Davis, California
June 1, 2009
The appearance of genetically
modified proteins in maize seed stocks throughout Mexico paints
a curious pattern that suggests why efforts to prevent the flow
of transgenic plant material into that country could fail,
reports a team of researchers in Mexico and at the
University of California, Davis.
The researchers hope that their findings, published May 29
online in the journal Public
Library of Science, will help guide development of methods
and public policies for regulating the movement of genetically
modified plant material into local seed stocks in centers of
crop origin and diversity.
The research team, led by UC Davis agricultural economist and
plant biologist George A. Dyer, used enzyme-based tests,
mathematical models of crop populations, and knowledge of
established seed-use patterns to analyze maize seed stocks in
Mexico for the presence of proteins from genetically modified,
or transgenic, maize varieties.
"We found that, nationwide, 5 percent of Mexico's maize seed
stocks contained transgenic proteins by 2002," Dyer said. "That
nationwide average included a surprising 13 percent in southeast
Mexico and 3 percent in the west-central part of the country."
Dyer noted that the possible spread of genetically modified seed
and grain from the United States might explain how the
transgenic plant material found its way into maize seed stocks
in Mexico's west-central region, where informal introduction and
sharing of improved seed is quite common. But that route of
introduction would not account for the strong presence of
transgenic seed in the country's southwest area, where use of
foreign seed is fairly uncommon.
The gene flow controversy
Although there have been no authorized commercial releases of
genetically modified corn or other maize species in Mexico,
which is the birthplace of maize, the potential for gene flow
from transgenic maize into Mexico has been controversial
throughout the past decade.
In 2001, a highly publicized study by UC Berkeley researchers
first reported the appearance of proteins from genetically
modified corn in native maize varieties in Oaxaca, Mexico. That
study raised concerns that the flow of genes from the transgenic
varieties threatened the genetic diversity embodied in Mexico's
native maize species. However, the study's methods were
criticized and its results questioned.
Dyer and colleagues addressed outstanding methodological issues
in two previous papers in the scientific journals Proceedings of
the National Academy of Science in 2008 and Molecular Ecology in
2009.
The first paper discussed how farmers' practices impact the
evolution and diversity of maize in Mexico, and the second paper
suggested monitoring protocols for detecting the presence of
transgenes among native maize varieties.
New findings on seed use
The research team's third article, published in the Public
Library of Science, builds on the two previous papers, with
special attention to how seeds are managed and shared in Mexico.
In this recent study, the researchers found that:
- informal seed exchange
between farmers was the main source of seed dispersal across
Mexico and was more important in the southeast than in the
north;
- seed obtained from
neighboring farmers was more likely to be saved from year to
year, while seed that was imported or obtained from
government programs was more likely to be replaced with
other seed in succeeding years; and
- marked differences in the
rate of spread of proteins from genetically modified maize
in different areas of Mexico suggest that the transgenic
material was dispersed through different routes in each
region.
"Many governments in developing
countries are planning to regulate the release of genetically
modified crops," Dyer said.
"In Mexico, current regulatory efforts assume that the spread of
genes from genetically modified plants into native plants can be
prevented or reversed by restricting commercial release of
genetically modified varieties to areas of industrialized
agriculture," he said. "Our study, however, suggests that this
approach might be ineffective because controlling or even
tracking the flow of grain within Mexico poses such a formidable
challenge."
He noted that, in order to develop systems for protecting
genetic diversity in areas where native crops originated,
further research is needed to explore how genetic material flows
through both formal and informal seed and grain systems.
Funding for this study was provided by UCMEXUS-CONACYT, the
William and Flora Hewlett Foundation and various agencies in
Mexico.
Collaborating with Dyer on this study were J. Edward Taylor and
Paul Gepts, both of UC Davis; Elena R. Alvarez-Buylla and Alma
Pineyro-Nelson of the Universidad Nacional Autonoma de Mexico;
J.
Antonio Serratos-Hernandez of Universidad Autonoma de la Ciudad
de Mexico; Hugo R. Perales of El Colegio de la Frontera Sur,
Mexico; Angeles Chavez and Antonio Yunez-Naude, both of El
Colegio de Mexico; and Noe Salinas-Arreortua of Universidad
Autonoma Metropolitana, Unidad Iztapalapa, Mexico.
For 100 years, UC Davis has engaged in teaching, research and
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world. Located close to the state capital, UC Davis has 31,000
students, an annual research budget that exceeds $500 million, a
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