Background Rapeseed is the third-largest oilseed crop after soybeans and palm that produces vegetable oil for human consumption and biofuel for industrial production. Silique length (SL) is an important trait that is strongly related to seed yield in rapeseed. Although many studies related to SL have been reported in rapeseed, only a few candidate genes have been found and cloned, and the genetic mechanisms regulating SL in rapeseed remain unclear. Here, we dissected the genetic basis of SL by genome-wide association studies (GWAS) combined with transcriptome analysis. Results We identified quantitative trait locus (QTL) for SL using a recombinant inbred line (RIL) population and two independent GWAS populations. Major QTLs on chromosomes A07, A09, and C08 were stably detected in all environments from all populations. Several candidate genes related to starch and sucrose metabolism, plant hormone signal transmission and phenylpropanoid biosynthesis were detected in the main QTL intervals, such as BnaA9.CP12-2, BnaA9.NST2, BnaA7.MYB63, and BnaA7.ARF17. In addition, the results of RNA-seq and weighted gene co-expression network analysis (WGCNA) showed that starch and sucrose metabolism, photosynthesis, and secondary cell wall biosynthesis play an important role in the development of siliques. Conclusions We propose that photosynthesis, sucrose and starch metabolism, plant hormones, and lignin content play important roles in the development of rapeseed siliques.

Background: Silique length (SL) is an important trait tightly related to seed yield in Brassica napus (B. napus). Many studies related to SL have been reported in B. napus, but only a few candidate genes have been found and cloned, and the regulatory mechanism of SL is not clear. Results: We identified QTL for SL by using a RIL population and two independent GWAS populations. Major QTL on A07, A09, and C08 chromosome were stably detected in all environments from all populations. As important candidate genes, several genes related to starch and sucrose metabolism, plant hormone signal transmission and phenylpropanoid biosynthesis were detected in the main QTL interval. Such as, BnaA9.CP12-2, BnaA9.NST2, BnaA7.MYB63, BnaA7.ARF17, etc. At the same time, the results of RNA-seq and WGCNA showed that starch and sucrose metabolism, photosynthesis, and secondary cell wall biosynthesis played an important role in the development of siliques. Conclusions: we propose that photosynthesis, sucrose and starch metabolism, plant hormones, and lignin content play an important role in the development of rapeseed silique.