Mutations in acetylcholinesterase genes of Rhopalosiphum padi resistant to organophosphate and carbamate insecticides

Abstract

Apple grain aphid, Rhopalosiphum padi (Linnaeus), is an important wheat pest. In China, it has been reported that R. padi has developed high resistance to carbamate and organophosphate insecticides. Previous work cloned from this aphid 2 different genes encoding acetylcholinesterase (AChE), which is the target enzyme for carbamate and organophosphate insecticides, and its insensitive alteration has been proven to be an important mechanism for insecticide resistance in other insects. In this study, both resistant and susceptible strains of R, padi were developed, and their AChEs were compared to determine whether resistance resulted from this mechanism and whether these 2 genes both play a role in resistance. Bioassays showed that the resistant strain used was highly or moderately resistant to pirimicarb, omethoate, and monocrotophos (resistance ratio, 263.8, 53.8, and 17.5, respectively), and showed little resistance to deltamethrin or thiodicarb (resistance ratio, 5.2 and 3.4, respectively). Correspondingly, biochemistry analysis found that AChE from resistant aphids was very insensitive to the first 3 insecticides (I50 increased 43.0-, 15.2-, and 8.8-fold, respectively), but not to thiodicarb (I50 increased 1.1-fold). Enzyme kinetics tests showed that resistant and susceptible strains had different AChEs. Sequence analysis of the 2 AChE genes cloned from resistant and susceptible aphids revealed that 2 mutations in Ace2 and 1 in Ace1 were consistently associated with resistance. Mutation F368(290)L in Ace2 localized at the same position as a previously proven resistance mutation site in other insects. The other 2 mutations, S329(228)P in Ace1 and V435(356)A in Ace2, were also found to affect the enzyme structure. These findings indicate that resistance in this aphid is mainly the result of insensistive AChE alteration, that the 3 mutations found might contribute to resistance, and that the AChEs encoded by both genes could serve as targets of insecticides.

RNAi of ace1 and ace2 in Blattella germanica reveals their differential contribution to acetylcholinesterase activity and sensitivity to insecticides

“…Alternatively, because a threefold greater reduction in AChE activity was observed in dsBgace1-injected cockroaches compared to injection with dsBgace2, our results could be explained by a lower concentration of total AChE protein remaining in AChE1-silenced insects. Most mutations conferring AChE insensitivity to organophosphates in non-Cyclorrhapha insects have been associated to ace1 (Cui et al, 2006;Kono and Tomita, 2006;Alout and Weill, 2008), whereas a few studies have suggested that resistance-associated amino acid substitutions seem to be associated to ace2 in Leptinotarsa decemlineata (Zhu and Clark, 1997) and Rhopalosiphum padi (Chen et al, 2007). Our data agree with most studies that point out a key role, qualitative and/or quantitative, of AChE1 as target of organophosphate insecticides in non-Cyclorrhapha insects.…”

Agrichemical use on wheat and barley crops in New Zealand in 2008–09

“…fragariae) (Teulon et al 2008). Insecticide resistance in these aphid species has generally not been recorded on cereals, although variability in the susceptibility of S. avenae to pirimicarb (Lu & Gao 2009) and of R. padi to carbamates and organophosphates (Chen et al 2007) has been reported recently in China. However, based on this survey, insecticide resistance in the important aphid species is not likely to be an issue in cereals in New Zealand.…”

Characterisation of imidacloprid resistance in the bird cherry‐oat aphid, Rhopalosiphum padi, a serious pest on wheat crops

“…Aside from direct feeding damage, R. padi also transmits the barley yellow dwarf virus (BYDV), which causes an economically important disease in small grains, leading to reduced quality and yield . In recent years, outbreaks of this pest have often occurred in China, and it has shown an increasing degree of resistance to some insecticides, including organophosphates and carbamates . Since its introduction in the early 1990s, imidacloprid has rapidly become one of the most commonly used neonicotinoid insecticides against aphids, whiteflies, and planthoppers .…”