| Rapeseed is one of the main oil crops in the world and the main source of vegetable edible oil and forage protein.With the continuous increase of population and the continuous improvement of living standards,the worldwide demand for edible vegetable oil and protein is increasing,and the production of rapeseed must be continuously increased to meet human needs.With the continuous decrease of arable land area,it is less likely to further increase rapeseed output by expanding the planting area.One of the effective way is to increase the yield of rapeseed per unit area.Dissection of the genetic basis of yieldrelated traits is a prerequisite for further increasing rapeseed yield.In our study,a rapeseed nested association mapping population(BN-NAM)had been constructed and contains 15 recombinant inbred line(RIL)populations.Based on this population,the linkage analysis and association analysis were both performed to dissect the QTLs of 8 yield-related trait,such as effective branch number,first branch height,seeds per silique,main inflorescence effective length,main inflorescence silique number,plant height,siliqua length and thousand seed weight.The main results are as follows.1.Phenotypic statistical analysis of 8 yield-related traits in the BN-NAM population.The eight yield-related traits,including effective branch number,first branch height,main inflorescence effective length,main inflorescence silique number,plant height,siliqua length and thousand seed weight,were investigated in Caidian,Yangluo,and Ezhou from 2015 to 2017,respectively.It was found that all eight yield-related traits displayed extensive phenotypic variations,with the largest variation coefficient for the first branch height(FBH).The two-way analysis of variance showed that the phenotypic variation of all these traits in the BN-NAM population was mainly controlled by the genotype.The correlation analysis showed that the significant correlations existed among most yield-related traits,and the plant height was significantly positively correlated with the other 6 traits,including effective branch number,first branch height,main inflorescence effective length,main inflorescence silique number,plant height and siliqua length.2.Linkage analysis of 8 yield-related traits of each RIL population.Based on the multi-year phenotypic data of 8 yield-related traits in the 15 RIL population,the linkage analysis was performed to obtain 1,731 QTLs(LOD>3),of which 725(41.88%)QTLs had a phenotypic variation explanation(R2)more than 10%.A total of 1,087 unique QTLs were obtained by meta-analysis,including 732 environment-specific QTLs only detected in one environment and 355 consensus QTL detected in two or more environments.The number of consensus QTLs for eight traits,including effective branch number,first branch height,main inflorescence effective length,main inflorescence silique number,plant height,siliqua length and thousand seed weight,was 8,48,40,31,32,43 and 66,respectively.3.GWAS analysis of 8 yield-related traits in the BN-NAM population.Genome-wide association analysis(GWAS)with the MLM model was performed based on the phenotypic data of 8 yield-related traits.515 significant associated markers were detected with the P value threshold of 4.49e-6,with the highest phenotypic variation explanation(R2)of single marker was 49.89%.Of which,34 markers were significantly associated with multiple traits at the same time,accounting for 6.60% of the total number of markers.The number of significant association markers in eight traits,including effective branch number,first branch height,main inflorescence effective length,main inflorescence silique number,plant height,siliqua length and thousand seed weight,was 45,130,42,38,68,78,93 and 60,respectively.4.Comparison and integration of QTLs between linkage analysis and association analysis.It's found that there were lots of overlaps between the QTLs identified by linkage analysis and association analysis.The percentage of overlapping QTLs for eight traits,including effective branch number,first branch height,main inflorescence effective length,main inflorescence silique number,plant height,siliqua length and thousand seed weight,was 68.89%,81.54%,69.05%,73.68%,79.41%,87.18%,97.85% and 98.33%,respectively.Taking PH as an example,by combined the results of linkage analysis and association analysis,we identified 42 candidate genes related to PH,most of which were related to plant hormones.5.GWAS of silique length in three genotype.Association analysis showed that there was an associated locus with a very large effect on siliqua length on chromosome A09.The presence of this locus may obscure the effects of other loci.In order to exclude the effect of this locus on chromosome A09,the 2141 individuals of BN-NAM population were divided into three subgroups by the genotype of peak loci M1837746(C/T)on chromosome A09.The number of individual of C/C type,T/T type and C/T type,was 1219,877 and 45,respectively.The silique length of C/C type(7.62±1.16 cm)is significantly higher than that of C/T type(6.95±1.09 cm,P<2.2E-16)and(5.81±0.83 cm,P<1.2E-4).A total of 31 significant associated markers were detected by GWAS in these three type subpopulation,with 20 in C/C type,8 in T/T type and 3 in C/T type,respectively.A total of 6 loci associated with siliqua length were detected on the chromosome A07,and the locus with the largest effect was identified in the C/T type subpopulation and could explain 42.65% of the phenotypic variation. |
PDF Full Text Request