such as "Introduction", "Conclusion"..etc
April 2008 -- The spiraling use of corn for food and fuel is creating heightened
concerns about contamination of this staple crop with deadly aflatoxin.
Produced by certain fungi that grow on corn, this contaminant is a
known human carcinogen that especially threatens food safety in the
developing world and can potentially cause the loss of hundreds of
millions of dollars in the United States each year.
Bruce Hammond, Ph.D., a lead researcher at Monsanto’s Product Safety
Center, says that aflatoxin is a potent liver carcinogen and source of
other health concerns in humans and animals. Tightly regulated by the
FDA, Hammond said threatening levels of the contaminant are kept out of
the food supply in the United States. But in Africa and the developing
world, poor regulation has made aflatoxin a significant food safety
At the 235th national meeting of the American Chemical Society in
New Orleans, Hammond and others presented advances towards the
production of corn less susceptible to aflatoxin contamination. The new
varieties could contribute to the reduction of the worldwide threat of
the deadly toxin, improve food quality in developing countries and
increase corn yield for food and in the United States.
Growing conditions in Africa are well-suited for Aspergillus flavus,
the fungus that produces aflatoxin. Environmental factors like drought,
high temperatures, nitrogen availability and insect damage in plants
allow the fungus to thrive. Fungal spores can enter the corn via
cavities created by insects, and later germinate and produce
mycotoxins, the problematic family of contaminants that includes
In Africa, where both animals and man eat feed corn, people die as a
result of acute aflatoxin exposure. In 2007, there were over a hundred
deaths in Kenya alone. Levels of the liver toxin rise to especially
dangerous levels in those with hepatitis.
However, the contaminant poses the biggest threat to children.
“There are studies documenting the correlation between growth issues
in West African children and ingestion of aflatoxins,” said Robert L.
Brown, a plant pathologist at the United States Department of
Agriculture who studies genes that might confer aflatoxin resistance in
corn. He also said the toxin has an effect on immune function in
children. Brown is in the process of releasing six new corn inbred
lines that are the result of crosses between U.S. aflatoxin-resistant
lines and African resistant lines. These new inbreds have been selected
for valued crop characteristics as well as for resistance.
Estimates suggest that 4.5 billion people in developing countries
are chronically exposed to aflatoxin. While the health threat looms in
developing nations, it is also a significant economic threat to
agriculture in the United States.
“Because of climate, you can find an aflatoxin breakout somewhere in
the southern U.S. pretty much every year,” said Brown. These outbreaks
can drive up prices for ethanol if it’s feed corn byproducts become
In the quest to engineer better corn crops, scientists at Monsanto
are targeting insect pests that can rob corn yield and decrease grain
quality. The first generation of their so-called “Bt corn” incorporated
a gene into the corn genome from Bacillus thuringiensis (Bt), a soil
microbe that produces a protein that kills harmful corn pests like the
European and southwestern corn borer. Bt is the active ingredient in
microbial pesticides widely used in organic and conventional
agricultural systems for close to 50 years.
“Bt is found commonly in the environment already. After inserting
the gene into the corn plant, the crop makes an insect control protein
within the plant that helps protect it from target species like
European corn borer, but doesn’t harm other non-target insects or
species. The use of this technology has also allowed farmers to
decrease other forms of pesticide protection, helping the environment
in the process,” said Hammond.
The Bt corn successfully resisted insect damage by the European corn
borer, rootworm and other insects that allow mycotoxin-producing fungi
to infect corn plants. Now, varieties of Bt corn make up 55 to 60
percent of all corn grown in the United States each year, according to
Subsequent studies confirmed a secondary benefit — with less insect
damage on corn ears, the Bt corn suffered less fungal infection and had
lower levels of certain mycotoxins, but not aflatoxin. Hammond’s team
followed up on these observations with the aim to reduce aflatoxin
Today, Monsanto researchers aim to confer even more insect
protection to the second generation of Bt corn. Pending regulatory
approval, the new varieties could include additional genes that guard
against a broader variety of pests like the fall armyworm, a particular
threat to the southern United States associated with aflatoxin
Preliminary trials found that the new Bt corn variety had reduced
levels of aflatoxin, said Hammond. Other sites in the US and in
Argentina also showed lower insect damage to the corn from other pests.
“These preliminary results are encouraging, and we look forward to
more trials performed under a variety of environmental conditions to
show that these reductions are reproducible,” said Hammond.
The researcher’s future efforts aim to lessen the effect of other
environmental stressors that can trigger fungal growth in plants.
“If we take insect protection, combine it with drought tolerance,
protect the roots against root damage, have herbicide resistance and
improved nitrogen utilization all in the same plant, maybe we will have
plants that are much less susceptible to these stress factors and, as a
secondary effect, reduced mycotoxin contamination,” said Hammond.
Source : American Chemical Society
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