Environ. Biosafety Res.
Volume 3, Number 2, April-June 2004
|Page(s)||73 - 81|
|Published online||15 September 2004|
Hybridization and backcrossing between transgenic oilseed rape and two related weed species under field conditions
Crop Science Department, North Carolina State University, Raleigh, NC, USA
2 Department of Plant Sciences, University of Tennessee, Knoxville, TN, USA
3 National Water Research Institute, Environment Canada, Saskatoon, SK, Canada
4 Agriculture and Agri-food Canada, Ottawa, Ontario, Canada
5 Georgia Experiment Station, University of Georgia, Griffin, GA, USA
Corresponding author: email@example.com
Determining the frequency of crop-wild transgene flow under field conditions is a necessity for the development of regulatory strategies to manage transgenic hybrids. Gene flow of green fluorescent protein (GFP) and Bacillus thuringiensis (Bt) transgenes was quantified in three field experiments using eleven independent transformed Brassica napus L. lines and the wild relatives, B. rapa L. and Raphanus raphanistrum L. Under a high crop to wild relative ratio (600:1), hybridization frequency with B. rapa differed among the individual transformed B. napus lines (ranging from ca. 4% to 22%), however, this difference could be caused by the insertion events or other factors, e.g., differences in the hybridization frequencies among the B. rapa plants. The average hybridization frequency over all transformed lines was close to 10%. No hybridization with R. raphanistrum was detected. Under a lower crop to wild relative ratio (180:1), hybridization frequency with B. rapa was consistent among the transformed B. napus lines at ca. 2%. Interspecific hybridization was higher when B. rapa occurred within the B. napus plot (ca. 37.2%) compared with plot margins (ca. 5.2%). No significant differences were detected among marginal plants grown at 1, 2, and 3 m from the field plot. Transgene backcrossing frequency between B. rapa and transgenic hybrids was determined in two field experiments in which the wild relative to transgenic hybrid ratio was 5–15 plants of B. rapa to 1 transgenic hybrid. As expected, ca. 50% of the seeds produced were transgenic backcrosses when the transgenic hybrid plants served as the maternal parent. When B. rapa plants served as the maternal parent, transgene backcrossing frequencies were 0.088% and 0.060%. Results show that transgene flow from many independent transformed lines of B. napus to B. rapa can occur under a range of field conditions, and that transgenic hybrids have a high potential to produce transgenic seeds in backcrosses.
Key words: transgenic oilseed rape / canola / Brassica napus / GFP / interspecific hybridization / Brassica rapa / Bacillus thuringiensis / introgression / Raphanus raphanistrum
© ISBR, EDP Sciences, 2004