Pollen Mediated Gene Flow in GM Crops: the Use of Herbicides as Markers for Detection. the Case of Wheat

Abstract

ISAAA has estimated that genetically modified (GM) crops, mainly soybean, maize, cotton and canola, are cultivated worldwide in an area that has increased from 1.7 million hectares in 1996 to 134 million hectares in 2009, of which more than 80% have an herbicide-tolerant trait (ISAAA 2010). This work reviews the agricultural and environmental concerns about the likelihood for gene flow from GM wheat (Triticum aestivum L.). Wheat is the world’s most important crop species, grown on over 210 million hectares. There are no GM wheat varieties commercially available but transgenic wheat varieties are being successfully developed and field-tested. That makes wheat in the pipeline of genetically engineered crops to be cultivated. Although wheat is predominantly a self-pollinating crop, pollen from one plant can travel via wind to other receptive plant, being outcrossing between wheat cultivars possible at variable rates. Coexistence problems in wheat could thus arise if no measures are taken before releasing and marketing any transgenic cultivar, as has occurred with other GM crops such as oilseed rape or maize, where measures were implemented after commercial transgenic introduction. Besides this, wild Aegilops species like Ae. geniculata Roth., Ae. cylindrica Host., Ae. biuncialis Vis. or Ae. triuncialis L. can form natural interspecific hybrids with wheat where they grow in sympatry. These natural hybrids are highly sterile, although seeds may occasionally be found. Data presented aim to contribute to the determination of the extent of this phenomena. These data are necessary to manage the possible impact of transgenic wheat hybrids before the transgenic crop can be grown under field conditions. Herbicide-tolerant wheat parental varieties can be used to obtain resistant progeny detectable by herbicide selection, providing a high approach to the potential occurrence of intra and interspecific pollen mediated gene flow.