Due to rapidly developed resistance,pest management relies less on pyrethroids to control economically damaging infestations of the tarnished plant bug(TPB),Lygus lineolaris(Palisot de Beauvois)in cotton fields of Mis...Due to rapidly developed resistance,pest management relies less on pyrethroids to control economically damaging infestations of the tarnished plant bug(TPB),Lygus lineolaris(Palisot de Beauvois)in cotton fields of Mississippi.Yet,pyrethroid resistance remains prevalent in TPB populations.This study assessed the resistance levels in adult TPB to six common pyrethroids and acephate.Resistant TBPs were collected from wild host plants in late October after harvest in the Mississippi Delta region of the United States.Based on LCso values,the field-resistant TPBs displayed higher resistance to permethrin,esfenvalerate,and bifenthrin(approximately 30 fold)and moderate resistance toα-cyhalothrin,β-cyfluthrin,5-cypermethrin,and acephate(approximately 15 fold).Further investigations showed that the inhibitors of three detoxification enzyme,triphenyl phosphate(TPP),diethyl maleate(DEM),and piperonyl butoxide(PBO)had synergistic effects on permethrin,γ-cyhalothrin,and bifenthrin in resistant TPBs.Furthermore,elevated esterase,GST,and P450 activities were significantly expressed in fieldresistant TPBs.Additionally,GST and esterase were reduced after 48 h exposure to certain pyrethroids at LCso dose.The synergistic and biochemical assays consistently indicated that P450 and esterase were involved in pyrethroid detoxification in TPBs.This study provides valuable information for the continued use of pyrethroids and acephate in controlling TPBs in cotton fields in the Mississippi Delta region of the United States.展开更多
Chemosensory proteins(CSPs)are soluble carrier proteins typically characterized by a six‐helix bundle structure joined by two disulfide bridges and a conserved Cys spacing pattern(C1‐X6‐8‐C2‐X16‐21‐C3‐X2‐C4)....Chemosensory proteins(CSPs)are soluble carrier proteins typically characterized by a six‐helix bundle structure joined by two disulfide bridges and a conserved Cys spacing pattern(C1‐X6‐8‐C2‐X16‐21‐C3‐X2‐C4).CSPs are functionally diverse with reported roles in chemosensation,immunity,development,and resistance.To expand our molecular understanding of CSP function in plant bugs,we used recently developed transcriptomic resources for Lygus lineolaris and Lygus hesperus to identify 17 and 14 CSP‐like sequences,respectively.The Lygus CSPs are orthologous and share significant sequence identity with previously annotated CSPs.Three of the CSPs are predicted to deviate from the typical CSP structure with either five or seven helical segments rather than six.The seven helix CSP is further differentiated by an atypical C3‐X3‐C4 Cys spacing motif.Reverse transcriptase PCR‐based profiling of CSP transcript abundance in adult L.lineolaris tissues revealed broad expression for most of the CSPs with antenna specific expression limited to a subset of the CSPs.Comparative sequence analyses and homology modeling suggest that variations in the amino acids that comprise the Lygus CSP binding pockets affect the size and nature of the ligands accommodated.展开更多
Insect source-sink dynamics are vital to ecologically intensive pest management. Maintaining sink plant hosts,or "trap crops",and destroying alternate hosts or breeding places adjacent to the field crop are ...Insect source-sink dynamics are vital to ecologically intensive pest management. Maintaining sink plant hosts,or "trap crops",and destroying alternate hosts or breeding places adjacent to the field crop are effective pest management strategies for some arthropods. However,determining whether a host acts as a source or a sink is challenging, especially when the pest species is highly mobile and polyphagous. The western tarnished plant bug,Lygus hesperus,is highly polyphagous,and can utilize >300 hosts. Its presence has been documented in 26 roadside weed hosts in the Texas High Plains.Previous studies demonstrated that L. hesperus prefer alfalfa over cotton and several alternate weed hosts.A four-year project involved surveying and sampling for L. hesperus in the agricultural landscapes of several sub-regions of the southwestern United States,including the Texas High Plains. In Texas,geographic information of the landscape vegetation complex was compiled from a 150 km radius in the Texas High Plains. In one study,fifty irrigated cotton fields representing the crop diversity within this region were sampled via sweep-net for 10 weeks. This effort also included sampling of up to six noncotton insect habitats within a 3 km radius of each field. Seasonal average L. hesperus abundance data were regressed with 27 field characteristics( variables),including habitat-specific land cover,distance between focal cotton fields and non-cotton habitats,longitude,latitude,elevation,habitat heterogeneity index,and several environmental / ecological variables. Significant variables were selected using a stepwise regression at 15% probability rate. A 10-parameter linear model explained 93% of the variation in the data. Major parameters contributing significantly to variation in L. hesperus abundance in cotton were corn and sunflower acreages,focal cotton field distances from several non-cotton hosts,and habitat heterogeneity index. In addition,field marking-and-capture studies were conducted using protein markers and enzyme-linked immunosorbent assays to characterize L. hesperus intercrop movement behavior. The field marking-and-capture approach can be used to study the effects of various crop management practices on L. hesperus intercrop movement and can potentially be applied to other pests and cropping systems.展开更多
With the increased cultivation of Bt crops in China,Apolygus lucorum and other mirid bugs have emerged as important agricultural pests because they are insensitive to the Bt proteins.In addition,the reduction of pesti...With the increased cultivation of Bt crops in China,Apolygus lucorum and other mirid bugs have emerged as important agricultural pests because they are insensitive to the Bt proteins.In addition,the reduction of pesticide applications after planting Bt crops also increases the severity of mirid bug outbreaks.Peristenus spretus is a parasitoid of mirid nymphs,but its sensitivity to Bt proteins is not known.In the current study,we developed a dietary exposure assay to assess the effects of Bt proteins(Cry1Ab,Cry1Ac,Cry1F,Cry2Aa,and Cry2Ab)on P.spretus adults using a diet consisting of a 10% honey solution with or without Bt proteins at 400μg g^(-1) diet.The results showed that the survival and reproduction of P.spretus adults were reduced by the cysteine protease inhibitor E-64(a positive control)but were not affected by any of the five Bt proteins.The activities of digestive,detoxifying,and antioxidant enzymes in P.spretus were also unaffected by diets containing the Cry proteins,but they were significantly affected by the diet containing E-64.We then developed a tritrophic bioassay to determine the effects of the five Bt proteins on P.spretus larvae and pupae.In this assay,A.lucorum nymphs fed an artificial diet containing Cry proteins were used as the hosts for P.spretus.The results of the tri-trophic assay indicated that neither the pupation rate nor the eclosion rate of the P.spretus parasitoids were significantly affected by the presence of high concentrations of Bt proteins in the parasitized A.lucorum nymphs.The overall results indicate that these two assays can be used to evaluate the toxicity of insecticidal compounds to P.spretus and that the tested Cry proteins are not toxic to P.spretus.展开更多
A boll infection caused by non-traditional cotton pathogens was first reported to occur in the southeastern U.S. Cotton Belt (year 2000) and has since spread to Texas causing significant yield losses. This study was a...A boll infection caused by non-traditional cotton pathogens was first reported to occur in the southeastern U.S. Cotton Belt (year 2000) and has since spread to Texas causing significant yield losses. This study was aimed towards investigating the verde plant bug (<em>Creontiades signatus</em>) link between interior boll disease in Texas, USA. Using glasshouse grown bolls, bacteria recovered from locules with disease symptoms from field-grown cotton bolls caged with the piercing-sucking <em>C. signatus</em> were analyzed for the capacity to inflict the disease. For pathogenicity testing, spontaneously generated rifampicin resistant (Rifr) variants were utilized to track the antibiotic resistant bacterium and deter growth of endophytic and contaminating bacteria. To simulate <em>C. signatus</em> feeding, a needle (31 gauge) was employed to inoculate bolls at 13 - 15 days after flower bloom. Bacterial suspensions ranged from 10<sup>1</sup> - 10<sup>6</sup> colony forming units/ml. Field infection symptoms were duplicated after two weeks of bacterial exposure. Infectious strains were best categorized as <em>Serratia marcescens</em> based on traditional carbon utilization and enzyme production testing, and a 99% nucleotide sequence identity of 16S ribosomal DNA. Putative <em>S. marcescens</em> representatives isolated from rotted bolls exposed to<em> C. signatus</em> were shown to reproduce field infection symptoms upon inoculation into greenhouse grown fruit. <em>Serratia</em> spp. can inflict disease in alfalfa, cucurbits, and sunflower. The presented data are the first to definitively show that a <em>Serratia</em> sp. has the capacity to infect cotton.展开更多
文摘Due to rapidly developed resistance,pest management relies less on pyrethroids to control economically damaging infestations of the tarnished plant bug(TPB),Lygus lineolaris(Palisot de Beauvois)in cotton fields of Mississippi.Yet,pyrethroid resistance remains prevalent in TPB populations.This study assessed the resistance levels in adult TPB to six common pyrethroids and acephate.Resistant TBPs were collected from wild host plants in late October after harvest in the Mississippi Delta region of the United States.Based on LCso values,the field-resistant TPBs displayed higher resistance to permethrin,esfenvalerate,and bifenthrin(approximately 30 fold)and moderate resistance toα-cyhalothrin,β-cyfluthrin,5-cypermethrin,and acephate(approximately 15 fold).Further investigations showed that the inhibitors of three detoxification enzyme,triphenyl phosphate(TPP),diethyl maleate(DEM),and piperonyl butoxide(PBO)had synergistic effects on permethrin,γ-cyhalothrin,and bifenthrin in resistant TPBs.Furthermore,elevated esterase,GST,and P450 activities were significantly expressed in fieldresistant TPBs.Additionally,GST and esterase were reduced after 48 h exposure to certain pyrethroids at LCso dose.The synergistic and biochemical assays consistently indicated that P450 and esterase were involved in pyrethroid detoxification in TPBs.This study provides valuable information for the continued use of pyrethroids and acephate in controlling TPBs in cotton fields in the Mississippi Delta region of the United States.
文摘Chemosensory proteins(CSPs)are soluble carrier proteins typically characterized by a six‐helix bundle structure joined by two disulfide bridges and a conserved Cys spacing pattern(C1‐X6‐8‐C2‐X16‐21‐C3‐X2‐C4).CSPs are functionally diverse with reported roles in chemosensation,immunity,development,and resistance.To expand our molecular understanding of CSP function in plant bugs,we used recently developed transcriptomic resources for Lygus lineolaris and Lygus hesperus to identify 17 and 14 CSP‐like sequences,respectively.The Lygus CSPs are orthologous and share significant sequence identity with previously annotated CSPs.Three of the CSPs are predicted to deviate from the typical CSP structure with either five or seven helical segments rather than six.The seven helix CSP is further differentiated by an atypical C3‐X3‐C4 Cys spacing motif.Reverse transcriptase PCR‐based profiling of CSP transcript abundance in adult L.lineolaris tissues revealed broad expression for most of the CSPs with antenna specific expression limited to a subset of the CSPs.Comparative sequence analyses and homology modeling suggest that variations in the amino acids that comprise the Lygus CSP binding pockets affect the size and nature of the ligands accommodated.
文摘Insect source-sink dynamics are vital to ecologically intensive pest management. Maintaining sink plant hosts,or "trap crops",and destroying alternate hosts or breeding places adjacent to the field crop are effective pest management strategies for some arthropods. However,determining whether a host acts as a source or a sink is challenging, especially when the pest species is highly mobile and polyphagous. The western tarnished plant bug,Lygus hesperus,is highly polyphagous,and can utilize >300 hosts. Its presence has been documented in 26 roadside weed hosts in the Texas High Plains.Previous studies demonstrated that L. hesperus prefer alfalfa over cotton and several alternate weed hosts.A four-year project involved surveying and sampling for L. hesperus in the agricultural landscapes of several sub-regions of the southwestern United States,including the Texas High Plains. In Texas,geographic information of the landscape vegetation complex was compiled from a 150 km radius in the Texas High Plains. In one study,fifty irrigated cotton fields representing the crop diversity within this region were sampled via sweep-net for 10 weeks. This effort also included sampling of up to six noncotton insect habitats within a 3 km radius of each field. Seasonal average L. hesperus abundance data were regressed with 27 field characteristics( variables),including habitat-specific land cover,distance between focal cotton fields and non-cotton habitats,longitude,latitude,elevation,habitat heterogeneity index,and several environmental / ecological variables. Significant variables were selected using a stepwise regression at 15% probability rate. A 10-parameter linear model explained 93% of the variation in the data. Major parameters contributing significantly to variation in L. hesperus abundance in cotton were corn and sunflower acreages,focal cotton field distances from several non-cotton hosts,and habitat heterogeneity index. In addition,field marking-and-capture studies were conducted using protein markers and enzyme-linked immunosorbent assays to characterize L. hesperus intercrop movement behavior. The field marking-and-capture approach can be used to study the effects of various crop management practices on L. hesperus intercrop movement and can potentially be applied to other pests and cropping systems.
基金supported by the Key Project for Breeding Genetically Modified Organisms,China(2016ZX08011-002)China’s Donation to the CABI Development Fund。
文摘With the increased cultivation of Bt crops in China,Apolygus lucorum and other mirid bugs have emerged as important agricultural pests because they are insensitive to the Bt proteins.In addition,the reduction of pesticide applications after planting Bt crops also increases the severity of mirid bug outbreaks.Peristenus spretus is a parasitoid of mirid nymphs,but its sensitivity to Bt proteins is not known.In the current study,we developed a dietary exposure assay to assess the effects of Bt proteins(Cry1Ab,Cry1Ac,Cry1F,Cry2Aa,and Cry2Ab)on P.spretus adults using a diet consisting of a 10% honey solution with or without Bt proteins at 400μg g^(-1) diet.The results showed that the survival and reproduction of P.spretus adults were reduced by the cysteine protease inhibitor E-64(a positive control)but were not affected by any of the five Bt proteins.The activities of digestive,detoxifying,and antioxidant enzymes in P.spretus were also unaffected by diets containing the Cry proteins,but they were significantly affected by the diet containing E-64.We then developed a tritrophic bioassay to determine the effects of the five Bt proteins on P.spretus larvae and pupae.In this assay,A.lucorum nymphs fed an artificial diet containing Cry proteins were used as the hosts for P.spretus.The results of the tri-trophic assay indicated that neither the pupation rate nor the eclosion rate of the P.spretus parasitoids were significantly affected by the presence of high concentrations of Bt proteins in the parasitized A.lucorum nymphs.The overall results indicate that these two assays can be used to evaluate the toxicity of insecticidal compounds to P.spretus and that the tested Cry proteins are not toxic to P.spretus.
文摘A boll infection caused by non-traditional cotton pathogens was first reported to occur in the southeastern U.S. Cotton Belt (year 2000) and has since spread to Texas causing significant yield losses. This study was aimed towards investigating the verde plant bug (<em>Creontiades signatus</em>) link between interior boll disease in Texas, USA. Using glasshouse grown bolls, bacteria recovered from locules with disease symptoms from field-grown cotton bolls caged with the piercing-sucking <em>C. signatus</em> were analyzed for the capacity to inflict the disease. For pathogenicity testing, spontaneously generated rifampicin resistant (Rifr) variants were utilized to track the antibiotic resistant bacterium and deter growth of endophytic and contaminating bacteria. To simulate <em>C. signatus</em> feeding, a needle (31 gauge) was employed to inoculate bolls at 13 - 15 days after flower bloom. Bacterial suspensions ranged from 10<sup>1</sup> - 10<sup>6</sup> colony forming units/ml. Field infection symptoms were duplicated after two weeks of bacterial exposure. Infectious strains were best categorized as <em>Serratia marcescens</em> based on traditional carbon utilization and enzyme production testing, and a 99% nucleotide sequence identity of 16S ribosomal DNA. Putative <em>S. marcescens</em> representatives isolated from rotted bolls exposed to<em> C. signatus</em> were shown to reproduce field infection symptoms upon inoculation into greenhouse grown fruit. <em>Serratia</em> spp. can inflict disease in alfalfa, cucurbits, and sunflower. The presented data are the first to definitively show that a <em>Serratia</em> sp. has the capacity to infect cotton.
