Abstract: Sea-island cotton (Gossypium barbadense) is important due to its fine fiber quality. However, genetic diversity analysis of this specie is still poorly documented, which is important for in situ and ex situ germplasm conservation and useful for breeding programs. Using 132 out of 238 SRAP markers, genetic diversity of 56 sea-island cotton cultivars including 20 introduced from other countries was assessed, 419 polymorphism loci were detected. The number of polymorphic loci per primer ranged from 2 to 9 with an average of 3.17. Jaccard’s genetic similarity coefficients were calculated and dendrograms were constructed by the unweighted pair group method of arithmetic average (UPGMA) using the NTSYS-pc version 2.10. The most of the accessions with relative relationship in their pedigrees were clustered into the same group. The genetic similarity coefficient of 56 accessions ranged from 0.312 to 0.876, with an average of 0.497, indicating that there was high level of genetic variation in the G. barbadense collections. The average genetic similarity coefficients of the domestic accessions in the first, second and third breed-ing periods were 0.501, 0.507, and 0.548, respectively, which implied that the genomic difference among the modern accessions has been gradually decreasing compared to that among the early accessions. These results suggest an overview of the genetic di-versity of the sea-island cotton accessions, and provide a reference for breeders to develop new cultivars efficiently.

Key words: Sea-island cotton, SRAP, Genetic diversity