Construction Of SSR Genetic Map And QTL Mapping Of Fiber Quality Traits In Upland Cotton

Cotton is the major nature fiber crop and important oil and protein source corp. Gossypium genus includes four cultivated species, Gossypium arboretum L., G. herbaceum L., G. barbadense L.(sea-island cotton) and G. hirsutum L.(upland cotton). Among these four cotton species, upland cotton provides more than95%of raw cotton worldwide. Compared to sea-island cotton, the fiber quality of upland cotton is relatively lower. With the improvement of living standards and requirements of textile industry, people pay more attention to the fiber quality of upland cotton.Improvement of fiber yield and quality is always the important goal in cotton breeding programs. However, the fiber yield and quality of cotton are quantitative traits controlled multiple genes, and the negative association exists between fiber yield and quality. It is difficult to improve fiber quality and yield simultaneously for cotton breeders. Thus, innovative approaches need to be incorporated in cotton breeding. Based on the relatively saturated map constructed with DNA molecular markers and QTL identified for targeted traits, the marker assisted selection can significantly improve the efficiency of cotton breeding.The present study established an F2population from a cross between upland cotton high fiber quality cultivar Yumianl and high oil line M11, constructed a genetic linkage map with microsatellite markers, and identified QTL affecting fiber quality traits. The main results are as following:Primer polymorphism analysis and population genotypingIn this study,12443SSR primer pairs were used to screen the polymorphism between Yumianl and M11. Among them,663polymorphism primer pairs were detected, accounting for5.2%of total primers. These polymorphic primer pairs were used to genotype180individuals from F2population, and produced666loci, including107dominant loci and559co-dominant loci.Construction of upland cotton genetic mapA total of614SSR loci were conducted on genetic linkage analysis, a genetic map was constructed. The map spanned3096.9cM with an average interval about5.04cM between adjacent markers, accounting for69.7%of the total recombination length of the cotton genome. This genetic map includes79linkage groups and they were located on26chromosomes.QTL mapping of fiber quality traitsWith fiber quality traits data of three generations (F2、F2：3and F2:4), a total of54QTL were detected for five fiber quality traits, including37significant QTL (LOD threshold3.0), and17putative QTL (LOD thresholds between2.5and3.0). Among these QTL,12for fiber length explained4.7-40.0%phenotypic variation. Fifteen for fiber uniformity explained3.4-42.8%of phenotypic variation, including one detected in two generations. Thirteen QTL for fiber strength explained3.8-36.5%of phenotypic variation. Nine QTL for fiber micronaire explained6.6-36.7%of phenotypic variation. Five QTL for fiber elongation explained3.3-15.8%of phenotypic variation.