Fine Mapping Of A Major QTL SWA7for1000-Seed Weight In Brassica Napus

Based on the initial QTL mapping for1000-seed weight using SG-DH population (282lines) over nine environments, one major QTL SWA7located on linkage group7which stable expressed in seven environments was selected for further fine mapping. SWA7located between the flanking marker EST12a and ZAAS864, the confidence interval was40.3cM and the average additive effect is0.148g. Subsequently, Liu fine mapping this QTL using BC3F2/BC3F3, BC4F1/BC4F2(genotype-phenotype) population, narrowed down the confidence interval to4.3cM genetic distance between the flanking marker sR0282R and ZAA864.The results of previous research has laid a good foundation for the following fine mapping and Map-based cloning.In this study, through the target range for marker-assisted selection, near-substitution lines containing introgressions from donor parent Gaoyou were selected using advanced backcross approach to get BC4F2,BC5F1,BC4F3,BC5F2and BC6F1generations. B. rapa BAC sequences were screened for locus specific markers development to further confirm and fine mapping SWA7. The main results as follows:1. The cultivation of Near substitute lineThe research developped the generation of BC4F3, BC5F2and BC6F1, which lines chromosomal segments overlapping the target interval.2. The validation of SWA7The QTLSWA7for1000-seed weigh was validated by using the marker genotypes from BC4F2and BC5F1single plants and trait phenotypes from their corresponding selfing progenies BC4F3and BC5F2. Through the single marker association and multiple comparisons between near-substitution lines, the results showed that between the marker sR0282R and ZAA864, significant difference (P<0.001) of0.217g in1000-seed weight.3. Increasing markers in the target interval of SWA722markers have been added to LG-A7map by developing locus specific markers based on B. rapa A7-BAC sequences between the marker RF36and S158-7.4. Fine mapping of SWA7Fine mapping of SWA7was used the marker genotypes from BC4F3, BC5F2and BC6F1single plants and trait phenotypes from their corresponding selfing progenies. Through the single marker association and multiple comparisons between near-substitution lines, we narrowed down the interval to78kb physical distance between the marker N7-109and A07-2, significant difference (P<0.05) of0.230g in1000-seed weight between the parental alleles.5. Bioinformatic analysisBioinformatic analysis of the78kb physical distance, we found12genes. Currently we developing locus specific markers for the future fine mapping, at the same time developing advanced near-substitution lines to screening differences in gene. Focus on the4genes on molecular resistance and lipid metabolism.