Scientists at the International Institute of Tropical Agriculture (IITA) have assembled a set of eight non-toxin producing (atoxigenic) strains of Aspergillus flavus capable of radically reducing aflatoxin in maize using the biological control approach. Toxin-producing strains of Aspergillus flavus are the causative fungi of aflatoxin contaminations that impairs growth and development of millions of West African children.
Aflatoxin contamination is widespread in staple crops in Africa, as a consequence, millions of people are chronically exposed to this chemical poison through their diets. The so-called Kenyan-killer fungus, a distant cousin of the Nigerian toxic fungus, was responsible for over 125 deaths during 2004 in Kenya. Prolonged exposure to minute doses of aflatoxins can result in liver cancer and suppression of the immune system, which makes people more vulnerable to diseases.
The team led by Dr Ranajit Bandyopadhyay, IITA plant pathologist use the highly competitive atoxigenic strains of Aspergillus to eliminate their highly toxic relatives, and in so doing reduce aflatoxins. “The atoxigenic strains were able to reduce aflatoxin contamination by up to 99.8% in field trials”, says Ranajit. In addition, the most effective atoxigenic strain could out-compete toxigenic strains in grains by 99% after field release.
The next step now is to test the efficacy of biocontrol after releasing multiple strains in large-scale field trials in several sites in Nigeria. “The biocontrol project is at an exciting stage where we need to finally prove that the atoxigenic strains can dramatically reduce aflatoxin contaminations in real farming situation in Africa.” says Ranajit.
The safe atoxigenic strains were identified after rigorously testing thousands of strains collected from moldy maize stored by farmers in Nigeria. “In this case, the use of indigenous atoxigenic strains, and not imported ones, is crucial to ensure that the released strains are highly competitive under local conditions and safe in the local ecosystem”, says Dr. Peter Cotty of the United States Department of Agriculture’s Agriculture Research Service. The research was funded by the German Government.
IITA
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