Karyotype And Identification Of Each Chromosome Of Brassica Carinata And Brassica Juncea

Both Brassica carinata (2n=4x=34, BBCC) and B. juncea (2n=4x=36, AABB) are important oilseeds and economic crops in the genus of Brassica. Compared with the other species, such as B. rapa (AA,2n=20), B. oleracea (CC,2n=18) and B. napus (AACC,2n=38) in Brassica, the karyotype analyses to reliably distinguish each chromosome of B. juncea and B. carinata have not been reported.In this thesis, the distinctive banding pattern for each chromosomes of B. carinata and B. juncea was generated by using rDNA repetitive sequences (45 S rDNA,5S rDNA), centromeric tandem satellite repeats (CentBrl and CentBr2) and subtelomeric repeat sequences pBrSTR as well as B-genome-specific repeat pBNBH35 as probes. A multicolor fluorescence in situ hybridization (FISH) procedure allowing the identification of all the chromosomes of B. carinata and B. juncea was developed by two-step successive hybridizations. At the same time, the karyotypes of four B. carinata accessions from different regions were comparatively studied and we found that the distributions and compositions of the repetitive sequences were conserved among the four accessions of B. carinata.Combined the karyotype analyses described above with the BAC-FISH using eight BACs, which were known their linkage groups from B. rapa, the homoeologous chromosomes between B and C genomes were identified and the relationships between the cytogenetic map and the genetic linkage map were established in B. carinata.Finally, the chromosome behaviors at diakinesis of meiosis cell was analysed. We showed that the genome of B. carinata was relatively stable with most of the homologous chromosomes to form bivalents, and just a few non-homologous chromosomal associations to form monovalent, trivalent and tetravalent.