QTL Location Of Earliness And Fiber Quality In Cotton Using RILs

As an important strategic material, cotton plays an important role in the national economy of the country. The population of the China day by day increased, but the used land for agriculture reduces, which makes the competition between grain and cotton to be prominent increasingly. While shorten the growth period of cotton and do some early studies in cotton are particularly important. The breeding cycle can greatly shortened, and the efficiency of breeding can be improved by the application of marker-assisted selection in cotton genetics and breeding. The research of precocious and fiber quality trait-related QTL in cotton provided the theoretical foundation for early maturity and fiber quality of cotton.In this study, an early maturing variety; a shorted-season cotton CRI36 and G2005 (Island cotton introgression hybridization plus upland cotton genes), were crossed. The progenies self pollinated were selected and got a family that containing 190 recombinant inbred lines. Three environmental tests were done to study the QTL position of early traits in cotton using the recombinant inbred lines, providing the support for the application of molecular marker-assisted selection in early and fiber quality traits of cotton.The statistical analysis of phenotype revealed that the genetic differences between parents and among the lines within the population were large and the distribution was continuous, which consistent with the genetic characteristics of quantitative traits and the requirements of normal distribution. Correlation analysis showed that there was a significant positive correlation between growth period and seedling stage, extra significant positive correlation between growth period and bell in different environmental conditions. The growth period and the node of first fruiting branch existed extra significant positive correlation in the environments of Anyang and Hainan. These results suggested that seedling and boll were key factors influencing the length of growth period, deciding the length of the whole growth period. As a key character of early trait, the growth period was shorter, if the node of first fruiting branch was lower.The 4540 pairs of SSR primers were applied for polymorphism screening of two parents,307 primer pairs performed well in polymorphism between the parents, of which 168 pairs of primers were detected polymorphism in the population. A total of 248 SSR molecular markers were received, and a genetic linkage map, containing 48 linkage groups,164 SSR markers, was constructed using the mapping software (Joinmap 3.0). The map covered a genetic distance of 673.63cM, the largest linkage group containing 40 loci, with the length being 95.20cM, the smallest linkage group including 2 loci, with the length being 0.63cM.While the composite interval mapping (CIM) of WinQTLcart5.0 software was used for QTL location analysis of early and fiber quality traits in the recombinant inbred lines of environment. A total of 47 earliness-related QTLs were obtained, including 4 QTLs controlling seedling stage,9 QTLs controlling seedling stage,4 QTLs about the bud stage, 6 about the bell,8 of the whole growth period related,6 QTLs being got about the node of first fruiting branch. The QTLs controlling height of the node of first fruiting branch was 4 and 6 QTLs for plant height. Fiber uniformity-related QTL, Fiber micronaire-related QTL and Fiber strength QTL was 1 respectively, while Fiber elongation-related QTL were 2.The 7 higher rate of phenotypic QTLs and 4 QTLs were detected in multiple environments among the earliness-related QTLs. There were 2 seedling-related QTLs: qPQ-1-2,qPQ-1-3; 1 QTL related to plant high:qPH-1-4; 1 QTL related to node of first branch:qNFB-1-4,1 QTL controlling the growth period,1 QTL controlling the fiber elongation:qFE-13-1 and 1 QTL related to the fiber uniformity:qFU-13-1. The 4 QTLs which were detected in two different environments,2 QTLs related to plant high: qPH-1-2,qPH-1-4; 1 QTL related to bud stage:qQF-1-1 and 1 QTL related to the bell: qFB-1-3. While the major QTL:qQF-1-4 was detected in 2 different environments. Therefore, these QTLs studies further analysis of location research, applied to marker-assisted selection of early traits in cotton and breeding practice.