U.S. Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, Western Ecology Division, 200 SW 35th Street, Corvallis, Oregon 97333, USA.
Ecol Appl. 2011 Mar;21(2):525-38. doi: 10.1890/09-2366.1.
We constructed a mixed-species community designed to simulate roadside and field edge plant communities and exposed it to glyphosate drift in order to test three hypotheses: (1) higher fitness in transgenic Brassica carrying the CP4 EPSPS transgene that confers resistance to glyphosate will result in significant changes in the plant community relative to control communities; (2) given repeated years of glyphosate drift selective pressure, the increased fitness of the transgenic Brassica with CP4 EPSPS will contribute to an increase in the proportion of transgenic progeny produced in plant communities; and (3) the increased fitness of Brassica carrying the CP4 EPSPS transgene will contribute to decreased levels of mycorrhizal infection and biomass in a host species (Trifolium incarnatum). Due to regulatory constraints that prevented the use of outdoor plots for our studies, in 2005 we established multispecies communities in five large cylindrical outdoor sunlit mesocosms (plastic greenhouses) designed for pollen confinement. Three of the community members were sexually compatible Brassica spp.: transgenic glyphosate-resistant canola (B. napus) cultivar (cv.) RaideRR, glyphosate-sensitive non-transgenic B. napus cv. Sponsor, and a weedy B. rapa (GRIN Accession 21735). Additional plant community members were the broadly distributed annual weeds Digitaria sanguinalis, Panicum capillare, and Lapsana communis. Once annually in 2006 and 2007, two mesocosms were sprayed with glyphosate at 10% of the field application rate to simulate glyphosate drift as a selective pressure. After two years, changes were observed in community composition, plant density, and biomass in both control and treatment mesocosms. In control mesocosms, the weed D. sanguinalis (crabgrass) began to dominate. In glyphosate drift-treated mesocosms, Brassica remained the dominant genus and the incidence of the CP4 EPSPS transgene increased in the community. Shoot biomass and mycorrhizal infection in Trifolium incarnatum planted in 2008 were significantly lower in mesocosms that had received glyphosate drift treatments. Our results suggest that, over time, glyphosate drift can contribute to persistence of Brassica that express the CP4 EPSPS transgene and that increased representation of Brassica (a non-mycorrhizal host) within plant communities may indirectly negatively impact beneficial ecosystem services associated with arbuscular mycorrhiza.
我们构建了一个混合物种群落，旨在模拟路边和田间边缘植物群落，并使其暴露于草甘膦飘移中，以检验三个假设：（1）携带 CP4 EPSPS 转基因赋予抗草甘膦的转基因芸薹具有更高的适应性，这将导致相对于对照群落的植物群落发生显著变化；（2）鉴于多年来草甘膦飘移的选择压力，具有 CP4 EPSPS 的转基因芸薹的适应性增加将导致植物群落中产生的转基因后代的比例增加；（3）携带 CP4 EPSPS 转基因的芸薹的适应性增加将导致宿主物种（三叶草属）的菌根感染和生物量水平降低。由于监管限制，我们的研究无法在户外进行实地试验，因此，2005 年我们在五个大型圆柱形户外阳光充足的中型生物群落（塑料温室）中建立了多物种群落，这些生物群落是为了限制花粉而设计的。三个群落成员是有性繁殖的芸薹属植物：抗草甘膦的转基因油菜（B. napus）品种（cv.）RaideRR、对草甘膦敏感的非转基因 B. napus cv. 赞助者和一种杂草芸薹（GRIN 访问号 21735）。其他植物群落成员是广泛分布的一年生杂草狗尾草、狗尾草和雀麦。2006 年和 2007 年，每年一次，将两个中型生物群落用草甘膦喷洒 10%田间用量，模拟草甘膦飘移作为选择压力。两年后，在对照和处理中型生物群落中观察到群落组成、植物密度和生物量的变化。在对照中型生物群落中，杂草狗尾草（稗草）开始占主导地位。在接受草甘膦飘移处理的中型生物群落中，芸薹属仍然是主要的属，群落中 CP4 EPSPS 转基因的发生率增加。2008 年种植的三叶草属生物量和菌根感染在接受草甘膦飘移处理的中型生物群落中显著降低。我们的结果表明，随着时间的推移，草甘膦飘移可能有助于表达 CP4 EPSPS 转基因的芸薹属的持续存在，并且植物群落中芸薹属（非菌根宿主）的代表性增加可能会间接对与丛枝菌根相关的有益生态系统服务产生负面影响。
