| Summary: | Genes encoding desaturases in the polyunsaturated fatty acid (PUFA) biochemical pathway have been identified by mutation analyses and utilized in oilseed rape (Brassica napus) breeding programs. However the regulation mechanisms of these genes are as yet unknown and pursued by the oil industry for further manipulation of seed oil quality. In order to identify loci involved in such regulatory mechanisms, Arabidopsis thaliana, a close relative of B. napus, was used as a model plant. Seed oil characteristics such as PUFA composition and oil content are regarded as adaptative traits (Linder, 2000) which are typically the result of complex genetic components controlled by multiple loci. Therefore QTL analysis was performed using six recombinant inbred populations derived from wild accessions rich in natural variations. QTL analysis identified loci involved in PUFA composition and oil content and 13 QTL were selected for the development of Near Isogenic lines (NIL). NILs were used to test the robustness of QTL by ANOVA and 11 QTL were successfully validated for their effect on phenotype in this work. Finally a QTL detected in the NG population for 18:2/18:1 was chosen for fine mapping and the region containing the causative locus for the QTL was narrowed down to 2Mb. Seven candidate genes within that region were identified which could be targeted in further fine mapping in the future. In addition, a comparative mapping of QTL between A. thaliana and B. napus was performed through a unigene based B. napus map developed in the Bancroft group. This map facilitated the integration of results found in A. thaliana with B. napus and allowed the detection of coincident QTL regions between these two species and candidate gene analysis within these regions. The genes MTACP2, PKP-BETA1, DGAT1 and LTP4 were identified repeatedly during the analysis and are likely candidate genes affecting seed oil and could be target genes for future breeding.
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