While challenges persist for GM detection and monitoring, transgenes continue to flow into landraces of maize in Mexico


Two recently published papers have revisited the issue of transgene flow into landraces of maize in Mexico. The first documents contamination in landraces grown by indigenous farmers and sold in government stores as grain, which some farmers plant as seed. It also demonstrates how societal organization and the seed management systems of local communities significantly influence the extent and frequency of transgene flow. The second paper reviews key methodological aspects under dispute in previously published papers on Mexican maize, highlights the ongoing challenges for transgene detection in landraces and wild relatives, and describes the research needs to enable effective monitoring of transgene flow into centres of origin and diversity.

This research was funded by the Research Council of Norway under their Latin America Program and it was a collaboration between GenØk, farmers in Mexico, the detection laboratories in Brazil, Lebanon and Switzerland at ETHZ. More about the project can be found at www.biodiverseedy.com , the webpage available in English and Spanish.

Agapito-Tenfen, S., Rivera Lopez, F., Mallah, N., Abou-Slemayne, G., Trtikova M., Nodari, R.O., Wickson, F. (2017). “Transgene flow in Mexican maize revisited: Socio-biological analysis across two contrasting farmer communities and seed management systems” Ecology and Evolution (published online 25 August) first) 1-12. DOI: 10.1002/ece3.3415

Agapito-Tenfen, Sarah Z. and Wickson, Fern. (2017) “Challenges for transgene detection in landraces and wild relatives: learning from 15 years of debate over GM maize in Mexico” Biodiversity Conservation https://doi.org/10.1007/s10531-017-1471-0


Maize is one of the world’s five staple cereals. Its traditional varieties are an important component of agricultural biodiversity and as such, also an important global resource critical for the future of agricultural development. The potential for transgene flow into both landraces and wild relatives is a well recognized biosafety issue and therefore an important component of the regulatory risk assessment performed on GM crops prior to their approval for cultivation.

The case of transgene flow into traditional maize landraces was first reported in Mexico 15 years ago and drew the world’s attention to the possibility of contaminating crop varieties at their center of origin and diversity. The reported presence of transgenes in Mexican maize sparked an intense scientific, political and environmental dispute over the extent to which the culture and traditions of indigenous people were being threatened by the unchecked spread of GMOs owned as the patented inventions of multinational corporations. This controversy lead to a long-standing legal battle over the regulatory status of GM crops in Mexico, which continues today as approvals of GM maize for cultivation remain subject to contestation in the courts. Although maize is currently not permitted for cultivation in Mexico, trasngenes continue to be found in the landraces being farmed by local communities.

The debate over transgene flow into landraces of maize in Mexico includes significant scientific debate over appropriate methods for GM detection. The use of diverse approaches and a lack of harmonized methods specific to transgene detection in landraces have generated both positive and negative results regarding GM contamination of Mexican maize over the years. In a newly published paper, the scientific debate over appropriate methods for detecting transgenes in landraces and wild relatives is reviewed and recommendations for sampling, testing and policy are presented. These recommendations include: an integration of social and biological data, development of threshold levels and limits of detection relevant for environmental monitoring of low level presence, and the establishment of a public registry with open access to transgene sequence information and all event approvals.

In a second recent study, it was demonstrated that communities that cultivate seeds and/or grains from outside or unknown varieties, including grains from the government stores of DICONSA, are more vulnerable to transgene spread into their landrace varieties. The work showed how socio-biological factors (such as seed saving and sharing practices, communitarian organization and land tenure arrangements) are highly important determinants affecting the frequency of transgene presence and the potential for spread within farming communities. In doing so, the work also highlighted how social practices and arrangements may be used as a resource to minimize the potential for or scale of transgene flow.

Both of these new papers seek to advance the establishment of good practices for transgene detection and monitoring in centres of origin and diversity. The importance of conserving genetic biodiversity in crop plants in the face of the rapid expansion of new biotechnological organisms, especially across mega diverse countries, makes this task even more urgent and pressing now than it was 15 years ago.