Sequence comparison of two codominant RAPD markers in Brassica nigra: deletions, substitutions and microsatellites.

Two RAPD fragments segregating codominantly were investigated in a F2 population of Brassica nigra. Southern hybridization of these DNA fragments to genomic B. nigra DNA digested with several endonucleases revealed similar restriction profiles. Sequencing of the two fragments disclosed 93% homology. The differences were due mainly to an internal 41 nucleotide deletion in one of the fragments. Minor deletions of one to three bases, including a microsatellite of CTT motif were also observed. In addition, base substitutions, mostly transitions were detected. These relatively small differences suggested that the two RAPD products were indeed different versions of the same sequence. The larger fragment of 1154 bp was denominated A05(1) whereas the shorter one, denominated A05(2), had 1116 bp.