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[SANET-MG] the maize in mexico paper
Published online before print August 10, 2005
Proc. Natl. Acad. Sci. USA, 10.1073/pnas.0503356102
Absence of detectable transgenes in local landraces of maize in Oaxaca,
Mexico (2003-2004)
S. Ortiz-García *, E. Ezcurra *, B. Schoel , F. Acevedo , J. Soberón ¶,
and A. A. Snow ||**
*Instituto Nacional de Ecología, Secretaría del Medio Ambiente y
Recursos Naturales, Avenue Periférico Sur 5000, Colonia Insurgentes
Cuicuilco, Delegación Coyoacán, 04530 México D.F., Mexico; Genetic ID
North America, Inc., Fairfield, IA 52556; Comisión Nacional Para el
Conocimiento y Uso de la Biodiversidad en México, Avenida Liga
Periférico-Insurgentes Sur 4903, Colonia Parques del Pedregal,
Delegación Tlalpan, 14010 México, D.F., México; and ||Department of
Evolution, Ecology, and Organismal Biology, Ohio State University,
Columbus, OH 43210
In 2000, transgenes were detected in local maize varieties (landraces)
in the mountains of Oaxaca, Mexico [Quist, D. & Chapela, I. H. (2001)
Nature 414, 541-543]. This region is part of the Mesoamerican center of
origin for maize (Zea mays L.), and the genetic diversity that is
maintained in open-pollinated landraces is recognized as an important
genetic resource of great cultural value. The presence of transgenes in
landraces was significant because transgenic maize has never been
approved for cultivation in Mexico. Here we provide a systematic survey
of the frequency of transgenes in currently grown landraces. We sampled
maize seeds from 870 plants in 125 fields and 18 localities in the state
of Oaxaca during 2003 and 2004. We then screened 153,746 sampled seeds
for the presence of two transgene elements from the 35S promoter of the
cauliflower mosaic virus and the nopaline synthase gene (nopaline
synthase terminator) from Agrobacterium tumefaciens. One or both of
these transgene elements are present in all transgenic commercial
varieties of maize. No transgenic sequences were detected with highly
sensitive PCR-based markers, appropriate positive and negative controls,
and duplicate samples for DNA extraction. We conclude that transgenic
maize seeds were absent or extremely rare in the sampled fields. This
study provides a much-needed preliminary baseline for understanding the
biological, socioeconomic, and ethical implications of the inadvertent
dispersal of transgenes from the United States and elsewhere to local
landraces of maize in Mexico.
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