Fine Mapping And Candidate Gene Screening Of A Major Qtl For Oil Content On Linkage Group7in Brassica Napus L.

Rapeseed is one of the most important sources as edible oil in the world. So improving oil content in seeds is one of the major objectives in rapseed breeding. Up to date, a number of QTLs for oil content in rapeseed have been identified. However fine mapping and map based cloning for any of oil QTL had not yet been reported. The current study were based on the previous mapping analysis of oil content in multiply environments and aim to fine mapping the most significant QTL for oil content in linkage group7(OilA7) and search for candidate gene/genes underlying this QTL.Previous fine mapping for OilA7has been narrowed it in a genomic region of528kb, which was the starting point in present research. Brassica rapa Scaffold sequences were selected for locus specifical marker design. Aim at the flanking region of OilA7around582kb. Near-isogenic lines (NILs) were developed up to BC4F2/BC4F3、BC4F3/BC4F4、BC5F2/BC5F3and BC6F2/BC6F3progenies. The single plants from BC4F2, BC4F3, BC5F2and BC6F2populations were genotyped in each of marker loci within the target region. Phenotypic data of oil content were obtained from selfing single plant and/or two replicated field experiments of lines (BC4F3, BC4F4, BC5F3and BC6F3). Oil content of seed was determined by near-infrared reflectance spectroscopy (NIRS) for three times per sample, and the average of them was needed. The main results are as following:On the basis of closing molecular markers and developing higher generations of NILs, we continue to fine mapping of OilA7. We have mapped35of149specific markers between marker EST1017and EST12a, and21of35were mapped between marker EST1087and EST1094. Then OilA7was narrowed down to230KB (BC4F2) and106KB (BC4F3, BC5F2and BC6F2) regions by1861BC4F2,3280BC4F3,32BC5F2and362BC6F2families respectly. Finally, we used8newest mapped primers to analysis588BC4F3and362BC6F2, and narrow OilA7down to65kb region between maker S03-23and S03-6.The comparative analysis of oil content between NILs carrying homozygous "Gaoyou/Gaoyou" fragment (n=47,43.25%) and NILs containing homozygous "Sollux/Sollux" segment (n=47,41.58%) in the65KB region showed significant difference of2%(p=0.000) in oil content with BC6F2families. In the finally fine mapped65KB region, we found14highly homologous ORFs by comparing with the oil related genes in Arabidopsis, and6ORFs of them are probably more functional important for oil content cumulation in rapeseed and might be considered as candidate genes for functional analysis.