| Cotton (Gossypium spp.) is the world’s most important natural textile fiber crop and the major sources of vegetable protein and oil. Since the reform and opening up, especially China’s access to WTO, people’s living standards have been significantly improved and consumers have higher requirement of the quality of cotton fiber products. With the quick development of textile technology, companies and organizations related to textile industry are introducing new equipments, such as Air-jet spinning, Air spinning, and so on, which require better fiber quality to improve efficiency and quality of final products. However, the present cotton fiber can’t meet the requirements of the new technology in China, because the fiber quality is low, for example, the fiber strength is low, and the micronaire value is too high for most cotton cultivars. Thus, fiber quality has become one of the most critical objectives in cotton breeding programs.High yield, good fiber quality and multiple-resistance are the common pursuit of cotton breeders worldwide. However, these traits have significant negative correlation among them in heritance, which therefore prompts breeders to stress on different goals in their breeding projects. During the1980s in China, the major breeding goals were yield and disease resistance. With the successful breading of high yield cultivars, textile technology development and economic improvement, high fiber quality cultivars are demanded. Traditional breeding methods have low efficiency and cann’t meet the need of market.DNA molecular marker technology is a quick and accurate selection method for cotton breeders. DNA molecular marker technology is used to construct high marker density genetic map and detect quantitative trait loci (QTL). The makers closely-linked with QTL are used to select quantitative trait (marker-assisted selection, MAS), could greatly improve the breeding efficiency. The previous study in our laboratory has identified environment-stable QTL controlling fiber quality traits on chromosome24in composite cross population [(Yumian1×CCRI35)×(Yumian1×7235)]. The present study establishes a recombinant inbred line population (Yumian1×7235), constructs a saturated genetic map of chromosome24, and map QTL controlling fiber quality traits. The main results are as following.1. Polymorphic primers selection and coarse linkage analysis In total,25329SSR primer pairs were used to screen for polymorphic primers between mapping parents Yumian-1and7235, and1469polymorphic primers were obtained. The polymorphic primers were used to genotype45lines from recombinant inbred line population (Yumian1×7235), and1582loci were obtained. The coarse linkage analysis showed447loci produced by447primers were coarsely mapped on chromosome24.2. Genetic map constructionFour hundred and forty-seven primers on chromosome24were used to genotype the other135lines from recombinant inbred line population (Yumian1×7235), and516loci were obtained. Among447primers,60primers produced two loci and two produced three loci. All516loci were conducted on genetic analysis, and a genetic map with447loci was constructed. The map covered56.5cM, with average marker distance0.125cM.3. Marker distortion segregation testThe447loci on chromosome24were conducted χ2-test (P<0.05), and all447loci showed severe distortion segregation from the expected ratio (1:1). All loci were skewed to parent Yumian-1.4. QTL analysisThe genetic map and fiber quality traits tested in three years were used to detect QTL for fiber quality traits, and four QTL controlling fiber length, Micronaire, strength and elongation were identified. Fiber length QTL (qFL24.1) detected in one year explains6.8%of phenotypic variation and the favorable allele from7235increases fiber length by0.42mm. Fiber Micronaire QTL (qFM24.1) detected in three year explains the phenotypic variation from6.5%to12.8%, and the favorable allele from Yumian-1decreases Micronaire by0.10-0.22. Fiber strength QTL (qFS24.1) detected in three years explains the phenotypic variation from7.6%to14.8%, and the favorable allele from7235increases strength by0.99-1.37cN/tex. Fiber elongation QTL (qFE24.1) detected in two years explains the phenotypic variation from14.4%to28.1%, and the favorable allele from7235increases elongation by0.09. |
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