Persistent C genome chromosome regions identified by SSR analysis in backcross progenies between <i>Brassica juncea</i> and <i>B. napus</i>

Abstract

Given that feral transgenic canola (Brassica napus) from spilled seeds has been found outside of farmer’s fields and that B. juncea is distributed worldwide, it is possible that introgression to B. juncea from B. napus has occurred. To investigate such introgression, we characterized the persistence of B. napus C genome chromosome (C-chromosome) regions in backcross progenies by B. napus C-chromosome specific simple sequence repeat (SSR) markers. We produced backcross progenies from B. juncea and F1 hybrid of B. juncea × B. napus to evaluate persistence of C-chromosome region, and screened 83 markers from a set of reported C-chromosome specific SSR markers. Eighty-five percent of the SSR markers were deleted in the BC1 obtained from B. juncea × F1 hybrid, and this BC1 exhibited a plant type like that of B. juncea. Most markers were deleted in BC2 and BC3 plants, with only two markers persisting in the BC3. These results indicate a small possibility of persistence of C-chromosome regions in our backcross progenies. Knowledge about the persistence of B. napus C-chromosome regions in backcross progenies may contribute to shed light on gene introgression.

Possibilities of direct introgression from <i>Brassica napus</i> to <i>B. juncea</i> and indirect introgression from <i>B. napus</i> to related Brassicaceae through <i>B. juncea</i>

“…On the other hand, Di et al (2009) reported that F 1 hybrids from wild B. juncea × GM canola showed higher fertility than that reported previously (Bing et al 1991, 1996, Frello et al 1995, Tsuda et al 2012b). Di et al (2009) also reported that the vigorous vegetative and reproductive growth of wild B. juncea resulted in higher fertility rates of the F 1 hybrids.…”

“…Most of the hybrids had chromosomes and an AABC genome composition (Choudhary and Joshi 1999, Tsuda et al 2012b). Pollen fertility of F 1 ranged from 0 to 35.6% (Choudhary and Joshi 1999, Frello et al 1995, Heenan et al 2007, Liu et al 2010, Sandhu and Gupta 2000, Song and Qiang 2003), with the highest fertility (78%) observed in nine samples of the F 1 hybrid.…”

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

“…The probability of stable introgression events depended on the survival and population growth of hybrid and backcross generations (Pallett et al ). There have been several studies demonstrating the transfer of either Bt (Frello et al , Halfhill et al , Zhu et al , Liu et al , Yang et al ) or herbicide‐resistance transgenes (Guéritaine et al , Tsuda et al ) to backcross generations. However, a low level of transgene introgression from transgenic herbicide‐resistant B. napus to different B. juncea varieties was estimated by artificial pollination (Tang et al ).…”

“…SSR locus 83b1, which used a pair of C‐genome‐specific SSR primers (Szewc‐McFadden et al ), was also employed, although it was unknown on which C‐chromosome it was located. PCR reactions were performed according to Lowe et al () and Tsuda et al (). The annealing temperatures of all primer pairs are listed in Table 2.…”

“…To minimize the potential ecological risk of transgene flow, the insertion of transgenes into chromosome regions of B. napus with a very low probability of transfer to backcross generations with some relatives has been proposed (Metz et al , Lu et al , Tsuda et al ). The amphidiploid Brassica napus (AACC) has evolved through hybridization of two diploids of Brassica oleracea L. (CC) and Brassica campetris/rapa (AA), whereas the amphidiploid B. juncea (AABB) is derived from the hybridization of B. nigra (L.) W. D. J. Koch (BB) with B. rapa subsp.…”