Genomic affinities between Brassica napus and Raphanu s raphanistrum as revealed by meiotic GISH

An intergeneric hybrid between Brassica napus ( AC , n = 19) and Raphanus raphanistrum (Rr, n = 9) was developed using the sequential ovary–ovule culture. Morphological, molecular, cytological studies and fluorescent genomic in situ hybridization were conducted to establish the hybridity and genomic relatedness. F 1 hybrid plants were male sterile and morphologically intermediate between the two parents. Cytological analysis of the hybrid plants revealed 10 II  + 8I as the predominant meiotic configuration with the mean bivalent frequency of 8.83. A maximum of 13 II were observed in 8.24% of the pollen mother cells ( PMC s). GISH studies facilitated the identification of two allopairs, confirming homoeologous pairing between A/C and Rr genomes. This may have significant implications in terms of transgene flow and possible introgression into R .  raphanistrum , which is a common canola weed in Canada and Australia. The intergeneric hybrid B .  napus  ×  R .  raphanistrum so produced also has the potential to be used as a bridging species for the transfer of desirable genes to amphiploid crop Brassica species carrying A/C genomes.