Hybridizations among Brassica napus, B. rapa and B. juncea and their two weedy relatives B. nigra and Sinapis arvensis under open pollination conditions in the field

The rate of natural crosses occurring among the cultivated Brassica species B. napus, B. rapa, and B. juncea and their two weedy relatives B. nigra and Sinapis arvensis was studied in co‐cultivation experiments under field conditions in Saskatchewan, Canada, with special reference to evaluation of the possibility of transgene escape from the cultivated to the weedy species. Natural crosses occurred among B. napus, B. rapa, and B. juncea, indicating that hybridizations among these three species do occur under field conditions. On the other hand, no natural crosses occurred between the cultivated species and B. nigra or S. arvensis. It is concluded that the crosses between the cultivated and weedy species are practically impossible under field conditions in Saskatchewan, and that the escape of transgenes from transgenic cultivars of B. napus, B. rapa and B. juncea into B. nigra and S. arvensis is basically zero in this region.