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

Abstract

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. F1 hybrid plants were male sterile and morphologically intermediate between the two parents. Cytological analysis of the hybrid plants revealed 10II + 8I as the predominant meiotic configuration with the mean bivalent frequency of 8.83. A maximum of 13II were observed in 8.24% of the pollen mother cells (PMCs). 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.