Stability of herbicide resistance and GUS expression in transgenic hybrid poplars (Populus sp.) during four years of field trials and vegetative propagation

摘要

We assessed the stability of transgene expression in 40 transgenic lines (i.e., transformation events) of hybrid poplars during four years of field trials. The population consists of 40 lines of hybrid cottonwood (Populus trichocarpa x P. deltoides) grown at three field sites. All lines were transformed with a binary construct that included two genes conferring resistance to glyphosate (GOX and CP4), a gene encoding resistance to the antibiotic kanamycin (NPTll), and a visible marker gene (GUS). Agrobacterium tumefaciens was used for transformation; callogenesis and organogenesis occurred under kanamycin selection. To test the stability of transgene expression, we began repeated applications of herbicide on all lines shortly after outplanting, and challenged ramets from 40 previously untreated lines during their fourth season of vegetative growth. Here we describe how maintenance of herbicide resistance and GUS expression is indicative of transgene stability, and how we will use growth, leaf morphology, and microsatellites to investigate somaclonal variation. Preliminary data reveal that all lines that were highly resistant in year 1 continued to be highly resistant in year 4.