Genetic variation exists in <i>Raphanus</i> that could be of use to <i>Brassica</i> breeders. Of particular interest is the Ogura system of cytoplasmic male sterility (CMS) which has been worked on extensively in a <i>Brassica napus</i> background. Problems have been experienced in <i>B. napus</i>restorer lines due to the inheritance of a large segment of <i>Raphanus</i> chromosome containing the fertility restoring locus. This restorer introgression is located on the <i>Brassica</i> C genome making it only of use for <i>B. napus</i> and not for <i>B. rapa</i> or <i>B. juncea</i>. This thesis describes the development of the materials necessary for the introgression into the <i>Brassica</i> A genome of a defined segment of <i>Raphanus</i> chromosome containing a restorer locus. Defined genetic stocks of <i>Raphanus</i> were developed that contained specific loci controlling restoration of Ogura CMS. This material was used to develop populations segregating for specific restorer loci. Extensive RFLP maps of three <i>Raphanus</i> populations were developed and aligned, resulting in a robust consensus map of the entire <i>Raphanus</i> genome. Three restorer loci were accurately mapped on three separate linkage groups. The segment of <i>Raphanus</i> that is implicated in the restoration of Ogura CMS in a <i>B. napus</i> restorer line developed by INRA was identified and it did not correspond to any of the regions containing the three mapped restorer loci, suggesting the presence of more restorer loci in <i>Raphanus</i>. Comparative mapping between the <i>Raphanus</i> genome map and previously generated <i>Brassica</i> A genome RFLP maps demonstrated large regions of collinearity between segments of chromosomes of the two species. Preliminary examination of the two genome maps suggest they contain essentially the same overall genetic content but with large segments of the genomes rearranged with respect to each other. Likely sites of <i>Raphanus</i> restorer introgression into the <i>Brassica</i> A genome were predicted. Trigenomic tetraploids were developed in which pairing and recombination between homoeologous segments of <i>Raphanus</i> and <i>Brassica</i> A chromosomes should result. Progeny of these individuals will allow an assessment of the pattern and extent of recombination that occurs between the chromosomes of the <i>Raphanus</i> and <i>Brassica</i> A genomes and should lead to the development of 'B. napus' lines carrying Ogura CMS restorer alleles from <i>Raphanus</i>.

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