| As one of the most important raw materials of textile, cotton plays an important role in the nationaldividend. It must be considered as the comprehensive breeding objectives that improve the production, fiber quality, insect resistance, disease resistance, stress resistance in cotton and so on. In production, Gossypium hirsutum, for high yield and better quality, accounts for 95% of the world’s total cotton area cultivated. However, because of not the origining region of Gossypium, the earliest germplasm sources for breeding in China mainly lie on imported from abroad and many of them derive from Deltapine, Foster and Delfos et al. So, most of the upland cotton varieties in China Resources are relevant to the American cotton. In the case of upland cotton germplasm in China increasingly narrow and difficult breeding breakthrough, distant hybridization is proved to be one of effective way to cultivate and create new germplasm.Many breeders have transfered the fiber quality, excellent character, high disease resistance, stress resistance and other outstanding traits from wild cotton and semi-wild cotton into upland cotton through distant hybridization method, and have successfully produced a new desirable agronomic characters varieties or new materials. With the rapid increasing of Biotechnology, SSR molecular marker technology has been used in distant hybridization and it is no doubt that this technology would greatly advance the theory and basic research and accelerate the process of cultivating new germplasm resources.This paper used 106 germplasm lines of G. hirsutum L.×G. darwinii Watt nurture progenies and the corresponding parents to analyze its genetic diversity and population structure with using SSR molecular marer technology to find markers relevant to fiber qualities by the association analysis which would be useful for molecular marker assisted breeding and new alleles hunting. The results obtained are as follows:1.307 pairs of SSR primers which are uniformity distribution in the linkage map produced 324 polymorphisms between 4 upland varities parents and G. darwinii Watt. In the offspring germplasm lines,288 different loci were detected and 247 markers in all materials generating 266 polymorphic loci. Polymorphic loci percentage (P) is 0.821. The number of alleles for per site is 2.105 on average; average effective numbers of alleles (Ne) is 1.186; the number of genotype for per site means for 2.831; the number of genetic diversity, on average, is 0.135, and average heterozygosity for 0.052. Each polymorphism PIC value is 0.122 and general average value for the Shannon index (I) is 0.254. The graphical genotypes shows that length of introgression fragments original from G. Darwinii is of 325.8 cM on average of single line,6.49% of the full-length genome.2. According to the different source material crosses and different generations, all of the offspring germplasm lines could be divided into four subgroups. Namely, K=4, the 5.67% molecular variation is exsiting among populations and 94.33% within populations. At p<0.001, the general genetic differentiation index (PhiPT) is 0.057 and the gene flow (Nm) is 4.16. Pop2 is the one whose level of gene diversity and linkage disequlibrium is the highest of four subgroups. Genetic similarity coefficient among one hundred-six germplasm lines is 0.757 on average, ranging from 0.561 to 0.958.3. At 0.05 gene frequency filter, r2>0.05 while p<0.05 significant condition, 5.2% of the combination revealed linkage disequilibrium. In extremely significant condition, two strong LD sites are detected (p< 0.0001). In r2=0.1, p<0.05 conditions, no significant linkage disequilibrium reducing points were found. However, at r2>0.2, p<0.05, linkage disequilibrium attenuates quickly within 50 cM genetic distance.4. We analyze fiber qualities by using the whole genome scanning association analysis with application Q+K+MLM model in three different environments. At p< 0.05 significant condition, there are 38,42 and 30 loci associated to the fiber quality respectively in three different environment and a total of 47 sites associated to fiber quality indexes of significant correlation. Variations the average rates that markers expain the variations are 6.0%, ranging from 2.2% to 14.8%. The rate of the model explaining characters variation in three environment are 38.2%,29.5% and 29.3% respectively on average.6 primers associated to fiber quality in the 3 environment while total five indexs of fiber qualities have significantly associated with 24 locus/times in two or three environment. Five EST-SSR loci associated to the fiber quality traits significantly. The results of our study are able to confirm previous research results and integrate with each other and provide a basis for the future lingkage mapping and candidate gene association mapping. |
PDF Full Text Request