Genetic Analysis Of Quantitative Traits And Recurrent Selection Of Yield Traits In Upland Cotton

In recent years, the molecular breeding engineering on cotton yield and fiber quality has already started, and would develop rapidly. As one main approach of molecular breeding, molecular maker -assisted selection(MAS) requires more QTLs located by DNA makers( especially those which could be identified easily) for all kinds of quantitative traits. Wanza40(I40006 X I40007), a popularized hybrid, was used to construct a F2:3 family for QTLs tagging. Moreover, P1,F1,P2and F2:3of Wanza40 were used to study genetic model of yield traits and fiber qualities.1. Heterosis of yield traits and quality charactersThe heterosis of lint yield and seed cotton yield for F1,F2 and F2:3, measured from the averaged mid-parent value, were 26. 2%, 27.1%, 14. 5%, 20. 3%, 8.8% and 13.3%, respectively. The heterosis descended rapidly from F1 to F2: 3,this indicated that the main genetic basis of heterosis of yield traits for Wanza40 was an effect of dominance. The heterosis of quality characters was small.2. Identification of mixed major gene plus polygenes inheritance modelA method of major gene plus polygenes mixed genetic model was used to analyze the inheritance of quantitative traits. The best fitness genetic models were: Lint yield, C-l, polygenes; Seed cotton yield, C-0, polygenes; Boll No., A-l, one major gene; Lint percent, B-2, two major genes; Seed index, B-3, two major genes; Boll size, B-3,two major genes; Node No. before "Hot Summer" season, A-l, one major gene; Node No. at "Hot Summer" season, B-3, two major genes; Boll No. at "Hot Summer" season , C-l, polygenes; Boll No. after "Hot Summer" season , D-4, one major gene plus polygenes; Fruiting branch No., B-2, two major genes; Ripe boll No. before 9/15, C-l, polygenes; No. of Bolls on the Lower Part of the Plant, B-2, two major genes; No. of Bolls on the Medium Part of the Plant, A-4, one major gene; No. of Bolls on the Upper Part of the Plant,C-O, polygenes; The Ratio of Seed yield of First and secondharvest/Seed yieldt A-2, one major gene; The Ratio of Seed cotton yield before frost/Seed cotton yield, B-1,two major genes;Len, C-1,polygenes; Unf, E-2, two major genes plus polygenes; Sfi, E-1,two major genes plus polygenes; Str, D-4, one major genes plus polygenes; Elg, B-1,two major genes; Mic, C-1,polygenes ; Mat, C-1,polygenes ; Rd, B-l, two major genes;+B, B-l, two major genes ? Sbr, B-6, two major genes. 3. Molecular tagging of major QTLs of yield traits and quality charactersF2 population was characterized for SSR and RAPD makers. 495 pairs of SSR primers and 1040 RAPD primers were used in population analysis, which resulted in 25 polymorphic loci. An analysis of these loci with the MAPMAKER program resulted in the establishment of three linkage groups with 7 loci, as well as 18 unlinked loci. These three linkage groups covered a total genetic distance of 77. 5 cM and one of the linkage was localized on the forth chromosome. In Guanyun, two QTLs controlling RD with 5.3% and 5.3% phenotype variance explained, one QTL controlling LEN with 5. 5% phenotype variance explained were mapped in Chromosome 4. In the other linkage groups, one QTL controlling Boll No. before "Hot Summer" season, one QTL controlling the Ratio of Seed cotton yield of First and second harvest/Seed cotton yield and one QTL controlling ELG with 5.8%, 7.0% and 5.1% phenotype variance explained, were identified, respectively. In Jiangpu, one QTL controlling the Boll No. with 8.7% phenotype variance explained was mapped.Xiangzamian 2, Wanza40 and Zhongza028 were popularized hybrids used F2 instead of F1 in the Changjiang River valley and in the Huanghe River valley. Every hybrid of these three was produced by a variety in the Changjiang River valley and one variety in the Huanghe River valley. This study was conducted to improve yield traits and to create new parent materials for new hybrids using marker-assisted recurrent selection(MAS). Two initial populations(Q10 and Q20) was combined with seven parents by pyramiding crosses, in which four parents(P1) in the Changjiang River valley we...