Isozyme characterization of sorghum aphid species and greenbug biotypes (Homoptera: Aphididae)

Seven isolates of greenbugs, Schizaphis graminum (Rondani), and one isolate each of corn leaf aphid Rhopalosiphum maidis (Fitch), and the yellow sugarcane aphid, Sipha flava (Forbes) were tested for diagnostic isozymes. Of 12 isozyme systems tested, six gave no rection with aphid extracts. Anodal and cathodal esterase showed isozyme patterns for aphids and corn or sorghum extracts, but the banding patterns did not show any differences among aphid species. Malate dehydrogenase and phosphoglucomutase assays demonstrated isozyme differences among aphid species but not among greenburg isolates. Three electromorphs of greenbugs and the single one of corn leaf aphid and one of the yellow sugarcane aphid were identified by electrophoresis. The electromorph groupings of the greenbugs were consistent with biotypes identified by plant host studies and mitochondrial DNA analysis.