Biochemical mechanisms of organophosphate resistance inRhyzopertha dominica(Coleoptera: Bostrichidae) populations from the United States and Brazil

Abstract

Four possible biochemical mechanisms of organophosphate resistance were examined in populations of Rhyzopertha dominica (Fabricius) collected from eight locations in the states of Minas Gerais and Sao Paulo in Brazil and from seven locations in northeast Kansas, United States. Results from insecticide bioassays with synergists (triphenyl phosphate, diethylmaleate, and piperonyl butoxide) suggested that metabolic detoxification mechanisms might be involved in organophosphate resistance in some of the populations of R. dominica. However, overall low synergism, non-synergism or even antagonism presented by these synergists in all 15 resistant populations suggested that carboxylesterases, cytochrome P450 monooxygenases and glutathione S-transferases were not likely to play a major role conferring organophosphate resistance in R. dominica. This hypothesis was strongly supported by our biochemical studies showing no significant difference in these enzyme activities, as well as cytochrome b-,, P420, and P450 levels between the susceptible and resistant populations. In contrast, all resistant populations of R. dominica showed higher acetylcholinesterase activity than the susceptible population both in the presence and absence of malaoxon. Furthermore, acetylcholinesterase from the resistant populations was less sensitive to inhibition by malaoxon than that from the susceptible. These results suggested that quantitative and qualitative changes in acetylcholinesterase might contribute to organophosphate resistance in these populations of R. dominica.

Contact Toxicity and Residual Effects of Selected Insecticides Against the Adult <I>Paederus fuscipes</I> (Coleoptera: Staphylinidae)

“…This phenomenon is widespread among Coleoptera. For example, the Colorado potato beetle is resistant to imidacloprid (GraÞus and Bishop 1996, Olson et al 2000, Zhao et al 2000, pyrethroids, and organophosphates (Jiang et al 2010); Tribolium castaneum (Herbst) (Collins 1990), Listronotus maculicollis Kirby (Ramoutar et al 2009), and Sitophilus zeamais Motschulsky (Ribeiro et al 2003) are resistant to pyrethroids; and Rhyzopertha dominica (F.) is resistant to organophosphates (Guedes et al 1997). All of these insects had been highly exposed to insecticides, and their mean generation times are relatively short, as is also true for P. fuscipes (Bong et al 2012).…”

Efeito do sinergista butóxido de piperonila na resistência de Oryzaephilus surinamensis (L.) (Coleoptera, Silvanidae) a deltametrina e fenitrotiom

“…Esses autores também testaram o sinergista DEF (S,S,S-tributilfosforotritioato) com deltametrina, nas mesmas populações de R. dominica, e não encontraram um efeito sinergista significativo, constatando que enzimas esterases possivelmente não estejam envolvidas na resistência a deltametrina em R. dominica. Guedes et al (1997a) demonstraram que a atividade específica da acetilcolinesterase diferiu significativamente entre populações resistentes e suscetíveis de R. dominica, indicando que a atividade aumentada da acetilcolinesterase parece estar associada com a resistência a organofosforados. E, com relação à resistência bioquímica aos piretróides, estudos de Collins (1990), com a espécie T. castaneum, indicam que o aumento do metabolismo enzimático na molécula do inseticida envolve oxidação e/ou hidrólise por ésteres.…”

Mutations of acetylcholinesterase which confer insecticide resistance in Drosophila melanogaster populations

“…Since then, resistance-modified AChEs have been described in many insect species [3-7]. Sequencing of the gene encoding AChE in resistant strains showed that the modifications arose from point mutations (Table 1).…”