1. ¹Botanical Institute, Øster Farimagsgade 2D, DK-1353 Copenhagen K, Denmark
2. ²Department of Evolutionary Biology, University of Copenhagen, Zoological Institute, Universitetsparken 15, DK-2100 Copenhagen Ø, Denmark
3. ³Risoe National Laboratory, Plant Research Department, Frederiksborgvej 399, PO Box 49, DK-4000 Roskilde, Denmark

Correspondence: RB Jørgensen, Risoe National Laboratory, Plant Research Department, Frederiksborgvej 399, PO Box 49, DK-4000 Roskilde, Denmark. E-mail: rikke.bagger.jorgensen@risoe.dk

Received 10 May 2003; Accepted 15 April 2003.

Abstract

We have earlier shown extensive introgression between oilseed rape (Brassica napus) and B. rapa in a weedy population using AFLP markers specific for the nuclear genomes. In order to describe the progress of this introgression, we examined 117 offspring from 12 maternal plants from the introgressed population with the same AFLP-markers; AFLP data were supported by chromosome counting. We also analysed the offspring with a species-specific chloroplast marker and finally evaluated the reproductive system in selected maternal plants. Our results indicated a high outcrossing rate of the introgressed maternal plants. It seemed that B. rapa most often functioned as the maternal plant in the introgression process and that the amount of oilseed rape DNA was highly diminished in the offspring compared to their introgressed maternal plants. However, our analysis of plants from the weedy population indicated that introgression can lead to both (1) exchange of chloroplast DNA between species producing B. rapa-like plants with B. napus chloroplasts and (2) incorporation of B. napus C-genome DNA into the B. rapa genome. Therefore, we question whether it can be regarded as containment to position transgenes in the chloroplast or in specific parts of the nuclear genome of B. napus.