| Cotton is the most important fiber crop in the world. Cotton genus comprises of about 50 species, and cultivated species include Asian cotton, African cotton, upland cotton and Sea Island cotton. Upland cotton accounted for 95% of the total production. China is the world's largest cotton producer and consumer, and also the largest textile producer and exporter. However, the fiber quality of domestic cotton cannot meet the needs of textile industry. The development of fiber quality can enhance the competitiveness of our raw cotton in the international market.The yield and quality traits result from the interaction between genotype and environment, so limted the efficiency of conventional breeding which based on phenotypic selection. Molecular marker-assisted selection technology can significantly improve the efficiency of breeding constructing. The molecular marker-assisted selection technology need construct linage map and locate quantitative trait locus (QTL). The present study uses three upland cotton cultivars to establish mapping population and construct genetic map with SSR marker. The fiber quality traits of three parent cross population (Yumian 1×Zhong 35)×(Yumian 1×7235) F1 were used to map QTLs affecting fiber quality. The mainly results were as following:1. Fiber quality of mapping parents and composite populationFiber quanlity traits including Micronaire, fiber strength and fiber length traits were quite different in three parents whereas fiber uniformity and elongation are not significantly different. The fiber length of 7235 was better than that of Zhong 35 and Ynmian 1. The mironaire of 7235 was lower than that of Zhong 35 and Ynmian 1. The fiber strength of Ynmian 1 was lower than that of Zhong 35 and 7235.For three parent cross population, fiber length ranges from 28.40 to 34.83 mm, with a mean of 32.20 mm. Length uniformity ranges from 81.60% to 87.50%, with a mean of 85.35%. Mironaire ranges from 3.20 to 5.20, with a mean of 4.11. Fiber elongation ranges from 6.30% to 6.80%, with a mean of 6.57%. Fiber strength ranges from 228.9 to 39.3cN/tex, with a mean of 34.02 cN/tex. Five fiber quality traits show continuous distribution and segregation beyond three parents. 2. Primer pair polymorphism between three parentsOut of 4612 cotton SSR primer pairs, a total of 238 show polymorphism among three mapping parents, Yumian 1, Zhong 35 and 7235, the polymorphic markers acconted for 5.2% of the total primer pairs.3. Genotyping tree parent cross populationThe 238 polymorphic primer pairs were used to genotype the 172 individual plants from (Yumian 1×Zhong 35)×(Yumian 1×7235) F1 population and 244 loci were obtained.4. Construction of upland cotton genetic linkage mapA total of 244 loci were comducted linkage analysis, and a map including 175 markers and 42 linkage groups was constructed whereas 84 markers were not located on any linakeage group. Thirty-nine linkage groups were located on 22 chromosomes. The map covered 1445.5cM. accounting for 32.5% of the cotton genome, with an average distance of 8.45 cM between two markers. The length of linkage groups ranged from 2.7 to 100 cM and the markers on the groups ranged from 2 to 40.5. QTL mapping of fiber qualityBased on composite interval mapping, ten QTLs for fiber quality was located on nine chromosomes. Three QTLs identified for fiber length distributed on Chr3. Chrl2, Chr15,and explained the fiber length variance from 10.2 to 35.8%. Two QTLs identified for length uniformity distributed on Chrl9 and Chr21, and explained the fiber length uniformity from 6.5% to 34.9%. Three QTLs for Micro were located on chrl 7, chr 23 and chr 24, and explained phenotypic variance from 8.8% to 29.2%. Two QTL for fiber strength were located on chr 15 and chr25, and explained 6.9% and 6.2% of phenotypic variance.
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