The occurrence of entomopathogenic nematodes(EPNs)in arable soil samples from Nigeria was investigated using Baermann extraction tray and insect-bait(White’s trap)techniques.Isolates were tested for infectivity using...The occurrence of entomopathogenic nematodes(EPNs)in arable soil samples from Nigeria was investigated using Baermann extraction tray and insect-bait(White’s trap)techniques.Isolates were tested for infectivity using the larvae of Galleria mellonella(greater moth)and Tenebrio molitor(mealworm).The study revealed a new species of Heterorhabditis(MT371593)in soil samples that were randomly collected from an arable farmland cultivated with cassava TMS-30572 at the Teaching and Research Farm of Landmark University,Nigeria.Amplification of the internal transcribed spacer region(ITS)of the ribosomal DNA produced a nucleotide sequence of 933 base pairs(bp).A BLASTN search of GenBank showed that the sequence of the Nigerian isolate is identical at 99%similarity to that of Heterorhabditis sp.from Thailand.Infectivity test of the isolate showed 100%mortality against T.molitor larvae within 48 h of exposure while only 80%mortality was recorded for G.mellonella after 1 week of exposure.This is the first account of Heterorhabditis sp.in Nigeria.The varying degrees of infectivity against mealworm and greater moth observed in this study proved that the Nigerian isolate of Heterorhabditis sp.could potentially be an attractive option in the management of insect pests of cash crops.展开更多
Background The emergence of pink bollworm(PBW),Pectinophora gossypiella(Saunders)(Lepidoptera:Gelechiidae),in cotton due to Bt resistance and concealed feeding habit has created a need for alternative,eco-friendly,and...Background The emergence of pink bollworm(PBW),Pectinophora gossypiella(Saunders)(Lepidoptera:Gelechiidae),in cotton due to Bt resistance and concealed feeding habit has created a need for alternative,eco-friendly,and cost-effective control methods.This study aimed to evaluate the bio-efficacy and reproductive potential of two native strains of entomopathogenic nematodes(EPNs),Heterorhabditis indica,namely CICR-HI-CL and CICR-HI-MN,against PBW larvae and pupae under in-vitro conditions.Results The larval assay revealed that strain CICR-HI-CL exhibited higher potency than strain CICR-HI-MN against 2nd,3rd,and 4thinstar larvae,with median lethal dose(LD50)values of 5.45,4.45,and 4.60 infective juveniles(IJs)per larva,respectively.In case of pupal bioassay,both EPN strains demonstrated greater virulence when applied directly(LD50values:29.65 and 73.88 IJs per pupa for strains CICR-HI-CL and CICR-HI-MN,respectively)compared to soil application(147.84 and 272.38 IJs per pupa).Both EPN strains successfully penetrated and reproduced on 4thinstar larvae,resulting in maximum production of 19.28 and 20.85 lakh IJs per larva in the next generation when inoculated at 30 IJs per larva.Conclusion The present study has generated useful information on the virulence and reproductive potential of two strains of EPN H.indica(CICR-HI-CL and CICR-HI-MN)against PBW,a dreaded pest of cotton.Higher virulence and reproductive potential of EPN strains demonstrated their ability to multiply,sustain and perpetuate on larval and pupal stages of PBW.The knowledge generated will help formulate effective management strategies for PBW with the inclusion of EPN as a potential biological control candidate.The soil-dwelling life stages viz.,last instar hibernating larvae and pupae of PBW can be the ideal weak links to make a successful use of H.indica for sustainable management of PBW in the cotton ecosystem.However,before taking these EPN strains to field for managing PBW,detailed studies investigating their biocontrol potential against PBW under field conditions are needed.展开更多
Heterorhabditis bacteriophora and Steinernema carpocapsae are microscopic entomoparasitic nematodes (EPNs) that are attractive, organic alternatives for controlling a wide range of crop insect pests. EPNs evolved with...Heterorhabditis bacteriophora and Steinernema carpocapsae are microscopic entomoparasitic nematodes (EPNs) that are attractive, organic alternatives for controlling a wide range of crop insect pests. EPNs evolved with parasitic adaptations that enable them to “feast” upon insect hosts. The infective juvenile, a non-feeding, developmentally arrested nematode stage, is destined to seek out insect hosts and initiates parasitism. After an insect host is located, EPNs enter the insect body through natural openings or by cuticle penetration. Upon access to the insect hemolymph, bacterial symbionts (Photorhabdus luminescens for H. bacteriophora and Xenorhabdus nematophila for S. carpocapsae) are regurgitated from the nematode gut and rapidly proliferate. During population growth, bacterial symbionts secrete numerous toxins and degradative enzymes that exterminate and bioconvert the host insect. During development and reproduction, EPNs obtain their nutrition by feeding upon both the bioconverted host and proliferated symbiont. Throughout the EPN life cycle, similar characteristics are seen. In general, EPNs are analogous to each other by the fact that their life cycle consists of five stages of development. Furthermore, reproduction is much more complex and varies between genera and species. In other words, infective juveniles of S. carpocapsae are destined to become males and females, whereas H. bacteriophora develop into hermaphrodites that produce subsequent generations of males and females. Other differences include insect host range, population growth rates, specificity of bacterial phase variants, etc. This review attempts to compare EPNs, their bacterial counterparts and symbiotic relationships for further enhancement of mass producing EPNs in liquid media.展开更多
Photorhabdus luminescens is a Gram-negative, bioluminescent, pigment producing enteric bacterium, which is pathogenic to insects and has the capability to undergo phase variation. The phase I variant of P. luminescens...Photorhabdus luminescens is a Gram-negative, bioluminescent, pigment producing enteric bacterium, which is pathogenic to insects and has the capability to undergo phase variation. The phase I variant of P. luminescens exists as a mutualistic symbiont where it plays a critical role in the life-cycle of the soil-dwelling nematode, Heterorhabditis bacteriophora. Both the bacterium and the nematode receive their nutritional requirements from the bioconversion of the insect host which is rich in many macromolecules such as the disaccharide, trehalose. Trehalose is a non-reducing disaccharide of glucose that is formed by an a-1,1-glycosidic bond and is associated with the physiology of many bacteria, insects and nematodes. Trehalose has been shown to be the most abundant storage sugar found within insect hemolymph （1%-2%）. The physicochemical properties of trehalose allow this carbohydrate to act as a stress protectant where it has been implicated with thermal stress, dehydration, and osmotic protection of many microorganisms. Due to these properties, trehalose may allow culture stability of the phase I variant in vitro and in vivo. Traits of the phase I variant that were studied in this work include bioluminescence and the production of the red anthroquinone-derived pigment. The carbohydrates that were utilized in this study were glucose and trehalose; where shake flask cultures of the phase I variant were cultured at room temperature for up to six days in carbohydrate supplemented basal media with increasing carbohydrate concentrations of 0. 1%, 0.5% and 1.0% （v/v）. Relative luminosity, pigmentation and pH were graphed as a function of time, carbohydrate used, and carbohydrate concentration. Data obtained from this study suggests that the supplementation of 1.0% trehalose, when culturing the phase I variant ofP. luminescens, can maintain bioluminosity and pigmentation over extended periods of time （five days） as compared to basal media and basal media supplemented with 1.0% glucose.展开更多
Background: The bollworm complex consisting of Helicoverpa armigera and Earias vittella is a major threat in cotton production globally. The habit of developing resistance to many insecticides including Bt transgenic ...Background: The bollworm complex consisting of Helicoverpa armigera and Earias vittella is a major threat in cotton production globally. The habit of developing resistance to many insecticides including Bt transgenic cotton necessitates the exploration of an alternate strategy to manage bollworms. The entomopathogenic nematodes(EPN) Steinernema carpocapsae strain APKS2 and Heterorhabditis bacteriophora strains KKMH1 and TRYH1 at different concentrations of 1 × 10^(9) infective juveniles(IJs)·hm^(-2), 2 × 10^(9)IJs.hm^(-2), and 3×10^(9)IJs·hm^(-2) in 500 L of water were evaluated as a foliar spray in fields naturally infested with H.armigera and F.vittella located at Eastern Block and and Cotton Research Farm of Tamil Nadu Agricultural University, Coimbaotre, India during October 2010–February 2011 and October 2011–February 2012, respectively.Results: In general, all three tested EPN strains reduced the larval population of H. armigera and E. vittella;reduced square and boll damage;and subsequently increased cotton yield compared with the untreated control. The S. carpocapsae APKS2 is most e ective against H. armigera whereas both S. carpocapsae APKS2 and H. bacteriophora KKMH1 were equally effective against E. vittella. The higher dose of 3×10^(9)IJs·hm^(-2) was highly significant in the reduction of H. armigera larvae. However, the doses 2×10^(9)IJs·hm^(-2)and 3×10^(9)IJs·hm^(-2) were equally effective for E. vittella control. The S. carpocapsae APKS2 at 3×10^(9)IJs·hm^(-2) caused a 62.2% reduction of H. armigera larvae, 34% reduction of square damage, 58.5% reduction of boll damage, and yielded 45.5% more seed cotton than the untreated control plots. In E. vittella infested field, S. carpocapsae strain APKS2 and H. bacteriophora strain KKMH1 at 2×10^(9)IJs·hm^(-2)resulted in 60.6%~62.4% larva reduction, 68.4%~70.7% square damage reduction, 66.6%~69.9% boll damage reduction and 45.9% yield increase over the untreated control. The effective EPN treatments were comparable to the chemical insecticide chlorpyriphos 20% emulsifiable concentrate spraying at 2 mL·L^(-1).Conclusions: This study has shown that EPN have great potential in the management of the bollworm complex in cotton. Foliar spraying EPN strain S. carpocapsae(APKS2) at 3×10^(9)IJs·hm^(-2) and S. carpocapsae(APKS2) or H. bacteriophora(KKMH1) at 2×10^(9)IJs·hm^(-2) five times at 10days intervals are the best for the management of H. armigera and E. vittella, respectively.展开更多
Parasites and pathogens can follow different patterns of infection depending on the host developmental stage or sex.In fact,immune function is energetically costly for hosts and trade-offs exist between immune defense...Parasites and pathogens can follow different patterns of infection depending on the host developmental stage or sex.In fact,immune function is energetically costly for hosts and trade-offs exist between immune defenses and life history traits as growth,de-velopment and reproduction and organisms should thus optimize immune defense through their life cycle according to their developmental stage.ldentifying the most susceptible target and the most virulent pathogen is particularly important in the case of insect pests,in order to develop effective control strategies targeting the most vulnerable individuals with the most effective control agent.Here,we carried out laboratory tests to identify the most susceptible target of infection by infecting different stages of the red palm weevil Rhynchophorus ferrugineus(larvae,pupae,male,and female adults)with both a generic pathogen,antibiotic-resistant Gram-negative bacteria Escherichia coli XL1-Blue,and two specific strains of entomopathogenic nematodes(EPNs),Steinernema carpocapsae ItS-CAO1 and Heterorhabditis bacteriophora ItH-LUI.By evaluating bacterial clearance,host mortality and parasite progeny release,we demonstrate that larvae are more resistant than adults to bacterial challenge and they release less EPNs progeny after infection despite a higher mortality compared to adults.Considering the two EPN strains,S.carpocapsae was more virulent than II.bacteriophora both in terms of host mortality and more abundant progeny released by hosts after death.The outcomes attained with unspecific and specific pathogens provide useful information for a more efficient and sustainable management of this invasive pest.展开更多
To study the difference in the accumulation of bioactive constituents in Spine gourd(Momordica dioica Roxb.),the changes in its phenolic compounds at mature green(fruit utilized)and ripe red(fruit wasted)stages were a...To study the difference in the accumulation of bioactive constituents in Spine gourd(Momordica dioica Roxb.),the changes in its phenolic compounds at mature green(fruit utilized)and ripe red(fruit wasted)stages were analysed,and it was correlated with their antioxidant and anthelmintic potential.The highest total phenolic content was observed in ripe peel ethyl acetate(RPEA),tannins in ripe seed hexane(RSH)and flavonoid in ripe peel ethanol(RPE)extracts.UPLC–MS analysis identified 15 phenolic compounds in the extracts.The highest antioxidant potential was shown by RSH in DPPH(IC_(50)1.47 mg/ml),RPEA in ABTS(IC_(50)2.40 mg/ml),and mature peel water(MPeW)extract in FRAP assays(0.58μg trolox equivalent per g dw).RPE induced the highest anthelmintic activity against Caenorhabditis elegans in egg hatch assay(LC_(50)-0.02 mg/ml),and adult worm mortality assay(LC_(50)-1.44 mg/ml),as well as 100%death of infective juveniles in Heterorhabditis indica(50 mg/ml).Correlation studies and Principal Component Analysis(PCA)indicated the relationship of catechins,quercetin,kaempferol,rutin,and gallic acid to anthelmintic activity.The study showed that the ripe stage of Spine gourd,which gets disposed of as postharvest waste,had better anthelmintic activity,and it can be utilized for the development of food formulations with anthelmintic potential.展开更多
基金The authors are grateful to the Management of Landmark University for financial assistance and to Prof.A.P.Malan of the Department of Conservation Ecology&Entomology,Stellenbosch University,South Africa for providing guidance with molecular identification.
文摘The occurrence of entomopathogenic nematodes(EPNs)in arable soil samples from Nigeria was investigated using Baermann extraction tray and insect-bait(White’s trap)techniques.Isolates were tested for infectivity using the larvae of Galleria mellonella(greater moth)and Tenebrio molitor(mealworm).The study revealed a new species of Heterorhabditis(MT371593)in soil samples that were randomly collected from an arable farmland cultivated with cassava TMS-30572 at the Teaching and Research Farm of Landmark University,Nigeria.Amplification of the internal transcribed spacer region(ITS)of the ribosomal DNA produced a nucleotide sequence of 933 base pairs(bp).A BLASTN search of GenBank showed that the sequence of the Nigerian isolate is identical at 99%similarity to that of Heterorhabditis sp.from Thailand.Infectivity test of the isolate showed 100%mortality against T.molitor larvae within 48 h of exposure while only 80%mortality was recorded for G.mellonella after 1 week of exposure.This is the first account of Heterorhabditis sp.in Nigeria.The varying degrees of infectivity against mealworm and greater moth observed in this study proved that the Nigerian isolate of Heterorhabditis sp.could potentially be an attractive option in the management of insect pests of cash crops.
基金the Indian Council of Agricultural Research,New Delhi for the grant in aid through ICAR-Central Institute for Cotton Research,Nagpur Institutional Project。
文摘Background The emergence of pink bollworm(PBW),Pectinophora gossypiella(Saunders)(Lepidoptera:Gelechiidae),in cotton due to Bt resistance and concealed feeding habit has created a need for alternative,eco-friendly,and cost-effective control methods.This study aimed to evaluate the bio-efficacy and reproductive potential of two native strains of entomopathogenic nematodes(EPNs),Heterorhabditis indica,namely CICR-HI-CL and CICR-HI-MN,against PBW larvae and pupae under in-vitro conditions.Results The larval assay revealed that strain CICR-HI-CL exhibited higher potency than strain CICR-HI-MN against 2nd,3rd,and 4thinstar larvae,with median lethal dose(LD50)values of 5.45,4.45,and 4.60 infective juveniles(IJs)per larva,respectively.In case of pupal bioassay,both EPN strains demonstrated greater virulence when applied directly(LD50values:29.65 and 73.88 IJs per pupa for strains CICR-HI-CL and CICR-HI-MN,respectively)compared to soil application(147.84 and 272.38 IJs per pupa).Both EPN strains successfully penetrated and reproduced on 4thinstar larvae,resulting in maximum production of 19.28 and 20.85 lakh IJs per larva in the next generation when inoculated at 30 IJs per larva.Conclusion The present study has generated useful information on the virulence and reproductive potential of two strains of EPN H.indica(CICR-HI-CL and CICR-HI-MN)against PBW,a dreaded pest of cotton.Higher virulence and reproductive potential of EPN strains demonstrated their ability to multiply,sustain and perpetuate on larval and pupal stages of PBW.The knowledge generated will help formulate effective management strategies for PBW with the inclusion of EPN as a potential biological control candidate.The soil-dwelling life stages viz.,last instar hibernating larvae and pupae of PBW can be the ideal weak links to make a successful use of H.indica for sustainable management of PBW in the cotton ecosystem.However,before taking these EPN strains to field for managing PBW,detailed studies investigating their biocontrol potential against PBW under field conditions are needed.
文摘Heterorhabditis bacteriophora and Steinernema carpocapsae are microscopic entomoparasitic nematodes (EPNs) that are attractive, organic alternatives for controlling a wide range of crop insect pests. EPNs evolved with parasitic adaptations that enable them to “feast” upon insect hosts. The infective juvenile, a non-feeding, developmentally arrested nematode stage, is destined to seek out insect hosts and initiates parasitism. After an insect host is located, EPNs enter the insect body through natural openings or by cuticle penetration. Upon access to the insect hemolymph, bacterial symbionts (Photorhabdus luminescens for H. bacteriophora and Xenorhabdus nematophila for S. carpocapsae) are regurgitated from the nematode gut and rapidly proliferate. During population growth, bacterial symbionts secrete numerous toxins and degradative enzymes that exterminate and bioconvert the host insect. During development and reproduction, EPNs obtain their nutrition by feeding upon both the bioconverted host and proliferated symbiont. Throughout the EPN life cycle, similar characteristics are seen. In general, EPNs are analogous to each other by the fact that their life cycle consists of five stages of development. Furthermore, reproduction is much more complex and varies between genera and species. In other words, infective juveniles of S. carpocapsae are destined to become males and females, whereas H. bacteriophora develop into hermaphrodites that produce subsequent generations of males and females. Other differences include insect host range, population growth rates, specificity of bacterial phase variants, etc. This review attempts to compare EPNs, their bacterial counterparts and symbiotic relationships for further enhancement of mass producing EPNs in liquid media.
文摘Photorhabdus luminescens is a Gram-negative, bioluminescent, pigment producing enteric bacterium, which is pathogenic to insects and has the capability to undergo phase variation. The phase I variant of P. luminescens exists as a mutualistic symbiont where it plays a critical role in the life-cycle of the soil-dwelling nematode, Heterorhabditis bacteriophora. Both the bacterium and the nematode receive their nutritional requirements from the bioconversion of the insect host which is rich in many macromolecules such as the disaccharide, trehalose. Trehalose is a non-reducing disaccharide of glucose that is formed by an a-1,1-glycosidic bond and is associated with the physiology of many bacteria, insects and nematodes. Trehalose has been shown to be the most abundant storage sugar found within insect hemolymph （1%-2%）. The physicochemical properties of trehalose allow this carbohydrate to act as a stress protectant where it has been implicated with thermal stress, dehydration, and osmotic protection of many microorganisms. Due to these properties, trehalose may allow culture stability of the phase I variant in vitro and in vivo. Traits of the phase I variant that were studied in this work include bioluminescence and the production of the red anthroquinone-derived pigment. The carbohydrates that were utilized in this study were glucose and trehalose; where shake flask cultures of the phase I variant were cultured at room temperature for up to six days in carbohydrate supplemented basal media with increasing carbohydrate concentrations of 0. 1%, 0.5% and 1.0% （v/v）. Relative luminosity, pigmentation and pH were graphed as a function of time, carbohydrate used, and carbohydrate concentration. Data obtained from this study suggests that the supplementation of 1.0% trehalose, when culturing the phase I variant ofP. luminescens, can maintain bioluminosity and pigmentation over extended periods of time （five days） as compared to basal media and basal media supplemented with 1.0% glucose.
基金the Life Science Research Board,Defense Research and Development Organization,New Delhi,India for the financial support through a grant (No. DLS/81/48222/LSRB-136/FSB/2007)
文摘Background: The bollworm complex consisting of Helicoverpa armigera and Earias vittella is a major threat in cotton production globally. The habit of developing resistance to many insecticides including Bt transgenic cotton necessitates the exploration of an alternate strategy to manage bollworms. The entomopathogenic nematodes(EPN) Steinernema carpocapsae strain APKS2 and Heterorhabditis bacteriophora strains KKMH1 and TRYH1 at different concentrations of 1 × 10^(9) infective juveniles(IJs)·hm^(-2), 2 × 10^(9)IJs.hm^(-2), and 3×10^(9)IJs·hm^(-2) in 500 L of water were evaluated as a foliar spray in fields naturally infested with H.armigera and F.vittella located at Eastern Block and and Cotton Research Farm of Tamil Nadu Agricultural University, Coimbaotre, India during October 2010–February 2011 and October 2011–February 2012, respectively.Results: In general, all three tested EPN strains reduced the larval population of H. armigera and E. vittella;reduced square and boll damage;and subsequently increased cotton yield compared with the untreated control. The S. carpocapsae APKS2 is most e ective against H. armigera whereas both S. carpocapsae APKS2 and H. bacteriophora KKMH1 were equally effective against E. vittella. The higher dose of 3×10^(9)IJs·hm^(-2) was highly significant in the reduction of H. armigera larvae. However, the doses 2×10^(9)IJs·hm^(-2)and 3×10^(9)IJs·hm^(-2) were equally effective for E. vittella control. The S. carpocapsae APKS2 at 3×10^(9)IJs·hm^(-2) caused a 62.2% reduction of H. armigera larvae, 34% reduction of square damage, 58.5% reduction of boll damage, and yielded 45.5% more seed cotton than the untreated control plots. In E. vittella infested field, S. carpocapsae strain APKS2 and H. bacteriophora strain KKMH1 at 2×10^(9)IJs·hm^(-2)resulted in 60.6%~62.4% larva reduction, 68.4%~70.7% square damage reduction, 66.6%~69.9% boll damage reduction and 45.9% yield increase over the untreated control. The effective EPN treatments were comparable to the chemical insecticide chlorpyriphos 20% emulsifiable concentrate spraying at 2 mL·L^(-1).Conclusions: This study has shown that EPN have great potential in the management of the bollworm complex in cotton. Foliar spraying EPN strain S. carpocapsae(APKS2) at 3×10^(9)IJs·hm^(-2) and S. carpocapsae(APKS2) or H. bacteriophora(KKMH1) at 2×10^(9)IJs·hm^(-2) five times at 10days intervals are the best for the management of H. armigera and E. vittella, respectively.
文摘Parasites and pathogens can follow different patterns of infection depending on the host developmental stage or sex.In fact,immune function is energetically costly for hosts and trade-offs exist between immune defenses and life history traits as growth,de-velopment and reproduction and organisms should thus optimize immune defense through their life cycle according to their developmental stage.ldentifying the most susceptible target and the most virulent pathogen is particularly important in the case of insect pests,in order to develop effective control strategies targeting the most vulnerable individuals with the most effective control agent.Here,we carried out laboratory tests to identify the most susceptible target of infection by infecting different stages of the red palm weevil Rhynchophorus ferrugineus(larvae,pupae,male,and female adults)with both a generic pathogen,antibiotic-resistant Gram-negative bacteria Escherichia coli XL1-Blue,and two specific strains of entomopathogenic nematodes(EPNs),Steinernema carpocapsae ItS-CAO1 and Heterorhabditis bacteriophora ItH-LUI.By evaluating bacterial clearance,host mortality and parasite progeny release,we demonstrate that larvae are more resistant than adults to bacterial challenge and they release less EPNs progeny after infection despite a higher mortality compared to adults.Considering the two EPN strains,S.carpocapsae was more virulent than II.bacteriophora both in terms of host mortality and more abundant progeny released by hosts after death.The outcomes attained with unspecific and specific pathogens provide useful information for a more efficient and sustainable management of this invasive pest.
文摘To study the difference in the accumulation of bioactive constituents in Spine gourd(Momordica dioica Roxb.),the changes in its phenolic compounds at mature green(fruit utilized)and ripe red(fruit wasted)stages were analysed,and it was correlated with their antioxidant and anthelmintic potential.The highest total phenolic content was observed in ripe peel ethyl acetate(RPEA),tannins in ripe seed hexane(RSH)and flavonoid in ripe peel ethanol(RPE)extracts.UPLC–MS analysis identified 15 phenolic compounds in the extracts.The highest antioxidant potential was shown by RSH in DPPH(IC_(50)1.47 mg/ml),RPEA in ABTS(IC_(50)2.40 mg/ml),and mature peel water(MPeW)extract in FRAP assays(0.58μg trolox equivalent per g dw).RPE induced the highest anthelmintic activity against Caenorhabditis elegans in egg hatch assay(LC_(50)-0.02 mg/ml),and adult worm mortality assay(LC_(50)-1.44 mg/ml),as well as 100%death of infective juveniles in Heterorhabditis indica(50 mg/ml).Correlation studies and Principal Component Analysis(PCA)indicated the relationship of catechins,quercetin,kaempferol,rutin,and gallic acid to anthelmintic activity.The study showed that the ripe stage of Spine gourd,which gets disposed of as postharvest waste,had better anthelmintic activity,and it can be utilized for the development of food formulations with anthelmintic potential.
