Analysis of intergeneric sexual hybridization between transgenic Brassica oleracea and Sinapis alba

Sinapis alba possesses a number of desirable traits that can be employed to broaden genetic variability in Brassica oleracea or B. napus. Using transgenic B. oleracea (CC, 2n = 18) as paternal plants and non-transgenic S. alba (SS, 2n = 24) as maternal plants, 11 hybrid plants were successfully obtained by using a combination of ovary culture and embryo rescue, while 2 seedlings of the reciprocal cross were generated but lost during the propagation. The hybridity of these plants was confirmed by flower color and other agronomic characteristics, chromosome counting, and pollen viability. Most of the intergeneric F-1 plants showed only one set each of S and C chromosome (SC, 2n = 21) and were male sterile, while a few plants were semi-fertile and had one set of S chromosomes but two sets of C chromosomes (CCS, 2n = 30). PCR, genomic Southern blotting and qRT-PCR for bar gene revealed that among the F1 hybrid plants only 9.1% was bar positive and could be forwarded to F-2 and F-3 generation. The majority of F3 plants obtained sufficient resistance to Alternaria brassicae. Thus, the generation of disease (A. brassicae) and herbicide (Bastar) resistant intergeneric hybrids was of importance for breeding program. The existence of bar gene in these intermediate materials will facilitate the identification of hybridity and transfer of S. alba traits into target genetic background.