Effect of transgene introgression site on gene migration from transgenic b. napus to b. rapa [abstract]

Abstract

There is a growing concern of the possible transgenic introgression from GM plants into agricultural weeds, which has stimulated research in the process of crop to weed gene flow. Crop to weed gene flow often involves the hybridization of a polyploidy crop to a diploid weed. An example is canola (Brassica napus with AACC genomes) which can hybridize with B. rapa (AA) to produce fertile triploid F1 hybrids (ACC) in the wild. It is hypothesized that there are "safe sites" on the C genome because the C genome is likely to be lost from wild populations after a few generations of repeated backcrossing with B. rapa. However, there is homoeology between the A and C genomes of Brassica, which allows potential recombination between genomes and the movement of transgenes from the C to A genomes by chromosomal rearrangements. Recent advances in molecular markers and fluorescent in situ hybridization (FISH) now allow us to observe the frequency of homoeologous exchanges following hybridization. Our research is focused on finding safe sites within the B. napus genome which are least likely to be transferred into B. napus and B. rapa hybrids and their progeny. To test this, we have crossed a transgenic B. napus with a natural B. rapa three times to make three different F1events. Then we backcrossed each of the three F1 three times with B. rapa. We are measuring the germination rate of each generation and using transgene specific PCR primers to check the presence or absence of the transgene in hybrids. We will also use molecular cytogenetics (FISH) to count chromosome numbers. This study will help determine the possibilities of a "safe" site in B. napus and offer insight in the mechanisms of crop to weed transgene introgression in B. napus x B. rapa hybrids.