Rising agricultural prices, combined with growing import dependence, have driven Mexico’s food import bill over $20 billion per year and increased its agricultural trade deficit. Mexico imports one-third of its maize, overwhelmingly from the United States, but three million producers grow most of the country’s white maize, which is used primarily for tortillas and many other pluricultural products for human consumption. Yield gaps are large among the country’s small to medium-scale maize farmers, with productivity estimated at just 57% of potential. To what extent could Mexico close this yield gap, using proven technologies currently employed in the country, to regain its lost self-sufficiency in maize? A comprehensive review of the literature highlights the potential for achieving that goal. With a new government coming to power in Mexico, policy options are examined, identifying those most likely to increase both maize productivity and sustainable resource use while reducing import dependence. With climate change likely to constrain input-intensive agricultural productivity growth, these involve an emphasis on farmer-led extension services, the promotion of sustainable agricultural practices, and improved water management, including expanded irrigation.
Gene flow of transgenes into non-target populations is an important biosafety concern. The case of genetically modified (GM) maize in Mexico has been of particular interest because of the country’s status as center of origin and landrace diversity. In contrast to maize in the U.S. and Europe, Mexican landraces form part of an evolving metapopulation in which new genes are subject to evolutionary processes of drift, gene flow and selection. Although these processes are affected by seed management and particularly seed flow, there has been little study into the population genetics of transgenes under traditional seed management. Here, we combine recently compiled data on seed management practices with a spatially explicit population genetic model to evaluate the importance of seed flow as a determinant of the long-term fate of transgenes in traditional seed systems. Seed flow between farmers leads to a much wider diffusion of transgenes than expected by pollen movement alone, but a predominance of seed replacement over seed mixing lowers the probability of detection due to a relative lack of homogenization in spatial frequencies. We find that in spite of the spatial complexities of the modeled system, persistence probabilities under positive selection are estimated quite well by existing theory. Our results have important implications concerning the feasibility of long term transgene monitoring and control in traditional seed systems.
Este artículo publicado en la revista Internacional, Molecular Ecology, confirma la presencia de transgenes en maíces nativos de Oaxaca y muestra modelos de simulación sobre la dinámica de dispersión de transgenes en poblaciones de maices nativos en México. Contribuye a la discusión sobre métodos de monitoreo,tanto en su componente molecular, como de muestreo.
Economic and environmental impacts of production intensification in agriculture: comparing transgenic, conventional, and agroecological maize crops
Adinor José Capellesso, Ademir Antonio Cazella, Abdon Luiz Schmitt Filho, Joshua Farley & Diego Albino Martins
A new study shows that glyphosate herbicide (e.g. Roundup) enhances the growth of aflatoxin-producing fungi.
GM Bt crops have long been touted as a solution to the problem of aflatoxins in grains. Aflatoxins are toxic and in some cases carcinogenic to animals and humans. The fungi that produce aflatoxins also cause plant diseases.