|Quist and Chapela's initial response to PNAS article (11/8/2005)|
1. Quist and Chapela's initial response to PNAS article
1.Response to PNAS article failing to detect transgenes in maize from Oaxaca, Mexico
Given the large number of requests for comment from us regarding the article recently appeared in PNAS (below), we would like to make the following statements, preliminary to a deeper commentary.
Initial statement by Ignacio Chapela and David Quist
We were surprised by the results and statements presented in this paper. We had no prior knowledge of the contents or conclusions of the paper until it was being discussed in the media, a few days ago. On first approach, it seems to us highly suspect that transgenic DNA [that] may have been widespread in local landraces of maize in Mexico in 2000-2001, as demonstrated in at least 3 separate studies, would suddenly become absent within a couple of years.
Part of our surprise stemmed also from our knowledge that three of the authors in this paper have made many categorical public representations prior to this paper which lie in diametrical contradiction to the negative results paper presented in PNAS. Although their statements were never published in a peer-reviewed journal, we must presume that those contradictory categorical statements were based on real samples and analyses. We do not know whether the results presented now in PNAS are derived from the same samples, what differences in method they applied, and how much the change in their conclusion is determined not by a biological or social phenomenon, but rather by a change in the author's assumptions and expectations. We reserve our judgement in this regard until these contradictions are explained. We call upon the authors of the PNAS paper to clearly explain the change in their statements from one year to the next.
We continue to be surprised by the interpretation of the significance of this paper as well as by the many representations made about it by the authors for the general public and the media. We are deeply concerned by the conclusions being drawn from those representations in terms of GMO policy and trade, since we feel that these conclusions are not warranted by this papers results or the interpretation of those results.
We have noticed troubling methodological and technical problems in the PNAS paper which would have deserved close attention before publication, and certainly before any conclusions could be drawn from it. We are writing a first rebuttal of the paper dealing with these questions, and will make this rebuttal public as soon as it is carefully reviewed and considered by our colleagues. News about this rebuttal will be posted at http://www.pulseofscience.org.
Given the fact that the paper was published nonetheless, and that conclusions from the biological to the policy and commercial levels are quickly being used in developing policy, we strongly recommend caution in deriving policy from this paper. The scientific community needs the opportunity to apply scrutiny to this work, so that discourse can help guide exactly what can be said about this work. For now, there are certainly more questions than answers brought by this research, will need to be answered through thorough scientific scrutiny and continued research on the fate of transgenes in and out of Mexican maize. Stay tuned.
2.Published online before print August 10, 2005
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.