More on the Mexican Corn Contamination Crisis
GRAIN Interview with David Quist
David Quist was one of the authors of the first study to report
the contamination of one of the centres of genetic diversity with
genetically modified (GM) crops. The paper erupted into what has
become known as the Mexican maize scandal . Here GRAIN talks to
Quist about the aftermath of the volcano and the implications for
farmers, scientists and consumers.
GRAIN: What is the story behind the study that ignited such
controversy around the world?
David Quist: The story began in a small laboratory
in Oaxaca in the highlands of Mexico. My professor Ignacio Chapela
had been serving as a scientific director for four indigenous communities
which had banded together to manage their natural resources. I had
been working with them on another project, but would also help them
with technical workshops. These were all indigenous-run projects
with the ideas and initiatives coming from the communities themselves.
One question that came up for them was whether GM crops were an
issue they should be concerned about. We said that Mexico had a
moratorium on planting transgenic crops at the time, so it should
not be something they needed to worry about immediately, but it
might be something they would want to consider down the line as
the situation might change.
The groups wanted to learn more, so on one of my trips there, I
brought some transgenic corn with me and we ran a workshop on testing
for transgenic DNA. We needed a transgenic-negative control, and
what better place than the highlands of Oaxaca, the birthplace of
maize? We worked out a sampling protocol, did the DNA extraction
and ran the analysis. The day before the workshop I ran a test sample
and couldn t believe the results - some of the native corn tested
positive. We had also taken a sample from the local food agency,
which also tested highly positive. These food agencies distribute
food in every village throughout the country, and while the maize
is supposed to be used only for consumption, there is no label on
it saying, Do not plant this . This means that in every village
in Mexico has these point sources of potential contamination.
We went back to the lab, did some new sampling, and more widespread
and stringent analysis, the results of which became the Nature paper.
 But first we felt we had to go to the Mexican
government to let them know what we had found, even if it might
compromise our ability to publish the work. In the Nature paper,
we made two main statements. The first was simply that genes from
the transgenic corn had migrated into native populations. For this
we used a technique called PCR, which is widely used to amplify
the DNA of interest into sufficient quantities to identify and analyse
it. It is the standard tool for GMO identification used by regulatory
agencies throughout the world for accepting or rejecting shipments
of GM-free grain. The second statement was more exploratory and
used a new technique called inverse PCR that allows us to look more
specifically at where in the plant s genome the transgenic DNA is
located. To our surprise we found it in a diversity of places within
the native maize genome. There could be various explanations of
why this might be, one of which is that the transgenes had become
reinserted through recombination.  We felt
there was sufficient evidence to suggest that this explanation might
be true, so we published it. And that is part of what science is:
proposing novel explanations from observed patterns in data, from
which further work is done to substantiate or refute the initial
findings. We knew this was a bit novel, a bit out there , because
there was no previous science behind it and no-one was doing it.
At least there was nothing in the peer-reviewed literature, but
it wouldn t surprise me if companies have done this kind of work
without publishing it, if they did not like what they saw. People
responded by saying that there is no evidence that this kind of
gene shuffling is what is going on, but no-one has looked, no-one
has asked these questions before. We wanted, and expected, a strong
reaction, but not in the way it came.
GRAIN:A year and a half on from the publication of your paper
in Nature, what is your perspective on why there was such a strong
reaction to this paper? 
DQ: The first wave of response was to trivialise
the first statement that we made, which simply said that the transgenes
were present in the native landraces. The proponents of biotech
were saying we know that commercial varieties cross with local varieties
all the time - no big deal. What created a bigger response was what
we were exploring in looking at what those genes were doing once
they got there. We were going against the propaganda of the industry
which says that this technology is precise, this technology is stable.
We were suggesting that it is unstable, which infuriated the pro-biotech
community. Another reason was that the timing of these findings
was really bad for the industry - our findings were biting up against
the debates on the moratoria in Europe, Mexico and Brazil. It was
a huge PR disaster. In addition, the industry was in a downturn
economically. When you look at where the strongest reaction was
coming from, there were very significant links to Berkeley and the
Berkeley-Novartis deal that was signed five years ago. 
At that time a number of groups were raising concerns about what
it meant for academic freedom, student education, and so on. Dr
Chapela was a leading opponent of the signing of the agreement within
the college and I was also involved in a vocal group opposing the
deal called Students for Responsible Research. I don t think it
is insignificant that the most vocal detractors of our paper came
from the camp that supported the Novartis deal back in 1998.
From Iowa to Oaxaca: Easy passage for the Bt gene
Maize is the most important crop in Mexico. About 1.5 million hectares
of the maize grown consists of hybrid varieties (developed mainly
by transnational companies), 0.9 million hectares are open pollinated
varieties (developed by the public sector and small companies) and
the remaining 5.5 million hectares are planted to local land races.
Some 68% of the maize grown in Mexico is used directly for human
Maize is also an extremely important crop to the US, the world s
largest maize producer and exporter. In 2000, Mexico was second
only to Japan as a market for US maize, absorbing 11% of US exports.
Some 24% of total corn consumption in Mexico now comes from the
US. Since 1996, US maize exports to Mexico have increased as exports
to Europe have decreased, owing to Europe s rejection of GM maize.
Of the 5-6 million tons of maize that were imported to Mexico in
2000, 30%-40% was transgenic, but was not segregated or labelled.
That same year Mexico had exactly the same amount of domestic maize
rotting away, unused.
The maize that comes into Mexico gets distributed through welfare
food systems around the country. It is subsidised from beginning
to end by US taxpayer dollars. Incredible amounts of money go into
the production of this grain that receives subsidised water, soil,
machinery and oil; is subsidised in international markets; and subsidised
again in Mexico through distribution. It just floods the country.
When you talk to a farmer in Oaxaca, they say, It costs six pesos
to grow seed; I can buy it for four. The farmer is paying out of
his or her pocket to plant his or her own seed. Small wonder that
transgenic maize is so widespread in the fields of Mexico..
Sources: Dr Ignacio Chapela on Controversy, Corn and What s Really
at Stake in Mexico , Global Pesticide Campaigner, August 2002; Chantal
Carpentier and Hans Herrmann, Maize and Biodiversity: The Effects
of Transgenic Maize in Mexico: Issues Summary, CEC, www.cec.org/programs_projects/other_initiatives
What has been the effect of all this on the work you are doing,
and has there been follow-up work?
DQ: The contamination of local maize varieties
was a completely unexpected discovery. I wasn t working on maize
when it happened, and I wasn t looking for this when it happened.
My training is in mycology. However, since this study I have switched
to asking questions about gene flow and how genes move in the environment,
both horizontally and vertically  and I
am doing some follow up work in that area. Transgene ecology is
a fledgling field. There are a couple of other institute, such as
the Norwegian Institute of Gene Ecology 
and the New Zealand Institute of Gene Ecology, 
which are doing some great work, but I don t think they are working
on agricultural issues to any great extent. And unfortunately, when
a particular branch of science becomes politicised, it becomes a
hot potato that scares others away from working in the field. In
the case of maize, who is asking the questions about the implications
for farmers, human health, and global food systems? In Mexico, those
questions have still to be answered. To its credit, the government
is doing follow up work to look at the scale of transgene contamination
around the country, but it has yet to employ any kind of strategy
to try and manage it or ascertain its significance.
On a different tack, a number of civil society groups, spearheaded
by Greenpeace,  applied in April 2002 to
the North American Free Trade Agreement s Commission for Environmental
Cooperation (CEC) to investigate the issue. CEC s mandate is to
look at the environmental impacts of the NAFTA agreement or environmental
issues that will impact the NAFTA agreement, and accepted the challenge.
But I m very sceptical that, given the composition of the committee
appointed to investigate the issue and also the nature of the CEC
s mandate, that the investigation will have the political fortitude
to state anything other than there is no evidence that this poses
any harm, therefore we should continue importing maize from the
US . However, there is no way they could make a statement like that
from a scientific, ecological point of view without conducting rigorous
science, which I do not think they are not doing, at least at this
point. They are just going to come up with the usual fallback position
that absence of evidence is evidence of absence, which is scientifically
The Mexican government did a follow-up study in response to your
findings. What kind of research did they do and how was their research
In the first round, samples were taken from 22 communities in Pueblo
in Mexico, 15 of which tested positive using the same PCR technique
that we used. Since then, they have done a much more expansive study
in terms of sampling and techniques. The government submitted its
results to Nature, but its paper was rejected in October 2002. 
Two reviewers rejected the paper for opposite reasons. One said
that the findings were obvious (having already been reported before
in Nature), while the other said they were so unexpected as to not
be believable. To have two reviewers making such drastically different
interpretations of the same data is interesting - there is obviously
a story behind that.
GRAIN:The Mexican Government established a moratorium on
planting GM corn in 1998, so how did the transgenic maize get there?
DQ: In our local setting, we suggested two
possible sources of contamination - very local sources (such as
the food agency maize) or that it was wind blown from the industrial
maize planted in the valley about 60 miles away in Puerta Vallerta.
The first explanation seems the most likely: farmers have admitted
that they have planted food agency maize. The food agency maize
we tested was highly transgenic - its positive signal was as strong
as our transgenic positive. There are also a number of agricultural
research stations that have been doing field tests of GM corn in
open field plots before and after the moratorium came into effect.
GRAIN:What are the implications of your work for farmers
in Mexico, and small farmers in particular? What are the biggest
threats to them?
DQ: One is all the unknowns - the ecological
significance, the effects on human health
and genetic diversity, for instance. Those kinds of studies should
have been done already, but weren t. We just don t know. The second
is the unresolved questions related to liability and intellectual
property issues. If Monsanto goes into the highlands of Oaxaca and
finds its genes in a farmer s field, who shoulders the liability
the farmer or the corporation? In the case of Percy Schmeiser, the
liability fell with the farmer (see p 10). But according to the
polluter pays principle, if the company has compromised the farmer
s ability to produce for certain markets, then the company should
be liable. The third major threat to farmers is the loss of markets
owing to the pollution of their maize crops.
GRAIN:What about the wider implications?
DQ: I am concerned about the impact on science.
It is unfortunate that the debate became so politicised and the
real issue was discredited because of some disagreements over the
interpretation of the I-PCR data. While there was a lot of noise
made about the paper, there has been what I call scientific silence
over it: no-one is doing the follow up work to refute or support
our findings and no-one is asking what the implications of them
are. People have reacted defensively: because they don t see what
they expect to see, they call our results erroneous . This kind
of approach is a disservice to science. What we are seeing more
and more is that the science of substantiating facts is overriding
science as a process, which is all about questioning and re-examining
our assumptions, in order to lead us to a better understanding of
reality. The way that the debates are framed and the inability of
corporate science to re-examine its paradigms are compromising good
science. What message does this send to other scientists who make
the wrong findings or ask the wrong questions , ie those that go
against the science of the corporate agenda?
The events that have occurred also raise a lot of questions about
the true objectivity of the peer-review process in scientific reporting.
Science recently published a fairy tale story about the success
of Bt cotton in India,  despite the fact
that Bt cotton is failing miserably all over India. Nature s handling
of our paper suggests that it was under pressure from the industry
camp. As the heat built up, the journal did not handle things very
well and made a lot of people angry, on both sides. Two of the three
referees said that they did not challenge the main conclusions of
our paper, but suggested writing a correction to part of it. Why
didn t the editor make this clear, point out that there were some
issues of contention over certain aspects of our findings, and put
out calls for more work on the subject? Why the need for a disavowal?
And why were most people left with the impression that the paper
had been retracted, when it was not? A hallmark of good science
is in asking exploratory questions - just as we were doing. We weren
t out of step with that, but the response we received was out of
step with the way that normal scientific discourse should happen
to advance scientific knowledge. Situations like this call into
question whether these journals can continue to be looked to as
a reliable source of objective science.
Since 1998, David Quist has been a graduate student in the
PhD Programme in Environmental Science, Policy and Management at
the University of California, Berkeley, California. A mycologist
by training (someone who studies fungus), he made the discovery
about the contamination of maize varieties in Mexico quite by chance.
Since the study that was published in Nature, his work has become
more focused on transgene ecology - ie how genes move about in the
environment. David Quist can be contacted by email at user ="dquist"
domain ="nature.berkeley.edu" subCon ="From the GRAIN
website: " document.write(''
+ user + '@' + domain +''); email@example.com
David Quist and Ignacio Chapela, Transgenic DNA introgressed into
traditional maize landraces in Oaxaca, Mexico , Nature Vol. 414,
pp541 - 543 (2001) www.cnr.berkeley.edu/chapelalab/Research/
ie the transgenic material had become fragmented and scattered throughout
For a fuller insight into what became publicly known as the maize
scandal , go to www.biotech-info.net/mexican_bt_flow.html
Under this agreement, Novartis provided $25 million to the Department
of Plant and Microbial Biology (a third of the department s income)
in return for first right to negotiate licenses on roughly a third
of the department s discoveries (including research funded by public
money) and 2 out of 5 votes on the committee that determines how
the department s money is spent.
Vertical gene flow is the way in which genes are passed on from
parent to offspring through cross-pollination. Horizontal gene flow
is the direct uptake and incorporation of foreign DNA into cells
Greenpeace press release, Mexican Groups, Greenpeace Launch NAFTA
Appeal To Force Action Against Genetic Contamination , April 24,
Food First Press Release, Nature Refuses to Publish Mexican Government
Report Confirming Contamination of the Mexican Maize Genome by GMOs
, October 24, 2002, www.foodfirst.org/media/press/2002/naturerefuses.html
Matin Qaim and David Zilberman, Yield Effects of Genetically Modified
Crops in Developing Countries , Science Vol. 299: 900
Reference for this article: Matt Mellen, 2003, Interview
with David Quist, Seedling, April 2003, GRAIN
Copyright notice: GRAIN publications may be reproduced, translated
and disseminated freely. We ask only that the original source be
acknowledged and that a copy of your reprint be sent to GRAIN.
Website link: www.grain.org/seedling/seed-interview-d-en.cfm
What is Seedling? Seedling is the quarterly magazine of GRAIN.
It provides thought-provoking articles on all aspects of GRAIN s
work and more. To receive Seedling in paper or electronic format
(on a CD Rom), or to inform us of a change of address, please user
="seedling" domain ="grain.org" subCon ="Seedling: