北京某垃圾处理厂家蝇对3种杀虫剂的抗性调查

目的评估北京市某垃圾处理厂采集的家蝇种群对氯氟醚菊酯、敌敌畏、残杀威的抗性水平,为合理用药提供科学依据。方法采用微量点滴法测定家蝇对氯氟醚菊酯、敌敌畏、残杀威3中杀虫剂的抗性,以及增效醚(PBO)、脱叶磷(DEF)的增效作用。结果氯氟醚菊酯、敌敌畏和残杀威对所采集家蝇野外种群的LD_(50)分别为0.082、0.327、>100μg/只,家蝇对3种杀虫剂的抗性倍数分别为20.50、40.88、>190;增效剂PBO、DEF对氟氯氰菊酯增效比分别为13.67,3.04;PBO和DEF对敌敌畏的增效比分别为1.42、20.43。结论北京市某垃圾处理厂家蝇对氯氟醚菊酯、敌敌畏、残杀威分别产生了不同程度的抗性,多功能氧化酶和羧酸酯酶调节的解毒代谢分别在家蝇野外种群对氯氟醚菊酯和敌敌畏的抗性中起着重要作用。

草地贪夜蛾幼虫对常用杀虫剂相对敏感基线的建立

【目的】本研究旨在建立草地贪夜蛾Spodoptera frugiperda对常用杀虫剂的相对敏感基线,为我国草地贪夜蛾的抗药性系统性监测提供依据。【方法】从玉米田采集草地贪夜蛾在室内不接触任何杀虫剂连续饲养5~7代,采用浸叶法和点滴法测定了草地贪夜蛾3龄幼虫以及采用饲料药膜法测定了草地贪夜蛾2龄幼虫对6大类共7种常用杀虫剂(甲维盐、乙基多杀菌素、虫螨腈、茚虫威、四氯虫酰胺、虱螨脲和氯虫苯甲酰胺)的敏感性,并据此建立了草地贪夜蛾幼虫对这7种杀虫剂的相对敏感基线。【结果】浸叶法测得上述7种药剂对草地贪夜蛾幼虫的LC_(50)值在0.054~12.131 mg/L之间;点滴法测得上述6种药剂(不含虱螨脲)对草地贪夜蛾幼虫的LD_(50)值在0.355~4.707μg/g之间;饲料药膜法测得上述7种药剂对草地贪夜蛾幼虫的LC_(50)值在0.003~0.238μg/cm^(2)之间。【结论】采用3种生测方法建立了草地贪夜蛾幼虫对几种常用杀虫剂的相对敏感基线,为我国草地贪夜蛾的抗药性监测和化学防治提供了依据。

Diversity and Genetic Differentiation of the Whitefly Bemisia tabaci Species Complex in China Based on mtCOI and cDNA-AFLP Analysis

The whitefly Bemisia tabaci are considered as a taxonomically complex that contained some destructive pests.Two of the most prevalent cryptic species are B.tabaci Middle East-Asia Minor 1（MEAM1）and Mediterranean（MED）.In an extensive field survey of the B.tabaci complex present throughout part of China from 2004 to 2007,we obtained 93 samples of B.tabaci from 22 provinces.We determined that these Chinese haplotypes included 2 invasive species（MEAM1 and MED）,and 4 indigenous cryptic species（Asia II 1,Asia II 3,China 3 and Asia II 7）by sequencing mitochondrial cytochrome oxidose one gene（mtCOI）.The diversity and genetic differentiation of a subset of 19 populations of B.tabaci were studied using cDNA amplified fragment length polymorphism（AFLP）.Prior to 2007,MEAM1 was a dominant species in many provinces in China.By 2007,MED was dominant in 11 provinces.Both invasive and indigenous species were simultaneously found in some regions.Indigenous species of B.tabaci were found in six provinces in southern China.MED and MEAM1 have broad ranges of host plants,and indigenous species appeared to have much narrower host ranges.All Asia II 3 samples were found on cotton except one on aubergine.China 3 has more host plants than Asia II 3.Twelve samples of China 3 were collected from sweet potato,Japanese hop,squash and cotton.A total of 677 reproducible bands amplified with 5 AFLP primer combinations were obtained.The highest proportion of polymorphic bands was 98.7% and the lowest was 91.9%.Unweighted pair-group method analysis indicated that the clustering was independent of the different species.MED showed the lowest degree of similarity than the other species.The data indicate that both MEAM1and MED were rapidly established in China.

Biochemical Mechanism of Chlorantraniliprole Resistance in the Diamondback Moth, Plutella xylostella Linnaeus

The insecticide chlorantraniliprole exhibits good efifcacy and plays an important role in controlling the diamondback moth, Plutella xylostella Linnaeus. However, resistance to chlorantraniliprole has been observed recently in some ifeld populations. At present study, diamondback moths with resistance to chlorantraniliprole （resistant ratio （RR） was 82.18） for biochemical assays were selected. The assays were performed to determine potential resistance mechanisms. The results showed that the selected resistant moths （GDLZ-R） and susceptible moth could be synergized by known metabolic inhibitors such as piperonyl butoxide （PBO）, triphenyl phosphate （TPP） and diethyl-maleate （DEM） at different levels （1.68-5.50-fold and 2.20-2.89-fold, respectively）, and DEM showed the maximum synergism in both strains. In enzymes assays, a high level of glutathione-S-transferase （GST） was observed in the resistant moth, in contrast, moths that are susceptible to the insecticide had only 1/3 the GST activity of the resistant moths. The analysis of short-term exposure of chlorantraniliprole on biochemical response in the resistant strain also showed that GST activity was signiifcantly elevated after exposure to a sub-lethal concentration of chlorantraniliprole （about 1/3 LC50, 12 mg L-1） 12 and 24 h, respectively. The results show that there is a strong correlation between the enzyme activity and resistance, and GST is likely the main detoxiifcation mechanism responsible for resistance to chlorantraniliprole in P. xylostella L., cytochrome P450 monooxygenase （P450） and carboxy-lesterase （CarE） are involved in to some extent.

Population life tables for the invasive fall armyworm,Spodoptera frugiperda fed on major oil crops planted in China

The fall armyworm(FAW),Spodoptera frugiperda,is a newly invasive,widespread agricultural pest in China.Understanding the suitability of the main field crops in Chinese agricultural system as host for this polyphagous herbivore is especially important for making control strategy.Here,after FAWs were fed three important oil-bearing crops(oilseed rape,soybean and sunflower)planted in China and resultant population parameters were compared using the age-stage,two-sex life table method,survival of larvae on soybean was significantly lower than that on oilseed rape and sunflower.Developmental duration of larvae on soybean was also the longest(23.3 days).The highest pupation rate was recorded on sunflower.The highest pupal mass(0.19 g)was attained on oilseed rape,significantly higher than on the other host plants;the lowest mass was on soybean(0.15 g).On soybean,oilseed rape and sunflower,respectively,the average generation period was 42.21,39.10 and 40.44 d;the intrinsic rate of increase(r)was 0.0844,0.1041 and 0.1134;the finite rate of increase(λ)was 1.0881,1.1098 and 1.1202.While the most suitable host plant overall was sunflower,S.frugiperda completed development and increased its population on all three host plants.Thus,soybean,oilseed rape and sunflower were all suitable for FAW,and population monitoring and management of FAW in these crops should be increased.

A Fragment of Cadherin-Like Protein Enhances Bacillus thuringiensis Cry1B and Cry1C Toxicity to Spodoptera exigua(Lepidoptera:Noctuidae)

Cry toxins produced by Bacillus thuringiensis（Bt） are effective biological insecticides against certain insect species.In this study,bioassay results indicated that Cry1B and Cry1C were toxic to Spodoptera exigua.We also identified a cadherin-like gene in S.exigua that could enhance the toxicity of Cry1B and Cry1C.The cadherin-like gene identified from the larvae midgut tissue was cloned by reverse transcription polymerase chain reaction（RT-PCR） and rapid amplification of cDNA ends（RACE）.The full-length cDNA of the gene consisted of 5 220 bp encoding 1 740 amino acid with a predicted molecular mass of 196 kD.BLAST search analysis showed that the predicted amino acid sequence had a high sequence identity to the published sequences of cadherin-like proteins from other Lepidoptera insects.Spatial expression of the cadherin-like gene detected by qRT-PCR analysis revealed that the cadherin-like gene was mainly present in the gut of 4th instar larvae and during different life stages.The results suggested that the commercial development of this synergist has the potential to enhance Cry1B and Cry1C toxicity against Lepidoptera insects.

Adult nutrition affects reproduction and flight performance of the invasive fall armyworm,Spodoptera frugiperda in China

Floral resources,such as carbohydrate-rich nectar or pollen,can bolster fitness and raise reproductive output of adult lepidopterans.Here,we used laboratory experiments to assess how those plant-derived foods impact adult fecundity,reproductive physiology and flight performance of an invasive strain of the fall armyworm,Spodoptera frugiperda(FAW;Lepidoptera:Noctuidae)in China.More specifically,supplementary feeding on bee pollen and honey enhanced FAW flight duration,testis size,ovarian development,longevity and adult fecundity.FAW adults attained the longest pre-oviposition(10.8 days)and oviposition period(6.8 days)and longevity(19.2 days)on 5%acacia honey.Upon access to 2.5%acacia honey and 2.5‰pine pollen,S.frugiperda attained the highest mating rate(79.7%),fecundity(644.9 eggs/female)and egg hatching rate(82.3%).Feeding on honey further delayed decay of male testes,while ovarian development was enhanced when female moths were allowed access to 2.5%honey and 2.5‰pine pollen.Upon feeding on 5%honey solution,S.frugiperda engaged in flight over the longest duration(9.5 h),distance(29.9 km)and speed(3.1 km h-1).Honey had a comparatively greater effect on the above parameters than pollen.Our findings help decipher FAW invasion patterns and population dynamics,facilitate the development of nutritional attractants,and contribute to integrated pest management of this newly-invasive pest in eastern Asia.

Ovipositional responses of Spodoptera frugiperda on host plants provide a basis for using Bt-transgenic maize as trap crop in China

Spodoptera frugiperda,the pest fall armyworm(FAW),is widespread in more than 100 countries.To date,planting insectresistant transgenic crops is one of the main control methods in its native countries.In this study we evaluated Bt-transgenic maize(Bt maize)and non-transgenic(conventional)maize and six other host plants in greenhouse pot experiments and field trials for oviposition preference by the Chinese populations of FAW.In laboratory trials,female moths preferred to oviposit on maize with no significant preference between conventional and Bt maize.However,after conventional and transgenic maize were exposed to FAW larvae and damaged,oviposition was significantly higher on transgenic maize than on the conventional one.Field trials showed that for plants less damaged at an early stage(seedling stage),oviposition of FAW on transgenic and conventional maize was significantly higher than that on wheat,sorghum,foxtail millet,peanut and soybean while showing no significant difference between transgenic or conventional maize.FAW adults mainly laid eggs on Bt maize,while the larval density and leaf damage rating or percentage of damaged plants were significantly lower than on conventional maize.Larval density and its damage on conventional maize were significantly higher than that on Bt maize and the other five hosts.Thus,maize is a highly preferred and suitable host for S.frugiperda feeding and ovipositing,and Bt maize can be used as trap crop to protect other crops.

A sublethal concentration of afidopyropen suppresses the population growth of the cotton aphid, Aphis gossypii Glover(Hemiptera: Aphididae)

The cotton aphid,Aphis gossypii Glover(Hemiptera:Aphididae),is an important insect pest of cotton crops worldwide.The objectives of this study were to determine the acute toxicity of afidopyropen and whether there are any effects of sublethal concentrations of afidopyropen on the biological characteristics of A.gossypii.The results showed that afidopyropen possesses high acute toxicity to adult A.gossypii with a 72 h LC_(50) value of 1.062 mg L^(–1).A sublethal concentration(LC_(10))of afidopyropen significantly decreased adult longevity,fecundity and oviposition days of female adults in both F0 and F1 generations.The total pre-adult survival of F_(1) progeny was also significantly reduced by 30%at the LC_(10) of afidopyropen.In addition,the nymph developmental time,pre-adult period,adult pre-reproductive period(APRP),and total pre-reproductive period(TPRP)of the F1 progeny were significantly prolonged compared with the control.Several population parameters,including the net reproductive rate(R_(0)),intrinsic rate of increase(r)and finite rate of increase(λ)of F_(1) progeny were significantly decreased by a sublethal afidopyropen concentration exposure.These results indicated that sublethal concentration of afidopyropen can significantly suppress A.gossypii population growth.It would be useful for assessing the overall effects of afidopyropen on A.gossypii.

Sublethal Effects of Metaflumizone on Plutella xylostella (Lepidoptera: Plutellidae)

Metaflumizone is a novel sodium channel blocker insecticide, which has been registered for controling the diamondback moth （DBM）, Plutella xylostella （Lepidoptera： Plutellidae） in China. It is unavoidable for DBMs to be exposed to sublethal dose of metaflumizone in brassicaceous vegetable field. Sublethal effects of metaflumizone at LC15 （1.06 mg L-1） and LCz5 （2.03 mg L-1） on the biological characteristics were investigated. Pupation rate, pupal period and pupal weight were significantly declined comparing with the control （P=0.05） when third instar larvae were exposed to LC15 and LC25 of metaflumizone. Comparing the control group to LC15 and LC25 treatment groups, there were significant differences in the development periods of eggs, first instar larvae, pupae and total preoviposition period. The peak of age-specific fecundity in LC15 and LC25 treatment groups was lagged behind control group. Mean values of intrinsic rate of increase （rm）, net reproductive rate （R0） and finite rate of increase （λ） observed from the LCl5 and LC25 treatment groups were lower than those from the control group. But mean values of gross reproduction rate （GRR） was not different. The mean generation time （T） of the treatment groups was prolonged. Whether sublethal doses of metaflumizone could stimulate reproduction in the long term needs further investigation on continuous generations.

Sublethal effects of sulfoxaflor on the fitness of two species of wheat aphids, Sitobion avenae(F.) and Rhopalosiphum padi(L.)

Sitobion avenae(F.) and Rhopalosiphum padi(L.) are two important pests of wheat in China.They typically coexist in fields during the late period of wheat growth.Sulfoxaflor is a novel sulfoximine insecticide that demonstrates broad-spectrum efficacy,especially in targeting sap-feeding insects.This study was carried out to investigate the sublethal effects of sulfoxaflor on the development,longevity,and reproduction of two species of wheat aphids.Our results showed that sublethal concentrations of sulfoxaflor did not cause significant effects on the fecundity or the longevity of the parent generation(F0 generation) of either S.avenae or R.padi.However,it caused transgenerational sublethal effects.For S.avenae,adult longevity of F1 generation was significantly decreased.No significant differences were observed on the population parameters of S.avenae in the F1 generation.For R.padi,the adult preoviposition period(APOP) and the total preoviposition period(TPOP) of F1 generation were significantly reduced.The mean generation time(T) was significantly reduced in the R.padi F1 generation.What’s more,the intrinsic rate of increase(rm) and the finite rate of increase(λ) were significantly increased in the R.padi F1 generation.Taken together,these results suggest that exposure to the LC25 of sulfoxafl had no effects on the parent generation of S.avenae or R.padi,but it reduced adult longevity of S.avenae as a negative effect and increased the rm and λ of R.padi in the first progeny generation,which may have an impact on the population dynamics of R.padi.

Characterization of carboxylesterase PxαE8 and its role in multi-insecticide resistance in Plutella xylostella(L.)

Carboxylesterase(CarE)was considered as important phase-I detoxifying enzymes which participated in detoxification of different types of insecticides.Up-regulation of CarE genes has been proved playing a major role in insecticide resistance in many pest insects,but its involvement in resistance to insecticides in Plutella xylostella has been rarely reported.In this study,a CarE cDNA named PxαE8 was identified in P.xylostella,which has an open reading frame of 1599 nucleotides and putatively encodes 532 amino acids.The investigation of spatial expression profiles of PxαE8 revealed that it was expressed in all developmental stages,especially in larvae and adults.The body part/tissue-specific expression profiles showed that the PxαE8 mainly expressed in fat body,malpighian tubule and hemolymph of larvae.Further,the relative expression of PxαE8 in two multi-resistant field populations,Hainan(HN)and Guangdong(GD)populations,was found 24.4-and 15.5-fold higher than that in susceptible population,respectively.Knockdown of PxαE8 by RNA interference dramatically increased the mortalities of larvae of HN population treated with LC_(50) of beta-cypermethrin and phoxim by 25.3 and 18.3%,respectively.These results suggested that up-regulation of PxαE8 was involved in resistance to both beta-cypermethrin and phoxim in P.xylostella,which shed light on further understanding of molecular mechanisms of multi-insecticide-resistance in P.xylostella and other pest insects.

The Binding Characterization of Cry Insecticidal Proteins to the Brush Border Membrane Vesicles of Helicoverpa armigera, Spodoptera exigua, Spodoptera litura and Agrotis ipsilon

Cry toxins produced by Bacillus thuringiensis （Bt） are effective biological insecticides against certain insect species. However, there are potential risks of the evolved resistance of insects to Cry toxin owing to decreased binding of toxins to target sites in the brush border membranes of the larva midgut. The Cry toxins with different binding sites in the larval midgut have been considered to be a good combination to deploy in delaying resistance evolution. Bioassay results demonstrated that the toxicity of different Cry toxins ranked differently for each species. The toxicity ranking was CrylAc〉CrylAb〉Cry2Ab for Helicoverpa armigera, CrylB〉CrylC〉Cry2Ab for Spodoptera exigua, and Cry2Ab〉CrylB〉 CrylC for S. litura. Only Cry2Ab was toxic to Agrotis ipsilon. Binding experiments were performed with ^125I-CrylAb, ^125I-CrylAc, ^125I-CrylB, ^125I-CrylC, ^125I-Cry2Ab and the brush border membranes vesicles （BBMV） from H. armigera, S. exigua, S. litura and A. ipsilon. The binding of CrylAb and CrylAc was shown to be saturable by incubating with increasing concentrations of H. armigera BBMV （Kd=（45.00＋2.01） nmol L-1 and （12.80＋0.18） nmol L^-1, respectively; Bmax=（54.95±l.79） ng and （55.44±0.91） ng, separately）. The binding of CrylB was shown to be saturable by incubating with increasing concentrations ofS. exigua BBMV （Kd=（23.26±1.66） nmol L^-1; Bmax=（65.37±1.87） ng）. The binding of ^125I-Cry toxins was shown to be non-saturable by incubating with increasing concentrations of S. litura and A. ipsilon BBMV. In contrast, CrylB and CrylC showed some combination with the BBMV orS. litura, and a certain amount of Cry2Ab could bind to the BBMV ofA. ipsilon. These observations suggest that a future strategy could be devised for the focused combination of specific cry genes in transgenic crops to control target pests, widen the spectrum of insecticide effectiveness and postpone insect resistance evolution.

Selection and evaluation of potential reference genes for gene expression analysis in greenbug(Schizaphis graminum Rondani)

In order to precisely assess gene expression level, a suitable internal reference gene must be chosen to quantify real-time reverse transcription polymerase chain reaction （RT-qPCR） data. For greenbug, Schizaphis graminum, a suitable reference gene for assessing the level of transcriptional expression of target genes has yet to be explored. In our study, eight reference genes, elongation fator 1 beta （Ef1β）, TATA box binding protein （TBP）, alpha-tubulin （a-TUB）, 18S ribosomal （18S）, 28S ribosomal （28S）, glyceraldehyde-3-phosphate （GAPDH）, actin （ACT）, and ribosomal protein L18 （RPL18） were evaluated in S. graminum at different developmental stages, tissues, and insecticide treatments. To further explore whether these genes are suitable to serve as internal control, three software-based approaches （geNorm, BestKeeper, and NormFinder）, ACt method, and one web-based comprehensive tool （RefFinder） were employed to analyze and rank the tested genes. The optimal number of reference genes was determined using the geNorm program, and the suitability of particular reference genes was empirically validated according to normalized gene expression data of three target genes, heat shock protein gene （HSP70）, cytocrome P450 gene （SgraCYP18A1）, and glutathione S-transferase （GST）. We found that the most suitable reference genes varied considerably under different experimental conditions. For developmental stages, a-TUB and 28S were the optimal reference genes; for different tissues, 18S and ACTwere suitable reference genes; for insecticide treatments, 28S and a-TUB were suitable for normalizations of expression data. In addition, 28S and a-TUB were the suitable reference gene as they had the most stable expression among different developmental stages, tissues and insecticide treatments. This should be useful for the selection of the suitable reference genes to obtain reliable RT- qPCR data in the gene expression of S. graminum.

Response of Cytochrome P450 Expression to Maize Volatiles in Helicoverpa armigera (Hner)

The 7-ethoxycoumarin O-deethylase （ECOD） activities of cytochrome P450s and differential expression of six cytochrome P450 genes induced by the volatiles from both damaged and undamaged maize plants were investigated in the cotton bollworm, Helicoverpa armigera （Hiabner）. The ECOD activity changed with time of exposure to maize volatiles. At 36 h after cotton bollworm larvae exposure to maize volatiles, the ECOD activities in cotton bollworm damaged and artificially damaged groups were 2.36 and 4.53 times higher than the control group respectively. The relative expression levels of CYP4S1, CYP6B2 and CYP6B7 in the cotton bollworm were significantly increased in artificially damaged plant group, which was 2.93, 5.09 and 10.66 times higher than that in the control group, respectively. The expression levels of CYP6B2, CYP6B6, CYP9A12, and CYP9A14 were much lower in the larvae exposure to volatiles from both healthy and pest damaged maize seedlings than in the control group at 12 h after larvae exposure to maize volatiles. For the cotton bollworm damaged maize group, the expression of CYP4S1 and CYP9A14 increased.

Differential effects of insecticides on mitochondrial membrane fluidity and ATPase activity between the wolf spider and the rice stem borer

Differential effects of methamidophos and three pyrethroids on ATPase activity and membrane fluidity of mitochondria were investigated between the wolf spider（Pirata subpiraticus（Boes.et Str.））and the rice stem borer（Chilo suppressalis（Walker））.Based on a comparison of LD_（50） values,the toxicities of the tested insecticides were higher to the wolf spider than to the rice stem borer.Cyhalothrin at 1×10^（–4） mmol L^（–1） caused inhibition of the mitochondrial Na~＋-K~＋-ATPase and Ca^（2＋）-Mg^（2＋）-ATPase activities,and it’s inhibitions on Na＋-K＋-ATPase and Ca^（2＋）-Mg^（2＋）-ATPase activities were significantly higher in the wolf spider（44 and 28%）than in the rice stem borer（19 and 11%）.Methamidophos at 1×10^（–4） mmol L^（–1） decreased Ca^（2＋）-Mg^（2＋）-ATPase activity by 16 and 27%in the wolf spider and the rice stem borer,respectively,but no significant effect on the specific activity of Na＋-K＋-ATPase was observed.The DPH（1,6-diphenyl-1,3,5-hexatriene）fluorescence polarization values of mitochondrial membranes were not significantly affected by methamidophos in either species.However,cyhalothrin and alpha-cypermethrin induced the values of DPH polarization of mitochondrial membrane increasing with the concentration of cyhalothrin and alpha-cypermethrin from 20 to 100μmol L^（–1） in the rice stem borer and the wolf spider.Effect of ethofenprox on fluidity of the wolf spider and the rice stem borer was contrary.These results suggest that both inhibition of membrane ATPase and changes of membrane fluidity could be appended to the action mechanisms of pyrethroid insecticides.

Insecticide induction of O-demethylase activity and expression of cytochrome P450 genes in the red imported fire ant (Solenopsis invicta Buren)

The red imported fire ant （Solenopsis invicta） is a global major invasive pest, and has caused significant economic, social and environmental impacts since its invasion to mainland of China in 2004. To date, chemical control has been the most effective measure. However, the long-term use of chemicals would lead to an unexpected rebound. To understand the risks and explore the mechanisms of detoxification or induction to insecticides in S. invicta, the O-demethylase activity and expression of cytochrome P450 genes of workers and queens, and the effects of chlorpyrifos and fipronil exposure in workers were investigated. Biochemical assays showed the O-demethylase activity of cytochrome P450 was significantly higher in workers than in queens （1.66-fold）, and was significantly induced in workers exposed to chlorpyrifos and fipronil, reaching a maximum （3.00- and 1.95-fold） at 48 h and then decreasing dramatically compared to controls （exposed to acetone counter- part）. The relative expression levels of 12 cytochrome P450 expressed sequence tags （ESTs） in workers were significantly higher than in queens （from 2.3- to 36.4-fold）. Multiple cytochrome P450 genes （except 9E4） were co-up-regulated （from 1.5- to 2.86-fold） in workers exposed to fipronil. These results indicated that the increased O-demethylase activity may result from the increased transcription levels of cytochrome P450 related to detoxification of insecticides in S. invicta. It appears that cytochrome P450 plays an important role in enhanced metabolic detoxification of insecticides. At the same time, it also provides the theoretical basis for resistance management and rational usage of insecticides to control S. invicta.

Characterization and functional analysis of β-1,3-galactosyltransferase involved in Cry1Ac resistance from Helicoverpa armigera(Hübner)

Carbohydrate chains are the principal antigens by which Bacillus thuringiensis（Bt） identify receptor proteins. The interaction between the antigen and Bt causes a pore in the membrane of midgut epithelial cells of insects. Receptor proteins, such as aminopeptidase N and alkaline phosphatase, are glycoproteins. Cadherin is another cell surface receptor protein which has potential glycosylation sites. Glycosyltransferase is very important for the synthesis and modification of receptor proteins. It can indirectly influence the function of Bt. The 1 950 bp full-length c DNA encoding β-1,3-galactosyltransferase was cloned from the the midgut of Helicoverpa armigera by degenerative PCR combined with RACE techniques（GAL-Harm, Gen Bank accession no.： GQ904195.1） with two potential N-glycosylation sites（^157NNTI^160 and ^272NKTL^275）. Protein sequence alignments revealed that H. armigera β-1,3-galactosyltransferase shared high identity with β-1,3-galactosyltransferase in other insect species. The expression level of the β-1,3-galactosyltransferase gene in Cry1Ac-resistant H. armigera larvae was 9.2-fold higher than that in susceptible strain. The function of β-1,3-galactosyltransferase was investigated using RNAi technique. The result showed Cry1 Ac enhanced the toxicity against the si RNA-treated larvae compared with non-si RNA-treated ones, which indicated β-1,3-galactosyltransferase played an important role for the insecticidal toxicity of Cry1 Ac in H. armigera.

Alteration of glutathione S-transferase properties during the development of Micromelalopha troglodyta larvae (Lepidoptera: Notodontidae)

Micromelalopha troglodyta （Graeser） is an important pest of poplar in China. Glutathione S-transferases （GSTs） are known to be responsible for adaptation mechanisms of M. troglodyta. The activities and kinetic constants of glutathione S-transferases in M. troglodyta were studied. Significant differences in glutathione S-transferase activity and kinetic characteristics were observed among five instars of M. troglodyta larvae. Furthermore, the inhibition of glutathione S-transferase activity in five instars by 24 inhibitors was conducted. The results show the inhibition of GST activity of different instars by 24 inhibitors was different. For GST activity in the 1st instar, chlorpyrifos, lambda-cyhalothrin, endosulfan, abamectin, fipronil and pyridaben were the best inhibitors tested, and for GST activity in the 2nd instar, tannic acid and quercetin were the most potent inhibitors tested, and for GST activity in the 3rd instar, the inhibitory effects of quercetin, chlorpyrifos and lambda-cyhalothrin were the highest, and for GST activity in the 4th instar, quercetin and lambda-cyhalothrin were the best inhibitors, and the inhibitory effect of phoxim was the highest for GST activity in the 5th instar. Our results show that glutathione S-transferases in different instars are qualitatively different in isozyme composition and thus different in sensitivity to inhibitors.

The influence of Tetranychus cinnabarinus-induced plant defense responses on Aphis gossypii development

Carmine spider mites （Tetranychus cinnabarinus） and cotton aphids （Aphis gossypii） are both serious pests of cotton, and cause reductions in yields of this key agricultural crop. In order to gain insights into how plant defense responses induced by one herbivore species affect the behavior and performance of another, we examined how infestation with T. cinnabarinus influences the development of A. gossypfi using cotton as a model. In this study, we measured the activities of several important biochemical markers and secondary metabolites in the leaves of cotton seedlings responding to infestation by T. cinnabarinus. Furthermore, the influences of T. cinnabarinus infestation on the development ofA. gossypfi in cotton were also examined. Our data showed that the activities of several key defense enzymes, including phenylalanine ammonia-lyase （PAL）, peroxidase （POD）, lipoxygenase （LOX）, and polyphenol oxidase （PPO）, were substantially increased in cotton seedlings responding to spider mite infestation. Further, the contents of gossypol and condensed tannins, key defensive compounds, were significantly enhanced in leaves of cotton seedlings following T. cinnabarinus infestation. Moreover, the T. cinnabarinus-induced production of defense enzymes and secondary metabolites was correlated with infestation density. The developmental periods of A. gossypii on cotton seedling leaves infested with T. cinnabarinus at densities of 10 and 15 individuals cm-2 were 1.16 and 1.18 times that of control, respectively. Meanwhile, the mean relative growth rates of A. gossypfi on cotton leaves infested with T. cinnabarinus at densities of 8, 10 and 15 individuals cm-2 were significantly reduced. Therefore, these data suggested that the developmental periods of A. gossypfi were significantly lengthened and the mean relative growth rates were markedly reduced when cotton aphids were reared on plants infested with high densities of spider mites. This research sheds light on the role that inducible defense responses played in plant-mediated interspecific interactions between T. cinnabarinus and A. gossypfi.