Genetic and correlation analysis of silique-traits in Brassica napus L. by quantitative trait locus mapping

Rapeseed yield is directly and indirectly influenced by the silique-traits, such as silique length (SL), seeds per silique (SS), seed weight (SW), because the silique is an organ which produced yield and a major photosynthesis organ as well. In this study, a linkage map comprising 150 simple sequence repeat and 195 amplified fragment length polymorphism markers covering 1,759.6 cM was constructed in a doubled haploid population from a cross between two genotypes of 'HZ396' and 'Y106'. In field experiments across three seasons and two locations in China 140 doubled haploid lines and their corresponding parents were evaluated for silique-traits. In total, 26 quantitative trait loci (QTL) were detected, of which 15 were clustered and integrated into 5 pleiotropic unique QTL by meta-analysis. These unique QTL, which in a certain sense reflected the significant positive correlation between SS and SL and the significant negative correlation between SW and SS by the genomic location and effects of QTL detected, were mapped on linkage groups N7, N8 and N13. A trait-by-trait meta-analysis revealed 5, 2 and 3 consensus QTL for SL, SS and SW, respectively. Epistatic effects varied according to the specific traits performed. All the epistatic interactions showed significant additive by additive effects while no significant epistasis by environment effect was identified. These findings provided a better understanding of the genetic factors controlling silique-traits and gained insights into the gene networks affecting silique-traits at QTL level in rapeseed.