Coexistence in Maize: Effect of the Genetically Modified Maize Field Depth on Pollen-mediated Gene Flow

Although it is generally accepted that field depth of the recipient non–genetically modified (non-GM) neighboring maize (Zea mays L.) field is significantly affecting pollen-mediated gene flow, information about the influence of GM donor field depth is extremely scarce. Therefore, we investigated the effect of 75-m compared with 150-m donor field depth. In 2007 and 2008, one field experiment each was established in northern Germany at Mariensee. In both GM field depth variants, the distance between GM and non-GM maize field was 25 m. Sizes of non-GM maize fields were generally 1.5 ha, whereas two GM field sizes (1.5 and 3.0 ha) were compared in a field arrangement side-by-side oriented to favor pollen-mediated gene fl ow from GM to non-GM field. The GM percentages of individual samples taken at recipient fi eld depths between 0 and 60 m were quantified by realtime polymerase chain reaction. In both years, no difference in pollen-mediated gene fl ow in dependence on the two compared donor field depths was observed. Calculated GM contents of the total non-GM fields harvests were 1.4% (75 m) and 1.5% (150 m) in 2007 as well as 1.0% (both 75 and 150 m) in 2008. In consequence, maize pollen-mediated gene fl ow seems not to be considerably affected by GM field depth if fields are at least 75 m deep.