Pollen-mediated gene flow in wheat (Triticum aestivum L.) in a semiarid field environment in Spain
Departamento de Protección Vegetal, Laboratorio de Malherbología, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Ctra. La Coruña Km 7.5, 28040, Madrid, Spain.Transgenic Research (Impact Factor: 2.32). 05/2012; 21(6). DOI: 10.1007/s11248-012-9619-x
Transgenic wheat (Triticum aestivum L.) varieties are being developed and field-tested in various countries. Concerns regarding gene flow from genetically modified (GM) crops to non-GM crops have stimulated research to estimate outcrossing in wheat prior to the release and commercialization of any transgenic cultivars. The aim is to ensure that coexistence of all types of wheat with GM wheat is feasible in accordance with current regulations. The present study describes the result of a field experiment under the semi-arid climate conditions of Madrid, Spain, at two locations ("La Canaleja" and "El Encin" experimental stations) in Madrid over a 3-year period, from 2005 to 2007. The experimental design consisted of a 50 × 50 m wheat pollen source sown with wheat cultivars resistant to the herbicide chlortoluron ('Deganit' and 'Castan' respectively) and three susceptible receptor cultivars ('Abental', 'Altria' and 'Recital') sown in replicated 1 × 1 m plots at different distances (0, 1, 3, 5, 10, 20, 40, 80 and 100 m) and four directions. Outcrossing rates were measured as a percentage of herbicide-resistant hybrids using an herbicide-screening assay. Outcrossing was greatest near the pollen source, averaging 0.029 % at 0 m distance at "La Canaleja" and 0.337 % at "El Encin", both below the 0.9 % European Union regulated threshold, although a maximum outcrossing rate of 3.5 % was detected in one recipient plot. These percentages declined rapidly as the distance increased, but hybrids were detected at different rates at distances of up to 100 m, the maximum distance of the experiment. Environmental conditions, as drought in 2004-2005 and 2005-2006, may have influenced the extent of outcrossing. These assays carried out in wheat under semi-arid conditions in Europe provide a more complete assessment of pollen-mediated gene flow in this crop.
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ABSTRACT: This review summarises the history of transgenic (GM) cereals, principally maize, and then focuses on the scientific literature published in the last two years. It describes the production of GM cereals with modified traits, divided into input traits and output traits. The first category includes herbicide tolerance and insect resistance, and resistance to abiotic and biotic stresses; the second includes altered grains for starch, protein or nutrient quality, the use of cereals for the production of high value medical or other products, and the generation of plants with improved efficiency of biofuel production. Using data from field trial and patent databases the review considers the diversity of GM lines being tested for possible future development. It also summarises the dichotomy of response to GM products in various countries, describes the basis for the varied public acceptability of such products, and assesses the development of novel breeding techniques in the light of current GM regulatory procedures.
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ABSTRACT: Three-year field assessment of gene flow from the genetically modified herbicide-resistant spring wheat variety ‘Andros’ to its non-transgenic counterpart has been conducted. A circular field trial design where the wheat plants containing the bar and gfp genes were planted in a central plot, while the recipient non-transgenic plants were grown in eight compass sectors at a distance of 1–5 m from the pollen source, has been developed. Gene flow was analyzed by testing the glufosinate-based herbicide resistance in seedling progeny. The phenotypic and molecular examination of more than 712,000 germinated seeds allowed us to draw a conclusion that the pollen-mediated transgene flow might occur at a low frequency (<0.8 %) even if the nontransgenic wheat was located in the proximity to its transgenic counterpart. The strong asymmetric distribution of gene flow and the maximum outcrossing rate were detected in compass sectors following the direction of the dominant wind. The gene flow rate averaged over all wind direction varied in different years from 0.134 to 0.416 %. The dramatic reduction in transgene flow frequencies was observed while increasing the distance between transgenic and non-transgenic plots. The rise of average gene flow due to significant increase of the transgene pollen area was not confirmed statistically. These results predict that the pollen-mediated transgene flow in spring wheat can be maintained at negligible levels while the existence of a short isolation distance in order to prevent contamination of adjacent non-GM wheat.
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