Surveying of pollen-mediated crop-to-crop gene flow from a wheat field trial as a biosafety measure

Abstract

Outcrosses from genetically modified (GM) to conventional crops by pollen-mediated gene flow (PMGF) are a concern when growing GM crops close to non-GM fields. This also applies to the experimental releases of GM plants in field trials. Therefore, biosafety measures such as isolation distances and surveying of PMGF are required by the regulatory authorities in Switzerland. For two and three years, respectively, we monitored crop-to-crop PMGF from GM wheat field trials in two locations in Switzerland. The pollen donors were two GM spring wheat lines with enhanced fungal resistance and a herbicide tolerance as a selection marker. Seeds from the experimental plots were sampled to test the detection method for outcrosses. Two outcrosses were found adjacent to a transgenic plot within the experimental area. For the survey of PMGF, pollen receptor plots of the conventional wheat variety Frisal used for transformation were planted in the border crop and around the experimental field up to a distance of 200 m. Although the environmental conditions were favorable and the donor and receptor plots flowered at the same time, only three outcrosses were found in approximately 185,000 tested seedlings from seeds collected outside the experimental area. All three hybrids were found in the border crop surrounding the experimental area, but none outside the field. We conclude that a pollen barrier (border crop) and an additional isolation distance of 5 m is a sufficient measure to reduce PMGF from a GM wheat field trial to cleistogamous varieties in commercial fields below a level that can be detected.

Assessment of the pollen-mediated transgene flow from the plants of herbicide resistant wheat to conventional wheat (Triticum aestivum L.)

“…3) and phenotypic data (Table 3) did not reveal any escapes among the seedlings survived after the herbicide treatment. Those data showed that the method of screening for herbicide-resistant hybrids applied in the present study was much more reliable than those used in the previous experiments (Messeguer et al 2004;Gatford et al 2006;Foetzki et al 2012).…”

“…Gatford et al (2006) reported only one transgenic hybrid out of 58 seedlings that survived the spraying with 0,3 % Basta (15 mg/L PPT). The most of 900 survived wheat seedling found by Foetzki et al (2012) during several years of field trials by application of the similar herbicide concentration (10 mg/L PPT) were also false-positive. Messeguer et al (2004) reported the same problem of transgenic hybrids identification among herbicide resistant seedlings in rice transgene flow experiment.…”

“…On the other hand Gatford et al (2006) reported extremely low transgene flow frequency from 0.0037 to 0.012 % in adjacent field plots. Despite the previous observation that single outcrosses could be found at considerable distance from the pollen donor, Foetzki et al (2012) found only a limited number of outcrosses within the border crop surrounded the GM wheat plot, however the experimental field was set up at a distance of 200 m.…”

“…In 1996-1998 transgenic wheat plants contained bar gene conferring the resistance to glufosinate-based herbicides were grown in South Australia and Australian Capital Territory (Gatford et al 2006). Several field trials involved transgenic wheat lines expressed two pathogenesis-related genes (chi, glu) and herbicide resistance gene (bar) were planted in Switzerland in 2008-2010(Riebien et al 2011Foetzki et al 2012). In cereal biotechnology bar (pat) gene conferring the resistance to phosphinotricin (PPT), the active ingredient of glufosinate ammonium based commercial herbicides, is commonly used for transgenic plants generation (Jones and Sparks 2009).…”

“…GM wheat plants expressing bar gene successfully survive the spraying with a high herbicide concentration up to 100 mg PPT/L (Cannell et al 1999;Barro et al 2002;Becker et al 2004). Generally the same level of herbicide tolerance exists between homozygous and heterozygous T 1 -T n transgenic wheat progenies (Miroshnichenko et al 2007a;Foetzki et al 2012).…”