QTL Mapping For Fiber Quality Properties In Cotton Cultivar Cv. Yumian No.1

Cotton is an important cash crop. Improving the fiber quality is the one of main breeding objectives in cotton breeding. The parameters evaluating fiber quality include fiber length, fiber strength, fiber elongation, fiber fineness and fiber uniformity. The development of DNA markers linked to the fiber quality QTL would allow cotton breeders to trace this important trait in early plant-growing stage or early segregating generations. The use of these DNA markers is increasing the prospect for streamlining the cotton breeding programs for improving fiber quality while maintaining fiber yield. QTL location of cotton fiber quality provides favorable conditions for molecular marker-assisted selection, which greatly enhance selection efficiency of high quality cotton variety.At present, there are many reports about QTLs screening of fiber quality in cotton. But in previous studies, the genetic linkage maps used to tag QTLs are usually constructed from interspecies population of Sea Island cotton and Upland cotton. It is difficult to be used directly to improve quality in upland cotton. So it is necessary to select upland cotton parents with target traits to construct the genetic linkage maps, indentify QTLs linked with target traits, and provide more high quality QTLs derived from different upland cotton lines. This will put a solid foundation for molecular marker-assisted selection and MAS breeding of pyramiding unallelic QTLs.The main results are as follows:1. A genetic linkage map was constructed by the F₂ segregating population derived from the cross of TM-1, a genetic standard line, and Yumian No.1, a high quality cotton cultivar. By screening 5544 pairs of SSR primers, 177 polymorphic loci were identified including 21 distorted markers. The genetic map with 157 loci was constructed, which had a total of 1163.11cM and covered 33.95% of the whole cotton genome.2. The fiber characteristics of the F₂ individuals and the F₃ family lines were analyzed using composite interval mapping (CIM) method and 17 putative quantitative trait loci(QTLs) were detected for 5 traits, 3 for fiber length, 4 for fiber strength, 5 for fiber fineness, 3 for fiber uniformity and 2 for fiber elongation. These QTLs explained their corresponding phenotypic variations with 6.12%-8.4%, 4.82%-10.31%, 4.99%-28.13%, 7.4%-11.73% and 7.25%-56.29%, respectively. 3. QTLs were clustered on Chromosome 2, Chromosome 5, Chromosome 14 and Chromosome 23. Combining with the QTLs tagging results from different elite fiber lines in the lab, many QTLs associated with fiber quality were rich in Chromosome 23 and Chromosome 24 by chromosome tagging analysis, which indicated that Chromosome 23 and Chromosome 24 were QTLs cluster regions for fiber quality.These results provide references for genetic map construction and utilizing reasonably the fiber quality QTLs from Yumian No.1 in fiber quality breeding improvement in Upland cotton.