2-Plants: Scientists link RR crops with higher fusarium pest attacks
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TITLE: Scientists eye glyphosate-fusarium link
SOURCE: The Western Producer, Canada, by Adrian Ewins
DATE: Jul 9, 2003
------------------- archive: http://www.genet-info.org/ -------------------
Scientists eye glyphosate-fusarium link
The National Farmers Union has come up with another reason to resist the
introduction of genetically modified Roundup Ready wheat -- fusarium.
Appearing before the House of Commons agriculture committee recently, NFU
president Stewart Wells said studies linking glyphosate-based herbicides
and fusarium are cause for serious concern.
The production of Roundup Ready wheat would result in a dramatic increase
in the amount of glyphosate applied during the growing season, he said,
which in turn could increase the incidence of fusarium.
"More work needs to be done in this area, but Roundup Ready wheat should
not be approved until we understand the links between formulations of
glyphosate and fusarium," Wells told the committee.
In fact, the battle over the introduction of GM wheat will almost
certainly be determined by issues such as market acceptance and consumer
concerns over food safety, rather than by any alleged link between
glyphosate and fusarium.
And so far no direct causal link has been definitively established
between Roundup and fusarium head blight, which has caused tens of
millions of dollars of losses for wheat growers in the eastern Prairies
in recent years.
Trish Jordan, manager of public affairs for Monsanto Canada, which
manufactures Roundup and is developing Roundup Ready wheat, said that
while Monsanto is aware of the concerns, the data gathered so far are
"It's important in something like this to look at a full body of research
and not to jump to conclusions, as the NFU seems to be doing," she said,
adding that Monsanto is not about to abandon its Roundup Ready wheat
project over the issue.
But scientists in Canada and the United States say there are reasons to
be cautious about introducing new technologies such as Roundup Ready
crops that might boost the use of glyphosate-based herbicides.
"There are some linkages here that we need to investigate further," said
Keith Hanson, a microbiologist at Agriculture Canada's research centre in
Swift Current, Sask.
Laboratory research by Hanson and plant pathologist Myriam Fernandez has
shown that applying glyphosate-based herbicides usually stimulates the
growth of fusarium pathogens that cause fusarium head blight.
"The biggest thing overall that we've found is that there is a
relationship here, mostly causing significant increases in vegetative
fungal growth of these plant pathogens," Hanson said.
Those results correspond to field surveys conducted by Fernandez, which
found that fields where glyphosate had been applied in the previous year
had higher levels of fusarium head blight pathogens and a greater
incidence of FHB.
Robert Kremer, a microbiologist with the U.S. Department of Agriculture's
research service, has done research showing that Roundup Ready soybeans
receiving the recommended application of Roundup have significantly
greater colonization of fusarium on their roots than untreated soybeans.
He said in an interview from his office at the University of Missouri
that while it's dangerous to extrapolate the situation with soybeans to
other crops, there is reason to be cautious about introducing Roundup wheat.
"Probably the first year that it's planted there may not be any problem,"
he said. "But in subsequent years in the same field there is always the
chance that it could trigger an increase in fusarium."
Hanson acknowledged that many questions remain unanswered.
For example, to what extent is the growth of pathogenic fungi in the soil
increased by the glyphosate herbicide, to what degree does that translate
into the appearance of FHB and what effect does it have on future crops?
There are questions about how different varieties of plants react,
whether specific fusarium fungi respond more than others and exactly why
the glyphosate herbicides stimulate fusarium growth.
It also appears from Hanson and Fernandez's research that not all
glyphosate products have the same effect on the fusarium, leading to
speculation that non-active ingredients in the commercial formulation may
account for the apparent fusarium link.
"It's not the glyphosate itself necessarily, but the glyphosate herbicide
on the whole that is stimulating something in the fusarium species and
possibly increasing growth and creating increased populations," Hanson said.
Jordan said there are other possible explanations. For example, Roundup
and other glyphosate formulations are used extensively in zero- and
minimum-till situations. Since the fusarium fungi survive on wheat crop
residues, any cultural practice that results in more residue will also
result in more fusarium if other conditions are favourable.
She said Monsanto is aware of the research, but isn't doing any of its
own and likely wouldn't unless peer-reviewed studies are published
pointing to a definite link.
Hanson said the Swift Current researchers will continue with laboratory
and greenhouse work to evaluate the production and viability of fusarium
spores under glyphosate application, and then move on to growth chambers
to test the effect of glyphosate on infected cereal residues. There are
no immediate plans for field-scale studies.
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