The entomopathogenic nematode,Steinernema carpocapsae,was evaluated for control of the potato tuber moth,Phthorimaea operculella,under laboratory conditions.We evaluated different concentrations of S.carpocapsae for c...The entomopathogenic nematode,Steinernema carpocapsae,was evaluated for control of the potato tuber moth,Phthorimaea operculella,under laboratory conditions.We evaluated different concentrations of S.carpocapsae for control of 2 nd,3 rd,and 4 th instar P.operculella.The median lethal concentration(LC50)of S.carpocapsae infective juveniles(IJs)to 2 nd,3 rd and 4 th instar larvae of P.operculella was 200,363,181 IJs mL–1,respectively.With the extension of treatment time,the cumulative mortality increased for 2 nd,3 rd,and 4 th instar larvae and pupae of P.operculella.Fourth instars were the most susceptible for all observation periods.Therefore,our results suggest that S.carpocapsae could be an effective biological control agent for P.operculella.展开更多
Cells and cell-free solutions of the culture filtrate of the bacterial symbiont, Xenorhabdus nematophila taken from the entomopathogenic nematode Steinernema carpocapsae in aqueous broth suspensions were lethal to lar...Cells and cell-free solutions of the culture filtrate of the bacterial symbiont, Xenorhabdus nematophila taken from the entomopathogenic nematode Steinernema carpocapsae in aqueous broth suspensions were lethal to larvae of the diamondback moth Plutella xylostella. Their application on leaves of Chinese cabbage indicated that the cells can penetrate into the insects in the absence of the nematode vector. Cell-free solutions containing metabolites were also proved as effective as bacterial cells suspension. The application of aqueous suspensions of cells of X.nematophila or solutions containing its toxic metabolites to the leaves represents a possible new strategy for controlling insect pests on foliage.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
The infective juveniles （IJs） ofSteinernema carpocapsae ‘All＇ were osmotically stressed by a mixture of ionic （fortified artificial seawater） and non-ionic （3.2 mol/L glycerol） solutions to establish a method ...The infective juveniles （IJs） ofSteinernema carpocapsae ‘All＇ were osmotically stressed by a mixture of ionic （fortified artificial seawater） and non-ionic （3.2 mol/L glycerol） solutions to establish a method for osmotic storage of entomopathogenic nematodes. Seven combinations （termed solution A to G） with different proportions of these two solutions were tested, with sterile extra pure water （sepH20, termed solution H） as a control. The mortality of the IJs at a concentration of 5×10^5 IJ/mL in the solutions A to G, and H were 13.2%, 16.2%, 16.7%, 13.5%, 25.2%, 31.6%, 44.6%, and 1.0%, respectively, after 21 days storage at 25℃. Most of the IJs shrunk and stopped motility after 6-9 hours incubation at 25℃ in solutions A to D. Based on the results, solutions A to D and H were chosen to further test the osmotic survival of the IJs at different IJ concentrations （5× 10^5, 2.5×10^5, 2 000 IJ/mL） and incubation temperature （30℃, 25℃, 10℃）. The resulting IJs were exposed to a high temperature assay （45℃ for 4 h, HTA）. Osmotically stressed IJs showed improved heat tolerance. The mortality of the Lls increased with the increasing concentrations of the test Lls and the storage temperatures after exposing to the HTA. More than 88.4%, 62.3% or 2.4% of the treated IJs died at the above three IJ concentrations, respectively. At the three IJ concentrations （2 000 IJs/mL, 2.5×10^5 IJs/mL or 5 ×10^5 IJs/mL）, the highest mortality was recorded in solution D （11.6%, 85.9% or 98.0%, respectively）, and the lowest mortality in solution B （2. 4%, 62.3% or 86.6%, respectively）. No untreated IJs survived after the heat treatment. During 42 days storage at 10℃, the IJs mortality in the solutiors A to D and H were 7.19%, 5.97%, 4.41%, 4.34%, and 4.34% respectively, and showed no significant differences. In conclusion, osmotic treatment of the IJs of S. carpocapsae ‘ All＇ in a mixture of ionic and non-ionic solutions enhances the heat tolerance. The mortality of the IJs after HTA increased with the increasing concentrations of the test IJs and the storage temperatures after exposure to the HTA. The result is promising for the osmotic storage of the entomopathogenic nematodes.展开更多
Aim of this study was to investigate relationships between the red palm weevil （RPW） Rhynchophorusferrugineus （Olivier） and the entomopathogenic nematode Stein- ernema carpocapsae （EPN）; particularly, the work w...Aim of this study was to investigate relationships between the red palm weevil （RPW） Rhynchophorusferrugineus （Olivier） and the entomopathogenic nematode Stein- ernema carpocapsae （EPN）; particularly, the work was focused on the immune response of the insect host in naive larvae and after infection with the EPN. Two main immunological processes have been addressed： the activity and modulation of host prophenoloxidase- phenoloxidase （proPO） system, involved in melanization of not-self and hemocytes recog- nition processes responsible for not-self encapsulation. Moreover, immune depressive and immune evasive strategies of the parasite have been investigated. Our results suggest that RPW possess an efficient immune system, however in the early phase of infection, S. carpocapsae induces a strong inhibition of the host proPO system. In addition, host cell- mediated mechanisms of encapsulation, are completely avoided by the parasite, the elusive strategies orS. carpocapsae seem to be related to the structure of its body-surface, since induced alterations of the parasite cuticle resulted in the loss of its mimetic properties. S. carpocapsae before the release of its symbiotic bacteria, depress and elude RPW immune defenses, with the aim to arrange a favorable environment for its bacteria responsible of the septicemic death of the insect target.展开更多
基金supported in part by the National Key Research and Development Program of China (2018YFD0200802)
文摘The entomopathogenic nematode,Steinernema carpocapsae,was evaluated for control of the potato tuber moth,Phthorimaea operculella,under laboratory conditions.We evaluated different concentrations of S.carpocapsae for control of 2 nd,3 rd,and 4 th instar P.operculella.The median lethal concentration(LC50)of S.carpocapsae infective juveniles(IJs)to 2 nd,3 rd and 4 th instar larvae of P.operculella was 200,363,181 IJs mL–1,respectively.With the extension of treatment time,the cumulative mortality increased for 2 nd,3 rd,and 4 th instar larvae and pupae of P.operculella.Fourth instars were the most susceptible for all observation periods.Therefore,our results suggest that S.carpocapsae could be an effective biological control agent for P.operculella.
文摘Cells and cell-free solutions of the culture filtrate of the bacterial symbiont, Xenorhabdus nematophila taken from the entomopathogenic nematode Steinernema carpocapsae in aqueous broth suspensions were lethal to larvae of the diamondback moth Plutella xylostella. Their application on leaves of Chinese cabbage indicated that the cells can penetrate into the insects in the absence of the nematode vector. Cell-free solutions containing metabolites were also proved as effective as bacterial cells suspension. The application of aqueous suspensions of cells of X.nematophila or solutions containing its toxic metabolites to the leaves represents a possible new strategy for controlling insect pests on foliage.
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The infective juveniles （IJs） ofSteinernema carpocapsae ‘All＇ were osmotically stressed by a mixture of ionic （fortified artificial seawater） and non-ionic （3.2 mol/L glycerol） solutions to establish a method for osmotic storage of entomopathogenic nematodes. Seven combinations （termed solution A to G） with different proportions of these two solutions were tested, with sterile extra pure water （sepH20, termed solution H） as a control. The mortality of the IJs at a concentration of 5×10^5 IJ/mL in the solutions A to G, and H were 13.2%, 16.2%, 16.7%, 13.5%, 25.2%, 31.6%, 44.6%, and 1.0%, respectively, after 21 days storage at 25℃. Most of the IJs shrunk and stopped motility after 6-9 hours incubation at 25℃ in solutions A to D. Based on the results, solutions A to D and H were chosen to further test the osmotic survival of the IJs at different IJ concentrations （5× 10^5, 2.5×10^5, 2 000 IJ/mL） and incubation temperature （30℃, 25℃, 10℃）. The resulting IJs were exposed to a high temperature assay （45℃ for 4 h, HTA）. Osmotically stressed IJs showed improved heat tolerance. The mortality of the Lls increased with the increasing concentrations of the test Lls and the storage temperatures after exposing to the HTA. More than 88.4%, 62.3% or 2.4% of the treated IJs died at the above three IJ concentrations, respectively. At the three IJ concentrations （2 000 IJs/mL, 2.5×10^5 IJs/mL or 5 ×10^5 IJs/mL）, the highest mortality was recorded in solution D （11.6%, 85.9% or 98.0%, respectively）, and the lowest mortality in solution B （2. 4%, 62.3% or 86.6%, respectively）. No untreated IJs survived after the heat treatment. During 42 days storage at 10℃, the IJs mortality in the solutiors A to D and H were 7.19%, 5.97%, 4.41%, 4.34%, and 4.34% respectively, and showed no significant differences. In conclusion, osmotic treatment of the IJs of S. carpocapsae ‘ All＇ in a mixture of ionic and non-ionic solutions enhances the heat tolerance. The mortality of the IJs after HTA increased with the increasing concentrations of the test IJs and the storage temperatures after exposure to the HTA. The result is promising for the osmotic storage of the entomopathogenic nematodes.
文摘Aim of this study was to investigate relationships between the red palm weevil （RPW） Rhynchophorusferrugineus （Olivier） and the entomopathogenic nematode Stein- ernema carpocapsae （EPN）; particularly, the work was focused on the immune response of the insect host in naive larvae and after infection with the EPN. Two main immunological processes have been addressed： the activity and modulation of host prophenoloxidase- phenoloxidase （proPO） system, involved in melanization of not-self and hemocytes recog- nition processes responsible for not-self encapsulation. Moreover, immune depressive and immune evasive strategies of the parasite have been investigated. Our results suggest that RPW possess an efficient immune system, however in the early phase of infection, S. carpocapsae induces a strong inhibition of the host proPO system. In addition, host cell- mediated mechanisms of encapsulation, are completely avoided by the parasite, the elusive strategies orS. carpocapsae seem to be related to the structure of its body-surface, since induced alterations of the parasite cuticle resulted in the loss of its mimetic properties. S. carpocapsae before the release of its symbiotic bacteria, depress and elude RPW immune defenses, with the aim to arrange a favorable environment for its bacteria responsible of the septicemic death of the insect target.
