Unexpected Diversity of Feral Genetically Modified Oilseed Rape (Brassica napus L.) Despite a Cultivation and Import Ban in Switzerland

Despite cultivation and seed import bans of genetically modified (GM) oilseed rape (Brassica napus L.), feral GM plants were found growing along railway lines and in port areas at four sites in Switzerland in 2011 and 2012. All GM plants were identified as glyphosate-resistant GM event GT73 (Roundup Ready, Monsanto). The most affected sites were the Rhine port of Basel and the St. Johann freight railway station in Basel. To assess the distribution and intra- and interspecific outcrossing of GM oilseed rape in more detail, we monitored these two sites in 2013. Leaves and seed pods of feral oilseed rape plants, their possible hybridization partners and putative hybrid plants were sampled in monthly intervals and analysed for the presence of transgenes by real-time PCR. Using flow cytometry, we measured DNA contents of cell nuclei to confirm putative hybrids. In total, 2787 plants were sampled. The presence of GT73 oilseed rape could be confirmed at all previously documented sampling locations and was additionally detected at one new sampling location within the Rhine port. Furthermore, we found the glufosinate-resistant GM events MS8xRF3, MS8 and RF3 (all traded as InVigor, Bayer) at five sampling locations in the Rhine port. To our knowledge, this is the first time that feral MS8xRF3, MS8 or RF3 plants were detected in Europe. Real-time PCR analyses of seeds showed outcrossing of GT73 into two non-GM oilseed rape plants, but no outcrossing of transgenes into related wild species was observed. We found no hybrids between oilseed rape and related species. GM plants most frequently occurred at unloading sites for ships, indicating that ship cargo traffic is the main entry pathway for GM oilseed rape. In the future, it will be of major interest to determine the source of GM oilseed rape seeds.

尽管瑞士已针对转基因（GM）甘蓝型油菜（Brassica napus L.，oilseed rape）实施种植与种子进口禁令，但2011至2012年，研究人员在瑞士四个站点的铁路沿线及港口区域发现了野生转基因油菜植株。所有检出的转基因植株均被鉴定为抗草甘膦转基因事件GT73（Roundup Ready，孟山都Monsanto）。受影响最为严重的两个站点分别为巴塞尔莱茵港与巴塞尔圣约翰货运火车站。

为更细致地解析转基因油菜的分布特征与种内、种间异交情况，研究团队于2013年对这两处站点开展了系统性监测。研究人员按月采集野生油菜植株、潜在杂交亲本及疑似杂交植株的叶片与荚果，通过实时PCR（real-time PCR）检测样品中的转基因成分。借助流式细胞术（flow cytometry），研究人员测定了细胞核DNA含量，以验证疑似杂交植株。

本次研究共采集2787株植株样本。在所有此前记录的采样点位均成功检出GT73转基因油菜，且在莱茵港内新增一处检测到该转基因油菜的采样点位。此外，研究团队在莱茵港的五处采样点位中检出了抗草丁膦转基因事件MS8×RF3、MS8及RF3（均以InVigor品牌上市销售，拜耳Bayer）。据我们所知，这是欧洲境内首次报道野生MS8×RF3、MS8或RF3转基因植株。

对种子的实时PCR分析显示，GT73发生了向两株非转基因油菜的异交，但未观测到转基因向相关野生近缘种的异交情况。研究未发现油菜与其近缘物种间的天然杂交植株。转基因植株最常出现在船舶卸货点位，这表明船舶货运是转基因油菜种子进入该区域的主要传播途径。未来，明确转基因油菜种子的初始来源将成为该领域的重要研究方向。