QTL Mapping Of Yield And Fiber Quality Traits In An Upland Cotton Population From A Cross Between High Fiber Quality Cultivar And Early Maturing Cultivar

Cotton is a leading natural fiber crop,and also an important protein crop and oil crop in the world.The yield and fiber quality of cotton is the most concerned part in cotton research,Cotton yield and fiber quality traits are both quantitative traits,and a certain negative relationship exists between yield and fiber quality traits.Therefore,researchers need to conduct in-depth research on cotton yield traits and fiber quality.In this study,high fiber quality cultivar Yumian 1 was crossed with early maturing cultivar Chaozao 3,and a recombinant inbred line population containing 184 lines was constructed in upland cotton.The SNP markers obtained by SLAF-seq and SSR markers were used to construct a high-density genetic map.The phenotypic data of yield and fiber quality traits detected in multiple environments were used to locate QTL for yield and fiber quality traits.The main findings are as follows:1.Phenotypic analysis of yield and fiber quality traitsThe nine traits were normally distributed in the four environments.Except for fiber strength,other traits have transgressive segregation phenomenon.The results of variance analysis showed that phenotypic traits were significantly affected by environment and genotype.Correlation analysis showed that fiber length was significantly positively-correlated with fiber uniformity,fiber strength,and fiber elongation;fiber uniformity was significantly positively-correlated with fiber strength and fiber elongation,fiber elongation was significantly positively-correlated with fiber strength,seed index was significantly positively-correlated with lint index.Fiber micronaire was significantly negatively-correlated with fiber length and fiber strength.2.Genetic mapA total of 145 polymorphic primers were obtained form 3578 pairs of primers,and the polymorphism ratio was 4.05%.Linkage analysis was conducted on 8020 markers distributed on 26 chromosomes,and a genetic map containing 2945(41 SSR and 2904SNP)loci were finally constructed.The genetic length of the constructed map was4650.71 cM,the average genetic distance between the two loci was 1.58 cM,and the map covered 98.30% of the upland cotton genome.A total of 1525 loci distributed on At subgenome,and the genetic length of At subgenome covered 2415.27 cM,accounting for 98.42% of the At subgenome;1420 loci distributed on Dt subgenome,the genetic length of Dt subgenome covered 2235.44 cM,accounting for 98.10% of the Dt subgenome.4.QTL mapping for yield and fiber quality traitsSeventy-eight QTL for yield and fiber quality traits were located on 26 chromosomes,including 37 QTL for yield traits and 41 QTL for fiber quality traits.The QTL explained 6.4% to 23.4% of the phenotypic variation,and the LOD value of QTL ranged from 2.50 to 7.76.A total of 38 QTL were located in the At subgenome and 40 QTL were located in the Dt subgenome.Fourty-two favorable QTL alleles derived from Yumian 1 whereas 36 favorable QTL alleles derived from Chaozao 3.Ten QTL were detected in more than two environments,and five QTL clusters including 17 QTL were detected on four chromosomes.The QTL detected mutiple enviroments will be helpful for fine mapping and map-based cloning,and can be used in marker assisted selection for high yield and high fiber quality breeding.