Dispersal of transgenes through maize seed systems in Mexico.

ObjectivesCurrent 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.MethodsWe use immunoassays (ELISA) to screen for the activity of recombinant proteins in a nationwide sample of farmer seed stocks. We estimate critical parameters of seed population dynamics using household survey data and combine these estimates with analytical results to examine presumed sources and mechanisms of dispersal.ResultsRecombinant proteins Cry1Ab/Ac and CP4/EPSPS were found in 3.1% and 1.8% of samples, respectively. They are most abundant in southeast Mexico but also present in the west-central region. Diffusion of seed and grain imported from the United States might explain the frequency and distribution of transgenes in west-central Mexico but not in the southeast.ConclusionsUnderstanding the potential for transgene survival and dispersal should help design methods to regulate the diffusion of germplasm into local seed stocks. Further research is needed on the interactions between formal and informal seed systems and grain markets in centers of crop origin and diversification

Economic impact of Melanaphis sacchari (Zehntner) ON Sorghum bicolor (L) Moench, and its management in the southwestern of Puebla, Mexico

Objective: To evaluate the economic impact of sorghum aphid (Melanaphis sacchari) and the sorghum crop profitability in Western Puebla, Mexico, considering the management practices application-index (IAPM), related to the control practices suggested by the State Plant Health Committee (CESAVEG). Design/Methodology/Approach: Data on socioeconomic aspects of the producer and the production units were collected. The questionnaire was applied to producers affiliated to PROAGRO. Results are shown using descriptive statistics. Results: The aphid infestation in sorghum had its most relevant effect on yield during 2014-2016. Income obtained from sorghum sales is decreasing due to a downward trend in the purchase price per ton. After the arrival of M. sacchari the primary control strategy was to increase the number of insecticide applications, increasing production costs. Limitations of the study/implications: Since producers; incomes do not depend solely on sorghum production, the effect of the pest on their economy was relatively minor. Findings/Conclusions: The management practices application index indicates a moderate use of the recommended practices to manage this pest. The B/C ratio suggests that even after the establishment of M. sacchari, sorghum is still a profitable activity

Transgenes in Mexican maize: molecular evidence and methodological considerations for GMO detection in landrace populations.

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

Dispersal of transgenes through maize seed systems in Mexico.

ObjectivesCurrent 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.MethodsWe use immunoassays (ELISA) to screen for the activity of recombinant proteins in a nationwide sample of farmer seed stocks. We estimate critical parameters of seed population dynamics using household survey data and combine these estimates with analytical results to examine presumed sources and mechanisms of dispersal.ResultsRecombinant proteins Cry1Ab/Ac and CP4/EPSPS were found in 3.1% and 1.8% of samples, respectively. They are most abundant in southeast Mexico but also present in the west-central region. Diffusion of seed and grain imported from the United States might explain the frequency and distribution of transgenes in west-central Mexico but not in the southeast.ConclusionsUnderstanding the potential for transgene survival and dispersal should help design methods to regulate the diffusion of germplasm into local seed stocks. Further research is needed on the interactions between formal and informal seed systems and grain markets in centers of crop origin and diversification

Altitude and source effects on rates of maize seed-lot replacement (<i>1−p</i>) and diffusion (<i>q</i>) in Mexico¹.

<p>Significant at the 0.05 level is indicated by **; significance at the 0.10 level is indicated by *. G-tests exclude seed from formal seed systems; masl: meters above sea level.</p>1<p>Expressed as a ratio, rates vary between 0 and 1. Replacement implies that seed is not saved by a farmer across cycles; diffusion entails the exchange of saved seed among farmers.</p>2<p>The terms “local” and “introduced” refer to the location of the immediate source of seed; e.g., seed is local if acquired from neighbors, while seed acquired from farmers in another locality is introduced.</p>3<p>Seed acquired during the current cycle is “new;” seed saved by the farmer from a previous cycle is his/her “own.”</p

Percentage distribution of original sources of maize seed across regions in Mexico in 2002.

*<p>Confidence intervals (in parentheses) were estimated using profile-likelihood and binomial ln(-ln) transformations.</p>1<p>Friends, neighbors and relatives.</p>2<p>Farmers who sell seed openly to the public.</p>3<p>Government agencies and programs, e.g., Kilo por Kilo.</p>4<p>Intermediaries, private firms and banks.</p>5<p>Private seed companies.</p>6<p>Any source outside of Mexico.</p>7<p>Any source of grain other than Diconsa.</p

Expression of transgenic proteins in Mexican maize seed lots in 2002.

1<p>Confidence intervals (in parentheses) were estimated using profile-likelihood and binomial ln(-ln) transformations.</p

Source effects on rates of maize seed-lot replacement (<i>1−p</i>) and diffusion (<i>q</i>) in Mexico¹.

<p>Significant at the 0.05 level is indicated by **. G-tests exclude seed from formal seed systems.</p>1<p>Expressed as a ratio, rates vary between 0 and 1. Replacement implies that seed is not saved by a farmer across cycles; diffusion entails the exchange of saved seed among farmers.</p>2<p>The terms “local” and “introduced” refer to the origin of the immediate source of seed; e.g., seed is local if acquired from neighbors, while seed acquired from farmers in another locality is introduced.</p>3<p>Seed acquired during the current cycle is “new;” seed saved by the farmer from a previous cycle is his/her “own.”</p

Distribution of survey sample and maize populations.

<p>ENHRUM localities (blue), including those where transgenic proteins were detected (black circles). Distribution of teosinte (red) and maize landrace (green) according to INIFAP and CIMMYT genebank collections. Geographic data provided by ENHRUM and Campo Experimental Valle de México, Instituto Nacional de Investigaciones Forestales y Agropecuarias (INIFAP) were processed with ArcInfo.</p