxin is present at an unsafe level, the corn is not sold for human food consumption. But, in cultures that consume large quantities of corn in their diet and are in countries that do not test for the presence of fumonisin, there have been higher cases reported of embryo abortions and deformities in newborns," Bohn said.
Fusarium ear and kernel rot is primarily a problem in drought-stricken areas with high humidity. "Farmers in parts of North Carolina, California and other coastal areas have been forced to take a loss and sell their entire crop for animal feed instead of getting the premium prices for human food when the grain is tested at the elevator and high levels of fumonisin are found," said Don White, U of I plant pathologist.
Bohn was a member of a team when he was in Germany studying the resistance of corn cultivars to the European corn borer. They believe that corn borer larvae feed on the corn, injuring the stalks and ears, creating an opening for fungi to develop and rotting to occur. They were also investigating the association between these resistant corn varieties and the presence of a fumonisin.
The study also evaluated genetically modified Bt corn for its resistance to the European corn borer. "The study showed that although insect management did not reduce contamination by some fungi diseases, using Bt corn did reduce mycotoxins produced from Fusarium rot," said Bohn. "We believe that at least a short-term solution is to plant corn carrying the Bt gene in order to increase the resistance to European corn borer and, in so doing, reduce the incidence of ear rot and the concentration of fumonisin.
White believes that the corn borer is just one of the injury-causing elements that can give fumonisin an opening to take hold in corn. High levels of fumonisin can be found in corn grain with little or no evidence of insect damage or kernel rot. He has a collection of 1,500 inbred lines that have been screened for resistance to Fusarium ear rot and the production of fumonisin. He has already narrowed the search to four or five highly resistant inbreds and knows where the resistance is located in the molecular make-up of two inbreds. "If we had funding, we could have a commercial hybrid available in a few years. Without it, the process will take a decade," said White.
"It's a big problem, especially for people in Latin American countries like Guatemala for whom corn is a major part of their diet and the food systems may not be regulated as closely as they are in the U.S.," said Bohn.
White hopes that genes for resistance can be added to locally grown varieties that will replace the currently used local varieties. "The technology exists to develop resistant varieties," said White. "We just need the funding to keep the research moving forward."
Corn contaminated by fumonisin even at very low levels can be deadly to horses and cause some diseases in pigs, but it can be sold to use safely in cattle feed.
Bohn's research was supported by grants from the German Federal Ministry of Education and Research, Monsanto and Syngenta Seeds. The study is scheduled for publication in the January 2005 journal of the American Society of Agronomy.
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