Understanding the potential impact of transgenic crops in traditional agriculture: maize farmers’ perspectives in Cuba, Guatemala and Mexico

The Household Context of In Situ Conservation in a Center of Crop Diversity: Self-Reported Practices and Perceptions of Maize and Phaseolus Bean Farmers in Oaxaca, Mexico

Crop diversity conservation in situ is an ecosystem service with benefits at household, community, and global scales. These include risk reduction and adaptation to changing physical and sociocultural environments—both important given the accelerating changes in climate, human migration, and the industrialization of agriculture. In situ conservation typically occurs as part of small-scale, traditionally based agriculture and can support cultural identity and values. Although decisions regarding crop diversity occur at the household level, few data detail the household context of in situ crop diversity management. Our research addressed this data gap for maize and Phaseolus bean in Oaxaca, Mexico, a major center of diversity for those crops. We defined diversity as farmer-named varieties and interviewed 400 farming households across eight communities in two contrasting socioecological regions. Our research asked, “In a major center of maize and Phaseolus diversity, what are the demographic, production, and consumption characteristics of the households that are stewarding this diversity?” We describe the context of conservation and its variation within and between communities and regions and significant associations between diversity and various independent variables, including direct maize consumption, region, and marketing of crops. These results provide a benchmark for communities to understand and strengthen their maize and bean systems in ways they value and for scientists to support those communities in dynamically stewarding locally and globally significant diversity.

Maize Germplasm Conservation in Southern California's Urban Gardens: Introduced Diversity Beyond ex situ and in situ Management

Contemporary germplasm conservation studies largely focus on ex situ and in situ management of diversity within centers of genetic diversity. Transnational migrants who transport and introduce landraces to new locations may catalyze a third type of conservation that combines both approaches. Resulting populations may support reduced diversity as a result of evolutionary forces such as genetic drift, selection, and gene flow, yet they may also be more diverse as a result of multiple introductions, selective breeding and cross pollination among multiple introduced varietals. In this study, we measured the amount and structure of maize molecular genetic diversity in samples collected from home gardens and community gardens maintained by immigrant farmers in Southern California. We used the same markers to measure the genetic diversity and structure of commercially available maize varieties and compared our data to previously reported genetic diversity statistics of Mesoamerican landraces. Our results reveal that transnational dispersal creates an opportunity for the maintenance of maize genetic diversity beyond its recognized centers of diversity.

Farmer knowledge and risk analysis: postrelease evaluation of herbicide-tolerant canola in Western Canada

The global controversy regarding the use of genetically modified (GM) crops has proved to be a challenge for "science-based" risk assessments. Although risk analysis incorporates societal perspectives in decision making over these crops, it is largely predicated on contrasts between "expert" and "lay" perspectives. The overall objective of this study is to explore the role for farmers' knowledge, and their decade-long experience with herbicide-tolerant (HT) canola, in the risk analysis of GM crops. From 2002 to 2003, data were collected using interviews (n= 15) and mail surveys (n= 370) with farmers from Manitoba and across Canada. The main benefits associated with HT canola were management oriented and included easier weed control, herbicide rotation, and better weed control, whereas the main risks were more diverse and included market harm, technology use agreements (TUAs), and increased seed costs. Benefits and risks were inversely related, and the salient factor influencing risk was farmer experiences with HT canola volunteers, followed by small farm size and duration using HT canola. These HT volunteers were reported by 38% of farmers, from both internal (e.g., seedbank, farm machinery, etc.) and external (e.g., wind, seed contamination, etc.) sources, and were found to persist over time. Farmer knowledge is a reliable and rich source of information regarding the efficacy of HT crops, demonstrating that individual experiences are important to risk perception. The socioeconomic nature of most risks combined with the continuing "farm income crisis" in North America demonstrates the need for a more holistic and inclusive approach to risk assessment associated with HT crops and, indeed, with all new agricultural technology.

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.