Detection of ryanodine receptor target-site mutations in diamide insecticide-resistant Spodoptera frugiperda in China

Spodoptera frugiperda(Lepidoptera:Noctuidae)is a widely distributed pest of corn.Since it invaded China in 2018,it has caused serious damage to local corn production.Chlorantraniliprole,an anthranilic diamide insecticide,has been widely used to control lepidopteran pests.Tetrachloropyramid is a new allosteric modulator insecticide devel-oped based on chlorantraniliprole,so it has a similar mechanism and insecticidal effect.In this study,we investigated resistance levels to chlorantraniliprole and tetrachloropyramid in S.frugiperda from 13 populations in China.Among the populations tested,the relative highest resistance to chlorantraniliprole occurred in the Guangzhou population,and the most susceptible to chlorantraniliprole was found in the Wuhan population.The lethal dosage LD50 value of the Guangzhou population against chlorantraniliprole was 27.8-fold higher than that of the Wuhan population.Minimal differences were observed among 5".frugiperda populations in terms of sensitivity to tetrachloropyramid.Heterozygous mutations at the 14734 site of the ryanodine receptor(RyR)were found,while no mutations were found in the G4891 site.The mutations were detected in only two of the 786 individuals analyzed one from the Qinzhou population and other from the Anshun population(frequency below 2%in both cases).There were no significant differences in the expression levels of RyR between Guangzhou and Wuhan populations.In summary,our results indicate that:(i)S.frugiperda has low resistance levels to diamide insecticides in China;and(ii)the differences in relative resistance among the 13 populations analyzed are not caused by the mutations in RyR or the expression of RyR.

Identification of the ryanodine receptor mutation I4743M and its contribution to diamide insecticide resistance in Spodoptera exigua (Lepidoptera: Noctuidae)

Insect ryanodine receptors(RyRs)are the targets of diamide insecticides.Two point mutations G4946E and I4790M(numbering according to Plutella xylostella,PxRyR)in the transmembrane domain of the insect RyRs associated with diamide resistance have so far been identified in three lepidopteran pests,P.xylostella,Tuta absoluta and Chilo suppressalis.In this study,we identified one of the known RyR target site resistance mutations(I4790M)in a field-collected population of Spodoptera exigua.The field-collected WF population of S.exigua exhibited 154 fold resistance to chlorantraniliprole when compared with the susceptible WH-S strain.Sequencing the transmembrane domains of S.exigua RyR(SeRyR)revealed that the resistant WF strain was homozygous for the 14743M mutation(corresponding to I4790M in PxRyR),whereas the G4900E allele(corresponding to G4946E of PxRyR)was not detected.The 4743M allele was introgressed into the susceptible WH-S strain by crossing WF with WH-S,followed by three rounds of backcrossing with WH-S.The introgressed strain 4743M was homozygous for the mutant 4743M allele and shared about 94%of its genetic background with that of the recipient WH-S strain.Compared with WH-S,the near-isogenic 4743M strain showed moderate levels of resistance to chlorantraniliprole(21 fold),cyantraniliprole(25 fold)and flubendiamide(22 fold),suggesting that the I4743M mutation confers medium levels of resistance to all three diamides.Genetic analysis showed diamide resistance in the 4743M strain was inherited as an autosomal and recessive trait.Results from this study have direct implications for the design of appropriate resistance monitoring and management practices to sustainably control S.exigua.

Design, synthesis and insecticidal activity of biphenyl-diamide derivatives

Diamides acting on insect ryanodine receptors are an intensive research area now. In order to search for novel candidates, a series of diamides containing biphenyl substructure were designed and synthesized.Their insecticidal activities against armyworms（Mythimna sepatara） and aphis（Aphis craccivora） were screened. The compounds with 3,5-dichloro-4-（1,1,2,2-tetrafluoroethoxy）phenyl substituent were found to be insecticidal to armyworms with the similar symptoms to poisoning by flubendiamide. In this research, we presented a novel type of diamide insecticide as a lead compound for further optimization.

Design,synthesis and insecticidal activity of novel anthranilic diamides with benzyl sulfide scaffold

A series of novel anthranilic diamides with benzyl sulfide scaffold were synthesized,in which N-pyridylpyrazole moiety generally regarded as key pharmacophore was abandoned.The target compounds were characterized by ~1H NMR,^（13）C NMR,^（19）F NMR and HRMS.The preliminary bioassays indicated that half of the title compounds were endowed with good insecticidal activities against armyworm（Mythimna sepatara） at the concentration of 500 mg/L,Exhilaratingly,the synthesized compound 3a was also active against Tetranychus cinnabarinus at 100 mg/L.The difference in activities between the target compounds was influenced by the substituents,which provided some hints for further investigation on structure modifications.

Design,synthesis and insecticidal activities of novel anthranilic diamides containing fluorinated groups as potential ryanodine receptors activitors

In order to search for novel potent and environmentally benign insecticides,a series of anthranilic diamides containing various fluorinated groups were designed and synthesized.Their structures were confirmed by -1H NMR,-（13）C NMR,-（19）F NMR,elemental analysis,HRMS or mass spectra.Their insecticidal activities against oriental armyworm（Mythimna separata） and diamondback moth（Plutella xyiostella）were evaluated.The preliminary structure-activity relationship（SAR） was discussed in detail.The biological assay indicated that most of the compounds exhibited moderate to excellent insecticidal activities.Especially,Ia showed high larvicidal activity against oriental armyworm.Meanwhile,Iu had better larvicidal effects against diamondback moth than commercial chlorantraniliprole.

Design, Synthesis and Insecticidal Evaluation of Novel N-Pyridylpyrazolecarboxamide Derivatives Containing Isoxazole, Isoxazoline and 1,3,4-Thiadiazole Rings

With the introduction of various heterocyclic rings at the benzene part of anthranilic diamides, a series of N-pylidylpyrazolecarboxamide derivatives containing isoxazole, isoxazoline and 1,3,4-thiadiazole rings was designed, synthesized and evaluated for their insecticidal activities. The structures of the obtained novel target compounds were confirmed by means of 1H NMR, 13C NMR and HRMS. The bioassay results indicated that most of the target compounds displayed moderate or good insecticidal activities against oriental armyworm and diamondback moth at the adopted concentrations compared with chlorantraniliprole, especially compounds Ii andII , of which the LC50 and LC95 values against oriental armyworm were further measured. The structure-activity relationship demonstrated that the introduction of chlorine in benzene ring, bromomethyl and acetoxyl substituents in 4,5-dihydroisoxazole part was more advantageous to improve the corresponding insecticidal activities than the introduction of other substitnents and heterocycles.