Genetic analysis of the B-genome chromosomes in the Brassica species

Zahra Navabi
iii Dedicated to my beloved parents Hossein and Pari and to my ever supportive brothers Kamran and Kourosh iv Abstract The family Brassicaceae includes a number of important species used as vegetables, oilseeds and medicine. The Brassica B-genome is significantly diverged from the A-and C-genomes, and species containing the B-genome possess many valuable agronomic and disease resistance traits. In this thesis, two populations of interspecific crosses between Brassica napus (AACC) and Brassica
more » ... ACC) and Brassica carinata (BBCC) were studied, and microsatellite (SSR) markers and genomic in situ hybridization (GISH) techniques were applied to characterize the B-genome chromosome introgressions in the advanced backcross populations and their effect on disease resistance, morphological and seed quality traits. A BC 2 S 3 derived doubled haploid (DH) population was genotyped with 184 SSR markers and DH lines carrying stable B-genome chromosomal segments were identified. The GISH assay demonstrated that three of the 60 DHs were substitution lines in which the B-genome chromosome J13 was common to all. The lines with B-genome chromosomes, "B+", were significantly different (P <0.01) from the lines without B-genome chromosomes, "B-" for some morphological and seed quality traits, such as days to flowering, days to maturity and erucic acid content. Further study revealed that resistance to Sclerotinia stem rot (caused by Sclerotinia sclerotiorum) has been inherited from the B or C genomes of B. carinata in some of the DH lines. Several BC 3 S 1 families of another cross, derived from well-characterized BC 3 plants containing introgressed B-genome chromosomes, were analyzed using SSR markers and the GISH assay to study the inheritance of the B-genome v chromosome(s) and their association with morphological traits. This study revealed that the B-genome chromosomes tend to transfer through generations, either as whole chromosome(s) or as chromosomes without small terminal segments, as evidenced by low recombination frequencies (~ 0%) between the B and A/C-genome chromosomes. These results were supported by the GISH assay and chromosomes counts, and revealed that many of the BC 3 S 1 lines were addition lines carrying extra B-genome chromosomes. vi Acknowledgments Science is the discipline of lighting one more small point of light, adding slowly to a firmament of stars which eventually become bright enough that all of us can see truth clearly. However, the process of sparking that new light, as every candidate for a doctorate can attest to, is a long, arduous road. Thankfully, we are usually not alone in the effort. My journey, in particular, has been aided so many times by tremendous people who have gone far beyond the call of duty. Albert Schweitzer once said: "Sometimes our light goes out but is blown into flame by another human being. Each of us owes deepest thanks to those who have rekindled this light." These are the people who rekindled my light when it wavered. What I have accomplished is directly attributable to their help.
doi:10.7939/r3pm08 fatcat:2nm7yvkotrae7pykij5hlatchy