QTL Mapping Of Fiber Qualities And Yield Components In Ultra High Strength Upland Cotton

Cotton fiber is the most important natural textile fiber and a significant oilseed crop, and China is a big country of cotton production and consumption in the world. With the improvement of technologies in textile industry, especially the emergence of new types of jet spinning method, as well as the unceasing improvement of people’s living standard, higher fiber production and fiber quality are needed. Although the fiber quality of sea island cotton is better than that of upland cotton, the yield of sea island cotton is much less than upland cotton, the major goal of cotton breeding have been developing upland cotton cultivars characterized with high yield and high qualities of the fiber. Identifying the molecular markers that tightly link to the major genes controlling the interested traits and using them to assist selection will greatly improve the efficiency of cotton breeding and have important significance on improving cotton yield and fiber quality simultaneously.Suyou6167is an upland cotton line producing super fiber properties characterized by long, strong, and fine fibers that were introgressed from Gossypium anomalum by interspecific hybridization between Gossypium anomalum and Gossypium hirsutum and intensive breeding by Jiangsu Academy of Agricultural Sciences for decades, whose fiber qualities are even better than ordinary sea island cotton. In the present study, an F2segregation population containing348individuals was constructed using Suyou6167and Sumian22as parents and F2:3families were generated by selfing of F2. The SSR polymorphic loci of the parents were screened and the SSR genetic linkage map was constructed by using F2population. The Composite Interval Mapping (CIM) method was taken to detect the QTLs of the yield components and fiber properties in F23families. The main results are as follows:1. Polymorphism of SSR markers and F2genotypingA total of3581pairs of SSR primers were used to screen the DNA polymorphism between the parents of Suyou6167and Sumian22, and141polymorphic loci were detected. These SSR markers were further used to genotype the individuals of F2 population. Chi-square test showed that46loci were significantly distorted from the Mondelism segregation ratio (P<0.05), accounting for32.62%of the total loci.2. Construction of genetic mapThe SSR genetic map was generated by using348individuals of F2population and141loci with Joinmap3.0software. This map contains120loci distributing across25linkage groups, covering705.99cM that accounts for about15.9%of the whole tetraploid cotton genome, with an average distance of5.88cM between the two adjacent markers. The length of25linkage groups arranges from2.7to85.3cM, fifteen of them were assigned to different chromosomes of tetraploid cotton, the remaining10linkage groups could not be linked to any chromosome, and it is notable that up to37.5%of marker loci were built into the D8chromosome.3. QTL mapping of yield and fiber quality traitsThe Composite Interval Mapping (CIM) method was used to detect the QTLs of the traits related to fiber yield and quality in F23families. Fifteen QTLs of fiber properties were identified, including four QTLs for fiber upper-half mean length, two QTLs for fiber length uniformity, three QTLs for micronaire value, two QTLs for fiber elongation, and four QTLs for fiber strength, each QTL explained3.98%～32.99%of the its corresponding phenotypic variation.Twelve QTLs of yield traits were identified, including one QTL for lint percentage, three QTLs for boll size, one QTL for bolls per plant, three QTLs for fruit notes per plant, two QTLs for seed-cotton yield per plant, and two QTLs for a hundred seeds weigh, each QTL explained5.08%～32.86%of its corresponding phenotypic variation.In the present work,20QTLs were mapped to a very short region of17.9cM between NAU3424and NAU1262on D8chromosome, among them,4major QTLs for fiber strength,2major QTLs for boll size can explain about30%of the phenotypic variation. Our findings pave the way for genetic improvement of fiber quality and yield and cloning the underlying function genes.