Breakthrough in battle against aflatoxin in African food crops

Ibadan, Nigeria - IITA researchers and partners have developed a safe and natural method that could drastically cut aflatoxin contamination in African food crops by as much as 99 per cent.

Scientists of the African Agricultural Technology Foundation (AATF), Kenya, the United States Department for Agriculture (USDA) and IITA have collaboratively demonstrated the ability of a natural fungi found in Nigeria to significantly reduce concentrations of aflatoxins in maize. In the long-term, this research would lead to the improvement of the health of vulnerable groups, especially women and children, and help reduce related global trade losses estimated at US$ 1.2 billion. African economies lose about US$ 450 million annually to aflatoxin contamination.

On-station field trials of the biocontrol method in Zaria, Ikenne, Mokwa and Ibadan in Nigeria showed 50 to 99 per cent reductions in aflatoxin contamination in maize. Under the biocontrol method, native strains of Aspergillus flavus that do not produce aflatoxins (called atoxigenic strains) can be applied in order to alter the fungal community on crops and throughout an area so that maize becomes less contaminated with aflatoxins. When properly applied, these native atoxigenic strains competitively exclude aflatoxin producers.

This competitive exclusion principle of biological control will be used as a new type of aflatoxin intervention strategy to mitigate the negative effect of aflatoxins on human health and trade in Kenya and Nigeria.

“Aflatoxins are silent killers. They undermine human health and stunt the growth of children but is not often visible on maize when purchased.” says Dr Ranajit Bandyopadhyay, IITA Pathologist, during an AATF-USDA-IITA meeting last week which examined the prospects of a biological method to drastically reduce aflatoxin contamination in food crops. They are also non-tariff barriers to international trade since agricultural products that have more than the permissible levels of contamination are rejected in the global market.

Aflatoxins are chemical poisons produced mainly by the fungus Aspergillus flavus in maize, groundnuts, cassava, and yam chips. These toxins are also potent causes of cancer and suppress the immune system causing humans and animals to be more susceptible to diseases.

Dr Peter Cotty of the Agricultural Research Service, USDA, who collaborated with IITA on the project, says natural populations of Aspergillus flavus consist of toxigenic strains that produce copious amounts of aflatoxin and atoxigenic strains that lack this capacity. He explains that competitive exclusion works by applying selected native atoxigenic strains to out-compete and exclude aflatoxin-producers during colonization of grains, thereby reducing levels of aflatoxin contamination. There are several atoxigenic strains native to Nigeria that are useful for reducing aflatoxins.

Bandyopadhyay says atoxigenic strains can be directed at reducing aflatoxin contamination in several crops throughout an area simultaneously. “Manipulation of the composition of fungal communities (i.e., replacing high aflatoxin-producers with their cousins that do not produce aflatoxins) so that high aflatoxin-producers are less common, is a viable approach for reducing aflatoxin contamination throughout all crops grown in a target area,” he says.

He reveals that atoxigenic strains for use in biocontrol have been identified for use in Kenya and Nigeria by USDA and IITA. Farmers, policy makers, the food and feed industry and various NGOs have expressed their desire and support to convert this technology into a readily-available product in Nigeria and other countries in Africa where the technology would be applied for the first time. - IITA


June 2009