| As the leading natural fiber source, cotton has been playing an important role in the economy of China, one of the largest cotton producing and textile manufacturing countries in the world. With the development of spinning technology, the better fiber quality will be required. Compared to sea-island cotton, upland cotton generally had low-quality fibers, i.e., short or coarse fibers of relatively low strength. Owing to narrow genetic basis of upland cotton and weak fiber quality and resistance to verticillium wilt, it was very important. to introgress elite QTL alleles of G. barbadense L. for fiber quality and resistance to verticillium wilt into G. hirsutum L. and enlarge the narrow genetic base of G. hirsutum and provid more new gerplasm resource for the variety developmentIn this study, the elite G. hirsutum variety'34B'and G. barbadense'Giza70'were crossed, backcrossed with 34B as recurrent parent and produced backcross advanced recombinational populations'BC2F4:6 and BC2F4:7 lines'. These lines were used to analysis the correlation between fiber quality and yield related traits under three environments. And 196 pairs of SSR primers from 26 chromosomes were used to filter these lines. QTL analysis of fiber quality, yield-related trait and verticillium wilt resistance trait in three environments were proceeded by the Single Marker Mapping.Most of fiber quality traits, yield-related traits and verticillium wilt traits fitted the normal distribution in the Kolmogorov-Smirnov test.The correlation analysis indicated that fiber length was positive significantly correlated with strength, negative significantly correlation with elongation.; spinning uniformity index was positive significantly correlation with fiber length, uniformity and strength, negative significantly correlation with elongation.;Micronaire tested by HVI900 was negative significantly correlation with strength and spinning uniformity index, maturity ratio showed no signification with fiber uniformity and spinning uniformity index,fiber linear density was positive significantly correlation with spinning uniformity index, negative significantly correlation with length and strength, no signification with fiber uniformity, and negative with elongation. This indicated that linear density was more stable than micronaire and maturity ratio, so it is necessary to strengthen the study of linear density.Fifty one QTLs for 10 fiber quality traits were found above two environments and the effect direction was unanimous. QTL numbers for fiber length, strength, micronaire, uniformity ,elongation ratio, spinning uniformity index ,yellowness index ,reflection ratio , linear density , maturity ratio were 7, 4, 9, 1, 17, 1,3,1,2,6 ,respectively.And 4 QTLs were detected under three environments, 1 for fiber length, 1 for fiber strength, 2 for fiber elongation ratio. Out of 51 QTLs, 22 QTLs (43.14%) with plus effect were from Sea Island cotton, which could be used for marker assisted selection. Each QTL could explain 2%～11% of phenotypic variance.Twenty eight QTLs for yield-related traits were found above two environments and the effect direction was unanimous. QTL numbers for boll weight and lint percentage were 19 and 9, respectively. And 10 QTLs for boll weight were detected under three environments. Out of 28 QTLs, 4 QTLs (14.29%) with plus effect were from Sea Island cotton. Each QTL could explain 2%～7% of phenotypic variance.Two QTLs for verticillium wilt resistance were found above two environments and the effect direction was unanimous. 1 QTL (50%) with negative effect were from Sea Island cottons.The above QTLs , which could be detected in different environments and identified from Sea Island cottons, should be used to breed Near isogenic lines and further to improve fiber quality and yield simultaneously through marker assisted selection.Fifteen QTLs could control several traits simultaneously. And these QTLs could partially indicate the relationship among fiber fineness-related traits in phenotypic level. However, the present study could not distinguish linkage from pleiotropy. It is important how to eliminate the undesirable linkage QTLs when the desired traits were selected for cotton pyramiding breeding... |
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