CONICET | Buscador de Institutos y Recursos Humanos

Twenty-nine Schizaphis graminum (Rondani) populations and sixty clones collected from very contrasting regions of Argentina and Chile were investigated electrophoretically. A high degree of enzymatic polymorphism was found. The enzymatic structure was described for the esterase system, finding nine different loci. Latitudinal stratification was determined and populations were associated into three groups, according to 84 Rev. Soc. Entomol. Argent. 70 (1-2): 83-92, 2011 the latitude they were collected from. The 90% of loci resulted polymorphic in the first group and 100% of loci were polymorphic in the rest. Observed heterozygosity was lower than expected. No group had fixed alleles according to Fsr values; group one had a slight heterozygous excess, while the other groups showed slight positive Fsr values, because there was a homozygous excess. According to Frt, the third group showed the highest value that was in concordance with the highest gene flow value. Three populations could not be included in any group. The α-carboxyl-esterase was always present, also in clones and populations which were located in non agricultural zones, implicating that the insecticide resistance is well spread throughout the Argentinean and Chilean territory. No relationship was found between the enzymatic patterns and the biotype or with the host species where the aphids were collected from.