| Brassica napus is one of the most important oil crops in China.Brassica napus can extract oil from seeds and also be used as fresh vegetables,which has great potential.In order to breed high-quality Brassica napus shoots,genetic analysis of their main nutritional quality traits is crucial.In this study,quantitative trait loci(QTLs)and genome-wide association analysis(GWAS)were conducted for soluble solids content(SSC)and cellulose component content traits in Brassica napus shoots,aiming to find favorable alleles and superior parents for controlling quality traits and lay a foundation for breeding excellent germplasm.The main results were summed up as follows:1.This study uses 189 recombinant inbred line(RIL)populations as materials,based on the constructed high-density genetic map to perform QTL mapping on Brassica napus shoots SSC;A total of 6 SSC-related QTLs were detected in the two environments in 2021 Nanjing(21NJ)and 2021 Guiyang(21GY),located on chromosomes A1,A4,A8 and A9,respectively.The phenotypic variation(PV)of a single QTL ranged from 5.58% to 12.92%,among which the PVs of the two major QTLs,q SSC/21 GY.A4-1 and q SSC/21 NJ.A8-1,were 12.92% and 10.18%,respectively.At the same time,a total of 302 diverse rapeseed accessions were selected,and60 K SNP chips were used to perform GWAS on SSC in 20 NJ and 21 NJ.Based on mixed linear models,a total of 8 significant SNPs associated with SSC were detected.There were mainly distributed on A1,A5,A9,C1,C2,C3 and C6 chromosomes,and the PV ranged from 5.62% to 10.18%.Comparing QTL mapping and GWAS results,the same locus was not detected in the same chromosome segment.By comparing the rapeseed "Darmor-bzh" genome,seven candidate genes were identified,of which Bna C02g20320 D and Bna A09g41790 D were two important candidate genes.2.Using the RIL population,QTL mapping was carried out on the content of the three components of(cellulose,hemicellulose,lignin)in Brassica napus shoots,and 6,4 and 5 QTLs were detected,and the PV was 5.26%~7.32%,5.38%~16.70% and6.67%~9.61%,respectively.A major QTL q H/21 GY.C3-1 was detected,with a PV of16.70%.In addition,a C7 linkage group was detected to control both cellulose content and the lignin content of sites q C/21 NJ.C7-1 and q L/21 NJ.C7-2,PV was 5.26% and6.77%,respectively.A total of 3 candidate genes were identified,including Bna C03g13110 D,Bna A02g29640 D and Bna A02g29340 D.3.According to phenotypic data statistics,3 accessions with high SSC were selected in the two populations,RIL population AH174(7.55°Brix and 7.9°Brix),GWAS population L166(8.9°Brix and 8.38°Brix)and L380(8.9°Brix and 7.74°Brix).In addition,one accession,AH182,was selected in the RIL population with low cellulose components content,cellulose content(6.97%),hemicellulose content(15.68%)and lignin content(1.56%).Combined with the selected phenotype data of high SSC and low cellulose components content,four lines,AH120,AH169,AH182 and AH194,were selected in the RIL population and could be considered as superior parental materials. |
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