Genetic variation in the Green apple aphid, Aphis pomi De Geer (Aphididae, Homoptera) detected using microsatellite DNA flanking sequences

Microsatellite DNA flanking sequences (MDFS) were generated using specific primers that were downstream from a core (GT)(n) microsatellite repeat and did not include any portion of it. Three primer sets corresponding to independent loci, ap05, ap22 and ap28, were designed to produce a single PCR product suitable for sequencing. For this study, colonies of the green apple aphid, Aphis pomi De Geer (n = 29) were collected from commercial orchards in the Okanagan Valley in British Columbia (BC), Canada, and from geographically distant sites (n = 16) in Vancouver BC, Ontario, New York State, United States and United Kingdom. A parallel study of a closely-related sister species, the Spirea aphid, A. spiraecola Patch, was also performed on aphid samples collected from some of the sites. Preliminary data using these markers reveal that all the loci described a basal cluster for A. spiraecola collected from Spirea discriminating them from a core of A. pomi samples from Malus sp. Hence the molecular markers differentiated between the two morphometrically-similar species. Within species, the samples tested showed little detectable variation in a colony, but there were distinct regional genotypes. The degree of resolution varied across the three loci with most definition found in the ap22 locus followed, respectively, by ap28 and ap05. Incidentally, the latter locus was able to sequence more distantly related Aphis species. The results show that MDFS will prove useful both for phylogenetic as well as population genetic studies.