WIDE MAPPING OF A T-DNA INSERTION SITE IN OILSEED RAPE USING BULK SEGREGANT ANALYSIS AND COMPARATIVE MAPPING

Doubled haploid oilseed rape lines segregating for a transgene inducin g herbicide resistance (bar gene) were investigated for the wide mappi ng of the T-DNA insertion site. Bulk segregant analysis using presence /absence and intensity polymorphisms between the bulks, as well as com parative mapping with a linkage group deriving from another cross, led to the identification of 11 random amplified polymorphic DNA (RAPD) m arkers tightly or loosely linked to the bar gene. Ten RAPD loci out of 11 were located on the same side of the bar locus, strongly suggestin g that the T-DNA integrated in a telomeric or subtelomeric position. T he eleventh RAPD marker exhibited a strong segregation distortion, whi ch could be the result of a heteroduplex formation. Comparison of the linkage groups obtained from the two crosses showed different recombin ation rates between markers, possibly reflecting differences in parent al genetic backgrounds. Consequences and potential applications in tra nsgene dispersal safety assessment studies are discussed.