| As a common industrial crop,cotton is suitable for planting in many regions around the world,and the increasing demand for high-yield and superior-fiber cotton has been put forward by the publish based on the rapid development of textile technology.However,Verticillium wilt（VW）,also known as“cancer”in Gossypium,is seriously hindering the development of cotton planting industry.Therefore,it is the top priority of crop breeding at present to cultivate and promote novel cotton varieties with VW resistance.The chromosome segment substitution line（CSSL）MBI9626 and CCRI36 were chosen as parents in this study to conduct cross and selfing,and their F2 offsprings were separately cultivated by plant-to-line method to obtain F2:3 and F2:4 populations,which were utilized for investigating the phenotypic traits.Totally,2292 SSR（simple sequence repeat）markers covering 26 chromosomes of cotton were used to detect polymorphism and genotype of parents and F2 population,respectively.The corresponding relationship between phenotype and genotype was identified,and QTL（quantitative trait loci）mapping of cotton yield,fiber quality and VW resistance were performed on MBI9626.1.A total of 16 QTL associated with fiber yield were detected,including 7 QTL for boll weight（BW）and 9 QTL for lint percentage（LP）,and could explain 2.25%-6.14%of the phenotypic variation rate,of which 6 stable QTL were identified in multi-year environments.Twelve QTL were detected to be associated with fiber quality,including 3 QTL for fiber length（FL）,4 QTL for fiber strength（FS）,4 QTL for fiber micronaire（FM）,and 1 QTL for fiber uniformity（FU）,and could explain 2.49%-12.30%of the phenotypic variation rate,of which 2 stable QTL were identified in multi-year environments.Ten QTL were totally detected to be associated with VW resistance,including 6 QTL for disease incidence and 4QTL for disease index,and the phenotypic contribution rate ranged from 3.32%to 10.00%,of which 7stable QTL were identified in multi-year environments.The stable QTL q VW-5-1 was chosen as the target interval for increasing marker density,and the position was finally anchored between the primers A05-130 and A05-238,which presented a physical distance of 95 Kb and contained 9 genes（GH＿A05G0220-GH＿A05G0228）.2.Transcriptome sequencing was performed on the root tissues（0,7 and 15 days post inoculation）of MBI9626 and its parents（Hai1 and CCRI36）infected by V991,and 8453 differentially expressed genes（DEGs）were totally screened among the samples.GO（Gene ontology）enrichment analysis was further conduct on the DEGs clustered in the most significant temporal expression pattern,which were mainly annotated into subgroups related to metabolic processes,cell processes,single biological processes,and biological regulation in biological process（BP）,cell membrane,cell membrane part,cell and cell part in cellular component（CC）,and binding and catalytic activity in molecular function（MF）.Moreover,KEGG（Kyoto encyclopedia of genes and genomes）annotation results showed that the DEGs were mostly associated with plant hormone signal transduction pathways and secondary metabolism.3.Finally,the transcriptome sequencing data were combined with the fine mapping results of q VW-5-1,and 7 of the 9 genes were differentially expressed in this region.Based on the expression level,annotation information and the progress of biological research by domestic and overseas scholars,we believe that GH＿A05G0221,GH＿A05G0223,GH＿A05G0225 and GH＿A05G0226 might be involved in the defense process of cotton VW,of which the related gene functions need further experimental proofs. |
