DISCRIMINATION AND COMPARISON OF 3 WHEAT APHID SPECIES BASED ON ISOENZYME PATTERNS (HOMOPTERA, APHIDIDAE)

The electrophoretic patterns of the isoenzymes esterase (EST), glutama te oxalacetate transaminase (GOT) and malate dehydrogenase (MDH) were studied at three different ontogenetic moments (nymphs, apterous and a late adults) in Sitobion avenae, Rhopalosiphum padi and Schizaphis gra minum collected from Passe Fundo, Rio Grande do Sul State. The latter species was also studied from two other Brazilian localities: Jaguariu na, Sao Paulo and Dourados, Mate Grosso do Sul. Nine electromorphs wer e found for EST, 12 for GOT and five for MDH. Generally nymphs showed a larger number of electromorphs. Some electromorphs were limited to a single species, therefore electrophoresis could be used to distinguis h aphid species despite their parthenogenetic mode of reproduction. Po pulations of the same species may also be differentiated by this techn ique. The populations in Dourados and Jaguariuna were more similar to each other than to the Passe Fundo population at all stages. S. avenae and R. padi were more similar to each other than io S. graminum, whic h presented different isoenzymatic patterns for each ontogenetic stage . S. avenae, R. padi and S. graminum can be differentiated by the clus tered ontogenetic pattern observed for GOT, MDH and EST, respectively. Electrophoresis would be a useful tool for species identification for aphid control on wheat.