Isolation of Maize from Pollen‐Mediated Gene Flow by Time and Distance

Abstract

grains, a number greatly in excess of that needed for fertilization (Uribelarrea et al., 2002). However, the pol-Development of improved genetic traits in maize (Zea mays L.) relen of maize is among the largest and heaviest of the quires robust measures to prevent pollen-mediated gene flow (PMGF) grasses, with a diameter of about 90 m. For compariand assure isolation of new traits, whether these traits are the result son, the pollen grains of ragweed (Ambrosia spp.) and of conventional breeding or of modern genetic techniques. Studies were conducted in California and Washington to evaluate the relation-Timothy (Phleum pratense L.) are 20 and 34 m in ship of distance and temporal separation for isolation from PMGF. diameter, respectively (Raynor et al., 1972). Most maize Kernel color was used to detect outcrossing from source plots of 0.4 pollen is dispersed by gravity downward from the tassel, to 1.2 ha in size to receptor plots planted at distances up to 750 m falling in the vicinity of the originating plant. Bateman and planting intervals of up to 3 wk from the pollen source. Outcross- 1947) found pollen deposition at 27 m was Ͻ1% of ing from source to receptor plots was observable to 0.0002% (1 kernel that close to the source plants. Raynor et al. (1972) in ≈500 000 kernels). Increasing temporal separation reduced the disestimated that 98% of maize pollen remains close to tance required to achieve genetic isolation. Outcrossing was Ͻ0.01% the originating plant, and that Ͻ1% would be found at 500 m when source and receptors flowered at the same time, whereas beyond 60 m. Jarosz et al. (2003) estimated that 95% this level of confinement was achieved at 62 m or less when 2 wk of of the pollen produced was deposited within 10 m of temporal separation was used. No outcrossing was detected at 750 m and 2 wk of temporal separation. This is the first practical evaluation M. Qualls, Qualls Ag Labs, Ephrata, WA 98823; S.A. Berberich, Chesterfield, MO 63017. Received 12 Dec. 2003. *Corresponding au-color inside yellow maize fields. The farthest distance thor (Philip.j.eppard@monsanto.com).studied was 50 m from the edge of the source plot, and a low but undefined level of outcrossing was observed

Hybridization between GM soybean (Glycine max(L.) Merr.) and wild soybean (Glycine sojaSieb. et Zucc.) under field conditions in Japan

“…Similar reductions in hybridization rates have been reported for corn, a wind pollinating species (Della Porta et al, 2008;Halsey et al, 2005;Messeguer et al, 2006;Palaudelmas et al, 2008;Rognli et al, 2000). These studies also evaluated the relationship between flowering overlap, distance, and hybridization frequency, and showed that increasing temporal isolation reduced the spatial distance required to achieve lower levels of cross pollination.…”

Implementing isolation perimeters around genetically modified maize fields

“…However, defining the appropriate isolation perimeter width is complicated: various biological, physical, experimental and analytical factors with varying levels of importance play a role in the study of cross-fertilisation in maize (Devos et al, 2005). To take the factors that are relevant for co-existence into account, recent empirical crossfertilisation studies mimic worst-case commercial on-farm situations (Halsey et al, 2005;Della Porta et al, 2006;Goggi et al, 2006;Pla et al, 2006;Weber et al, 2007;Weekes et al, 2007). In Spain, out-crossing studies are even performed in real agricultural situations of co-existence.…”

Evaluating the Performance of Transgenic Corn Producing Bacillus thuringiensis Toxins in South Carolina

“…Plots were planted under biosafety conditions, isolated by at least 500 m from commercial corn plantings, and planted at least 21 d later than recommended; delayed planting avoids cross-pollination with non-GM corn in accordance with government regulations for field tests with GM corn (Halsey et al 2005;LBOGM 2005). Bt corn hybrids used in these tests were Agrisure TM 3000 GT with Cry1Ab and mCry3A proteins that provide resistance to Lepidoptera and Coleoptera, respectively; Agrisure® Viptera TM 3110 with Cry1Ab and Vip3A20 providing resistance to Lepidoptera, and Agrisure® Viptera TM 3111 with proteins Cry1Ab and Vip3Aa20 providing resistance to Lepidoptera and mCry3A to Coleoptera.…”