Physiological and biochemical characteristics of boscalid resistant isolates of Sclerotinia sclerotiorum from asparagus lettuce

Laboratory mutants of Sclerotinia sclerotiorum(Lib)de Bary,resistant to boscalid,have been extensively characterized.However,the resistance situation in the lettuce field remains largely elusive.In this study,among the 172 S.sclerotiorum isolates collected from asparagus lettuce field in Jiangsu Province,China,132 isolates(76.74%)exhibited low-level resistance to boscalid(Bos^(LR)),with a discriminatory dose of 5μg mL-1.In comparison to the boscalid-sensitive(BosS)isolates,most Bos^(LR)isolates demonstrated a slightly superior biological fitness,as evidenced by data on mycelial growth,sclerotium production and pathogenicity.Moreover,most Bos^(LR)isolates showed comparable levels of oxalic acid(OA)accumulation,increased exopolysaccharide(EPS)content and reduced membrane permeability when compared to the BosS isolates.Nevertheless,their responses to distinct stress factors diverged significantly.Furthermore,the effectiveness of boscalid in controlling Bos^(LR)isolates on radish was diminished compared to its efficacy on BosS isolates.Genetic mutations were identified in the SDH genes of Bos^(LR)isolates,revealing the existence of three resistant genotypes:I(^(A11V)at SDHB,SDHB^(A11V)),II(^(Q38R)at SDHC,SDHC^(Q38R))and III(SDHB^(A11V)+SDHC^(Q38R)).Importantly,no cross-resistance was observed between boscalid and other fungicides such as thifluzamide,pydiflumetofen,fluazinam,or tebuconazole.Our molecular docking analysis indicated that the docking total score(DTS)of the type I resistant isolates(1.3993)was lower than that of the sensitive isolates(1.7499),implying a reduced affinity between SDHB and boscalid as a potential mechanism underlying the boscalid resistance in S.sclerotiorum.These findings contribute to an enhanced comprehension of boscalid’s mode of action and furnish valuable insights into the management of boscalid resistance.

First report of field resistance to cyantraniliprole, a new anthranilic diamide insecticide, on Bemisia tabaciMED in China

The Bemisia tabaci （Gennadius） cryptic species complex comprises important insect pests that cause devastating damage to agricultural crops worldwide. In China, the B. tabaci Mediterranean （MED） （or biotype Q） species is threatening agricul- tural production all over the country as resistance to commonly used insecticides has increased. This situation highlights the need for alternative pest control measures. Cyantraniliprole, a novel anthraniiic diamide insecticide, has been widely employed to control Hemipteran pests. To monitor the levels of resistance to cyantraniliprole in B. tabaci field populations in China, bioassays were conducted for 18 field samples from nine provinces over two years. Compared with median lethal concentration （LC^0） for the MED susceptible strain, all field samples had significantly higher resistance to cyantraniliprole. Furthermore, resistance factors （RFs） increased significantly in samples from Shanxi （from 5.62 in 2015 to 25.81 in 2016）, Hunan （3.30 in 2015 to 20.97 in 2016） and Hubei （from 9.81 in 2015 to 23.91 in 2016） provinces. This study indicates a considerable decrease in the efficacy of cyantraniliprole against B. tabaci and establishes a baseline of susceptibility that could serve as a reference for future monitoring and management of B. tabaci resistance to cyantraniliprole.

Characterization of field-evolved resistance to cyantraniliprole in Bemisia tabaci MED from China

Cyantraniliprole is a novel anthranilic diamide insecticide with significant efficacy against Bemisia tabaci,an important pest insect worldwide.In this study,we conducted reversion and selection work and genetic analysis,and determined cross-resistance spectrum and synergism of cyantraniliprole resistance based on the reported population,SX population,of B.tabaci collected from Shanxi Province,China.Compared with a susceptible strain(MED-S),SX population,the field-evolved cyantraniliprole-resistant population exhibited 26.4-fold higher resistance to cyantraniliprole.In SX,a sharp decline of cyantraniliprole resistance was shown in the absence of selection.Another tested strain,SX-R,was established from SX population after successive selection with cyantraniliprole and recently developed 138.4-fold high resistance to cyantraniliprole.SX-R had no cross-resistance to abamectin,imidacloprid,thiamethoxam,sulfoxaflor,or bifenthrin.Genetic analysis illustrated that cyantraniliprole resistance in SX-R was autosomally inherited and incompletely dominant.Additionally,piperonyl butoxide(PBO)significantly inhibited cyantraniliprole resistance in the SX-R strain.In conclusion,the selection of SX with cyantraniliprole led to high resistance to cyantraniliprole which is incompletely dominant and no cross-resistance to several common types of insecticides.Enhanced oxidative metabolism is possibly involved in the resistance of SX-R,yet target-site resistance could not be excluded.

Identification and tissue distribution of odorant binding protein genes in Harmonia axyridis (Coleoptera:Coccinellidae)

The olfactory system of insects is crucial in modulating behaviors such as host seeking,mating,and oviposition.Odorantbinding proteins(OBPs)are involved in semiochemical recognition.OBPs recognize and bind odorants and transport them to odorant receptors located in olfactory neurons.Harmonia axyridis(Coleoptera:Coccinellidae)is a widely used predacious biological control agent for many agricultural and forestry pests.This study identified 19 OBPs in H.axyridis based on the antennal and whole-body transcriptomes of adults and obtained all the full-length open reading frames,including 11‘Classic’OBPs,7‘Minus-C’OBPs and 1‘Plus-C’OBP.They encoded 125 to 241 amino acid proteins with molecular weights ranging from 13.75 to 27.75 kDa and isoelectric points ranging from 4.15 to 8.80.Phylogenetic analyses were used to study the relationships between H.axyridis OBPs and OBPs from other species of Coleoptera.Quantitative real-time PCR(qPCR)analysis showed that HaxyOBP2,3,5,8,10,12,13,14,and 15 were highly expressed in antennae of both adult females and males.Moreover,HaxyOBP2,3,5,12,and 15 were more abundantly expressed in antennae than other body parts,while HaxyOBP13 and HaxyOBP14 were expressed predominantly,and at similar levels,in the head and antennae.The other OBP genes were highly expressed in non-olfactory tissues including the thorax,abdomen,legs,and wings.These results provide valuable information for further study of H.axyridis olfaction,which may ultimately enhance its use as a biocontrol agent.

Genetics and fitness costs of resistance to flupyradifurone in Bemisia tabaci from China

Flupyradifurone is a promising new insecticide used for controlling Bemisia tabaci during vegetable production.In this study,we assessed the fitness costs and mode of inheritance associated with resistance to flupyradifurone in B.tabaci by comparing the susceptible strain(MED-S)to one field-evolved flupyradifurone-resistant strain(WH-R,with 199-fold resistance)and one laboratory-selected flupyradifurone-resistant strain(FLU-SEL,with 124-fold resistance).Progenies of reciprocal crosses between WH-R and MED-S(F_(1A),F_(1B),and pooled F_(1)),and between FLU-SEL and MED-S(F_(1C),F_(1D),and pooled F_(1)’),showed varying degrees of dominance,indicating that resistance to flupyradifurone in WH-R was autosomal and incompletely dominant,yet in FLU-SEL it was autosomal and incompletely recessive.Furthermore,the development of resistance to flupyradifurone occurred at the expense of fitness costs for the resistant populations.Compared to the MED-S strain,WH-R showed a relative fitness of 0.50 with significantly prolonged developmental durations and reduced survival rates of the nymphal and pseudopupal stages,as well as decreased fecundity and hatchability.Similarly,FLU-SEL showed a relative fitness of 0.65 and also demonstrated prolonged developmental durations and reduced survival rates of nymphs and pseudopupae,as well as decreased hatchability in comparison with the MED-S strain.However,no significant differences in fecundity were observed between MED-S and FLU-SEL.The present study provides useful knowledge for formulating pest management strategies in the field,which will allow growers to slow the development of resistance to flupyradifurone and to sustainably control B.tabaci.

Development of an analytical method based on solid-phase extraction and LC-MS/MS for the monitoring of current-use pesticides and their metabolites in human urine

Pyrethroids,organophosphorus pesticides and fipronil have been listed as priority chemicals in human biomonitoring studies because of their wide use and potential health effects in humans.The determination of 13 pesticides,including pyrethroids(deltamethrin,cypermethrin,permethrin,cyfluthrin,bifenthrin),organophosphorus(chlorpyrifos,chlorpyrifosmethyl,and malathion),fipronil,neonicotinoids(imidacloprid,acetamiprid and thiacloprid)and triazole(prothioconazole),together with 13 corresponding metabolites in human urine samples was achieved by solid-phase extraction and analysis by liquid chromatography coupled to tandem mass spectrometry.All targeted compounds,except malathion dicarboxylic acid,were measured with a mean within-accuracy(n=5)of 71%–114%(RSD:1%–14%)and between-run(n=15)accuracy of 80%–118%(RSD:2%–14%).Limits of quantitation of the targeted analytes ranged from 0.1 to 16 pg/m L.The detection result of urine samples from 25 volunteers indicated that the detection frequencies of 3,5,6-trichloro-2-pyridinol(median:448 pg/m L),6-chloropyridine-3-carboxylic acid(median:193 pg/m L),2-methyl-3-phenylbenzoic acid(median:181 pg/m L),3-phenoxybenzoic acid(median:99 pg/m L),2-isopropyl-6-methyl-4-pyrimidinol(median:77 pg/m L),cyfluthrin(median:59 pg/m L),cis-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid(cis-DCCA,median:53 pg/m L),trans-DCCA(median:25 pg/m L),prothioconazole(median:21 pg/m L),imidacloprid(median:7 pg/m L),and prothioconazole-desthio(median:1 pg/m L)were>50%.The obtained results show that the validated method is suitable for the human biomonitoring of these currentuse pesticides and their metabolites.

Effects of abamectin selection on the genetic differentiation within Plutella xylostella （Lepidoptera： Plutellidae） based on amplified fragment length polymorphism

Diamondback moth, Plutella xylostella （L.） is one of the most serious insect pests for its remarkable ability to develop resistance to virtually every insecticide that has been used against it. In the present study, amplified fragment length poly- morphism （AFLP） is used to study the genetic differentiation as well as the effects of abamectin-selection on population genetic differentiation for P. xylostella. A dendrogram was constructed from the matrix of genetic distances using the STATISTICA software （Version 4.5） and unweighted pair-group method with arithmetic averages （UPGMA）. The data demonstrated that compared to the susceptible strain （ABM-s）, the heterozy- gosity in the abamectin-resistant strain （ABM-r） decreased with the increased selection pressure and resistant level. When the resistance ratio was below 4.3, there was no sig- nificant differentiation at the genome DNA level. When the resistance ratio reached 5.8, a fairly significant differentiation began to appear, and when the resistance ratio reached and exceeded 8.1, there appeared a significant genetic differentiation. The results suggest that abamectin selection is associated with increased genetic polymorphism in P. xylostella.