Do Low‐Growing Gap Crop Types Affect Pollen‐Mediated Gene Flow in Maize?

Abstract

ABSTRACTOne of the most accepted and adopted measures to assure coexistence of genetically modified (GM) maize (Zea mays L.) and conventional or organic maize is an isolation distance between GM and non‐GM fields. If crop types used as “gap crops” differ in their effect on pollen‐mediated gene flow this might have implications for the development of coexistence measures. Therefore, in a 3‐yr study, the effect of a 25 m wide strip of barley (Hordeum vulgare L.) stubble and clover‐grass (Trifolium pratense L. and Lolium spp.) as a gap crop on pollen‐mediated gene flow in maize was investigated at two sites in northern Germany. It was hypothesized that different thermal conditions above the dry (barley stubble) and the wet (clover‐grass) gap crop may cause differences in pollen‐mediated gene flow into the adjacent recipient fields. Due to a ban on GM‐maize cultivation in Germany, kernel color was used as a phenotypic marker to assess gene flow. Outcrossing was mainly concentrated to the downwind areas of the recipient fields with a pronounced edge effect. The application of a general linear mixed effect model showed that there was no significant effect of the gap crop type on the amount of pollen‐mediated gene flow. It is concluded that the crop type planted between GM and non‐GM maize has no major importance for the development of coexistence measures.