Absence of detectable transgenes in local landraces of maize in Oaxaca, Mexico (2003-2004) (original) (raw)
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Ecology and evolution, 2017
The flow of transgenes into landraces and wild relatives is an important biosafety concern. The case of transgene flow into local maize varieties in Mexico (the center of origin of maize) has been intensively debated over the past 15 years, including legal, political, and environmental disputes fanned by the existence of a significant scientific controversy over the methods used for the detection of transgenes. The use of diverse approaches and a lack of harmonized methods specific to the detection and monitoring of transgenes in landraces have generated both positive and negative results regarding contamination of Mexican maize with genetically modified material over the years. In this paper, we revisit the case of transgene contamination in Mexican maize and present a novel research approach based on socio-biological analysis of contrasting communities and seed management systems. Two communities were used to investigate how different social and biological factors can affect trans...
Evaluation proposal of possible impact of transgene accumulation in Mexican maize landraces
Agrociencia, 2009
The liberation of genetically modified maize (GMM) on commercial scale in Mexico, potentially involves the genetic interaction among over 30 independent transgenic events (probably more than 30 different transgenic loci) and more than 50 Mexican maize landraces (MML) in Mexican farmlands. Although the Law of Biosecurity of Genetically Modified Organisms (LBGMO) and its Norms establish the assumption that the control of pollen makes it possible to minimize the genetic interaction between the two maizes, it is possible that the "seed- pollen" alternative, not forseen in this law, contradicts the realism of this assumption. The present status of recombinant DNA technology does not allow the predetermination of the transgenic locus of each transformation, thus the more than 30 independent transgenic loci of the seed market would be dispersed in the chromosomic space. This is the central cause of transgene accumulation in the MML, when the GMM and the MML interact genetically, ...
Molecular Ecology, 2009
A possible consequence of planting genetically modified organisms (GMOs) in centres of crop origin is unintended gene flow into traditional landraces. In 2001, a study reported the presence of the transgenic 35S promoter in maize landraces sampled in 2000 from the Sierra Juarez of Oaxaca, Mexico. Analysis of a large sample taken from the same region in 2003 and 2004 could not confirm the existence of transgenes, thereby casting doubt on the earlier results. These two studies were based on different sampling and analytical procedures and are thus hard to compare. Here, we present new molecular data for this region that confirm the presence of transgenes in three of 23 localities sampled in 2001. Transgene sequences were not detected in samples taken in 2002 from nine localities, while directed samples taken in 2004 from two of the positive 2001 localities were again found to contain transgenic sequences. These findings suggest the persistence or re-introduction of transgenes up until 2004 in this area. We address variability in recombinant sequence detection by analyzing the consistency of current molecular assays. We also present theoretical results on the limitations of estimating the probability of transgene detection in samples taken from landraces. The inclusion of a limited number of female gametes and, more importantly, aggregated transgene distributions may significantly lower detection probabilities. Our analytical and sampling considerations help explain discrepancies among different detection efforts, including the one presented here, and provide considerations for the establishment of monitoring protocols to detect the presence of transgenes among structured populations of landraces.
Transgenes in Mexican Maize, Ten Years On: Still not addressing the right questions on risks
Ten years ago, the discovery of transgenes in Mexican maize sparked an international discussion on the use of GM crops in centers of origin and genetic diversity. Since then, the pertinent question is no longer if transgenes will contaminate Mexico´s maize landraces, but more importantly, what we might lose if this continues. Answering this requires addressing the right questions within Mexico’s context--not only the scientific concerns of environmental, health and biodiversity-level effects--but also their inter-related social and economic impacts. Domestic society should therefore play a role in the assessment of whether genetically modified (GM) maize is appropriate for Mexico as the center of origin and genetic diversity. Today, a more integrative decision-making process on the appropriateness of GM maize for Mexican agriculture is needed, including consideration of whether alternative approaches to meeting maize production challenges may provide greater benefits with fewer risks.
Dispersal of Transgenes through Maize Seed Systems in Mexico
PLOS One, 2009
Objectives: Current models of transgene dispersal focus on gene flow via pollen while neglecting seed, a vital vehicle for gene flow in centers of crop origin and diversity. We analyze the dispersal of maize transgenes via seeds in Mexico, the crop's cradle.
In September of 1995, the National Institute of Forestry, Agriculture, and Livestock Research (INIFAP), the National Committee of Agricultural Biosafety (CNBA), and the International Maize and Wheat Improvement Center (CIMMYT), with financing from the United Nations Development Programme (UNDP), organized the forum and workshop, “Gene Flow between Landraces, Improved Maize and Teosinte: Implications for Transgenic Maize,” which was held in the facilities of CIMMYT in El Batán, Mexico. This meeting brought together experts in maize and teosinte genetics to analyze and discuss information and relevant studies on genetic flow between maize and teosinte in Mexico in view of current biotechnological developments, particularly the production of transgenic maize. With experts from different areas, attempts were made to examine the consequences of this genetic interaction and the implications for the regulation, management and evaluation of transgenic maize. There was confidence that the exchange of ideas and information between experts could help clarify the situation in the near future. This meeting was considered particularly relevant for Mexico, the location of maize origin, diversity, and domestication and where teosinte is found in close association with maize in some agricultural regions. In addition, maize in Mexico is a staple for a large part of the population. The structure of the forum and discussion workshops are defined with minor modifications in the Table of Contents of this volume. The subjects presented and discussed included: 1) teosinte distribution in Mexico, 2) the study of genetic flow between different types of maize and teosinte, and 3) the evaluation of probable risks arising from the release of transgenic plants in their center of origin. The presentations of each one of the subjects served as an introduction for the discussion groups that were composed of scientists invited to the forum. Each group, which functioned as a workshop, was assigned a moderator and a secretary who would present a report and a summary to the plenary session. These drafts were generated in response to questions devised by the organizers and additional queries that arose during the discussions. More than 20 individuals — mainly Mexican scientists from public research and teaching agencies, together with some foreign specialists — participated in the seminars, discussion panels, and plenary sessions. Among other activities, researchers concentrated on two principal objectives: 1) to establish scientific criteria for the proper regulation of transgenic maize, and 2) to identify research topics on basic aspects of biosafety and risk analysis resulting from the introduction of transgenic maize into the environment. Work was extremely intense and, at times, full of interesting and fruitful controversies — in many ways, the outcomes surpassed the expectations of the organizers. Despite the intense polemic generated during the meeting, some very important conclusions were reached. Among these, one in particular stands out: that field tests with transgenic maize may be permitted if certain, very strict containment conditions are observed. In an assessment of costs and benefits, it was considered that such a measure would allow an increased understanding of the behavior of genetically engineered organisms and their environmental impact. Nevertheless, it was also emphasized that a much more thorough knowledge of transgenic maize would be needed to make a wellinformed decision on whether or not to permit the commercial release of transgenic maize to farmers. Advances in methodologies for manipulating the intrinsic bases of life have led to controversy and confrontation on highly complex ethical, legal, and scientific issues, and will undoubtedly involve difficult decisions. A suitable strategy for meeting this challenge is to gather and weigh the most recent and reliable information on the subject, and to use fair judgment in making decisions. Those sectors of society that have something to contribute to the process should be involved. For this reason, we believe that the publication of these proceedings will be of great interest for a wide variety of readers, including researchers in the field of genetic engineering, biodiversity, and those interested in technology transfer. Other potential beneficiaries would include representatives of public and private seed companies who may seek to market transgenic crops, government officials in the agricultural and livestock sector, and representatives of nongovernmental organizations in Mexico and other countries where centers of origin of cultivated species are found. Finally, but of no less importance, is the relevance of these discussions for farmers who may someday sow transgenic seed.
Environmental Biosafety Research, 2005
There is much discussion of the probability of transgene flow from transgenic crop varieties to landraces and wild relatives in centers of origin or diversity, and its genetic, ecological, and social consequences. Without costly research on the variables determining gene flow, research on transgene frequencies in landrace (or wild relative) populations can be valuable for understanding transgene flow and its effects. Minimal research requirements include (1) understanding how farmer practices and seed systems affect landrace populations, (2) sampling to optimize N e /n (effective /census population size), (3) minimizing variance at all levels sampled, and (4) using N e to calculate binomial probabilities for transgene frequencies. A key case is maize in Mexico. Two peer-reviewed papers, based on landrace samples from the Sierra Juárez region of Oaxaca, Mexico, reached seemingly conflicting conclusions: transgenes are present (Quist and Chapela, 2001, Nature 414: 541-543; 2002, Nature 416: 602) or "detectable transgenes" are absent (Ortiz-García et al., 2005, Proc. Natl. Acad. Sci. USA 102: 12338-12343 and 18242). We analyzed these papers using information on Oaxacan maize seed systems and estimates of N e . We conclude that if Quist and Chapela's results showing presence are accepted, Ortiz-García et al.'s conclusions of no evidence of transgenes at detectable levels or for their introgression into maize landraces in the Sierra de Juárez of Oaxaca are not scientifically justified. This is because their samples are not representative, and their statistical analysis is inconclusive due to using n instead of N e . Using estimates of N e based on Ortiz-García et al.'s n, we estimate that transgenes could be present in maize landraces in the Sierra Juárez region at frequencies of ~1-4%, and are more likely to be present in the 90% of Oaxacan landrace area that is not mountainous. Thus, we have no scientific evidence of maize transgene presence or absence in recent years in Mexico, Oaxaca State, or the Sierra Juárez region. et al. 198 Environ. Biosafety Res. 4, 4 (2005) (Quist y Chapela, 2001, Nature 414: 541-543; 2002, Nature 416: 602) o no hay "transgénicos detectables" (Ortiz-García et al., 2005, Proc. Natl. Acad. Sci. USA 102: 12338-12343 y 18242). Nosotros hemos analizado estos artículos usando información de los sistemas de semilla de Oaxaca y cálculos de N e . Concluimos que si los resultados de Quist y Chapela mostrando la presencia de transgénicos son aceptados, las conclusiones de Ortiz-García et al. de que no existen transgénicos detectables en los maíces de la Sierra Juárez de Oaxaca no se justifican científicamente. Esto se debe a que los tamaños de muestra usados por Ortiz-García no son representativos y su análisis estadístico no es concluyente por que usaron n en lugar de N e . Usando estimadores de N e basado en el n de Ortiz-García et al., nosotros estimamos que transgénicos pueden ser presente en las razas de maíz de la región de Sierra Juárez en frecuencias de ~1-4%, además es posible que estén presentes en el 90% del área sembrado con maíz criollo que se encuentra en las zonas no montañosas de Oaxaca. Por lo tanto no hay evidencias científicas de la presencia o ausencia de maíz transgénico en años recientes en México, o en el estado de Oaxaca, o en la región de la Sierra Juárez.
Gene flow scenarios with transgenic maize in Mexico
Environmental …, 2004
Maize diversity is widespread in Mexico and it has been stewarded by campesinos in small communities until the present. With the arrival of transgenic maize, the objective of this study is to analyze possible scenarios that could result if genetically modified maize were not regulated and openly available in Mexico. By applying a simple logistic model based on the conditions of maize production in Mexico, the dispersion of transgenic maize in different situations within fields of farmers is described. In traditional open systems of freely exchanged seed within communities it is concluded that the most likely outcome of GM maize release is the incorporation of transgenes in the genome of Mexican germplasm and possibly in that of teosinte.