| Summary: | 碩士 === 國立中興大學 === 農藝學系所 === 100 === There is an increasing concern about the coexistence between GM (genetically modified) and non-GM (non-genetically modified) crops. Maize (Zea mays L.) is a cross-pollinated crop, so pollen dispersion is an important way of gene flow (pollen-mediated gene flow, PMGF) in maize. Cross-pollination can occur between non-GM maize planted in open environments next to GM maize field. Therefore, the combination of isolation distance and border rows could keep the gene flow less than labeling threshold.
The field experiments were conducted at Taiwan (R.O.C) Agricultural Research Institute in Wufeng District, Taichung City in 2009 and 2010. There were two crop seasons in each year. In our study, the Black Pearl (source plot: purple kernel) was planted in the center while the White Pearl (receptor plot: white kernel) was planted in the surroundings in 2009. In 2010, using four varieties (Honey 236, Black Pearl, Tainung 1, Tainung 4) to simulate GM maize as pollen source and using Snow Jean to simulate non-GM maize as receptor. Our objectives was to confirm the isolation of maize from gene flow by distance (2009 experiment) and time (2010 experiment).
Overall, when the isolation distance was 18.75 m (pollen source and pollen receptor synchrony in flowering times), the mean of outcrossing rate can decrease to 0.64%. We provide a security distance between GM and non-GM fields of about 20 m should be sufficient to maintain the adventitious presence of GM maize from gene flow below the 0.9% threshold (labelling threshold in the European Union). Increasing temporal separation reduced the distance required to achieve gene flow isolation. Outcrossing rate was <0.9% at 0.75m when 1 week of temporal separation was used. In previous researches, atmospheric dispersion model was used to simulate the pollen spread of maize. However, in this study, the simplified Gaussian plume model was fitted well (R2=0.845) for the outcrossing rate data.
In our study, a model based on Gaussian plume model was used to calculate the pollen concentration and pollution rate of non-GM maize by GM maize in down wind. The modified model of Gaussian plume model can simulate the outcrossing rate of serious cases by simple parameters (data from 2009-1 and 2009-2), which also could provide an useful tool to control coexistence of GM and non-GM maize in the future.
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