Investigations on flowering time genes from oilseed rape (Brassica napus L.)
In rapeseed (Brassica napus), flowering time is crucial for environmental adaptation and to maximize yield. I analyzed the transcriptome data of Ningyou7 leaf material harvested from vernalized and non-vernalized plants at different developmental stages and investigated the differentially expressed flowering time orthologs between different treatments and developmental stages. To further verify the functions of these differentially expressed genes (DEGs), I used the genome wide association study (GWAS) and QTL (quantitative trait loci) mapping data, which was generated by using Brassica Infinium 60K SNP Chip. I found 36 DEGs to be associated with flowering time, seed yield or both. Among the 36 genes, Bna.VIN3.A02 showed a DNA polymorphism between winter and spring rapeseed as well as winter and semi-winter rapeseed in a region encoding a functional protein domain. In another experiment, I investigated the phenotypic effect of mutations in a gene (Bna.AP1). For this, I analyzed three stop codon mutant families of Bna.AP1.A02 in the greenhouse. One mutant family ap1_1 showed altered plant architecture, floral morphology, and yield related traits. This data suggested that Bna.AP1.A02 has a pleiotropic effect on seed yield and plant architecture in rapeseed. For my last experiment, I hypothesized that Bna.FT gene in heterozygous stage affect heterosis in F1 hybrids. To study the effect of Bna.FT mutations, I performed field trials in two locations in Germany. Based on this preliminary data, it was evident that Bna.FT missense or splice site mutations have no effect on seed yield heterosis in rapeseed. However, the effect of background mutations on the phenotype of F1 hybrids was evident. From greenhouse data, I concluded that background mutations have a significant influence on flowering time and seed yield. Therefore, reduction of background mutations is necessary prior to phenotypic characterization of EMS induced mutants.
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