July 12, 2007
by Semiu Babola,
SciDev.Net
Scientists have developed an effective form of biological
control for a toxin-producing fungus that plagues crops in
sub-Saharan Africa and poses serious a health risk to humans.
Scientists — from the
International Institute of Tropical Agriculture (IITA) in
Nigeria, the United States
Department of Agriculture and three universities in Germany,
Nigeria and the United States — have discovered a means of
drastically reducing the amount of the fungus Aspergillus that
produces a toxic substance called aflatoxin in maize crops.
The method uses benign forms of the same type of fungus to
outcompete it.
The fungus Aspergillus grows on maize, an important cereal in
African diets, as well as on groundnut, rice, sorghum and
peanuts.
Millions of people in sub-Saharan Africa are exposed to
aflatoxin through food. Long-term exposure to the toxin can
result in liver cancer, immune suppression — making people more
vulnerable to disease — and developmental and growth problems in
young children. Cattle that eat contaminated feed can also
become sick.
Farmers in sub-Saharan Africa lose about 40 per cent of their
food crops to the fungus, and many maize-importing countries
have strict controls on the level of aflatoxin they will accept,
reducing grain exports.
The researchers collected 2,127 samples of Aspergillus, 1,000 of
which proved to be non-toxin producing. They narrowed down their
sample to just eight strains that were tested in both the
laboratory and field.
"Our approach was to identify non-toxin producing strains that
could competitively displace the toxin producing strains from
the grains," explains Ranajit Bandyopadhyay, a plant pathologist
with IITA .
The researchers found that when they applied both toxin and
non-toxin producing types of Aspergillus to soil, which then
spread to maize crops growing in the field, the levels of
aflatoxin in these crops was reduced by up to 99.8 per cent.
The researchers intend to test the efficacy of the strains in a
larger scale across Nigeria, with results due in late 2007.
Nigerian farmer, Samuel Ogunfolaji, says, "Many methods have
been introduced in the past without much success. If this new
approach will eliminate the disease, it will be a plus."
Peter Cotty, from the United States Department of Agriculture
and a member of the research team, explained in a press release
that using non-toxin producing strains that are indigenous to
the area is crucial, because this ensures that the strains they
release will be highly competitive under local conditions. They
also pose less of an ecological risk compared with imported
strains.
Samson Ayanlaja, a plant scientist at Nigeria's Olabisi Onabanjo
University, told SciDev.Net, that he approved of the team's
approach, "because it does not entail the use of chemicals that
can pollute the environment. It is environmentally friendly." |
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