QTL Mapping For Elite Fiber Quality Properties In Upland Cotton

Cotton is the most important textile fiber crop and the world's second-most important oil-seed crop after soybean.Demands for enhancement of fiber quality traits such as fiber length and strength have been increasing because of changes in spinning technology in the textile industry.The primary breeding goal for the worldwide cotton researcher is how to genetically improve both yield and fiber quality.The development on molecular marker technology offer plant breeders a powerful tool in breeding.Especially,if the marker linked tightly with major gene controlling interesting traits is identified,the marker would allow cotton breeders to trace this very important trait in early plant-growing stage or early separation generation,and selection assisted with the marker will improve the efficiency of selection.In this paper,molecular markers and two F₂ segregation populations derived from three parents were used to develop genetic linkage map and to exploit QTL concerned with fiber quality using upland cotton accessions 01525,J415 and TM-1,whose fiber quality is significantly different among them.The main results are followed:1.Two genetic linkage maps were constructed by the F₂ segregation population derived from 01525 hybridized with the J415,a high quality cotton accession and TM-1,a genetic standard line,respectively.By screening 6771 pairs of SSR primers,213 and 128 polymorphic loci were identified,respectively.Using(01525×J415)F₂ population,the genetic map is comprised of 28 linkage groups with 150 mapped loci,which could homologous with 22 chromosomes,except one linkage groups unknown to any chromosome.The 150 loci had a total genetic distance of 1161.1 cM,and covered 23%of the whole cotton genome.Using(01525×TM-1) F₂ population,the genetic map comprised of 24 linkage groups with 90 mapped loci was constructed,and could homologous with 17 chromosomes,except two unknown with any chromosome.The map had a total genetic distance of 1011.3 cM,and covered 22.48%of the whole cotton genome.A joinmap linkage map was integrated for the two F2 with SSR markers and JOINMAP3.0 software. The new integrated map is comprised of 39 linkage groups with 214 mapped loci,and could homologous with 23 chromosomes,with remained two linkage groups fail to be assigned to any chromosome.The 214 loci covered the genetic distance of 1762.03 cM, which was approximately 35.38%of the total recombination length of the cotton genome. The average distance between loci was 8.23 cM genome wide.2.The fiber characteristics QTL of the two F₂ populations were screened using composite interval mapping(CIM) method and 66 putative quantitative trait loci(QTL) were detected for 6 fiber qualities traits,11 for fiber length,10 for fiber strength,13 for fiber micronaire,12 for fiber uniformity,5 for fiber short index,and 15 for fiber elongation. These QTL explained their corresponding phenotypic variations with 5.3%-21.9%,4.5 %-24.5%,5.8%-15.7%,5.2%-34.2%,6.1%-15.7%and 5.3%-31.5%,respectively. Among them,9 stable QTL could be found in F₂ and F_2:3 simultaneously.At least 5 QTL could be identified at two different populations and different environments.It is also revealed that the direction of addition gene was consistent with the represent of expected value in two populations,which is inclined to the elite parents.We analyzed the relationship between clustered QTL and fiber quality,and it is also displayed to have singnificant correlation between them.3.QTL were clustered on Chromosome D1,Chromosome D2,Chromosome A6, Chromosome D6,Chromosome D8,Chromosome A9,Chromosome A10,Chromosome D10 and Chromosome A13.Combining with the QTL tagging results fi:om different elite fiber lines in the lab,many QTL associated with fiber quality were rich in Chromosome D6, Chromosome D8,Chromosome A10 and Chromosome A13.These results will provide references for the distribution of different QTL and utilizing the fiber quality QTL reasonably in fiber quality breeding improvement in Upland cotton.