QTL Identification For Yield And Fiber Quality Traits From(G.hirsutum Cultivar × G.hirsutum L.purpurascens) Population

Cotton is the premier fiber crop,and Upland cotton（Gossypium hisutum L.）produces more than 95%of the world’s raw cotton,but the narrow genetic basis of upland cotton hinders the further improvement of cotton yield and fiber quality.The rich variety resources of G.hirsutum can provide a broad genetic material basis for upland cotton genetic improvement.Effective use of cotton germplasm resources,which can accelerate the genetic analysis and breeding process of important traits in cotton.Gossypium hirsutum race has rich genetic variation,extensive genetic diversity of fiber quality for Gossypium hirsutum race is a research hotspot of cotton breeders.By constructing a G.hirsutum cultivar×G.hirsutum race population,QTL mapping and identification of relevant candidate genes for important traits,and effective utilization of its favorable genes is an important way to improve cotton yield and fiber quality.In this study,the high yield’s G.hirsutum cultivar CCRI 35 was used as the recurrent parent,and G.h.purpurascens as the donor parent.A backcross recombinant inbred lines（BIL）population was constructed.Construction of integrated genetic map of upland cotton based on SNP markers by SLAF-seq and SSR markers,combining the yield and quality trait phenotypes of the BC₁F_2:6,BC₁F_2:7,and BC₁F_2:8 lines.Mapping of QTLs for yield and quality traits of backcross recombinant inbred lines and identification of QTL favorable alleles.The main results are as follows:1.Integrated genetic map constructionTo detect the genotype of a single plant in the BIL population based on the SNP markers and SSR markers,an integrated genetic map was constructed.The integrated genetic map contains 3,621 ploymorphic loci,distributed in 26 linkage groups.The total length of the genetic map is 5558.02 c M（At subgenome is 2843.59 c M,and Dt subgenome is 2714.43 c M）,with an average genetic distance between adjacent marker of1.55 c M,and occupied approximately 96.25%of Gossypium hirsutum of TM-1 genome.2.QTL mapping of yield and fiber quality traitsA total of 146 QTLs were detected from BC₁F_2:6,BC₁F_2:7 and BC₁F_2:8 lines,including 90 QTLs for yield traits and 56 QTLs for fiber quality traits,distributed on other24 chromosomes besides D02 and D12.Among those QTLs,explaining 4.80%-15.40%of phenotypic variation in yield traits,and LOD is between 2.01～6.73;explaining4.90%～12.40%of phenotypic variation in fiber quality traits,and LOD is between2.02～5.35.Among the 146 QTLs,30 stable QTLs were detected,and a total of 34 QTL clusters were detected,which distributed on other chromosomes besides A08,A13,D02,D09 and D12.3.QTL analysis of BLUP（Best Linear Unbiased Prediction）values for yield and fiber quality traits from BIL populationIn this study,9 yield and fiber quality traits phenotypes were subjected to BLUP,and QTL analysis of yield and fiber quality traits BLUP values.A total of 101 QTLs related to yield and fiber quality traits were located,which explained 4.90%～14.80%of the phenotypic variation,and the LOD is between 2.02～6.47.The QTL significant marker sites related to yield traits were mainly concentrated on chromosomes A09 and D03 et al,and the QTL significant marker sites related to fiber quality traits were mainly concentrated on chromosomes A11 and D06 et al.4.Identification of QTL favorable alleles for yield and fiber quality traitsTo favorable allelic source identification for 146 QTLs,16 favorable alleles of QTL for yield traits were derived from G.h.purpurascens,and 74 were derived from CCRI 35;43 favorable alleles of QTL for fiber quality traits were derived from G.h.purpurascens,and 13 were derived from CCRI 35.These results can lay a foundation for the secondary segregated populations construction,fine mapping of related trait QTLs,candidate gene identification and functional research.