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CIMMYT Repeats: No GM in Maize GeneBanks

News: May, 2002
As part of their continuing effort to characterize maize gene bank accessions and breeding materials, scientists from CIMMYT's Applied Biotechnology Center and Maize Program recently conducted another set of screens aimed at detecting the presence of transgenes in an additional 28 Mexican landraces. None of the materials tested were positive for the common transgenic promoter (cauliflower mosaic virus 35S, abbreviated as CaMV 35S) associated with transgenic maize. If the promoter had been found and those results verified, it would have indicated that a transgenic maize plant had crossed with the sampled maize or a direct ancestor.
Seed for all 28 landraces was collected in the Mexican state of Oaxaca during 1997-99; 18 of the samples come from accessions maintained in CIMMYT's maize germplasm bank (part of the Wellhausen-Anderson Plant Genetic Resources Center) and are designated as being held "in trust" for the benefit of humanity under a 1997 agreement with FAO, which means they must be kept free from any intellectual property restrictions (such as patents). The other 10 samples represent varied maize races from the Mixteca, a region in southeast Mexico that includes parts of Oaxaca and Puebla states. To date, CIMMYT specialists have screened 152 Mexican landraces and failed to detect the presence of the CaMV 35S promoter.
Seeds of 28 Mexican maize accessions were received from Suketoshi Taba, head of the CIMMYT Maize Gene Bank. These seeds were germinated and DNA extracted according to the standard protocols of CIMMYT's Applied Biotechnology Center (ABC). DNA was amplified using a primer corresponding to the CaMV 35S promoter, a fragment of DNA found in most commercial transgenic maize and not known to exist naturally in the maize genome (sequence available upon request). DNA was extracted in a bulk of 10 plants, and a total of 10 plants were tested per population. DNA isolated from a known transformed plant containing the CaMV 35S promoter was run as a positive control. To further ensure that the reactions were working correctly, all DNA samples were amplified using a primer corresponding to a fragment of DNA known to exist naturally in the maize genome. All positive controls amplified correctly, and no bulk of gene bank maize amplified the CaMV 35S promoter sequence, indicating that, in the samples tested, there is no CaMV 35S promoter sequence.
CIMMYT commented "Among the assertions raised in the media are reports that our maize gene bank (part of the Wellhausen-Anderson Plant Genetic Resources Center) contains Mexican landraces carrying transgenes. CIMMYT has also been subjected to accusations of remaining silent and inactive on the broader transgene-landrace issue. Neither of these assertions are based on fact and both are untrue."
In a statement considering some of the issues raised by suggestions of maize landrace contamination, CIMMYT says a "widely held misconception about maize landraces is that what we find in remote areas of Mexico today is essentially the same as the maize found in the same location 100 years ago. It's not." CIMMYT points out that diversity in farmers' fields is not a static condition, but rather a dynamic process maintained by an influx of new genes, together with farmer selection. Likewise, landraces themselves are not static but are constantly evolving, while maintaining the traits desired by the farmers.
The organization also points out that the impact of introduction of single-gene traits, such as transgenic traits, would not necessarily reduce genetic diversity. "Whether this increased diversity is desirable is a different issue," it argues. Perhaps the most influential and least understood influence on genetic diversity and the "maintenance" of landraces is farmer management practices, particularly the practices farmers use to choose seed for planting the following year, says CIMMYT. "One can hypothesize that if small-scale Mexican farmers had access to transgenic varieties, and if farmers perceived these varieties as valuable, they would probably foster their diffusion into their local maize populations."
CIMMYT also speculates on potential impacts on the wild relatives of maize: Tripsacum and teosinte. "Given the difficulty of creating maize x Tripsacum hybrids, it seems extremely unlikely that transgenes would introgress into the Tripsacum genus. Introgression into teosinte would be much more likely, and the same principles related to natural and farmer selection cited earlier should apply. In short, one would not expect to see a negative impact on diversity per se, but only limited research has been conducted to date on this aspect of gene flow."
CIMMYT concludes that given its mandate and the need to resolve some of the issues in the current controversy, that the following would be particularly valuable.
Further research on farmer management practices
Establishment of a landrace database
Research on the reversibility, containment, and remediation of genes that have introgressed into maize landraces
Research on the long-term interaction between teosinte and modern maize varieties, including transgenic varieties
Contact: CIMMYT - International Maize and Wheat Improvement Center,
Apdo. Postal 6-641, Mexico, D.F., , 06600 , Mexico
Tel: +52 55 5804 2004
Fax: +52 55 5804 7558