The Evaluation And QTL Identifying Of Chromosome Segment Substitution Lines In Advanced Backcross Of Gossypium Hirsutum×G.Barbadense

Cotton is an important raw material for the textile industry which has an important effect ondevelopment of national economy. So it is very important for cotton breeder to develop cotton varietywith high quantity, good quality and resistance to disease.Island cotton has an advantage of better fiberquality and verticillium wilt resistance, which makes it to be an important research direction for cottonbreeder to introgress the excellent traits from island cotton into Upland cotton. In this study, Uplandcotton CCRI45（Chinese Cotton Research Institute45） was used as the recipient parent and Gossypiumbarbadense L.hai1as the donor parent. By crossing and advanced backcrossing, a population withupland cotton genetic background and a few of chromosome introgression segment from island cottonwas constructed. By evaluation of fiber quality and part of yield traits of BC₄F₃individuals, BC₄F_3:4lines and BC₄F_3:5strains and molecular identification of donor chromosome fragments in332BC₄F_3:5strains, QTLs for fiber yield and quality traits were detected, which offer a foundation for further QTLfine mapping and molecular-assisted breeding.1. A great deal of strains superior to CCRI45were acquired through phenotypic analysis of fiberyield and quality traits for the BC₄F₃individuals, BC₄F_3:4lines and BC₄F_3:5strains in two environments（Anyang, Henan and korla, Xinjiang）. The transgressive rate over the CCRI45for fiber length in allpopulations were the above79.0%, and the highest fiber length and fiber strength of BC₄F_3:5lines in2010reached to35.63mm and36.10cN/tex respectively. The transgressive rate over the CCRI45formicronaire value, fiber uniformity and fiber elongation rate in the4populations were from22.59%to79.22%. The transgressive rate over the CCRI45for boll weight and lint percentage were from18.67%to53.61%.2.SSR markers screened from26chromosomes were applied to detect the genotype of332selectedBC₄F_3:5strains. The totally tested length of chromosome fragments was5039cM, which covered99.03%of cotton genetic linkage map. The results demonstrated that the chromosome substitution rateof the recurrent parent in the BC₄F_3:5strains was93%～99.6%, the average rate was97.5%. The totallength of hai1chromosome fragments in BC₄F_3:5strains covered0.4-7.0%of tested length, the averagewas2.5%, and the average length is126.3cM. The total length of homozygous hai1chromosomefragments covered0.1%～3.3%of tested length with average of0.9%,the average length was44.1cM.The total length of heterozygous hai1chromosome fragments in BC₄F_3:5strains covered0.1%～4.9%oftested length, the average was1.6%, the average length was82.2cM. all of332BC₄F_3:5strains weredetected with G. barbadense L.hai1chromosome introgression fragment, and5strains with2hai1introgression fragments, and16strains with3introgression fragments, the other strains with4or moreintrogression fragments.3.With the result of SSR molecular markers and fiber yield and quality traits, A total of193QTLsof fiber yield and quality traits were detected in BC₄F₃、BC₄F_3:4and BC₄F_3:5in2environments,123QTLs controlled fiber quality traits, and70QTLs controlled fiber yield-related traits.the single QTL could explain2.29%-19.96%of phenotypic variance. A total of41QTLs could be detected in two ormore environments（32QTLs could be detected in two populations,3QTLs could be detected in threepopulations，and1QTL could be detected in four populations）, which include9for fiber length,10forfiber strength,4for fiber elongation,6for micronaire,2for lint percent,2for plant height,8for seedindex. A total of28QTLs could be detected in previous studies,7for fiber length,2for fiberuniformity,3for micronaire,7for fiber elongation,4for fiber strength,4for lint percent,1for seedindex.These QTLs detected in tow or more environments could be used in molecular assist selection.4. Plenty of strains with stable superior fiber quality were screened through evaluation of BC₄F₃individuals、BC₄F_3:4lines and BC₄F_3:5strains,9strains displayed stability in3generations with fiberlength and fiber strength above30.00mm and30.0cN/tex, which contained3～20hai1fragments.These CSSLs with excellent traits from G. Barbadense L.hai1could be used for selecting singlesegment substitution lines （SSSLs）,QTL fine mapping and could offer excellent parents for pyramidbreeding.