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Abstract
The western corn rootworm, Diabrotica virgifera virgifera LeConte, is a key pest of the field corn, Zea mays (L.), throughout the North American Com Belt. Resistance to methyl parathion in some Nebraska D. v. virgifera populations has been shown to involve increased hydrolytic metabolism and elevated activity of non-specific esterases.
In this study, a group of resistance-associated esterases (referred to as Group II) were identified from Nebraska. D. v. virgifera populations. Group II esterase isozymes provide a reliable biochemical marker for detection of methyl parathion resistance in individual D. v. virgifera and a tool for monitoring the frequency of resistant individuals in field populations. Based on the presence and absence of group II esterases, a prototype biochemical-monitoring technique was developed to complement conventional bioassay methods.
The group II esterase isozymes were partially purified and characterized, and the biochemical, kinetic, inhibitory, and immunological properties of the partially purified group II esterase isozymes all indicated the presence of a B-type esterase in both resistant and susceptible populations. Resistance-associated esterases involve either quantitative or qualitative modification to confer resistance. The results of this investigation provide evidence that the esterase-mediated resistance in D. v. virgifera is likely the result of overproduction of esterase in the resistant population. However, definitive molecular evidence is still needed to elucidate the genetic basis of this esterase-mediated resistance.
