Identification of Quantitative Trait Loci Influencing Seed Oil Content, Fatty Acid Profile and Flowering Time in Brassica napus L.

Exported Canadian canola seed contains on average 44% seed oil. Increasing seed oil content by one percent equals a 2.5% gain in seed yield that subsequently results in enhanced oil production per unit area. Identification of trait enhancing alleles using quantitative trait loci (QTL) analysis and selection via marker-assisted selection is playing an increasingly important role in plant breeding. In this study, a doubled haploid (DH) population was produced using the parents Polo and Topas and consisted of 156 DH lines. This population was phenotyped at two locations for two years for oil content, fatty acid profile and flowering time. At the same time, this population was genotyped using 620 marker loci, mostly SSR (383), ISSR (29), SRAP (191) and SCAR (17) markers. These markers were assembled into 19 linkage groups (LG), and anchored on 19 chromosomes. This linkage map covered a genetic distance of 2244.1 cM with an average marker interval of 3.7 cM. Fourteen QTL for oil content and flowering time and 131 QTL for six fatty acids were detected. A major QTL, DH109OIL.1 with a positive Topas-allele was identified on A10 that explained 26.99% of oil content variation. Transgressive segregation in oil content beyond the parental phenotypes was observed (31.5% to 55.5%). An early flowering QTL, DH110FLR.6 containing a Polo-allele was detected on A2 in the vicinity of a known Brassica vernalization gene. Our study supports a positive correlation (r=0.30**) between seed oil content and flowering time. Collocation of different QTL on thirty-one genomic regions was observed. Two genomic regions on C13, 147.83 cM and 154.55 cM were associated with QTL for all six fatty acids studied. We hypothesize this genomic region on C13 modulates the correlations between fatty acids and further investigation of this region could provide insight into genes determining total seed oil content in B. napus.