Construction Of Linkage Map And QTL Mapping Of Fiber Quality Traits In Low Generation Population Of Upland Cotton

China is a big country of cotton planting and consumption,and cotton,as one of the important economic crops,is the main source of natural fiber.In recent years,the continuous innovation of textile industry technology and the continuous improvement of people's living standards have put forward new requirements for high-quality breeding.Therefore,it is of great significance to cultivate high-yield and high-quality upland cotton varieties as soon as possible.Fiber quality traits are complex quantitative traits controlled by multiple genes.in the past,conventional breeding methods based on phenotypic selection had long cycle and low accuracy.Molecular marker-assisted selection?Molecular marker assisted selection,MAS?breeding can select progeny traits by using molecular markers closely linked to the target quantitative trait locus?Quantitative trait locus,QTL?.As a result,the accuracy is greatly improved and the breeding process is accelerated.CCRI 679 is a high strength fiber strain of upland cotton bred by CCRI.In order to map its fiber quality traits,a F₂ population composed of 200 individual plants and 200 corresponding F_2:3 families were constructed by crossing CCRI 679 with common material Nongken-5.The fiber quality traits of the two generations were detected,and the simple repeat sequence?Simple repeat sequence,SSR?markers were used to screen the polymorphism of the two parents.The polymorphic markers were used to genotype the F₂ population and construct a linkage map.Based on the genotypes of F₂ population,QTL mapping of Fiber length,Fiber uniformity,Fiber strength,Micronaire value and Fiber elongation of F₂ and F_2:3 populations was carried out.The main results are as follows:1.Screening of polymorphic SSR primers between parents and genotyping of F₂population:a total of 6688 pairs of SSR primers were used to screen polymorphism between parents,and 149 pairs of high-quality polymorphic primers were obtained,the proportion of polymorphism was 2.2%.2.Construction of genetic map:149 pairs of SSR polymorphic primers were used for genotyping and marker linkage analysis in F₂ population,and a genetic linkage map including119 loci and 28 linkage groups was constructed.The total length of the map is 1173.5 cM,of which the largest linkage group contains 14 markers at 153.2 cM,and the smallest linkage group contains 2 markers at 3.3cM.On average,each linkage group contained 4.25 markers,and the average distance between markers was 9.86 cM.3.Using the genetic map constructed based on F₂ genotypic information and combining with five fiber quality traits of F₂ and F_2:3 populations,a total of 20 fiber quality QTL,were detected,of which 9 QTL,were detected in F₂ population and 11 QTL were detected in F_2:3population.These QTL are distributed in 11 linkage groups,explaining the phenotypic variation of 3.81%-10.31%.Three fiber lengths were detected by QTL,and three QTL were distributed in three linkage groups,explaining 6.07%-9.80%percent of phenotypic variation.The synergistic genes of these QTL were all from CCRI 679,and qFL-D11-1 could be detected in both F₂ population and F_2:3 population;five uniformity QTL,were detected,of which one was detected in F₂ population and 4 were detected in F_2:3 population,explaining 4.83%-9.01%phenotypic variation.Three fiber strength QTL were detected from F₂ population,these QTL explained 5.47%-8.07%of phenotypic variation,and 4 micronaire QTL were detected,including 2 from F₂ population and 2 from F_2:3 population,explaining 3.81%of phenotypic variation.Four elongation QTL,were detected,including one from F₂ population and three from F_2:3 population,which explained 7.13%-8.78%of phenotypic variation.The identification of stable QTL loci is of great significance for fine mapping and improving the accuracy of MAS breeding.Through the joint mapping of two populations,we identified a QTL,located in both generations and found that the genes controlling fiber quality traits may exist in clusters.This study will lay a foundation for mining fiber quality traits related genes and MAS breeding.