Transgenic Crops and Crop Varietal Diversity: The Case of Maize in Mexico

Implementing the nature's contributions framework: A case study based on farm typologies in small-scale agroecosystems from the Mexico highlands

Introduction

Integrating the heterogeneity of small-scale agriculture with the regulation, material, and non-material contributions is key to complementing the rural-support policy instruments. The objectives of the present study were to analyze the diversity of agricultural types of management in small-scale maize agroecosystems and discuss their implications for nature's contributions in the region of Valles Altos, México.

Methods

The methodology was conducted by constructing an agricultural management typology with multivariate statistical analysis for 112 small plots interviews. The operationalization of regulation, material, and non-material nature's contributions was based on the definition and counting of cultural elements from agronomic management for each class of contribution.

Results

The results indicate three different types of agricultural management defined mainly by the type of seed, the destination of harvest, and the type of tillage. This management diversity is guided by farmers' motivation to achieve food self-sufficiency or generate income from grain sales. Each management type has a unique provision of regulation, material, and no material contributions defined by the use of the native seed, use of stover, and management diversification.

Discussion

The integration of farm typology methods and nature's contributions framework reveals that it is critical to establish new incentives that include the biological and cultural diversity of agroecosystems and the individual motivations of farmers. This may help conserve the natural and cultural values of agriculture and design appropriate incentives for small-scale agriculture.

Pollen-mediated gene flow and seed exchange in small-scale Zambian maize farming, implications for biosafety assessment

Gene flow in agricultural crops is important for risk assessment of genetically modified (GM) crops, particularly in countries with a large informal agricultural sector of subsistence cultivation. We present a pollen flow model for maize (Zea mays), a major staple crop in Africa. We use spatial properties of fields (size, position) in three small-scale maize farming communities in Zambia and estimate rates of cross-fertilisation between fields sown with different maize varieties (e.g. conventional and transgene). As an additional factor contributing to gene flow, we present data on seed saving and sharing among farmers that live in the same communities. Our results show that: i) maize fields were small and located in immediate vicinity of neighboring fields; ii) a majority of farmers saved and shared seed; iii) modeled rates of pollen-mediated gene flow showed extensive mixing of germplasm between fields and farms and iv) as a result, segregation of GM and non-GM varieties is not likely to be an option in these systems. We conclude that the overall genetic composition of maize, in this and similar agricultural contexts, will be strongly influenced both by self-organised ecological factors (pollen flow), and by socially mediated intervention (seed recycling and sharing).

Detection of transgenes in local maize varieties of small-scale farmers in eastern cape, South Africa

Small-scale subsistence farmers in South Africa have been introduced to genetically modified (GM) crops for more than a decade. Little is known about i) the extent of transgene introgression into locally recycled seed, ii) what short and long-term ecological and socioeconomic impacts such mixing of seeds might have, iii) how the farmers perceive GM crops, and iv) to what degree approval conditions are followed and controlled. This study conducted in the Eastern Cape, South Africa, aims primarily at addressing the first of these issues. We analysed for transgenes in 796 individual maize plants (leaves) and 20 seed batches collected in a village where GM insect resistant maize was previously promoted and grown as part of an governmental agricultural development program over a seven year period (2001–2008). Additionally, we surveyed the varieties of maize grown and the farmers’ practices of recycling and sharing of seed in the same community (26 farmers were interviewed). Recycling and sharing of seeds were common in the community and may contribute to spread and persistence of transgenes in maize on a local or regional level. By analysing DNA we found that the commonly used transgene promoter p35s occurred in one of the 796 leaf samples (0.0013%) and in five of the 20 seed samples (25%). Three of the 20 seed samples (15%) included herbicide tolerant maize (NK603) intentionally grown by the farmers from seed bought from local seed retailers or acquired through a currently running agricultural development program. The two remaining positive seed samples (10%) included genes for insect resistance (from MON810). In both cases the farmers were unaware of the transgenes present. In conclusion, we demonstrate that transgenes are mixed into seed storages of small-scale farming communities where recycling and sharing of seeds are common, i.e. spread beyond the control of the formal seed system.

The Anthropology of Genetically Modified Crops

By late in the twentieth century, scientists had succeeded in manipulating organisms at the genetic level, mainly by gene transfer. The major impact of this technology has been seen in the spread of genetically modified (GM) crops, which has occurred with little controversy in some areas and with fierce controversy elsewhere. GM crops raise a very wide range of questions, and I address three areas of particular interest for anthropology and its allied fields. First are the political-economic aspects of GM, which include patenting of life forms and new relationships among agriculture, industry, and the academy. Second is the wide diversity in response and resistance to the technology. Third is the much-debated question of GM crops for the developing world. This analysis is approached first by determining what controls research agendas and then by evaluating actual impacts of crops to date.

Detecting (trans)gene flow to landraces in centers of crop origin: lessons from the case of maize in Mexico

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 Ne/n (effective/census population size), (3) minimizing variance at all levels sampled, and (4) using Ne 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 Ne. 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 Ne. Using estimates of Ne 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 approximately 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.