Loss of C‐genome‐specific markers during transgene introgression from Brassica napus to wild Brassica juncea

Abstract

Transgene flow from engineered Brassica napus to wild weed relatives could potentially have an environmental effect. To evaluate the introgression of transgenic B. napus into wild Brassica juncea, the hybrid F1 and backcross progenies derived from B. juncea (genome constitution AABB) and transgenic B. napus (AACC) crosses were investigated. C‐genome‐specific simple sequence repeat (SSR) markers corresponding to linkage groups N11–N19 in B. napus were screened and used to estimate the marker frequency in hybrid F1 and backcross progenies. C‐genome‐specific markers could be stably detected in hybrid F1 and backcross BC1 plants, but were only rarely found in the BC2–BC5 generations. For example, a specific SSR marker for linkage group N12 segregated in BC2 generation but were completely lost in BC3–BC5, while a specific SSR marker of linkage group N15 segregated in BC1, BC2 and BC3 generations and was absent in more advanced backcrossed generations (BC4 and BC5). The results indicate that a certain gene regions in Brassica napus plants are transmitted at a relatively lower frequency to wild relatives, and more rapidly disappeared in subsequent backcross generations. We propose that a foreign gene or transgene that is integrated in the C‐chromosome of Brassica napus could reduce the risk of introgression in nature.