Intra- and intergenomic relationships in interspecific hybrids between Brassica

Interspecific hybridization plays a crucial role in plant genetics and breeding. The efficiency of interspecific crosses to a considerable extent depends on the genetic relatedness of genomes from parental species. Interspecific hybrids involving Brassica maurorum (2n = 16, MM) and two Brassica crop species, viz B. rapa (2n = 20, AA) and B. napus (2n = 38, AACC), were produced and analyzed for their meiotic chromosome pairings in pollen mother cells (PMCs) by using genomic in situ hybridization (GISH) with the labeled DNA of B. maurorum (MM) as probe. In hybrids B. maurorum x B. rapa (2n = 18, MA), all chromosomes remained unpaired in 28% PMCs, and the maximum of autosyndetic bivalents was two and one among the chromosomes of A and M genomes, with the average per cell being 0.27 and 0.12, respectively. Up to two allosyndetic bivalents between A and M genomes appeared, averagely 0.48 per cell. In hybrids B. maurorum x B. napus (2n = 27, MAC), the maximum of autosyndetic bivalents in M genome was two and the average was 0.11, while the maximum of allosyndetic bivalents between M and A/C genomes was two and the average was 0.78. The 2-7 bivalents formed by A/C-genome chromosomes showed their high homology. The results were compared and discussed with the chromosome pairings in the hybrids of B. maurorum with B. juncea and B. carinata with respect to the genome relationships and the potential for chromosome recombination.