Assessment of transgene escape from Brassica rapa (B. campestris) into B. nigra or Sinapis arvensis

The possibility of gene transfer between Brassica rapa and the two weedy species B. nigra and Sinapis arvensis was evaluated with the special concern on transgene escape from B. rapa to these two weedy species. B. rapa cultivar Tobin was reciprocally crossed to five and four strains of B. nigra and S. arvensis, respectively, using controlled cross. A single interspecific hybrid was obtained from the cross B. rapa×B. nigra, but no other cross was successful. The fertility of this hybrid on open pollination, selfing and backcrosses was investigated. The data of the present study and the information available to date indicate that gene transfer between B. rapa and B. nigra is possible. The chance of transgene escape from B. rapa to B. nigra depends essentially on whether natural cross can occur between these two species. Gene transfer between B. rapa and S. arvensis is at the most difficult, whereas trans-gene escape directly from B. rapa to S. arvensis appears very unlikely.