Abstract
BackgroundRapeseed 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.ResultsWe 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.ConclusionsWe propose that photosynthesis, sucrose and starch metabolism, plant hormones, and lignin content play important roles in the development of rapeseed siliques.
Highlights
Brassica napus L., an amphidiploid species formed by natural hybridization of Brassica rapa and Brassica oleracea, is an important oilseed crop with strong adaptability, wide use and high economic value
The results showed that Silique length (SL) differed tremendously among rapeseed lines, with 76.26% broad-sense heritability, ranging from 4.81 to 10.89 cm in the recombinant inbred line (RIL) population and ranging from 3.39 to 12.74 cm in the genome-wide association studies (GWAS) population; 74.07% of lines were concentrated in the range of 5.00–8.00 cm (Fig. 1a, Additional file 1: Table S1, Additional file 2: Fig. S1a, b)
A correlation analysis showed a strong correlation between SL and thousand seed weight (TSW), seed yield per plant (YP), seed number per silique (SN), seed number per plant (SNPP), siliques per the main inflorescence (SMI), and harvest index (HI), and a weak correlation with seed oil content (SOC) (Additional file 3: Fig. S2)
Summary
Brassica napus L., an amphidiploid species formed by natural hybridization of Brassica rapa and Brassica oleracea, is an important oilseed crop with strong adaptability, wide use and high economic value. As the important oilseed crop in the world, Brassica napus (B. napus) is cultivated worldwide and is increasingly used for animal feed, vegetable oil and biodiesel [1]. Long siliques produce more or larger seeds than short siliques. It is of great significance to determine the genetic basis of long silique and cultivate long siliques rapeseed varieties to improve the yield of rapeseed. 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. 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. We dissected the genetic basis of SL by genome-wide association studies (GWAS) combined with transcriptome analysis
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