Abstract: 【Objective】The objective of the experiment is to study and understand the genetic law of brown cotton fiber, to find and locate the molecular markers linked with the locus of brown fiber gene for laying a foundation for fine-mapping, molecular cloning of the brown fiber gene and brown fiber quality improvement at the cotton genome level. 【Method】 Based on the upland cotton dominant multi-gene markers Line T586 (possesses the dark brown fiber gene Lc1) crossing with the sea island cotton Xinhai 16, the F2 population were constructed. Combined with fiber color classification and analysis by colorimeter, taking full advantage of the molecular marker genetic linkage map information of the cotton genome, the molecular markers tightly linked with the dark brown fiber Lc1 gene were mapped by screening of the polymorphism molecular markers and map-based cloning method. 【Result】 The F2 population of T586 crossing with Xinhai 16 were composed of 443 individuals, which of them were classified into the dark brown fiber, brown (middle color) and white by the fiber color. Finally, the Lc1 was located in the A subgroup of the cotton genome chromosome 7, which was flanked by the SSR marker NAU4030 and CGR5119 with a genetic distance of 8 cM, corresponding to the genetic distance of 5.1 cM and 2.8 cM, respectively. 【Conclusion】The trait of dark brown fiber is controlled by single gene, possesses the semi-dominant inheritance in tetraploid cotton. The information of molecular markers tightly linked with Lc1 locus could be used in marker-assisted selection in brown fiber cotton breeding.

Key words: cotton, dark brown fiber, Lc1, genetic mapping, microsatellite