Interspecific hybridization between Brassica napus L . (2n = 38, alaicici) and B. oleracea var. capitata L . (2x-and 4x-cabbage ; 2n = 2x =18, cc and 2n = 4x = 36, cccc) was carried out for the purpose of transferring clubroot disease resistance from the amphidiploid species to cabbage . Nineteen hybrids with three different chromosome levels (2n = 28, a,cic ; 2n = 37, aiclcc and 2n = 55, aicicccc) were obtained . The F, plants were mostly intermediate between the two parents but as

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Meiosis in 14 interspecific FI hybrids with three chromosomal levels (triploid, tetraploid, hexaploid: 2n = 28, 37 and 55) between Brassica napus L. and 2x and 4x cabbage (B. oleracea var. capitata L.) was studied. The oleracea genome from B. napus maintained close homology with the c genome of cabbage while the campestris genome of B. napus showed partial homology with the c genome contained in the hybrids. Genotypic influence on chromosome pairing was indicated. Structural chromosome differences and spontaneous chromosome breakage and reunion were suggested as causes for the abnormalities which related to the unbalance of the genotypes. The divergence of the genomes of B. napus and B. oleracea and the need for the qualification of the term secondary association were discussed.

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