Lilongwe, Malawi
July 26, 2007
African farmers and agriculture
enterprises now have a fast and inexpensive way to detect and
manage a costly, naturally occurring and potentially deadly
poison (aflatoxin) that infects their crops via a common fungus
that makes them unfit for consumption or export.
Scientists at the International
Crops Research Institute for the Semi-Arid Tropics
(ICRISAT), supported by the
Consultative Group on International Agricultural Research
(CGIAR), have devised a fast, simple and affordable test kit for
detecting the poison, which is known as aflatoxin. Aflatoxin is
produced by a fungus that can easily grow on many crops
including common food crops like maize, groundnut, sorghum, and
cassava. It can infect them both in the field and after harvest,
while they are being stored in grain bins and elevators.
Many countries reject agriculture imports exceeding certain
levels of aflatoxin, costing African farmers millions of dollars
each year in lost sales. Meanwhile, people who inadvertently
consume a large quantity of the contaminated food can get very
sick, as the toxin can cause potentially fatal problems in the
liver and intestines. For example, in 2004, 300 people in Kenya
were sickened by aflatoxin and 125 people died. Even consuming
lower quantities can, over the long term, cause cancer.
Since the aflatoxin contamination is invisible in commodities,
the key is detection. In developed countries, farmers routinely
use detection technologies to manage outbreaks. But in
developing countries, the tests have in the past been too
expensive and too difficult for most farmers to implement. The
new detection kit developed by ICRISAT has changed the situation
by cutting the cost of testing crops from US$25 to $1 per
sample. It’s available as a small, simple kit that can be used
even for most remote rural farms to monitor grains and nuts and
improve storage techniques to avoid serious contaminations. The
end result is safer products for consumers and higher returns
for African farmers.
“We have put another strong weapon in the hands of poor farmers
to fight a problem that was making it particularly hard for
African agricultural products to get fair treatment in
international markets,” said Dr. William Dar, director general
of ICRISAT.
The test uses what scientists call an enzyme-linked
immunosorbent assay or ELISA test to rapidly detect the presence
of aflatoxin.
In Malawi, which saw its status in the 1970s as a major
groundnut exporter eroded by aflatoxin outbreaks, the National
Small Farmer Association of Malawi (NASFAM) has successfully
used the new aflatoxin detection kit as part of a broader effort
to regain and re-establish itself with its once-lucrative
European export markets. Several years ago, there were fears
that new standards in developed countries for acceptable levels
of aflatoxins in groundnuts could cost African countries $670
million in lost exports.
“Testing groundnuts has worked as a monitoring tool to ensure
that buyers do not get produce with higher aflatoxin
concentrations than their market requirements or
specifications,” says Moses Siambi, an ICRISAT scientist based
in Lilongwe. “We’ve seen a very positive impact. Malawian
groundnuts are now available on the Fair Trade market and also
in some of the biggest supermarkets in the UK.”
Aflatoxin is the toxic waste product of two fungi, Aspergillus
flavus and Aspergillus parasiticus, which occur naturally in air
and soil. They especially infect crops weakened by droughts,
when pest activity is higher. Poor harvest and post-harvest
handling techniques open up another route for contamination.
Storage of grains and nuts before they are properly dry, or in
damp conditions, also creates an opportunity for contamination.
Several CGIAR-supported centres, including ICRISAT, the
International Maize and Wheat Improvement Center (often referred
to by its Spanish language acronym CIMMYT), and the
International Institute of Tropical Agriculture (IITA), are
putting into place a range of innovative practices to combat
aflatoxin contamination in maize, groundnut, sorghum, cassava,
pistachio, almonds, and chilli peppers. In addition to the
detection test, the techniques include efforts to control the
toxin using bacteria as a bio-control agent, breeding crops that
are resistant to aflatoxin, and changing cultivation practices
to limit opportunities for contaminations.
For example, recent field trials led by Dr Ranajit
Bandyopadhyay, an IITA plant pathologist, have employed strains
of atoxigenic Aspergillus to eliminate their highly toxic
relatives, and in doing so to reduce aflatoxins. "The atoxigenic
strains were able to reduce aflatoxin contamination by up to
99.8% in field trials," says Ranajit.
More than 5 billion people in developing countries are
constantly exposed to aflatoxins by unknowingly consuming
contaminated foods. So reducing aflatoxin contamination of
African crops could offer considerable health benefits,
particularly to African children.
Rodomiro Ortiz, a plant geneticist at CIMMYT, says, “Children
exposed to aflatoxin can suffer from poor growth and immune
suppression, making them susceptible to HIV and malaria.” CIMMYT
researchers have been working at combining biotic and abiotic
stress resistance to identify stress-tolerant maize lines or
hybrids that have a reduced incidence of A. flavus. This
approach to reducing mycotoxin load has been successful. Now the
efforts aim to breed maize source populations and synthetics
against the maize weevil and larger grain borer, which further
serve as vectors and create portals of entry for fungi.
Since the problem is a complex one, ICRISAT is developing
resistant groundnut cultivars through breeding and
biotechnological methods. Trials on an integrated management
approach using bio-control agents, application of calcium, and
farmyard manure, showed a 99 percent reduction in aflatoxin,
says Farid Waliyar.
The CGIAR Centers have also established strong linkages with
several universities and advanced research institutions in
several developed countries to bring a long term solution to
combat aflatoxins
The CGIAR is a strategic agricultural research alliance
dedicated to generating and applying the best available
knowledge to stimulate agricultural growth, raise farmers’
incomes, and protect the environment. It supports 15 research
centres worldwide conducting groundbreaking work to nourish the
future. For more information, please visit
www.cgiar.org. |
|
