QTL Mapping For Fiber Length And Other Related Traits Of Cotton Using Elite Germplasm With Introgression Of Gossypium Barbadense

Cotton provides natural renewable fiber raw material for textile industry.As the rapid development of textile technology and people's requirements for quality of life,the fiber quality improvement of high-yielding cotton has become one of the targets to which breeders pay close attention.Fiber length is one of the important parameters to determine fiber quality.It has attracted much attention in the practice of cotton breeding.It is difficult to realize simultaneous improvement on cotton fiber quality and yield traits by using conventional breeding method mainly because of linkage drags between fiber length and main yield traits.With the rapid development of genomics and molecular marker technology,marker assisted selection has shown great potential and application prospect.Sealand?Se?is an introgression upland cotton?G.hirsutum L.?germplasm with excellent quality fiber genetic components from G.barbadense L.,while Lumianyan 37 Hao?LMY37?is a transgenic G.hirsutum variety with high yield and multiple resistances.In this study,we constructed F₂ and F_2:3 mapping population by crossing Sealand with Lumianyan 37 Hao,and identified the QTLs for fiber length and other relation traits.We identified QTLs with high genetic effects for target traits.It will lay a foundation for further fine mapping and identification and cloning of candidate genes for cotton fiber length major QTLs.The following are the main results of this study:1?Normality test for the phenotypic data of six traits in F₂ population showed that the phenotypic data of fiber length and fiber strength conform to normal distribution law.Similarly,normality test for the phenotypic data of 7 traits in F_2:3:3 population showed that fiber length,fiber strength,uniformity,lint percentage and boll weight all conform to normal distribution law.We analyzed the correlation between the seven fiber traits from F₂ and F_2:3 populations.The results indicated that the fiber length highly significant positively correlated with the fiber strength,while highly significant negative correlated with lint percentage.The fiber strength is highly significant positive correlated with the uniformity,while highly significant negatively correlated with the lint percentage.Boll weight is highly significant positively correlated with the fiber length,fiber strength and fiber micronaire.2?A total of 10139 markers were used to screen polymorphism between Sealand and Lumianyan 37 Hao,which resulted in 366 pairs of polymorphic primer,and the polymorphism accounted for about 3.61%of the total screened primer pairs.The 336 polymorphic markers were used to genotype the F₂ population.The results show that majority of markers produced a single polymorphic locus,except two markers produced two polymorphic loci and one marker produced three polymorphic loci in the population.Using the genotype date of F₂ population,a genetic linkage map was constructed,which containing 305 marker locis and covering a total genetic distance of 2663.66 cM,approximately 59.86%of cotton genome.The average of marker loci per chromosome was 11.73,which spanned 8.76 cM.Each chromosome contains between 3 and 42 marker locis.The mean length for each chromosome was about 102.45 cM.3?Based on the genetic link map,WinQTLCart QTL 2.5 was used to map the QTL of fiber length and other fiber related traits.A total of 26 QTLs were identified.Five stable QTLs were detected in both F₂ and F_2:3 populations.Nine QTLs which distributed on four chromosomes?Chr.A07,Chr.A12,Chr.A13 and Chr.D06?were associated with fiber length,and explains7.71%-14.46%of phenotype variation.In addition,seven QTLs related to fiber strength were identified,which explain 3.98%-25.76%of phenotypic variation,respectively.Two QTLs related to micronaire were identified,which explain 7.03%-11.93%of phenotypic variation.Five QTLs related to lint percentage were identified,which explain 4.59%-16.28%of phenotypic variation.Three QTLs related to boll weight were identified,which explain 4.68%-8.41%of phenotypic variation.Of the 26 QTLs,we identified 18 QTLs whose favorable alleles come from the Sealand with excellent fiber and among which nine QTLs related to fiber length,seven to fiber strength and two to boll weight.Eight QTLs's favorable alleles are from the upland cotton parent Lumianyan 37 Hao with high yield and multiple resistances,among which two of these QTLs related to micronaire,five to lint percentage,and one to bell weight.4?In this study,we identified three QTL-clusters,which include nine QTLs and distributed on three chromosomes?Chr.A07,Chr.A12 and Chr.D06?.There are three QTLs related to fiber length,three to fiber strength,and one each to micronaire,lint percentage and boll weight,respectively.In addition,the three QTL-clusters are C7-cluster,C12-cluster and C25-cluster.Of the three QTL clusters,one cluster related to fiber quality traits only,while the other two clusters related to both fiber quality and yield traits.By bioinformatics analysis,Gh_D06G0142 and Gh_D06G0145 were identified as candidate genes associated with fiber development.