| Brassica rapa bolting traits are complex quantitative traits controlled by multiple genes and are greatly affected by the environment.In the past 20 years,QTL analysis or association analysis was performed based on the primary or natural populations such as F2 and RIL constructed by the parents,and a large number of QTLs related to Brassica rapa extraction were identified.But up to now,only three major genes,BrFLC1,BrFLC2,and BrVIN3.1,have been cloned and verified,and these genes can only explain some of the genetic variations of cabbage bolting.This thesis is based on the RIL population.At the top of the A04 chromosome,a QTL with a late flowering time is located.The chromosome fragment substitution line population（CSSLs）and the interval where the QTL is located are used to construct the near isogenic line for fine mapping.The results showed that the mapping interval did not contain the three cloned genes.In this study,RcBr（early bolting and flowering）,17AW017（late bolting and flowering）,F1,and NIL-F2 were used as the research objects.First,we analyzed the significance of the two parents in multiple environments,and then we used NIL-F2 isolated population as materials to determine the initial location interval,Finally,based on the location interval of the initial mapping results and combined with the results of RNA-Seq analysis,candidate gene prediction was performed.The research content is as follows:（1）The CIM method in Windows QTL Cartographer 2.5 software was used to analyze the QTL mapping of primary population RIL,secondary population CSSLs and NIL-F2 on the top of chromosome A04.Among the three populations,NIL-F2 had the highest LOD value,followed by CSSLs,and the lowest RIL,and the three values??were 25.64,8.86,and 3.77.The phenotypic contribution rate has the same trend as the LOD value,which are 43.26%,16.82%,and 4.71%,respectively.（2）Using cnu-m566a and BrID-90219 with polymorphism markers at both ends of the interval,12 recombinants were screened from 1152 nil-f2 individuals.Combined with the 4pairs of polymorphic markers selected from the interval,the genotypes were identified,and then combined with the representative genotypic data after recombination,the fragments controlling flowering time were narrowed from cnu-m566a and BrID-90219 marker 1.73mb to the marker BrID-90059-LY-2,with a physical distance of 127.54 KB.（3）Through screening the data of gene annotation information of Brassica rapa,it was found that Bra040420,a gene regulating flowering time of Brassica rapa,had the same function as At3g63010 in Arabidopsis database.It was found that At3g63010 was a GA receptor homolog encoding rice GA receptor gene（osgid1）.It has GA binding activity and higher affinity for GA4.At the same time,the gene is involved in the formation of flower organ morphology and gibberellin signaling.Therefore,we predict that Bra040420 gene is a candidate gene related to flowering time at the bottom of A04 chromosome,but it needs to be further verified.（4）In this experiment,BrapaV-3.0 was used as the reference genome.Transcriptome sequencing and analysis were performed on Chinese cabbage growth points.A total of 2796differential genes were identified,of which 2221 were down-regulated and 575 were up-regulated.Functional enrichment analysis of genes showed that the expression of the candidate gene Bra040420 screened in this experiment was not detected in this sequencing,but there was a plant signal transfer pathway in the KEGG pathway,and this pathway not only contained multiple A pathway that regulates cell elongation and division also has a pathway that regulates flowering. |
