| Cotton is not only an important commercial crop,but also one of the important raw materials for textile industry.The genus Gossypium comprises of approximate 7tetraploid species and 45 diploid,including 2 tetraploid cultivated species,Gossypium.hirsutum L.and Gossypium barbadense L..Of the cultivated species,upland cotton（G.hirsutum L.）supplies over 5%of the world’s total fiber production.The fiber quality of upland cotton is worse than that of island cotton,there is a lack of varieties for spinning high-grade cotton yarn,and a large number of imports are needed to meet the needs of the people in China.There is an interaction and complex negative correlation between cotton yield and fiber quality traits,so it is difficult to meet the synchronous improvement between fiber quality and yield traits by using traditional breeding methods.With the rapid development and application of biological technology,Reduced-Representation Sequencing technology has been widely used in cotton molecular breeding research,which lays a foundation for the genetic improvement of yield and fiber quality traits and the mining of favorable genes.In the present study,we used（Yumian 1×N274）F2:7recombinant inbred line population to mine the superior alleles for the traits of yield and fiber quality.The genetic linkage map was constructed by using SSR molecular technique and SLAF-Seq（Specific-Locus Amplified Fragment Sequencing）to detect the genotypes of 180 families in the recombinant inbred line population.Combined genotypes with the traits of yield and fiber quality in recombinant inbred line,the whole genome QTL was screened by using interval mapping method.The main research results are as follows:1.SSR genotypingIn this study,the high-quality variety Yumian 1 was used as the female parent and N274 as the male parent to construct（Yumian 1×N274）F2:7recombinant inbred line population.Genotyping of recombinant inbred line（RIL）population was detected by using 260 pairs SSR primers in the previous research of our laboratory.A total of 78effective SSR polymorphism loci were obtained.2.SLAF-Seq genotypingThe genotype of RIL population was detected by SLAF-seq technology,a total of1 246.78 M reads were obtained through the average sequencing depth of 59.29 x for parents and depth of 27.36 x for families.The sequencing results have developed 354046 SLAF labels,which showed polymorphism has 8 732 SLAF labels,acconting for2.47%of the tatal SLAF labels.A total of 8 732 polymorphic SLAF tags were developed based on the detection.After multiple filtering,the SNP（single nucleotide）loci information was analyzed,and a total of 2127 effective SNP polymorphisms were obtained.3.Construction of genetic mapIn this study,using SSR molecular technique and SLAF-Seq technique,a high density molecular marker genetic map with 78 SSR markers and 2127 SNP markers was constructed,based on the recombinant inbred line population of upland cotton.The recombinant length and density of the map were 3195.8c M and 1.45c M.The A subgenome contained 39 SSR markers and 1216 SNP markers,with a total length of1683.65c M and an average genetic distance of 1.34c M between markers.The D subgenome contained 39 SSR markers and 911 SNP markers,with a length of1512.15c M,and the average genetic distance between the markers was 1.59c M.4.QTL mapping for yield and fiber quality traitsOn the basis of genetic linkage map,in combination with four environments（2019 in Chongqing,2019 in Hainan and 2020 of KLrla and Kuytun in Xinjiang）of yield and fiber quality phenotypic results,interval mapping method was conducted to identify QTL by Map QTL6.0 with LOD threshold value>2.5 of whole genome.A total of 62 QTL for yield and fiber quality was detected,including 10 QTL of yield,52QTL of fiber quality traits.Among them,42 QTLs could be detected on chromosome A subgenome,and 20 QTLs could be detected on chromosome D subgenome.seven QTLs（q SIA01,q FLA01.1,q FLD13.1,q FSA07,q FMA01,q FMD06 and q FED07）were detected in two environments,and three QTLs（q SIA07,q FLA07.2,q FMA07）were detected in all three environments.These stable QTLs lay the foundation for fine mapping of QTLs,marker-assisted breeding or map-based cloning.In addition,6 QTL clusters were distributed on chromosomes of A01,A05,A07,A13,D06 and D13. |
