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| August 2010 |
Feature |
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Making Kenyan maize safe from deadly aflatoxins
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 Aspergillus sporulating on sorghum.Photo IITA |
Kenya is again grappling with high levels of aflatoxin contamination that has
rendered at least 2.3 million bags of maize unfit for human and livestock
consumption and trade, to the dismay of the millions of small-scale farmers that
depend on the crop for food and income.
The contamination of the country’s main staple with aflatoxin, a highly
poisonous cancer-causing chemical produced by a fungus scientifically known as
Aspergillus flavus, was a result of poor drying and storage of the grain
following heavy rainfall near harvest time.
Although the situation is grim, it is not hopeless! Scientists have developed
a cost-effective, safe, and natural method to prevent aflatoxin formation in
maize while in the field. The biocontrol technology works by introducing strains
of the A.flavus fungus that do not produce the aflatoxin or ‘the good
guys,’ in the affected fields, which, outcompete and drastically reduce the
population of the poison-producing strains or ‘the bad guys’.
Dr Peter Cotty of the Agriculture Research Service of the United States
Department of Agriculture (USDA-ARS) and Dr Ranajit Bandyopadhyay, a plant
pathologist with the Africa-based International Institute of Tropical
Agriculture (IITA), have identified biocompetitive strains of the good fungus
native to Kenya that can now be used to control aflatoxin contamination in the
country.
According to Dr Bandyopadhyay, a single application of this biopesticide 2-3
weeks before maize flowering is sufficient to prevent aflatoxin contamination
throughout and beyond a cropping season and even when the grains are in storage.
“A. flavus strains are either toxigenic (produce aflatoxin) or
atoxigenic (do not produce aflatoxin). Our biocontrol technology makes use of
carefully selected atoxigenic strains that can safely outcompete and virtually
eliminate their toxic relative, effectively reducing contamination of the maize
grains in fields,” said Dr Bandyopadhyay.
He says that the technology’s ability to continue working even when the grain
is in storage ensures the safety of maize from aflatoxin contamination. “These
atoxigenic strains are also carried in the grains from the field to the stores.
So, even if the grains are not stored properly or get wet during or after
harvest, as is happening this year, they continue to prevent aflatoxin
contamination during the postharvest period,” said Dr Bandyopadhyay.
Aflatoxin is a silent killer that causes liver cancer and suppresses the
immune system. It also retards growth and development of children. People
exposed to very high aflatoxin concentrations experience liver failure and rapid
death. From 2004 to 2006, nearly 200 unsuspecting people in Kenya died in this
manner after eating highly contaminated maize. Aflatoxin is a colorless chemical
that is invisible and only laboratory tests can confirm its presence and
contamination levels.
Kenya is one of the world’s hotspots for aflatoxin. Research performed by one
of Dr Cotty’s graduate students, Claudia Probst, has shown that in areas where
aflatoxin is a persistent and serious problem, there is a very high occurrence
of one of the most toxic strains of A. flavus in the world, the S strain.
According to Dr Cotty, the S strain produces very high levels of aflatoxins
and dominates in regions where contamination is very high, including some areas
of the US. In Africa, this S strain has been only found to be dominant in the
severely affected regions of Kenya. In the US, biocontrol with atoxigenics has
successfully reduced its contamination.
In Nigeria, IITA has obtained provisional registration of the technology
under the name Alfasafe™, a mixture of four atoxigenic strains of Nigerian
origin. In 2009, maize farmers in Nigeria were able to reduce aflatoxin
contamination by 80% by broadcasting 10 kg/ha Aflasafe™ 2-3 weeks before maize
flowering.
Research has shown that Aflasafe™ treatments provide long-term benefits and
that Aflasafe™ may not need to be applied every year. IITA, in partnership with
the Nigerian government and the United Nations Industrial Development
Organization (UNIDO), is working on obtaining full registration and identifying
an entity that would mass manufacture, market, and distribute Aflasafe™ in
Nigeria to save the health and income of millions of families.
The researchers are now calling upon the government and the private sector in
Kenya to partner with them and make this biocontrol option and other management
practices available to the farmers to save their much-needed harvests from
future aflatoxin contamination.
Institutions involved in the initiative include IITA, USDA-ARS, African
Agricultural Technology Foundation (AATF), and local partners.
More information:
Catherine
Njuguna, c.njuguna@cigar.org
Corporate Communications Officer (East & Southern Africa)
IITA-Tanzania
IITA (www.iita.org)
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