| Cotton (Gossypium spp.) is one of the most important cash crops worldwide. Improvements in the standard of living in the country and the elimination of textile quotas are expected to rapidly increase the consumption and export of textile products.Upland and Sea Island cotton are two cultivated tetraploid cotton varieties. Upland cotton (Gossypium hirsutum L.) is characterized by high yield and moderate fiber quality performance. Sea Island cotton (G barbadense L.) is characterized by low yield, increased fiber fineness and strength. Sea Island cotton is used as the raw material for fine count yarn. Intraspecific narrow genetic base has become a main problem for genetic improvement of Gossypium hirsutum L.Transmission of valuable genes extensively and efficiently between G.hirsutum Land G.barbadense L.is essential for their breeding improvements, which is limited mainly by linkage drag. Chromosome segment introgression lines (CSIL) consist of a battery of near-isogenic lines covering whole genome of crop. Except for one homozygous chromosome segment transferred from donor parent each line, the remaining parts of genome are the same as the recipient parent. It is an ideal material for genome research and especially for QTL mapping. Based on a advanced backcross population between G.hirsutum L.xG.barbadense L, Sea Island cotton chromosome segment introgression lines of cotton in background of genetic standard line of Upland cotton TM-1 were developed. QTLs were mapped by advanced backcross population and CSIL population. Fine mapping QTL for fiber strength by F2 and F2:3 populations. The main results were summarized as follows:1. Development of Gossypium barbadense chromosome segment substitution lines in the genetic standard line TM-1 of Gossypium hirsutum In the present research, we firstly developed one set of CSILs lines. The development of the CSILs lines:the F1 was generated by a cross using TM-1 as the recipient parent and Hai7124 as the donor parent. The TM-1 x Hai7124 F1 progeny were backcrossed with TM-1 untill BC5 and self-pollinated to produce BC5S1. MAS was conducted to identify individual BC5S1 genotypesan having 1-2 donor chromosome segments in the TM-1 background. The BC5S1 heterozygous individuals were self-pollinated to generate homozygous BC5S2-3. BC4S3 individuals were also identified by MAS.The CSILs consist of 169 different lines. Single segment introgression lines have 51 lines,30.18% percentage of total CSIL lines. There are more than 5 segments or heterozygous segments in few lines. The length of the substituted segments covered 3526.34cM in total with an average distance of segment by 17.70cM. The substituted segments of each line are different in length, ranging from the shortest segment 3.5 4cM to the longest 46.03cM.There are no absent segments in Chr.A5 (Chr.5) and Chr.A8 (Chr.8).50.8cM, most length segment, are absent in the Chr.Dl (Chr.15) and 2.2cM, shortest length segment are absent in the Chr.D7 (Chr.16). The absent segments were in the terminal and middle parts of each chromosome.2. QTLs mapping by advanced backcross population and CSIL populationBC5S1 and BC4S1 seeds were planted at intervals in twenty rows, including one row of TM-1 as a control in 2005. BC5S2and BC4S2seeds were planted at intervals in ten rows, including one row of TM-1 as a control in 2006. CSIL seeds were planted using a randomized block design having 2 replications at intervals in ten rows, including one row of TM-1 as a control in 2008. The phenotype variance of BC5S1 and CSIL individuals were evaluated including leaf shape, corollaceous colour, bottom red corolla, smooth stem and boll shape. Two yield components traits including boll weigth, lint percentage and seven fiber quality traits including fiber length, fiber strength, fiber maturity, micronaire, short fiber index, fiber uniformity ratio, fiber elongation were measured from BC5S1, BC5S2and CSIL individuals.In the present research, similar Immaturity fiber, nervate amalgamation, chicken-paw leaves, green stem, smooth stem and boll shape lines were indentified from the CSIL population.Marker regression was done by MapManagerQTXb20 at p<0.001. Significant makers were detected in the BC5 population including 17 significant makers for fiber quality and 6 significant makers for components of yield (boll weight and lint percentage).27 significant makers were detected in the BC5S1 population including 22 significant makers for fiber quality and 5 significant makers for components of yield (boll weight and lint percentage).14 significant makers were detected in the CSIL population including 12 significant makers for fiber quality and 2 significant makers for components of yield (boll weight and lint percentage).Interval mapping was done by MapManagerQTXb20. All the significant markers could be detected with interval mapping.3 QTLs identified in the BC5 population could affect more than one trait.5 QTLs identified in the BC5S1 population could affect more than one trait.3 QTLs identified in the CSIL population could affect more than one trait.3. Fine mapping QTLs for fiber strength using CSILOne CSIL line was found during the development of the CSIL, which carried single segment for fiber strength. The CSIL line was crossed with TM-1 in summer at Jiangpu Cotton Breeding Station, NAU. Seven fiber quality traits including fiber length, fiber strength, fiber maturity, micronaire, short fiber index, fiber uniformity ratio, fiber elongation were measured from 600 F2 and F2:3 individuals.2 QTLs for fiber quality were identified in F2 population including 1QTL for fiber strength,1 QTL for micronaire. They separately explained 6.51%,9.27% of the phenotypic variance.5 QTLs for fiber quality were identified in F2:3 population including3 QTLs for fiber strength,2 QTLs for fiber uniformity ratio. They separately explained 7.49%,4.96%,5.97%,5.89% and 9.61% of the phenotypic variance. |
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