Finding new ways to reduce aflatoxin in crops, particularly in corn where it thrives during drought conditions, is the focus of a Texas Agricultural Experiment Station study that researchers hope will lead to reducing the economic hardship the fungus places on the state's corn farmers.
Aflatoxin is a toxic and carcinogenic metabolite produced by Aspergillus, a fungus that thrives on oilseed crops. Aspergillus grows in warm temperatures, and is prevalent in the United States, but also affects other countries including China, Africa, and Mexico. The fungus attacks oil seed crops such as peanut seed, maize, cotton seed and corn. With corn, the fungus infects corn kernels by airborne spores any time after pollination. Kernel infection may occur through the silk or by direct contact, and damage by earworms or other insects can also lead to fungal infection. Consumption of high levels of aflatoxin by animals and humans can result in sickness, and in some cases, death, experts say.
"Aflatoxin destroys tissues in animals and can cause cancer in mammals," said Dr. Nancy Keller, a mycotoxin researcher with the Texas Agricultural Experiment Station. "It is a liver carcinogen, so we know in developing countries it is one of the leading causes of liver cancer."
By law, all crops must be checked for levels of aflatoxin including cotton, corn and peanut crops that are threatened by the fungus.
"It can lead to incredible financial losses," Keller said. "Every two to three years, an epidemic can cost $30 million to $200 million (in crop losses.) The losses can be even worse if people are getting sick." Keller's research is aimed at reducing aflatoxin production using nontraditional procedures.
"What I decided to do was find the genes in the Aspergillus that produce aflatoxin," Keller said. "If you can clone these genes, then you can ask what turns the genes on and off. That's a powerful thing. So we have cloned the genes in the fungus that make aflatoxin. Now we can perform experiments and see what makes the genes turn on and off--with the thought that those factors that turn on the genes should be eliminated."]>
Keller said there are a couple of factors controlling aflatoxin production, including a genetic pathway in the fungus itself that controls the aflatoxin genes. She said research also focuses on the factors involving the host seed that play a role in the interaction with Aspergillus.
"We are also looking to see if there are any components of the seed that may be turning on the aflatoxin genes or if there are any environmental factors such as pH that turn on the aflatoxin genes," she said.
By eliminating aflatoxin, farmers wouldn't have to worry about the added expense to test crops and enjoy larger profit margins.
"Removing or reducing aflatoxin would be a great benefit to everybody," Keller said. "If you have less aflatoxin, you won't have to destroy as many plants and funds could be going towards solving another problem."