Abstract: Insect expressed sequence tags (ESTs) database provides a valuable resource for developing well-characterized molecular markers. In this study, 1 217 ESTs from the salivary glands of the wheat midge, Sitodiplosis mosellana, were downloaded from NCBI database and assembled into unigenes. The characteristics of unigene-derived SSR were analyzed and partial EST-SSRs were screened. The results showed that 141 EST-SSRs distributed in 106 (10.12%) unigene sequences were detected, with an average of one SSR in every 3.49 kb of unigene sequence. Among 1-6 nucleotide repeat types, 1-3 nucleotide repeats are the main types, accounting for 97.16% of all SSR. A/T, AC/GT and AAC/GTT account for the highest proportion in mononucleotide, dinucleotide and trinucleotide, respectively. Furthermore, EST-SSR primer pairs were designed using the Primer Premier 5.0 program and 26 pairs were selected for marker development in S. mosellana adults. Of the 26 primer pairs, 20 pairs (76.92%) produced discernable polymerase chain reaction (PCR) products, and of these 20 primer pairs, 9 pairs (45%) displayed polymorphism. Fifty-one alleles were found in the 9 primer pairs, the mean number of alleles per locus was 5.67, the average expected heterozygosity was 0.65 and the average polymorphism information content (PIC) was 0.60. The SSRs identified in this study will help explore the population genetic structure and genetic diversity of S. mosellana in the near future.

Key words:  Sitodiplosis mosellana, expressed sequence tag, EST-SSR, molecular marker, polymorphism