Fine Mapping Of Two Major OTL For Oil Content OilA1and For1000-seed Weight SWA1on A1in Brassica Napus L.

Based on the initial QTL mapping for oil content and1000-seed weight using SG-DH population (282lines) over eleven environments, nine QTL for oil content and seven for1000-seeds weight were identified in eight and seven linkage groups, respectively. Among them, one major QTL for oil content (OilA1) and one for1000-seed weight (SWA1) were mapped in the same linkage group of A1, but around25cM apart. The additive effect for OilA1is0.44%and for SWA I is0.12g, all showing an increase in oil content and seed weight by Sollux allele, a parent from Germany.OilA1is located in flanking markers NTP3and ZAASA1-73, with confidence interval of17cM and SW1in the region between ZAASA1-6and ZAASA1-73, which confidence interval is29.3cM. Previous studies has validated the OilA1and narrowed it down to the interval of10.6cM (ZAASA1-77to ZAASA1-73) by BC5F2populations.In this study, through target range for marker-assisted selection, near-isogenic lines containing introgressions from donor parent Sollux were selected, to develop higher generations BC5F3and BC5F4for oil content, and to develop higher generations BC3F3and BC3F4for1000-seed weight. B. rapa A1genome sequences were screened for development locus specific markers to further fine mapping these two QTLs. The main results are as follows:1. The construction of near isogenic linesFor oil content, we developed BC5F3and BC5F4populations, and for1000-seed weight, we developed BC3F3and BC3F4populations. These lines chromosomal segments overlapped all target intervals.2. Development of high-density molecular markers in the QTL target regionBased on B. rapa A1genome sequence, seven markers have been added to SG-A1map by developing locus specific markers.Three of them are located in OilA1confidence interval between markers ZAASA1-77and ZAASA1-73. Other four markers were situated on region of SWA1between ZAASA1-6and ZAASA1-73.3. Fine mapping of OilA1and SWA1Fine mappings were conducted by using two generations of QTL-NILs,283lines from eight BC5F34families and428plants from six BC5F4sub-NILs and thus narrowed the OilA1interval to6.9cM and4.3cM (1.4Mb), respectively. The allelic differentia of OilAl effect between homozygous Sollux and Gaoyou alleles would be significant in1.26%in average.Similarly, two generations of QTL-NILs,844plants from BC3F3sub-NILs and804plants from BC3F4sub-NILs were used to narrowed down the SWA I interval to917.7Kb (9.1cM), and significant difference (P<0.05) of0.3g in1000-seed weight between the parents alleles.4. Bioinformatics alignment analysisBioinformatic alignment analysis for OilA1of the1.4Mb physical distances, we found294ORFs. Five of them share significant similarities with lipid related candidate genes identified in Arabidopsis. Three functional important candidates were observed with an E value of0. Simultaneously, this917.7Kb genomic region for SWA1was comprised of204ORF by FGENESH program.