Simulating the Gene Flow of Genetically Modified Maize in Taiwan

A field experiment was conducted in Taiwan to measure the cross-pollination (CP) rate of maize pollen recipients from pollen sources using phenotypic marker and to determine the isolation dis- tance between the 2 maize varieties. A waxy variety (Black Pearl) with purple kernels simulated the genetically modified (GM) pollen donor, and another waxy variety (White Pearl) with white kernels simulated the non-GM recipient. For the first crop, the total area was approximately1.5 hawith a pollen source and recipient acreage ratio of approximately 1:32. For the second crop, the total area was approximately1.83 hawith a ratio of approximately 1:17.3. The source fields were surrounded by the recipient fields for 2 crop seasons. The results showed that the rate of CP was <0.05% beyond15 mupwind and84.8 mdownwind in all crop seasons. The CP rate was below 5% at a distance of10min the downwind direction. A sample with 0.24% CP was recorded at107.3 mdownwind; however, the CP rate was 0% at68 mupwind. Three empirical models were used, that is, exponential, log/log and log/log, and a simplified Gaussian Plume model, to examine the relationship between the CP rates and the source-field distances. All of the models were appropriate for predicting CP rates, and the Gaussian Plume model performed better compared to the empirical models. The results show that it is possible to control CP from foreign pollen by using an appropriate isolation distance.