Transgenic Maize in Mexico:
Facts, Fears, and Research Needs
In late 2001, Nature (414: 541-542) published a controversial report that farmers were growing transgenic maize in Mexico and that, as a result, traditional Mexican maize landraces had become transgenic.
Mexico's maize landraces (strains developed over millennia by farmers) are considered a world treasure. The diversity they represent, like their cultural value, is priceless. The Nature report that Mexico's landraces were transgenic elicited a visceral response from people who feared that an important resource was lost forever. The report also elicited a strong response from scientists, some of whom felt that the research described in Nature did not support the conclusions that were drawn.
As an international research institution based in Mexico and charged with holding maize genetic resources in trust for humanity, CIMMYT was drawn into the controversy amid contentions that landraces in its genebank were transgenic.
The Situation in
CIMMYT's Genebank
In fact, there is no evidence that any of the Mexican landraces in the Wellhausen-Anderson Genetic Resources Center (CIMMYT's genebank) carry the most common promoter associated with transgenic plants—cauliflower mosaic virus 35S (CaMV 35S). CIMMYT has screened more than 150 Mexican landraces and has failed to find the presence of CaMV 35S. CIMMYT continues to screen landrace accessions collected after 1996, when commercial transgenic maize was first released for commercial use.
Several precautions are taken with the landraces held and distributed by CIMMYT. No new maize seed is added to the collection of landraces held in trust for humanity without being tested for transgenic material. To the extent possible, only accessions collected before 1996 are provided to our partners, unless the accessions have been screened for the general presence of transgenes (e.g., CaMV 35S) or unless the recipient guarantees that such screening will be done.
Seed cannot be held in cold storage in genebanks forever; periodically it must be taken out, tested to ensure that it still germinates, and planted to renew the stock of seed needed to meet research needs. When maize seed from the bank is regenerated in the field, researchers use controlled hand-pollination to ensure that the plants do not cross with plants of any other variety. To further ensure that all extraneous pollen is kept out, buffer zones protect the regeneration plots.
Once the regenerated seeds are safely in the genebank, CIMMYT follows strict identification procedures to prevent them from getting mixed with other seed. They are held under secure conditions and managed through unique computerized identifiers. The seed samples must conform to so-called "passport data" on seed type and color. Requests for seed are processed according to the seed passport information.
The Situation in
Farmers' Fields
It is easier to determine what is occurring in a genebank, where seed is kept under rigorously controlled conditions, than to determine what is happening in farmers' fields. If transgenes are present in Mexican landraces, what are the probable effects in farmers' fields, on genetic diversity, and on the wild relatives of maize? CIMMYT researchers have some idea of the effects (see "Are Mexico's Indigenous Maize Varieties at Risk?", opposite), but their hypotheses must be confirmed. It is urgent to pursue several scientific inquiries.
First, to determine which factors influence the diffusion of genes (including transgenes) into maize landraces and what the potential impacts might be, researchers need more knowledge of smallholders' management and seed selection practices. Related questions should also be addressed: How does this diffusion process affect the livelihoods of small-scale maize farmers? Can this process and its impacts be managed? If so, how?
Second, a centralized database on maize landraces of Mexico and the rest of the world must be created. It would contain information on agronomic and grain quality traits and, when feasible, genetic information. It would provide baseline information on diversity, be useful for breeding programs, and have other practical applications. For example, in the dispute on patenting high oil-content maize, no data were readily available to show that Mexican landraces with high oil content were cultivated prior to the patent applications. If we lack this kind of information, the value of biodiversity is reduced.
Third, if genes from new crops and crop products—transgenic or otherwise—should not be freely distributed but nevertheless make their way into the environment, what are the options for controlling or reversing their diffusion in farmers' fields? It is critical to have more information on factors affecting gene flow in maize and how they might be harnessed to reverse, contain, or ameliorate the impact of the diffusion of a deleterious or unwanted gene. Research in this area should be given high priority.
Finally, over the long term, how might modern varieties and farmer management practices affect the genetic diversity of teosinte, the closest wild relative of maize? More in-depth studies are needed to answer this question.
A Wake-Up Call for
More Research
"As pressure increases to participate in the global economy, it is easy to forget that agriculture can play many roles," says Masa Iwanaga, CIMMYT's director general. "Agriculture can have objectives other than producing high-yielding crops for export. Preserving traditional landraces in their centers of origin may be one such objective. The present concern in Mexico has reminded the world that we need to understand and assist the farmers who are the guardians of maize biodiversity."
"Mexican smallholders have fostered maize genetic diversity very efficiently for thousands of years," comments Mauricio Bellon, a CIMMYT social scientist who has intensively studied farmers' management of maize diversity. "The questions about transgenic maize have shown the many challenges these farmers face. Can they support their families just by growing landraces? Many farmers who grow these landraces are old, and their knowledge is dying with them. Will their children have incentives to continue the tradition?"
"The issues surrounding the maintenance of genetic diversity in the center of origin of maize are not simple, so it is not surprising that there are so many questions to answer," says Iwanaga. "The important point is that if no one funds research to answer these questions, the consequences will be serious for Mexico and the rest of the world."
"Agriculture can
have objectives other than producing high-yielding
crops for export.
Preserving landraces can be one
such objective."
 |
For more information: Mauricio Bellon (m.bellon@cgiar.org) Julien Berthaud (j.berthaud@cgiar.org) David Hoisington (d.hoisington@cgiar.org) Masa Iwanaga (m.iwanaga@cgiar.org) Suketoshi Taba (s.taba@cgiar.org) |
CIMMYT statements on transgenic maize in Mexico, including details of genebank screening: http://www.cimmyt.mx/whatiscimmyt/transgenic_index.htm
August, 2004