Transgene introgression from Brassica napus to different varieties of Brassica juncea

Transgene introgression from transgenic rapeseed (Brassica napus) to different varieties of B.juncea was assessed in this study. Crossability between a transgenic rapeseed line Z7B10 (pollen donor) and 80 cultivars of 16 B.juncea varieties (including two wild accessions) was estimated by artificial pollination in a greenhouse. As a result, interspecific crossability between the transgenic Z7B10 line and the 80 B.juncea cultivars varied considerably, with seeds per flower from 0.00-10.67. Seed germination rates of the interspecific F-1 hybrids ranged from 49.0%-89.3%. The estimated frequencies of natural gene flow from the transgenic Z7B10 line to 10 B.juncea cultivars with different uses in the experiment field varied from 0.08% to 0.93%. The natural F-1 hybrids were highly sterile, with seeds per silique ranging from 0.27 to 1.03. In addition, seeds per flower of hybrid descendants varied from 0.02 to 0.22 when F-1 hybrids were self-pollinated, and those ranged from 0.03 to 0.30 when F-1 hybrids were backcrossed with their corresponding B.juncea parents. Results of this study suggest a low level of transgene introgression from transgenic rapeseed to different B.juncea varieties, which provides a sound scientific basis for the safety management of coexisting transgenic B.napus and B.juncea varieties in China.