| Rapeseed is one of the most important oilseed crops in China,and the output of rapeseed oil accounts for more than 55% of domestic edible vegetable oil.With the increasing demand for edible oil,increasing rapeseed yield is an important objective of rapeseed breeding.A large number of studies have shown that the seed weight of rapeseed has the most direct influence on yield,therefore,analyzing the genetic basis of seed weight is a key step in rapeseed breeding.1000-seed weight is a quantitative character controlled by multiple genes,which is affected by the environment factors.In recent years,a large number of QTL mapping studies have been carried out concern about rapeseed seed weight,but these studies are independent of each other,and the research background and materials are different,which can not be widely used in practical production.Therefore,the scientific integration of these research results has important theoretical and practical significance to improve the potential of rapeseed seed weight breeding.In this study,we collected the QTL of rapeseed grain size,seed weight and 1000-seed weight related traits in the past 20 years,and sorted out the information of these QTL,and integrated these QTL by Meta analysis,so as to reduce the confidence interval and obtain the Meta-QTL highly related to seed weight traits.At the same time,the physical location of the obtained Meta-QTL is co-located with the SNP in the GWAS study,so as to verify the accuracy of Meta-QTL.The genes in Meta-QTL confidence interval were compared with the differential genes in four RNA-seq studies of seed weight in Brassica napus and the genes related to seed weight reported by others to further explore the candidate genes related to seed weight.In addition,this study used the hot spot MetaQTLA9-3 to develop SSR molecular markers and screened out SSR molecular markers related to seed weight traits.The main research results are as follows:1.In this study,using 13 genetic maps of rapeseed in previous studies,a public reference genetic map containing 40401 molecular markers with a length of 3047.08 cM was constructed by using the information of LPmerge package integrated map in R language,which can be used for subsequent Meta analysis and reference for future generations.2.1038 QTLs related to seed weight were collected,57 Meta-QTL were obtained after Meta analysis,and the physical locations of 50 Meta-QTLs were determined on the Darmor-bzh v10 genome.The confidence interval was significantly reduced compared with the original QTL,9.806 times in the A subgenome and 4.29 times in the C subgenome.the confidence interval of Meta QTLA9-3 was 76.88 times lower than that of the original QTL.After Overview analysis,27 "hot Meta-QTL" were obtained,among which the confidence intervals of Meta-QTLA3-2,A3-5,A7-3,A7-5,A9-3 and C9-2 were less than or equal to 2 cM and with high PVE,so it could be used for seed weight related molecular marker-assisted breeding.3.The 50 Meta-QTL were co-located with the previous SNP in the whole genome association analysis of seed weight in B napus.A total of 11 Meta-QTL and 39 MTA were co-located.In addition,a total of 33 genes were located,of which 21 genes contained SNP sites.4.The the 50 Meta-QTL include 11182 genes,compared with 2555 differential genes form RNA-seq and 1158 genes in the previous studies.Five genes include Bna A09g55530D(CYP78A9)、 Bna A10g13240D(AGL62)、 Bna C08g23100D(ETO1)、Bna Cnng41060D(CKX3)and Bna A03g04590D(TT4)were choosed as the candidate genes affecting seed weight in rapeseed.Fourty six genes with high expression level in seeds were screened from 448 common genes,and 23 hub genes were screened by coexpression network analysis with known genes related to seed weight.Further research can be carried out through gene function verification.Among these hub genes,Bna A09g40220 D 、 Bna A10g29580 D 、 Bna A08g03160 D 、 Bna C03g08370 D and Bna C06g38900 D are not only highly associated with other genes,but also highly expressed in seeds.5.One of the “hotpot Meta-QTL”,Meta-QTLA9-3,was used to design specific primers according to SSR loci.Finally,three pairs of SSR markers related to seed weight were screened,which can be used for marker-assisted selection for breeding program. |
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