Surveillance of Resistant Acetylcholinesterase in Heliothis virescens

Abstract

AceIn, a gene controlling acetylcholinesterase inhibition and dominantly-inherited resistance to methyl parathion, was monitored in Heliothis virescens across the southeastern USA. The resistant allele, AceIn-R, was detected in 13 collections from 1989 to 1993 with an average frequency of 14.1±3.9%. This resistance mechanism was found in pheromone-trapped moths from Texas, Mississippi, Georgia and South Carolina. Genotype frequencies agreed with Hardy-Weinberg predictions. This resistance allele occurs at a low frequency in apparent equilibrium despite the widespread substitution of pyrethroid insecticides for methyl parathion. Laboratory colonies collected from South Carolina in previous years when there was more extensive use of methyl parathion exhibited higher frequencies. Results are discussed regarding the evolution of resistance and in relation to resistance management strategies.Insecticide resistance evolves in populations under selection by insecticides as documented for hundreds of species (7,2); however, the role of specific genes in the development of resistance in the field has been studied in only a few cases (3). Examples of monitoring for specific genes using enzyme or nucleic acid analyses in microtiter plate readers has demonstrated the correlation to resistance of carboxylester hydrolase activity in aphids (4-6) and mosquitoes (7-9) and the correlation to resistance of insensitive acetylcholinesterase in planthoppers (10,11), house flies (12), whiteflies (13) and mosquitoes (14,15).In pests with several potential mechanisms for resistance, it will be most important to monitor susceptibility as well as several resistance genes in order to understand the population genetics of resistance development. The tobacco budworm, Heliothis virescens (L.) (Lepidoptera: Noctuidae), possesses several mechanisms giving resistance to methyl parathion (16-18); therefore, in order to diagnose resistance in a population of this pest, it will be necessary to assay individuals for several potential resistance genes. One step in this direction is to

Resistance to insecticides in Heliothine Lepidoptera: a global view

“…A large number of reports have shown that resistance to OPs in H. virescens may be due, at least in part, to a target-site resistance involving decreased sensitivity of acetylcholinesterase to inhibition (Brown & Bryson 1992;Brown et al 1996a;Harold & Ottea 1997). In resistant strains of H. virescens, Brown & Bryson (1992) and Gilbert et al (1996) demonstrated the presence of acetylcholinesterase insensitive to inhibition by methyl paraoxon and G. Zhao et al (1996) demonstrated acetylcholinesterase insensitive to paraoxon.…”

A single gene (yes) controls pigmentation of eyes and scales in Heliothis virescens

“…AceIn and hscp are convenient due to their clear codominant expression in a simple biochemical assays as described herein. Although these visible mutants are not known from wild populations at this time, AceIn was present at an average frequency of 14% (Brown et al, 1996b) and hscp1029H was observed at approximately 20% (Park, 1998) in collections from agricultural fields. It should be easy to capture these alleles for future genetic linkage studies.…”

Linkage of acetylcholinesterase insensitivity to methyl parathion resistance inHeliothis virescens

“…In addition, selection may have favored hybrids which were increased, while Aceln ss and Aceln m~ genotypes were lower than Hardy-Weinberg predictions in the mixed colony. In populations collected in the field for several years, genotypes were found according to Hardy-Weinberg predictions (Brown et al, 1996a). In a previous study, acetylcholinesterase activity from Woodrow83 was increased significantly compared to the activity from Florence87 (Brown and Bryson, 1992).…”