Seed Exchange Among Farmers Key to Transgene Presence in Mexican Maize

In 2001, a controversial study conducted by researchers at the University of California Berkeley made waves when it reported the appearance of proteins from genetically modified corn in native maize varieties in Oaxaca, Mexico, the birthplace of the crop. The study's methods were criticized and its results questioned. The journal Nature eventually withdrew the study. The study nonetheless raised the need for methods and public policies for regulating the movement of genetically modified plant material into local seed stocks. A paper published by PLoS ONE recently identified informal seed exchange and grain trade as key to transgenic gene flow in Mexican maize.

George A. Dyer and colleagues from the University of California Davis and National Autonomous University of Mexico 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 GM maize varieties. Dryer and colleagues claimed that the recombinant proteins Cry1Ab/Ac and CP4/EPSPS were found in 3.1% and 1.8% of the samples analyzed, respectively. The recombinant proteins were found to be most abundant in southeast Mexico but also present in the west-central region.

According to Dyer and colleagues, the possible spread of genetically modified seed and grain from the US might explain how the transgenic plant material found its way into West and Central Mexico, but not in the southeast, where the use of foreign seed is fairly uncommon.

The original article is available at http://www.news.ucdavis.edu/search/news_detail.lasso?id=9143 Read the paper published by PLoS ONE at http://dx.doi.org/10.1371/journal.pone.0005734