Microsatellite markers for genome analysis in Brassica. II. Assignment of rapeseed microsatellites to the A and C genomes and genetic mapping in Brassica oleracea L.

Microsatellites are highly polymorphic and efficient markers for the analys is of plant genomes. Primer specificity, however, may restrict the applicab ility of these markers even between closely related species for comparative mapping studies. We have demonstrated that the majority of microsatellites identified in oilseed rape (Brassica napus L; AC genome) correspond to loc i which can be easily assigned to the A and C progenitor genomes. A study w ith 63 primer pairs has shown that 54% detect two loci, one from each genom e, while 25% and 21%, respectively, are either A or C genome-specific. The distribution of rapeseed microsatellites in the C genome was investigated b y genetic mapping in Brassica oleracea L. Ninety two dinucleotide microsate llites were screened for polymorphism in an F, population derived from a cr oss between collard and cauliflower, for which an RFLP map has been constru cted previously. Thirty three primer pairs (35.7%) have yielded either unsp ecific or no PCR products whereas the remaining primer pairs amplified one or more distinct loci. The level of polymorphism found in the mapping popul ation was 49.2%. A total of 29 primer pairs disclosed 34 loci of which 31 a re evenly distributed on 8 of the 9 B. oleracea linkage groups. For the rem aining three markers linkage could not be established. Our results showed t hat microsatellite markers from the composite genome of B. napus can serve as a useful marker system in genetic studies and for plant-breeding objecti ves in B. oleracea.