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1.
Strains of sheep louse Bovicola ovis (Schrank) with various levels of resistance to pyrethroid and one strain with high degree of resistance to organophosphate (OP) insecticides were used to investigate the biochemical mechanisms of insecticide resistance, i.e., enhanced levels of general esterases, specific acetylcholinesterases (AChE), glutathione S-transferase (GST), and mixed function oxidases. Native gel electrophoresis combined with quantitative enzyme assays showed analogous expression profiles of several esterase isozymes in all the strains tested. The determination of the sensitivity of each esterase isozyme to five inhibitors (acetylthiocholine iodide, butyrylthiocholine iodide, paraoxon eserine sulfate, and pCMB) led to the identification of nine esterases in the B. ovis strain. Gel electrophoresis results are supported by enzyme assay studies where, except for the OP resistant strain, no differences in esterase activities were detected in all the pyrethroid resistant and susceptible strains assayed. Statistical analyses demonstrated that some strains have elevated GST activities compared to the susceptible reference strain.  相似文献   

2.
A field population of the rice stem borer (Chilo suppressalis Walker) with 203.3-fold resistance to triazophos was collected. After 8-generation of continuous selection with triazophos in laboratory, resistance increased to 787.2-fold, and at the same time, the resistance to isocarbophos and methamidophos was also enhanced by 1.9- and 1.4-fold, respectively, implying some cross-resistance between triazophos and these two organophosphate insecticides. Resistance to abamectin was slightly enhanced by triazophos selection, and fipronil and methomyl decreased. Synergism experiments in vivo with TPP, PBO, and DEM were performed to gain a potential indication of roles of detoxicating enzymes in triazophos resistance. The synergism results revealed that TPP (SR, 1.92) and PBO (SR 1.63) had significant synergistic effects on triazophos in resistant rice borers. While DEM (SR 0.83) showed no effects. Assays of enzyme activity in vitro demonstrated that the resistant strain had higher activity of esterase and microsomal O-demethylase than the susceptible strain (1.20- and 1.30-fold, respectively). For glutathione S-transferase activity, no difference was found between the resistant and the susceptible strain when DCNB was used as substrate. However, 1.28-fold higher activity was observed in the resistant strain when CDNB was used. These results showed that esterase and microsomal-O-demethylase play some roles in the resistance. Some iso-enzyme of glutathione S-transferase may involve in the resistance to other insecticides, for this resistant strain was selected from a field population with multiple resistance background. Acetylcholinesterase as the triazophos target was also compared. The results revealed significant differences between the resistant and susceptible strain. The Vmax and Km of the enzyme in resistant strain was only 32 and 65% that in the susceptible strain, respectively. Inhibition tests in vitro showed that I50 of triazophos on AChE of the resistant strain was 2.52-fold higher. Therefore, insensitive AChE may also involved in triazophos resistance mechanism of rice stem borer.  相似文献   

3.
Increased hydrolytic metabolism of organophosphate insecticides has been associated with resistance among Nebraska western corn rootworm populations. In this study, resistance-associated esterases were partially purified by differential centrifugation, ion exchange, and hydroxyapatite column chromatography, with a final purification factor of 100-fold and recovery of approximately 10%. Kinetic analysis of the partially purified enzyme indicated that the Km of the group II esterases was identical for the two populations, although Vmax was consistently threefold higher in the resistant population. A putative esterase, DvvII, was further purified to homogeneity by preparative polyacrylamide gel electrophoresis. DvvII is a monomer with a molecular weight of approximately 66 kDa, although three distinct isoforms with similar pIs were evident based on isoelectric focusing gel electrophoresis. Immunoassays with the Myzus persicae E4 antiserum indicated that group II esterases from D. v. virgifera were cross-reactive and expressed at much higher titers in the resistant population relative to the susceptible counterpart. These results suggest that the resistance is likely associated with overproduction of an esterase isozyme in resistant D. v. virgifera populations.  相似文献   

4.
Wheat aphid, Sitobion avenae (fabricius), is one of the most important wheat pests and has been reported to be resistant to commonly used insecticides in China. To determine the resistance mechanism, the resistant and susceptible strains were developed in laboratory and comparably studied. A bioassay revealed that the resistant strain showed high resistance to pirimicarb (RR: 161.8), moderate reistance to omethoate (32.5) and monocrotophos (33.5), and low resistance to deltamethrin (6.3) and thiodicarb (5.5). A biochemistry analysis showed that both strains had similar glutathione-S-transferase (GST) activity, but the resistant strain had 3.8-fold higher esterase activity, and its AChE was insensitive to this treatment. The I50 increased by 25.8-, 10.7-, and 10.4-folds for pirimicarb, omethoate, and monocrotophos, respectively, demonstrating that GST had not been involved in the resistance of S. avenae. The enhanced esterase contributed to low level resistance to all the insecticides tested, whereas higher resistance to pirimicarb, omethoate, and monocrotophos mainly depended on AChE insensitivity. However, the AChE of the resistant strain was still sensitive to thiodicarb (1.7-fold). Thus, thiodicarb could be used as substitute for control of the resistant S. avenae in this case. Furthermore, the two different AChE genes cloned from different resistant and susceptible individuals were also compared. Two mutations, L436(336)S in Sa.Ace1 and W516(435)R in Sa.Ace2, were found consistently associated with the insensitivity of AChE. They were thought to be the possible resistance mutations, but further work is needed to confirm this hypothesis.  相似文献   

5.
Beet armyworm, Spodoptera exigua is a major insect pest of vegetables in China, and has been reported to develop resistance to many broad-spectrum insecticides. Recently registered chlorantraniliprole provides a novel option for control of this pest resistant to other conventional insecticides. The susceptibilities of field collected populations were measured by diet incorporation assay with neonate, obvious variation of susceptibility was observed among the 18 field populations with LC50 values varying from 0.039 to 0.240 mg/liter. Moderate resistant level was discovered in 8 of 18 field populations, other 8 populations had become low level tolerance to chlorantraniliprole, and only one population in all the field colonies remained susceptible. Biochemical assays were performed to determine the potential mechanisms involved in tolerance variation. Field populations displayed varied detoxification enzyme activities, but the regression analysis between chlorantraniliprole toxicities and enzyme activities demonstrated each field population might have specific biochemical mechanisms for tolerance. Artificial selection in laboratory with chlorantraniliprole was carried out, 23 generations of continuous selections resulted in 11.8-fold increase in resistance to chlorantraniliprole, and 3.0-fold and 3.7-fold increases in mixed function oxidase and esterase, respectively. Compared with the susceptible strain kept in laboratory the selection strain had developed 128.6-fold resistance to this insecticide. Synergism assays showed the detoxification enzymes might not involved in the resistance observed in field collected populations and the selected strain.  相似文献   

6.
Resistance in Spodoptera litura (Fabricius) has been attributed to enhanced detoxification of insecticides by increased levels of esterases, oxidases and/or glutathione S-transferases. Enzyme inhibiting insecticide synergists can be employed to counter increased levels of such enzymes in S. litura. Dihydrodillapiole induced synergism of pyrethroid toxicity was examined in the laboratory-reared third instar larval population of S. litura collected in Delhi (susceptible), and Guntur (resistant) region of Andhra Pradesh, India. The Guntur population was found to be 7.04 and 10.19 times resistant to cypermethrin and lambdacyhalothrin, respectively. The activity of cypermethrin, lambdacyhalothrin and profenophos against susceptible and resistance populations of S. litura, was gradually increased when used along with a plant-derived insecticide synergist dihydrodillapiole. The α-naphthyl acetate hydrolysable esterase activity in Delhi population was less as compared to the Guntur population. Resistance associated esterases in Delhi population were inhibited by pre-treatment with dihydrodillapiole. The esterase level in insect was instantly reduced initially, sustained for about 3 h and equilibrated at 4 h post treatment. The esterase activity of Guntur population was increased to 1.28 μmoles/mg/min at 2 h post treatment and subsequently reduced to lower than 0.70 μmoles at 4-12 h post treatment. The variation in esterase activity is suggestive of its homeostatic regulation in test populations. Dihydrodillapiole thus caused significant reduction of resistance in S. litura to cypermethrin, lambda cyhalothrin and profenophos.  相似文献   

7.
The role of esterases as related to insecticide resistance was studied in an organophosphorus (OP)-resistant strain of the green rice leafhopper. As judged by p-nitrophenyl acetate hydrolysis, 21, 5, and 74% of the esterase activity was located in nuclei/mitochondria, microsomes, and the soluble fraction, respectively. All the fractions were active in hydrolyzing malathion, paraoxon, and fenvalerate. Hydrolysis of malathion and fenvalerate increased with time while that of paraoxon reached a plateau within 15 min. Since a considerable amount of p-nitrophenol was detected in the paraoxon reaction at 0°C and at zero time, the formation of p-nitrophenol may be due to phosphorylation of the esterases rather than phosphorotriesterase action. The results suggest a dual role for esterases in resistance mechanisms; a catalyst for hydrolysis of malathion and fenvalerate, and a binding protein for the oxygen analogs of other OP insecticides, both of which would protect the intrinsic target, acetylcholinesterase, from inhibition. Chromatofocusing of the soluble fraction resolved five esterase peaks, I–V. These esterases were active toward the three general substrates as well as for the three insecticides tested, except for Peak I in which the overall activity was too low. Thin-layer agar gel electrophoresis showed that the chromatofocusing peaks I–V corresponded to the electrophoretic bands E1–E5, some of which were previously shown to be associated with OP resistance. The dual role of these esterases may explain the cross-resistance between malathion and other OP insecticides as well as synergism between OP and carbamate insecticides.  相似文献   

8.
Transgenic Bt cotton expressing Cry1Ac is important in controlling various agricultural pests, including Helicoverpa armigera. Especially for transgenic crops that are cultivated in large expanses, avoiding resistance development is a key for ensuring sustainability of Bt technologies. Integrated pest management, in which transgenic crops are strategically combined with rational pesticide use, may help to prevent H. armigera resistance acquisition in Bt cotton. In this study, we evaluated the toxicity of a novel insecticide (chlorantraniliprole) on Cry1Ac-susceptible and resistant individuals of H. armigera. More specifically, we assessed the effect of chlorantraniliprole on the activity of two enzymes and conducted laboratory bioassays to determine its toxicity on H. armigera larvae. Chlorantraniliprole increased esterase and glutathione-S-transferase activities in Cry1Ac susceptible and resistant populations of H. armigera. Cry1Ac resistant populations XJ-F (Cry1Ac resistance ratio 21.8-fold), XJ-10.0 (95.8-fold) and BTR (3536.5-fold) did not show cross-resistance to chlorantraniliprole, with LC50 values of 0.0733 (μg/mL) in XJ-F, 0.0545 (μg/ml) in XJ-10.0 and 0.0731 (μg/mL) in BTR, which were close to that in the susceptible strain 96S (0.0954 μg/mL). Our work shows that chlorantraniliprole could be considered to be integrated in Bt cotton management schemes to delay the H. armigera resistance development.  相似文献   

9.
Microplate assay technique for estimation of esterase activity in a single insect was used in combination with dose mortality bioassays to detect pyrethroid resistance in three strains of Helicoverpa armigera and to study the frequency of pyrethroid resistant individuals within the population of the same strain at two larval stages, third and fifth instar. The third and fifth instar larvae of the field strains i.e., Nagpur strain and Delhi strain that displayed high degree of resistance towards deltamethrin, had higher esterase activity compared to a susceptible laboratory strain. The frequency distribution of individuals with elevated esterase activity above 1.00 absorbance unit was correlated with the resistance level of the strains. The frequency of resistant individuals in the third instar larvae of Nagpur strain and Delhi strain were 29% and 23%, respectively compared to 4% in the susceptible strain. The resistant individuals in the resistant strains have markedly increased in the fifth instar larvae with a frequency distribution of 63% and 90% in Delhi strain and Nagpur strain, respectively, while only 14% of individuals was found to have elevated esterase activity in the susceptible strain. The results demonstrated the role of esterase in pyrethroid resistance in H. armigera. Microplate assay proved to be a rapid and reliable biochemical technique for monitoring of pyrethroid resistance in H. armigera.  相似文献   

10.
Kinetic parameters were measured for glutathione S-transferase, an enzyme important in metabolic resistance to insecticides, in one susceptible and two insecticide-resistant strains of the house fly (Musca domestica L.), and in untreated and chemically induced flies. Both resistant strains differed from the susceptible strain in apparent Km values for the enzyme, while only one differed in apparent Vmax. Two of the strains were inducible with phenobarbital; the third with 3-methylcholanthrene. Kinetic analysis indicated enzyme induction was associated with changes in Km rather than Vmax, and genetic experiments showed that most variation relating to Km and Vmax was controlled by chromosome II. Based on these results, both metabolic resistance and induction of enzyme activity were associated primarily with the production of different forms of glutathione S-transferase rather than more of the enzyme present in susceptible flies.  相似文献   

11.
呼伦贝尔盟农田杂草计49科、198属、348种,其中包括6个亚种、29个变种和1个变型。杂草发生特点:种类多、多年生杂草多、恶性杂草多、群落结构特殊、危害严重。主要优势群落:茅香和光稃茅香群落、匍匐冰草群落、野燕麦群落与裂边鼬瓣花群落。防治措施与策略:适当压缩小麦,扩大油菜种植面积,在休闲地应用草甘膦防治多年生杂草,用2甲4氯取代2,4-D丁酯防治小麦田杂草,发展应用磺酰脲类除草剂与禾草灵混用,以兼治野燕麦与宽叶杂草。  相似文献   

12.
Fipronil resistance mechanisms were studied between the laboratory susceptible strain and the selective field population of rice stem borer, Chilo suppressalis Walker in the laboratory. The borer population was collected from Wenzhou county, Zhejiang province. After five generations of selection, fipronil resistance ratio was 45.3-fold compared to the susceptible strain. Synergism experiments showed that the synergistic ratios of PBO, TPP and DEF on fipronil in susceptible and resistant strains of C. suppressalis were 7.55-, 1.93- and 2.91-fold, respectively, and DEM showed no obvious synergistic action on fipronil. Activities of carboxylesterase and microsomal-O-demethylase in the resistant strain were 1.89- and 1.36-fold higher that in susceptible strain, and no significant difference of glutathione-S-transferase activity was found between the resistant and susceptible strains. The Km and Vmax experiments also demonstrated that fipronil resistance of C. suppressalis was closely relative to the enhanced activities of carboxylesterase and microsomal-O-demethylase. Moreover, cross-resistance between fipronil and other conventional insecticides and the multiple resistant properties of the original Wenzhou’s population were also discussed.  相似文献   

13.
The carmine spider mite Tetranychus cinnabarinus is the most serious of crop mite pests in China. Their ability to rapidly develop resistance to acaricides has caused difficulty in controlling this mite. In this study, the molecular mechanism of acaricide resistance associated with esterase genes TCE1 and TCE2 was investigated in susceptible and acaricide-resistant strains of T. cinnabarinus. The quantitative real-time PCR (qrtPCR) method was adopted to compare the expression level of two esterase genes TCE1 and TCE2 among four different strains (abamectin-resistant, AbR; fenpropathrin-resistant, FeR; omethoate-resistant, OmR and susceptible strains, S) of T. cinnabarinus. The relative expression level of TCE2 was 1.39-2.47 fold in the three resistant strains compared with the S strain. And after inducing with abamectin, fenpropathrin, and omethoate the highest expression level of TCE2 in the S was 1.64-, 2.92- and 2.24-fold compared with the control, respectively, and this difference was found to be significant. However, there was no obvious difference of the mRNA relative expression levels of TCE1 genes among the four strains, and those of TCE1 were not higher than the control throughout the study. Furthermore, the expression modes of TCE1 and TCE2 in AbR and FeR were similar with that in the S after being treated with abamectin and fenpropathrin, respectively. These results indicated that the enhanced expression of esterase gene TCE2 was associated with acaricide-resistance in T.cinnabarinus.  相似文献   

14.
Acetylcholinesterase (AChE), which is encoded by the ace gene, catalyzes the hydrolysis of the neurotransmitter acetylcholine to terminate nerve impulses at the postsynaptic membrane. AChE is a primary target of many insecticides including organophosphates (OP) and carbamates (CB). In this study, full-length cDNA sequences of two ace genes (Nlace1 and Nlace2) were sequenced from the brown planthopper (BPH) Nilaparvata lugens, the most destructive insect pest of rice crops. Nlace1 cDNA is 2842 nucleotides long and contains an ORF potentially encoding a 790 amino acid peptide. Nlace2 cDNA is 2852 bp in length and contains an ORF that potentially encodes a 672 amino acid peptide. NlAChE1 has an identity of 40% with NlAChE2 at the amino acid sequence level. Phylogenetic analysis of 59 AChEs from 32 animal species showed that NlAChE1 is most closely related to AChE1s from Blattella germanica and Nephotettix cincticeps, while NlAChE2 is most closely related to AChE2 from N. cincticeps. Quantitative RT-PCR analysis showed that Nlace1 is expressed at a much higher level than Nlace2 in all developmental stages and tissues, demonstrating that NlAChE1 may be the dominant AChE form of the two enzymes. This result will help reveal the resistance mechanism of N. lugens to organophosphorous and carbamate insecticides and promote development of more selective insecticides targeting the main NlAChE1.  相似文献   

15.
为明确普通小麦-簇毛麦易位系材料对不同条锈菌系的抗病水平、抗病基因组成和易位系间抗病基因关系,对V9125-3和V9125-4易位系进行了苗期抗条锈性遗传分析,并利用V9125-2抗条锈基因Yr WV的2个侧翼分子标记,分析了3个易位系抗病基因间的关系。结果表明,2个易位系对当前国内7个优势菌系均表现良好的抗病性,但对不同菌系抗病性的抗病基因遗传特点有所不同。V9125-3对CYR29、CYR30和CYR31的抗病性由2对显性基因独立控制,对CYR32、CYR33和Sun11-11的抗病性由1显1隐2对基因控制,对Sun11-4的抗病性由2对显性基因互补控制;V9125-4对CYR30、Sun11-4和Sun11-11的抗病性由2对显性基因独立控制,对CYR32和CYR33的抗病性由1显1隐2对基因控制,对CYR29和CYR31的抗病性由2对显性基因互补控制;V9125-3对CYR29的抗病基因其中之一可能是Yr WV,另一个为未知基因。  相似文献   

16.
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17.
The tarnished plant bug (TPB) has increasingly become an economically important pest of cotton. Heavy dependence on insecticides, particularly organophosphates and pyrethroids, for TPB control facilitated resistance development to multiple classes of insecticides. To better understand resistance and explore ways to monitor resistance in field populations, this study examined acephate susceptibility and the activities of two major detoxification enzymes in nine field populations collected in the Delta region of Mississippi and Arkansas in 2010. Two Arkansas populations from Reed and Backgate had 3.5- and 4.3-fold resistance to acephate, as compared to a susceptible laboratory strain. Extensive planting of cotton and heavy chemical sprays is a major driving force for resistance development to acephate in Mid-south cotton growing areas. Reduced susceptibility to acephate was highly correlated with elevated esterase activities. The acephate-resistant populations from Backgate, Lula, and Reed consistently had higher (up to 5.3-fold) esterase activities than susceptible populations. Regression analysis of LC50s with kinetic esterase activities revealed a significant polynomial quadratic relationship with R2 up to 0.89. Glutathione S-transferase (GST) also had elevated activity in most populations, but the variations of GST activities were not significantly correlated with changes of acephate susceptibility. Finally, examination of esterase and GST inhibitors indicated that suppression rates (up to 70%) by two esterase inhibitors in 2010 were slightly lower than those detected in 2006, and ethacrynic acid (EA) inhibited GST effectively in both years. Two other GST inhibitors (sulfobromophthalein and diethyl maleate) displayed significantly lower suppression rates in 2010 than those detected in 2006, suggesting a potential genetic shift in pest populations and a necessity of continued monitoring for insecticide resistance with both bioassay and biochemical approaches. Results indicated that using major detoxification enzyme activities for resistance monitoring may provide insight into acephate resistance in field populations of TPB.  相似文献   

18.
BACKGROUND: Heavy and constant use of organophosphorus (OP) larvicides selected Culex pipiens L. resistant populations through two main mechanisms of genetic resistance, the increased activity of detoxifying esterase and the production of alterate acetylcholinesterase‐1 (AChE1) by G119S mutation. The aim of this study was the assessment of the distribution of Cx. pipiens populations resistant to temephos and chlorpyrifos in the north‐eastern regions of Italy and the occurrence of the insensitive AChE in these populations. Data describe the situation in the last years before European legislation prohibited the use of OP larvicides in mosquito control, up until 2007. RESULTS: For the first time a high level of OP resistance in the samples from Ravenna (182‐fold, 80% A4/B4 or A5/B5 esterases and 38.3% Ester5), Emilia Romagna region, was detected; therefore, new data from the Veneto and Friuli Venezia Giulia regions were obtained and reinforced existing knowledge about resistance previously studied along the Adriatic coast. Nearby, in the Villa Verucchio locality, the highest (87.5%) AChE1R was found. CONCLUSION: Cx. pipiens resistance esterases A5/B5 and A4/B4 spread southward along the Adriatic coastal plain while OPs were being used in mosquito control, as confirmed by the first molecular screening of the AChE1 gene in these populations. Copyright © 2010 Society of Chemical Industry  相似文献   

19.
小偃6号成株期高温抗条锈性遗传分析   总被引：5，自引：4，他引：1  
为揭示小偃6号抗病机制和培育持久抗病品种,采用常规杂交分析方法,在小麦抽穗期利用小麦条锈菌小种CYR30、CYR32和Su11-4对小偃6号、铭贤169及其杂交F1、F2、F2∶3接种,平均气温达到21℃时对小偃6号进行了抗条锈性调查和遗传分析。结果显示,接种CYR30、CYR32时,F1代表现高感,F2代群体中抗感分离比例符合1 R∶15 S的理论比例。接种Su11-4时,F1代表现高抗,F2代群体中抗感分离比例符合3R∶1S的理论比例。研究表明小偃6号对CYR30、CYR32的抗病性均由2对隐性基因累加作用控制,对Su11-4的抗病性由1对显性基因控制。  相似文献   

20.
The metabolism of fenitrothion was investigated in highly resistant (Akita-f) and susceptible (SRS) strains of the house fly, Musca domestica L. The Akita-f strain was 3500 times more resistant to fenitrothion than the SRS strain. Fenitrothion, topically applied to the flies, was metabolized in vivo far faster in the Akita-f strain than in the SRS strain. In vitro studies revealed that fenitrothion was metabolized by a cytochrome P-450-dependent monooxygenase system and glutathione S-transferases. The former oxidase system metabolized fenitrothion in vitro into fenitrooxon and 3-methyl-4-nitrophenol as major metabolites, and into 3-hydroxymethyl-fenitrothion and 3-hydroxymethyl-fenitrooxon as minor metabolites. Glutathione S-transferases metabolized fenitrothion into desmethylfenitrothion. The cytochrome P-450-dependent monooxygenase system and glutathione S-transferases of the resistant Akita-f strain had 1.4 to 2.2 times and 9.7 times, respectively, as great activities as those of the susceptible SRS strain. These results suggest the importance of glutathione S-transferases in fenitrothion resistance in the Akita-f strain.  相似文献   

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