Characterization and improvement of Ogu-INRA CMS Brassica napus L. fertility restorers
Lobos Sujo, Valeria N.
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In oilseed rape (Brassica napus L.), the use of a pollination control system is essential for hybrid seed production. The Ogu-INRA CMS system is a cytological variant of the radish- (Raphanus sativus L.) derived Ogu CMS system introduced through interspecific introgression into B. napus. In this system, there are three different lines: A-lines are male sterile, B-lines are fertile maintainer lines for the respective A-lines and R-lines (restorer) are male fertility restorer lines. The nature of the introgression produces a variety of issues within the restorer genotypes. These genotypes tend to have poor agronomic performance and high levels of glucosinolates. Apart from the phenotypic caveats, there is limited genomic data regarding the specific size, location and sequence of the introgression. The work presented in this thesis addresses both the genotypic and phenotypic issues present in B. napus restorer genotypes. Homozygous restorer lines are required to produce a fertile F1 generation making a marker for the Rfo gene a requirement in any breeding program. In the first project, an allele-specific Rfo marker was developed using KASP assays. This was achieved for one restorer population and this marker development will aid in several screening processes for breeding programs. The second project focused on the development of high-density SNP-based linkage maps for the C9 chromosome in which the radish introgression had been previously mapped to. The developed maps provided a better understanding of the introgression in our improved restorer populations and will facilitate the development of further markers and guides for sequencing and editing that can result in improved agronomic performance of the restorers. In the third project, the number of intermating cycles required to obtain restorer lines with improved agronomic traits was evaluated using a recurrent selection protocol. Results showed that more than a third of the families had improved seeds per pod, pod number and yield when compared to the best parent after one (C1) and two cycles (C2) of random full-sib intermating in select crosses. This indicates that intermating restorer genotypes can produce improved restorer genotypes. All the findings of this thesis benefit the entire rapeseed industry and expand the knowledge available on the Ogu-INRA CMS restorers.