Environ. Biosafety Res.
Volume 3, Number 1, January-March 2004
|Page(s)||45 - 54|
|Published online||15 March 2004|
Inheritance of GFP-Bt transgenes from Brassica napus in backcrosses with three wild B. rapa accessions
National Water Research Institute, Environment Canada, 11 Innovation Blvd, Saskatoon, Saskatchewan, S7N 3H5, Canada
2 Agriculture and Agri-Food Canada-ECORC, 960 Carling Ave, Ottawa, Ontario, K1A 0C6, Canada
3 Agriculture and Agri-Food Canada-Saskatoon Research Centre, 107 Science Place, Saskatoon, Saskatchewan, S7N 0X2, Canada
4 Dept. of Plant Sciences, 2431 Centre Drive, Ellington Plant Sciences, University of Tennessee, Knoxville, Tennessee 37996-4561, USA
Corresponding author: email@example.com
Transgenes from transgenic oilseed rape, Brassica napus (AACC genome), can introgress into populations of wild B. rapa (AA genome), but little is known about the long-term persistence of transgenes from different transformation events. For example, transgenes that are located on the crop’s C chromosomes may be lost during the process of introgression. We investigated the genetic behavior of transgenes in backcross generations of wild B. rapa after nine GFP (green fluorescent protein)-Bt (Bacillus thuringiensis) B. napus lines, named GT lines, were hybridized with three wild B. rapa accessions, respectively. Each backcross generation involved crosses between hemizygous GT plants and non-GT B. rapa pollen recipients. In some cases, sample sizes were too small to allow the detection of major deviations from Mendelian segregation ratios, but the segregation of GT:non-GT was consistent with an expected ratio of 1:1 in all crosses in the BC1 generation. Starting with the BC2 generation, significantly different genetic behavior of the transgenes was observed among the nine GT B. napus lines. In some lines, the segregation of GT:non-GT showed a ratio of 1:1 in the BC2, BC3, and BC4 generations. However, in other GT B. napus lines the segregation ratio of GT:non-GT significantly deviated from 1:1 in the BC2 and BC3 generations, which had fewer transgenic progeny than expected, but not in the BC4 generation. Most importantly, in two GT B. napus lines the segregation of GT:non-GT did not fit into a ratio of 1:1 in the BC2, BC3 or BC4 generations due to a deficiency of transgenic progeny. For these lines, a strong reduction of transgene introgression was observed in all three B. rapa accessions. These findings imply that the genomic location of transgenes in B. napus may affect the long-term persistence of transgenes in B. rapa after hybridization has occurred.
Key words: transgene / oilseed rape / B. campestris / interspecific hybridization / backcross / introgression / green fluorescent protein (GFP) / Bacillus thuringiensis (Bt)
© ISBR, EDP Sciences, 2004