Abstract: Ten geographic populations of the orange wheat blossom midge, Sitodiplosis mosellana (Gehin) (Diptera: Cecidomyiidae) from all wheat grown area in China were investigated by RAPDPCR to determine their genetic structure. Samples of 10 adults were examined for each population. Five selected primers, S18 CCACAGCAGT, S32 TCGGCGATAG, S83 GAGCCCTCCA, S169 TGGAGAGCAG and S250 ACCTCGGCAC， produced a total of 326 RAPD markers. No specific band was observed for every population. The distance analysis shows that similarity within a geographic population is higher than that among different populations; the similarity index (Sxy) among the populations is inversely proportional to the direct distance among them. Cluster analysis by UPGMA shows that the 10 geographic populations could be gathered into two big groups: spring wheat region group and winter wheat region group.

Key words: Sitodiplosis mosellana, RAPDPCR, geographic population, genetic stru cture