Evidence for landscape-level, pollen-mediated gene flow from genetically modified creeping bentgrass with CP4 EPSPS as a marker

Abstract

Sampling methods and results of a gene flow study are described that will be of interest to plant scientists, evolutionary biologists, ecologists, and stakeholders assessing the environmental safety of transgenic crops. This study documents gene flow on a landscape level from creeping bentgrass (Agrostis stolonifera L.), one of the first wind-pollinated, perennial, and highly outcrossing transgenic crops being developed for commercial use. Most of the gene flow occurred within 2 km in the direction of prevailing winds. The maximal gene flow distances observed were 21 km and 14 km in sentinel and resident plants, respectively, that were located in primarily nonagronomic habitats. The selectable marker used in these studies was the CP4 EPSPS gene derived from Agrobacterium spp. strain CP4 that encodes 5-enol-pyruvylshikimate-3-phosphate synthase and confers resistance to glyphosate herbicide. Evidence for gene flow to 75 of 138 sentinel plants of A. stolonifera and to 29 of 69 resident Agrostis plants was based on seedling progeny survival after spraying with glyphosate in greenhouse assays and positive TraitChek, PCR, and sequencing results. Additional studies are needed to determine whether introgression will occur and whether it will affect the ecological fitness of progeny or the structure of plant communities in which transgenic progeny may become established.

Reconstitution of the enzyme AroA and its glyphosate tolerance by fragment complementation

“…For instance, when the intact herbicide tolerance aroA gene was used as a marker, evidence has been obtained for pollen-mediated gene flow from a transgenic A. stolonifera to its resident Agrostis spp. located at distances up to 14 km [22]. It has been proposed that transgene flow would be prevented or limited by dividing the gene into two inactive fragments and placing one fragment in the nucleus and the other in the chloroplast [15,23].…”

Tracing field hybridization in Ryegrass species using microsatellite and morphological markers

“…Significant pollen flow from Lolium perenne plots has been recorded by Giddings et al (1997), and developed into a landscape gene flow model by Giddings (2000). While this latter model did not incorporate the measurement of actual gene flow patterns as evidenced by pollination/hybridization events, this more precise kind of data has been generated in a landscape-level experiment on gene flow from a herbicide tolerant Agrostis stolonifera cultivar plot in the United States (Watrud et al, 2004). All three studies point to the extensive potential for gene flow from GM cultivar plots to surrounding receptive populations.…”

Pollen Sterility—A Promising Approach to Gene Confinement and Breeding for Genetically Modified Bioenergy Crops

“…This is because many of the traits that are beneficial to the commercial production of perennial plants potentially impact plant fitness and the ability of the plants to compete for resources [6,8]. Confinement of transgenes is thus an obvious regulatory and biosafety objective for the release and commercialization of transgenic bioenergy feedstocks [9,10] as the development of fertile reproductive structures in genetically modified perennial plants will result in undesirable gene flow to non-transgenic and wild plants [9,[11][12][13][14][15][16]. Hence, the control of gene flow is widely understood as a major obstacle to genetic improvement of perennial plants.…”