Identification Of QTL Favorable Allele For Fiber Quality Traits In Upland Cotton

Cotton is the vital important natural fiber crop in the world, providing main raw material for textile industry. China is the largest consumer of cotton fiber worldwide, and cotton textile industry plays a critical role in our national economy. Gossypium is comprised of 45 diploid and 5 allotetraploid species, four of them are cultivated, including two diploid species,G. arboreum, G. herbaceum, and two allotetraploid species, G. hirsutum and G. barbadense.Upland cotton(G. hirsutum) produces 95% of total fiber yield in the world.Fiber quality of cotton are controlled by multiple quantitative genes of minor effects,and quality traits exist the negative correlation with fiber yield. Traditional breeding strategies have made a lot of improvements in cotton yield and fiber quality, nevertheless, these traditional approaches are time-consuming and of low efficiency and they have limited potential to improve both fiber quality and lint yield. With the development of advanced molecular biology and molecular marker technique, marker assisted selection(MAS)provides a quick and accurate selection method for breeders.In the present study, a(Yumian1×TAM94L-25) F2:6 recombinant inbred line population(RIL) was constructed. Yumian1 is a high strength cultivar in upland cotton as well as TAM94L-25 is an overlength fiber cultivar. Based on construction of genetic map and phenotypic data, fiber quality QTL favorable alleles were detected. The main results are as follows:1.Polymorphism of SSR markersA total of 11439 SSR primer pairs were used to screen the polymorphisms between Yumian1 and TAM94L-25. 398 primer pairs showed polymorphism, accounting for 3.5% of total primers.2.Genotyping of F2:6 populationA total of 398 polymorphic primer pairs was used to genotype the 92 family lines of F2:6RIL population. 406 loci were obtained, 8 of all polymorphic primer pairs respectively produced two loci. According to chi-square test, a total of 69 loci deviated from Mendelian segregation ratio(χ2>3.85), accounting for 16.9% of the total loci.3. construction of Genetic map406 loci were used to construct the linkage groups, a map with 357 loci and 60 groups was obtained, all of the 60 groups were assigned to 26 chromosomes of tetraploid cotton. The map spanned 2143.2 c M with an average distance of 6.00 c M between the adjacent markers,accounting for about 48.2% of the tetraploid cotton genome.4.QTL mapping of fiber quality traitsInterval QTL mapping was conducted to identify QTL for fiber quality in two environments(in year 2014-2015) using Map QTL6.0. In the year of 2014, we identify 7 QTL for fiber quality. These QTL explained phenotypic variation between 23.2-45.5%. As for fiber length, we identified three QTL explaining phenotypic variation between 23.2-45.5%. For fiber uniformity, one QTL was detected, and explained phenotypic variation 30.8%. For fiber strength, three QTL were identified, and explained phenotypic variation between 26.3-37.6%.In year 2015, a total of 6 QTL were identified for fiber quality. As for fiber length, we identified four QTL explaining phenotypic variation between 23.2-45.5%. For fiber uniformity, one QTL was detected, and explained phenotypic variation 25.4%. For fiber strong, three QTL were identified, and explained phenotypic variation between 26.3-37.6%.