Characterization Of Donor Chromosome Fragments From Gossypium Barbadense L. In CCRI45 Background Of Gossypium Hirsutum L. And Identification Of QTL Related To Fiber Yield And Quality Traits

Owing to narrow genetic basis, weak fiber quality and resistance to verticillium wilt of G. hirsutum, it was of great importance to introgress the excellent traits genes from G. barbadense to G. hirsutum for enlarging the narrow genetic basis and creating more new gerplasm for breeding improvement. In this study, cotton poulations with genetic background of G. hirsutum and introgression genes of G. barbadense were developed by advanced backcross and selfcross with CCRI45, a commercial cultivar, as recipient parent and Hai1 as donor parent. 587 selected BC₄F₃ individuals and 186 BC₄F₃ superior individuals were selected to detect the donor chromosome fragments by SSR markers, and one-way analysis of variance was used to identify the QTL of fiber yield and quality trait in selected BC₄F₃ individual,BC₄F₃:4 line (587) and BC₄F₃ superior individual populations, which could lay the foundation for further screening single segment substitution lines (SSSLs) and fine mapping QTL of fiber yield and quality trait.Plenty of materials superior to CCRI45 were acquired through phenotypic analysis of fiber yield and quality traits. The transgressive rate over the recurrent parent in BC₄F₃ all individual,selected BC₄F₃ individual,BC₄F₃:4 line and BC₄F₃ superior individual populations were above 30% for fiber length,fiber strength,fiber uniformity and fiber elongation, specially, the rate in BC₄F₃ individuals was 74.79% for fiber strength. The transgressive rate in BC₄F₃:4 lines was 61.67% for micronaire, while it was 20.05%～28.49% in the other 3 populations. And the rates in 4 populations was 13.97%～55.88% for boll weight and lint percentage.155 SSR markers, which distribute into 11 linkage groups, were employed to analyze the genotype of 587 selected BC₄F₃ individuals. The results showed that the chromosome substitution rate of the recurrent parent in the BC₄F₃ individuals was 84.3%～100%, the average was 96.4%. Among them, 68 plants (11.58%) were detected without G. barbadense chromosome introgression fragment, 92 plants(15.67%) with one introgression fragment, and 92 plants (15.67%) with 2 introgression fragments, the others with 3 or more introgression fragments. The average length of heterozygous donor chromosome fragments in BC₄F₃ individuals was 27.5 cM, ranged from 1.1 cM to 187.5 cM, which covered 0.1%～16.4% of tested length, the average was 2.4%. The average length of homozygous donor chromosome fragments in every plant was 13.4 cM, ranged from 1.1 cM to 121.2 cM, which covered 0.1%～10.6% of tested length with average of 1.2%.The donor chromosome fragments in 186 BC₄F₃ superior individuals were detected by 276 SSR markers which distributed on 25 linkage groups and covered a total gentic distance of 2347.1 cM. The chromosome substitution rate of the recurrent parent was 96.2%～100%, the average was 98.4%. 31 plants (16.67%) were detected with one introgression fragment, and 35 plants(18.82%) detected with 2 introgression fragments, the other 120 plants (64.52%)with 3 or more introgression fragments, and the maximum introgression fragments was 8. The average length of heterozygous donor chromosome fragments in BC₄F₃ superior individuals was 26.9 cM, ranged from 2.3 cM to 77.5 cM, which covered 0.1%～3.3% of tested length, the average was 1.3%. The average length of homozygous donor chromosome fragments in BC₄F₃ superior individuals was 10.8 cM, ranged from 2.3 cM to 70.4 cM, which covered 0.1%～3.0% of tested length with the average of 0.4%.A total of 76 QTLs of fiber yield and quality trait were identificated in BC₄F₃,BC₄F_3:4and BC₄F₃ superior individual populations by one-way analysis of variance, among which 31 QTLs controlled fiber quality traits, 45 QTLs controlled fiber yield traits, and the single QTL could account for 2.60%～23.80% of phenotypic variance. 5 QTLs (2 for fiber length, 2 for fiber strength and 1 for lint percent) could be detected in 2 populations and 1 QTL tightly linked to fiber length could be detected in 3 populations. 17 QTLs (3 for fiber length, 4 for fiber strength, 2 for micronaire, 2 for boll weight, 4 for lint percent, 1 for plant boll number, and 1 for plant height) were proved to be stable in different populations and environments, which were reported in previous researchs.There were lots of materials with excellent fiber quality in these chromosome segments substitution lines(CSSLs) after advanced backcross and selfcrossing. 20 plants(lines) from 587 BC₄F₃ individuals, which contained 1～7 donor fragments, showed stability for 2 years with fiber length above 30.00 mm and the fiber strength above 31.0 cN/tex. These CSSLs with excellent trait genes from G. barbadense could further be used for QTL fine mapping, gene cloning and molecular assistant pyramid breeding.