Scientists at the Donald Danforth Plant Science Center in St. Louis, Mo., and their collaborators at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) in Hyderabad, India, the U.S. Department of Agriculture and Louisiana State University have made a significant research breakthrough by suppressing the aflatoxin-producing fungus in groundnut, or peanuts.
The discovery has the potential to drastically improve food safety and reduce losses caused by the contamination from the poisonous carcinogen aflatoxin. The discovery was recently published in the Plant Biotechnology Journal.
Aflatoxins pose a major risk to human and animal health worldwide and result in an enormous amount of food waste. The molds — Aspergillus flavus and Aspergillus parasiticus, which infect groundnut, maize/corn, cottonseed and chili — produce these toxins that suppress the immune system, hinder growth and even cause liver cancer.
The fungus that produces these toxins can stay dormant in soil for years. It infects maize and groundnut during drought and heat stress. Contamination also happens when grain is stored in hot, humid and poorly ventilated conditions. Since aflatoxins are potent carcinogens, the U.S. does not allow the sale and export of foods with aflatoxin levels exceeding 20 parts per billion. European Union standards are even more stringent, at just 2 ppb.
"Plant defensins exhibit potent antifungal activity against several economically important fungal pathogens, and it is exciting to see successful application of this technology for reducing the pre-harvest infection by aspergillus and alleviating the burden of mycotoxins in genetically modified groundnut. If deployed commercially, this technology has significant potential to contribute to food safety in the under-developed and developing countries where mycotoxin contamination of groundnut, maize, chili and cottonseed pose a major threat to human and animal health," said Dr. Dilip Shah, principal investigator at the Danforth Plant Science Center.
World peanut production totals about 29 million metric tons per year. The U.S. is the world's third-largest producer, after China and India. Peanuts are the 12th most valuable cash crop grown in the U.S., with a farm value of more than $1 billion. American consumers eat more than 6 lb. (kernel basis) of peanut products each year, worth more than $2 billion at the retail level. Worldwide peanut exports are about 1.25 mmt annually.
Two complementary approaches are being deployed to address the issue. Shah and his team transferred small proteins called defensins from alfalfa and Mediterranean clover to the DNA of an aspergillus-susceptible peanut variety widely grown in Africa and India, which allowed the groundnut to stop the fungus from infecting the plant.
ICRISAT scientists worked with collaborators at USDA and Louisiana State to transfer small RNA molecules from the aspergillus fungus that are involved in the aflatoxin synthetic pathway. The nuts produced these RNA molecules during fungal attacks and inactivated target genes responsible for aflatoxin synthesis.
The technology is also translatable to corn and de-oiled cakes used for animal feed, as well as to pistachios and almonds.
Collaborators plan to conduct field trials in India in coming years for further development of aflatoxin-resistant peanut.
Founded in 1998, the Donald Danforth Plant Science Center is a not-for-profit research institute with a mission to improve the human condition through plant science.