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A susceptible and two parathion-resistant strains of the green bug, Schizaphis Graminum (Rondani), exhibit three different patterns of general esterase isozymes in native polyacrylamide electrophoresis gels. Characterization of general esterase activity using a-naphtholic esters as model substrates indicated that the three strains differed in isozyme composition. The type-II strain, which had the highest level of resistance, exhibited the highest levels of general esterase activity under all assay conditions, and the type-I strain had consistently higher levels than the susceptible strain. In all three strains, these esterases were more active toward a-naphtholic esters with side chains of six or fewer carbon atoms. a-Naphthyl propionate was the optimal substrate for both susceptible and type-I strains, and a-naphthyl butyrate for type II. Over 90% of esterase activity was localized in the cytosolic fraction of type-II greenbugs. In susceptible and type-I greenbugs, the activity was distributed equally between the cytosolic and microsomal fractions. Differences in kinetic properties of the general esterases from the three strains also were evident, further indicating differences in isozyme composition. Although the three strains differed in properties of the general esterase activities, the differences do not provide sufficient discrimination to distinguish reliably among the three strains using single aphid activity measurements.
Document Type: Research Article
Publication date: December 1, 1994
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Journal of Economic Entomology is published bimonthly in February, April, June, August, October, and December. The journal publishes articles on the economic significance of insects and is divided into the following sections: apiculture & social insects; arthropods in relation to plant disease; forum; insecticide resistance and resistance management; ecotoxicology; biological and microbial control; ecology and behavior; sampling and biostatistics; household and structural insects; medical entomology; molecular entomology; veterinary entomology; forest entomology; horticultural entomology; field and forage crops, and small grains; stored-product; commodity treatment and quarantine entomology; and plant resistance. In addition to research papers, Journal of Economic Entomology publishes Letters to the Editor, interpretive articles in a Forum section, Short Communications, Rapid Communications, and Book Reviews.