Construction Of A Genetic Linkage Map And QTL Mapping Of Yield Traits In Gossypium Hirsutum L.

Cotton is the leading natural fiber crop, and fiber is the main resource of the textile manufacture. The world cotton production was supplied by two tetraploid species, G. hirsutum L. and G. barbadense L., and G. hirsutum L. accounting for 90% of the total production. However, as the basic raw materials of textile industry, upland cotton generally has lower quality fibers than sea-island cotton. With the advances in spinning technology and the needs of the people, the higher yield and better fiber quality will be required. These requirements of yield and fiber quality have attracted a lot of efforts of governments and scientists to improve cotton yield and fiber quality, especially that of upland cotton.Conventional genetic strategies have been employed to enhance the fiber properties of upland cotton for over half a century. Recent advances in DNA markers offer plant breeders a rapid and precise alternative approach to conventional selection schemes to improve quantitative traits. Using the markers which were close linked with yield and fiber quality QTL to conduct marker assited selection will be helpful to improve yield and fiber quality of cotton in China. A composite population developed from upland cotton cultivars Yumian1, Zhong 35 and 15407 was used to construct a genetic linkange map with SSR markers which have stable polymorphism, and the linkage map was used to map QTL affecting yield and fiber quality. The mainly results were as following:1. Yield trait performance of mapping parent and composite populationThe boll number, boll weight, seed cotton yield, lint cotton yield of Zhong 35 were better than that of Yumian 1and 15407. The lint percent of Yumian 1 was better than that of Zhong 35 and 15407. Five yield traits show segregation beyond three parents.2. Primer pair polymorphism among mapping parentsA total of 106 polymorphic primer pairs were obtained from 5569 cotton SSR primer pairs among the three mapping parents, acconting for 1.9% of the tatal primer pairs.3. Genotyping composite cross populationThe 105 polymorphic primer pairs were used to genotype the 172 individual plants from (Yumian 1×Zhong 35)×(Yumian 1×15407) F₁ population and 106 loci were obtained.4. Genentic linkage map constructionA total of 106 SSR loci were employed to perform linkage analysis, and a linkage map with 68 loci and 25 linkage groups was construced. Out of these linkage groups, 22 were assigned on 15 chromosomes, while the other 3 were not assigned on any chromosomes. The linkage groups included 2 to 6 molecular markers, with a length of 1.2cM to 70.4cM. The linkage map covered 837 cM with a average distance about 7.9cM between two markers, accounting for approximately 18.8% of the total recombination length of the cotton genome.5. Mapping QTL of yield traitsBased on the linkage map and the yield traits detected, nine QTL controlling yield traits were identified by using Map QTL5.0. One boll number explained 53.4% of phenotypic variance, one boll weight QTL explained 17.9% of phenotypic variance, one lint percentage QTL explained 23.9% of phenotypic variance, three QTL for seed cotton explained phenotypic variance from 58.6% to 60.4%, and three QTL for lint cotton explained phenotypic variance from 56.9% to 58.6%.