Allo‐genome‐induced chromosomal abnormalities of progeny reduces transgene flow risk from glufosinate‐resistant Brassica napus to wild Brassica juncea

BACKGROUND Herbicide‐resistant (HR) oilseed rape ( Brassica napus , AACC, 2 n = 38) is the potential for transgenes to spread to its wild relative, Brassica juncea (AABB, 2 n = 36). Previous research identified gene silencing in these progenies, observing plants that carried the HR gene PAT but did not express it normally (silenced, or r‐s plants). RESULT We found that r‐s plants exhibited more stable inheritance compared to plants normally expressing PAT (expressed, or r‐e, plants). Chromosome numbers in backcross progenies of r‐s plants were consistently around 2 n = 36. Specifically, r‐s plants self‐pollinated by r‐e plants also showed chromosome numbers concentrated around 2 n = 36, whereas in the r‐e plants self‐pollinated by r‐e plants displayed numbers concentrated around 2 n = 37. The meiotic indices of r‐s plants exceeded 90%, further indicating their superior genetic stability compared with r‐e plants. Despite these differences in genetic stability, r‐s plants and r‐e plants showed similar fitness. As the number of self‐pollinated generations increased, the fitness of succeeding progeny gradually approached that of wild B. juncea . CONCLUSION Integrating the transgene onto the C‐chromosome, which exhibits low genetic stability, holds significant promise for reducing the gene flow risk associated with HR crops.