Abstract: The western flower thrips (WFT), Frankliniella occidentalis Pergande (Thysanoptera: Thripidae), is an important agricultural pest worldwide. In recent years, it has spread into many provinces since its first detection in China. The research of the population genetic structure based on microsatellite marker (simple sequence repeats, SSRs) will contribute to revealing its invasion pathway. In this study, we analyzed the characteristics of SSRs from expressed sequence tags (ESTs) in F. occidentalis, screened PCR primers for EST-SSRs and tested the diversity of EST-SSR primers with the capillary electrophoresis. The results showed that 2 623 EST-SSRs were distributed in 1 930 uni-EST sequences, with an average of 1 SSR in every 2.21 kb of uni-EST sequence. Among mono- to hexa-nucleotide repeat types, mononucleotide repeats are the dominant type (83.00%), and tetranucleotide repeats are the second domainant type (11.17%). Furthermore, 4 of 22 pairs EST-SSR primers designed produced discernable PCR products. The capillary electrophoresis revealed that 3 of 4 pairs of EST-SSR primers are polymorphic. The average polymorphism information content (PIC) with the 3 polymorphic EST-SSR primers (0.48-0.69) is lower than that with 5 polymorphic Genomic-SSR primers (0.88-0.92). This study may contribute to further research on the analysis of genetic structure of F. occidentalis populations in future.

Key words: Frankliniella occidentalis, molecular marker, EST-SSR, Genomic-SSR, capillary electrophoresis, polymorphism