RFLP MAPPING OF BRASSICA-NAPUS USING DOUBLED HAPLOID LINES

The combined use of doubled haploid lines and molecular markers can pr ovide new genetic information for use in breeding programs. An F-1-der ived doubled haploid (DH) population of Brassica napus obtained from a cross between an annual canola cultivar ('Stellar') and a biennial ra peseed ('Major') was used to construct a linkage map of 132 restrictio n fragment length polymorphism loci. The marker loci were arranged int o 22 linkage groups and six pairs of linked loci covering 1016 cM. The DH map was compared to a partial map constructed with a common set of markers for an F, population derived from the same F-1 plant, and the overall maps were not significantly different. Comparisons of maps in Brassica species suggest that less recombination occurs in B. napus ( n = 19) than expected from the combined map distances of the two hypot hesized diploid progenitors, B. oleracea (n = 9) and B. rapa (n = 10). A high percentage (32%) of segregating marker loci were duplicated in the DH map, and conserved linkage arrangements of some duplicated loc i indicated possible intergenome homoeology in the amphidiploid or int ragenome duplications from the diploid progenitors. Deviation from Men delian segregation ratios (P<0.05) was observed for 30% of the marker loci in the DH population and for 24% in the F-1 population. Deviation towards each parent occurred at equal frequencies in both populations and marker loci that showed deviation clustered in specific linkage g roups. The DH lines and molecular marker map generated for this study can be used to map loci for agronomic traits segregating in this popul ation.