Phenotypic and molecular analyses in rice weevil, Sitophilus oryzae (Linneaus) (Coleoptera: Curculionidae): identification of a super kdr mutation, T929I, conferring resistance to deltamethrin

Abstract

BACKGROUND: The rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) is a cosmopolitan pest of stored cereal grains and other commodities globally. Infestations caused by S. oryzae makes grains unsuitable for consumption, processing, and export. Deltamethrin, a synthetic pyrethroid insecticide, is widely used in major grain storages in India as a prophylactic treatment to control this pest. However, recurrent use of this insecticide had led to genetic resistance in S. oryzae, questioning its ongoing use at the current recommended concentration. RESULTS: Dose response analysis of resistant (Delta-R) and susceptible (Lab-S) strains of S. oryzae collected from grain storages across southern India, revealed that Delta-R was 134-fold more resistant than the Lab-S at median lethal concentration (LC 50 ). A concentration of 180 ppm over 48 h effectively discriminated 16 resistant field populations from Lab-S with per cent resistance ranging from 8.72% to 75.86%. Exposing all the resistant populations to 1000 ppm over 48 h identified 12 populations with strongly resistant individuals and confirmed the existence of two distinct resistance phenotypes, 'weak' and 'strong' in S. oryzae. Furthermore, sequence analysis of the voltage-gated sodium channel (vgsc) gene in Delta-R identified a single target site mutation, T929I conferring resistance in S. oryzae. CAPS (Cleaved Amplified Polymorphic Sequence) marker analysis of this allele confirmed that frequency of resistance is high (up to 0.96) supporting the results of phenotypic analysis. CONCLUSION: Both phenotype and molecular marker analyses clearly demonstrated that deltamethrin at 180 and 1000 ppm can be used to discriminate weakly and strongly resistant populations in S. oryzae, respectively. Resistance diagnostics based on the mutation, T929I, supports our phenotypic data and indicates that resistance to deltamethrin in S. oryzae is prevalent in southern parts of India, stressing the need to identify a synergist or suitable alternatives.

Combined analysis of metabolome and transcriptome of wheat kernels reveals constitutive defense mechanism against maize weevils

“…Traditional methods to control maize weevils included fumigants (e.g., phosphine, methyl bromide, Korean spices, and medicinal plants) and insecticides (e.g., organophosphate fenitrothion, pyrethroid, and deltamethrin) ( Lee et al., 2001 ; Rajendran and Gunasekaran, 2002 ; Muhareb, 2010 ; Vásquez-Castro et al., 2012 ; Haddi et al., 2018 ; Singh et al., 2021 ). However, the recurrent use of fumigants and insecticides lead to marked increase of genetic resistance in stored insect pests ( Haddi et al., 2018 ; Nayak et al., 2019 ; Singh et al., 2021 ).…”

“…Traditional methods to control maize weevils included fumigants (e.g., phosphine, methyl bromide, Korean spices, and medicinal plants) and insecticides (e.g., organophosphate fenitrothion, pyrethroid, and deltamethrin) ( Lee et al., 2001 ; Rajendran and Gunasekaran, 2002 ; Muhareb, 2010 ; Vásquez-Castro et al., 2012 ; Haddi et al., 2018 ; Singh et al., 2021 ). However, the recurrent use of fumigants and insecticides lead to marked increase of genetic resistance in stored insect pests ( Haddi et al., 2018 ; Nayak et al., 2019 ; Singh et al., 2021 ). In addition, methyl bromide depletes the ozone in the atmosphere and several insecticides leave behind hazardous residues in stored grain, which seriously threaten environmental safety, food quality, and human health ( Sgarbiero et al., 2003 ; Joia et al., 2006 ; Phillips and Throne, 2010 ; Haddi et al., 2018 ).…”