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Trevor Williams - One of the best experts on this subject based on the ideXlab platform.
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application of juvenile hormone analogue and Optical Brightener technologies to the production of spodoptera frugiperda multiple nucleopolyhedrovirus
Proceedings of the IOBC WPRS Working Group "Insect Pathogens and Insect Parasitic Nematodes" and COST Action 862 "Bacterial Toxins for Insect Control", 2009Co-Authors: Rodrigo Lasa, Primitivo Caballero, Trevor Williams, I Moreno, R U Ehlers, N Crickmore, J Enkerli, I Glazer, M Lopezferber, C TkaczukAbstract:Final instar larvae of Spodoptera frugiperda grew to a maximum weight of 622 ± 13 mg on diet treated with 1% piriproxyfen, a juvenile horrnone analogue (JHA). or 695 ± 17 mg on diet treated with 1% fenoxycarb, both of which were significantly greater weights than observed in larvae that developed on untreated diet (512 ± 9 mg). Virus mortality in insects inoculated with SfMNPV occlusion bodies (OBs) was approximately 50% in all treatments, reflecting the resistance of late instar S. frugiperda larvae to infection. However, JHA treatment did not result in a significant increases in the total OB yield, or OBs per mg larval weight, compared to untreated infected insects. We deterrnined whether resistance to infection could be overcome by inoculation with mixtures of OBs and Optical Brighteners. Potentiation of OB activity was >2500-fold in mixtures with 1% Leukophor AP or Blankophor BA, or >15-fold in mixtures with 0.1 % of either Brightener, compared to SfMNPV OBs alone. We conclude that SfMNPV production was 110t increased in JHA treated larvae because the JHA did not result in a supernumerary instar in S. frugiperda. However, Optical Brighteners were highly effective in overcoming developmental resistance to infection in this species.
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efficacy of Optical Brightener formulations of spodoptera exigua multiple nucleopolyhedrovirus semnpv as a biological insecticide in greenhouses in southern spain
Biological Control, 2007Co-Authors: Rodrigo Lasa, Primitivo Caballero, Carmen Ruizportero, Maria D Alcazar, Jose E Belda, Trevor WilliamsAbstract:Abstract The efficacy of Optical Brightener formulations of a native Spanish isolate of Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV) was determined for control of S. exigua on greenhouse grown sweet pepper (Capsicum annuum) in Almeria, Spain. In laboratory bioassays involving diet surface contamination, the 50% lethal concentration in fourth instars was reduced 25-fold and 5731-fold, compared to SeMNPV occlusion bodies (OBs) alone, or in mixtures with 0.1% and 1% of the stilbene-derived Optical Brightener leucophor AP, respectively. The efficacy of spray applications of 1 × 1012 OBs/Ha SeMNPV alone, or in mixtures with 0.1% leucophor AP, was tested in a greenhouse planted with sweet pepper. The prevalence of virus infection in larvae collected at intervals post-application and reared on artificial diet in the laboratory was very high (62–97% mortality). Compared to the treatment involving SeMNPV OBs alone, OBs applied in mixtures with leucophor AP resulted in a significant increase in the prevalence of infection in larvae collected at 2 days post-application, but not in insects collected subsequently. In contrast, a chemical insecticide treatment, lufenuron, performed poorly (
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Optical Brighteners do not influence covert baculovirus infection of Spodoptera frugiperda.
Applied and Environmental Microbiology, 2005Co-Authors: Anamabel Martinez, Trevor Williams, Miguel López-ferber, Primitivo CaballeroAbstract:Covert infection with Spodoptera frugiperda multiple nucleopolyhedrovirus, detected by reverse transcription-PCR of virus gene transcripts (ie-0 and polh), was not significantly affected by the presence of an Optical Brightener (Tinopal UNPA-GX), indicating no change in virus virulence. Detection of the covert infection was dependent on insect life stage and the viral mRNA used for diagnosis.
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formulation with an Optical Brightener does not increase probability of developing resistance to spodoptera frugiperda nucleopolyhedrovirus in the laboratory
Journal of Economic Entomology, 2004Co-Authors: Anamabel Martinez, Primitivo Caballero, Maider Villanueva, Nagore Miralles, Ivan San Martin, Estibaliz Lopez, Trevor WilliamsAbstract:Abstract Stilbene-derived Optical Brighteners can markedly enhance the insecticidal activity of certain baculoviruses. We evaluated the influence of an Optical Brightener on the rate at which Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) developed resistance to nucleopolyhedrovirus (SfMNPV). Two laboratory colonies of S. frugiperda were inoculated with an LC50 of SfMNPV, in the absence or presence of the Optical Brightener Tinopal LPW (0.1%), over a period of two and 11 generations, in the first and second experiment, respectively. Compared with the initial susceptibility of the insect colony, resistance ratios of 11- and 12-fold were observed after two generations of treatment with SfMNPV + Tinopal LPW and SfMNPV alone. Similar, but variable degrees of resistance were observed in the long-term experiment with resistance ratios of 8- to 35-fold after seven to 11 generations. The presence of Tinopal LPW alone, or in mixtures with SfMNPV, did not cause any systematic change in insect resistanc...
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effects of an Optical Brightener on the development body weight and sex ratio of spodoptera frugiperda lepidoptera noctuidae
Biocontrol Science and Technology, 2004Co-Authors: Anamabel Martinez, Primitivo Caballero, Trevor WilliamsAbstract:The incorporation of stilbene-derived Optical Brighteners into baculovirus formulations can substantially enhance virus infectivity and persistence of inoculum in the field. We evaluated the effect of the Optical Brightener Tinopal UNPA-GX (Sigma Chemical Co.) on the weight, development time, adult emergence and sex ratio of the principal pest of maize in the Americas, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae). Tinopal UNPA-GX was incorporated into semi-synthetic diet at a final concentration of 0.1 or 0.05% (w/v) and larvae of S. frugiperda were individually reared on the Tinopal-treated or an untreated control diet. In both Tinopal treatments, the weights of larvae and pupae were significantly reduced by up to 36 and 13%, respectively. The duration of larval development was increased by up to 30% compared to the controls. Adult emergence was high in all treatments (≈90%) and was not affected by the presence of Tinopal in the diet. Significant differences in the proportion of adult fem...
Primitivo Caballero - One of the best experts on this subject based on the ideXlab platform.
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application of juvenile hormone analogue and Optical Brightener technologies to the production of spodoptera frugiperda multiple nucleopolyhedrovirus
Proceedings of the IOBC WPRS Working Group "Insect Pathogens and Insect Parasitic Nematodes" and COST Action 862 "Bacterial Toxins for Insect Control", 2009Co-Authors: Rodrigo Lasa, Primitivo Caballero, Trevor Williams, I Moreno, R U Ehlers, N Crickmore, J Enkerli, I Glazer, M Lopezferber, C TkaczukAbstract:Final instar larvae of Spodoptera frugiperda grew to a maximum weight of 622 ± 13 mg on diet treated with 1% piriproxyfen, a juvenile horrnone analogue (JHA). or 695 ± 17 mg on diet treated with 1% fenoxycarb, both of which were significantly greater weights than observed in larvae that developed on untreated diet (512 ± 9 mg). Virus mortality in insects inoculated with SfMNPV occlusion bodies (OBs) was approximately 50% in all treatments, reflecting the resistance of late instar S. frugiperda larvae to infection. However, JHA treatment did not result in a significant increases in the total OB yield, or OBs per mg larval weight, compared to untreated infected insects. We deterrnined whether resistance to infection could be overcome by inoculation with mixtures of OBs and Optical Brighteners. Potentiation of OB activity was >2500-fold in mixtures with 1% Leukophor AP or Blankophor BA, or >15-fold in mixtures with 0.1 % of either Brightener, compared to SfMNPV OBs alone. We conclude that SfMNPV production was 110t increased in JHA treated larvae because the JHA did not result in a supernumerary instar in S. frugiperda. However, Optical Brighteners were highly effective in overcoming developmental resistance to infection in this species.
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Effects of stilbene Optical Brighteners on the insecticidal activity of Bacillus thuringiensis and a single nucleopolyhedrovirus on Helicoverpa armigera
Biological Control, 2008Co-Authors: María A. Ibargutxi, Delia Muñoz, Alexandra Bernal, Iñigo Ruiz De Escudero, Primitivo CaballeroAbstract:The incorporation of certain stilbene Optical Brighteners into virus-based formulations has been demonstrated to increase viral pathogenicity (as indicated by reduced LD/LC50 values) but their effect on Bacillus thuringiensis activity has been scarcely investigated. We determined the effect of nine Optical Brighteners on the insecticidal activity of B. thuringiensis ser. kurstaki HD-1 strain (Bt HD-1) on Helicoverpa armigera and also compared the effect of two Optical Brighteners on the insecticidal activity of Bt HD-1 and occlusion bodies (OBs) of a Spanish isolate of H. armigera single nucleocapsid nucleopolyhedrovirus (HearNPV-SP1). Blankophor CLE, Blankophor DRS, Blankophor ER, and Leucophor SAC significantly increased the pathogenicity of Bt HD-1. In contrast, Tinopal UNPA-GX, Tinopal CBS, Blankophor BA, Leucophor AP, and Leucophor UO had an adverse or no effect on its insecticidal activity. Mixtures of HearNPV-SP1 OBs with Tinopal UNPA-GX or Leucophor UO resulted in 31.4- and 11.4-fold increases in pathogenicity, respectively, at 1%, and 11.4- and 6.3-fold increases in pathogenicity, respectively, at 0.1%, compared to the OBs alone. However, none of these Brighteners increased Bt HD-1 activity. These results appear consistent with the hypothesis that the enhancement of HearNPV-SP1 pathogenicity and the null or antagonistic effects observed in Bt HD-1 against H. armigera were due to Optical Brightener-mediated degradation of the peritrophic membrane, but additional systematic studies involving a broad range of Brighteners and electron microscope observations are required to confirm this premise.
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efficacy of Optical Brightener formulations of spodoptera exigua multiple nucleopolyhedrovirus semnpv as a biological insecticide in greenhouses in southern spain
Biological Control, 2007Co-Authors: Rodrigo Lasa, Primitivo Caballero, Carmen Ruizportero, Maria D Alcazar, Jose E Belda, Trevor WilliamsAbstract:Abstract The efficacy of Optical Brightener formulations of a native Spanish isolate of Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV) was determined for control of S. exigua on greenhouse grown sweet pepper (Capsicum annuum) in Almeria, Spain. In laboratory bioassays involving diet surface contamination, the 50% lethal concentration in fourth instars was reduced 25-fold and 5731-fold, compared to SeMNPV occlusion bodies (OBs) alone, or in mixtures with 0.1% and 1% of the stilbene-derived Optical Brightener leucophor AP, respectively. The efficacy of spray applications of 1 × 1012 OBs/Ha SeMNPV alone, or in mixtures with 0.1% leucophor AP, was tested in a greenhouse planted with sweet pepper. The prevalence of virus infection in larvae collected at intervals post-application and reared on artificial diet in the laboratory was very high (62–97% mortality). Compared to the treatment involving SeMNPV OBs alone, OBs applied in mixtures with leucophor AP resulted in a significant increase in the prevalence of infection in larvae collected at 2 days post-application, but not in insects collected subsequently. In contrast, a chemical insecticide treatment, lufenuron, performed poorly (
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Optical Brighteners do not influence covert baculovirus infection of Spodoptera frugiperda.
Applied and Environmental Microbiology, 2005Co-Authors: Anamabel Martinez, Trevor Williams, Miguel López-ferber, Primitivo CaballeroAbstract:Covert infection with Spodoptera frugiperda multiple nucleopolyhedrovirus, detected by reverse transcription-PCR of virus gene transcripts (ie-0 and polh), was not significantly affected by the presence of an Optical Brightener (Tinopal UNPA-GX), indicating no change in virus virulence. Detection of the covert infection was dependent on insect life stage and the viral mRNA used for diagnosis.
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formulation with an Optical Brightener does not increase probability of developing resistance to spodoptera frugiperda nucleopolyhedrovirus in the laboratory
Journal of Economic Entomology, 2004Co-Authors: Anamabel Martinez, Primitivo Caballero, Maider Villanueva, Nagore Miralles, Ivan San Martin, Estibaliz Lopez, Trevor WilliamsAbstract:Abstract Stilbene-derived Optical Brighteners can markedly enhance the insecticidal activity of certain baculoviruses. We evaluated the influence of an Optical Brightener on the rate at which Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) developed resistance to nucleopolyhedrovirus (SfMNPV). Two laboratory colonies of S. frugiperda were inoculated with an LC50 of SfMNPV, in the absence or presence of the Optical Brightener Tinopal LPW (0.1%), over a period of two and 11 generations, in the first and second experiment, respectively. Compared with the initial susceptibility of the insect colony, resistance ratios of 11- and 12-fold were observed after two generations of treatment with SfMNPV + Tinopal LPW and SfMNPV alone. Similar, but variable degrees of resistance were observed in the long-term experiment with resistance ratios of 8- to 35-fold after seven to 11 generations. The presence of Tinopal LPW alone, or in mixtures with SfMNPV, did not cause any systematic change in insect resistanc...
Anamabel Martinez - One of the best experts on this subject based on the ideXlab platform.
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reflectancia foliar crecimiento y respuestas fisiologicas de maiz y tomate a un abrillantador optico foliar reflectance growth and physiological responses of maize and tomato to an Optical Brightener
2010Co-Authors: Sandra P Velasco, Samuel Pineda, Aricely Mendez, Raul Cardenasnavarro, Jeannette S Bayuelojimenez, Javier Valle, Jose Isaac Figueroa, Philippe Lobit, Anamabel MartinezAbstract:RESUMEN Se evaluo el efecto del abrillantador optico Tinopal C1101 (derivado del etenedil bencenosulfonico) a 1 y 3 % (p/v) sobre la reflectancia foliar, crecimiento, fotosintesis y conductancia estoma-tica de dos cultivos agricolas, maiz ( Zea mays L.) y tomate ( Solanum lycopersicum L.). La aplicacion del abrillantador optico sobre las hojas de maiz y tomate incremento el porcentaje de reflectancia en un intervalo de 1.5 a 2.5 y de 1.6 a 1.9 veces, respectivamente, en las longitudes de onda correspondientes al espectro de absorcion de las clorofilas a y b . Su aplicacion continua a 1 y 3 % sobre plantas de maiz en condiciones de invernadero, afecto la altura de planta, area foliar y peso seco (P ≤ utilizan como bioinsecticidas en varios paises del mundo 0.05). En contraste, tales tratamientos no afectaron el crecimiento de las plantas de tomate. La aplicacion del abrillantador a 1 y 3 % no afecto la tasa de asimilacion de CO 2 ni la conductancia estomatica de maiz y tomate. Estos resultados indican que el efecto de este abrillantador optico sobre el crecimiento de las plantas puede estar relacionado con diferencias estructurales o fisiologicas de las mismas. Palabras clave
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Optical Brighteners do not influence covert baculovirus infection of Spodoptera frugiperda.
Applied and Environmental Microbiology, 2005Co-Authors: Anamabel Martinez, Trevor Williams, Miguel López-ferber, Primitivo CaballeroAbstract:Covert infection with Spodoptera frugiperda multiple nucleopolyhedrovirus, detected by reverse transcription-PCR of virus gene transcripts (ie-0 and polh), was not significantly affected by the presence of an Optical Brightener (Tinopal UNPA-GX), indicating no change in virus virulence. Detection of the covert infection was dependent on insect life stage and the viral mRNA used for diagnosis.
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formulation with an Optical Brightener does not increase probability of developing resistance to spodoptera frugiperda nucleopolyhedrovirus in the laboratory
Journal of Economic Entomology, 2004Co-Authors: Anamabel Martinez, Primitivo Caballero, Maider Villanueva, Nagore Miralles, Ivan San Martin, Estibaliz Lopez, Trevor WilliamsAbstract:Abstract Stilbene-derived Optical Brighteners can markedly enhance the insecticidal activity of certain baculoviruses. We evaluated the influence of an Optical Brightener on the rate at which Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) developed resistance to nucleopolyhedrovirus (SfMNPV). Two laboratory colonies of S. frugiperda were inoculated with an LC50 of SfMNPV, in the absence or presence of the Optical Brightener Tinopal LPW (0.1%), over a period of two and 11 generations, in the first and second experiment, respectively. Compared with the initial susceptibility of the insect colony, resistance ratios of 11- and 12-fold were observed after two generations of treatment with SfMNPV + Tinopal LPW and SfMNPV alone. Similar, but variable degrees of resistance were observed in the long-term experiment with resistance ratios of 8- to 35-fold after seven to 11 generations. The presence of Tinopal LPW alone, or in mixtures with SfMNPV, did not cause any systematic change in insect resistanc...
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effects of an Optical Brightener on the development body weight and sex ratio of spodoptera frugiperda lepidoptera noctuidae
Biocontrol Science and Technology, 2004Co-Authors: Anamabel Martinez, Primitivo Caballero, Trevor WilliamsAbstract:The incorporation of stilbene-derived Optical Brighteners into baculovirus formulations can substantially enhance virus infectivity and persistence of inoculum in the field. We evaluated the effect of the Optical Brightener Tinopal UNPA-GX (Sigma Chemical Co.) on the weight, development time, adult emergence and sex ratio of the principal pest of maize in the Americas, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae). Tinopal UNPA-GX was incorporated into semi-synthetic diet at a final concentration of 0.1 or 0.05% (w/v) and larvae of S. frugiperda were individually reared on the Tinopal-treated or an untreated control diet. In both Tinopal treatments, the weights of larvae and pupae were significantly reduced by up to 36 and 13%, respectively. The duration of larval development was increased by up to 30% compared to the controls. Adult emergence was high in all treatments (≈90%) and was not affected by the presence of Tinopal in the diet. Significant differences in the proportion of adult fem...
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Effect of Optical Brighteners on the insecticidal activity of a nucleopolyhedrovirus in three instars of Spodoptera frugiperda
Entomologia Experimentalis Et Applicata, 2003Co-Authors: Anamabel Martinez, Trevor Williams, Oihane Simón, Primitivo CaballeroAbstract:Certain Optical Brighteners are effective UV protectants, and can improve the insecticidal activity of baculoviruses. We evaluated the effect of 10 Optical Brighteners, from four chemically different groups, on the insecticidal activity of a nucleopolyhedrovirus (SfMNPV) in third instar Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae). The most effective Optical Brighteners were Blankophor BBH and Calcofluor M2R, both of which are stilbenes. The distyryl-biphenyl derivative, Tinopal CBS, had no effect, whereas the stilbenes, Blankophor CLE and Leucophor SAC and the styrylbenzenic derivative, Blankophor ER, resulted in a decrease in virus induced mortality compared to larvae infected with SfMNPV alone. Mixtures of SfMNPV + 0.1% Calcofluor M2R had relative potencies of 2.7, 6.5, and 61.6 in the second, third, and fourth instars, respectively. The mean time to death differed with instar, but was not affected by the addition of 0.1% Calcofluor M2R. Analysis of published studies indicated that the concentration of Calcofluor M2R-related stilbenes was positively correlated with the relative potency observed in mixtures with homologous NPVs. The average magnitude of Optical Brightener activity did not differ significantly between early instars of 10 species of Lepidoptera. We conclude that virus formulations containing Optical Brighteners may be valuable for control of late instar lepidopteran pests.
Eva Valcheva - One of the best experts on this subject based on the ideXlab platform.
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the role of the entropy factor on the adsorption of an Optical Brightener on pulp
Turkish Journal of Chemistry, 2009Co-Authors: Greta Radeva, Eva Valcheva, Stefka VelevaAbstract:The present paper reports results of the thermodynamic study of adsorption of 2 Optical Brighteners (Tinopal UP and Leucophor AP) on pulp. The entropy non-homogeneity of the pulp surface was confirmed and the coefficients of entropy non-homogeneity were determined. The entropy effect on the variation of Gibbs free energy of the process studied was followed.
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a correlation between the kinetic and thermodynamic adsorption characteristics of an Optical Brightener on a pulp surface
Adsorption Science & Technology, 2008Co-Authors: Greta Radeva, Stefka Veleva, Eva ValchevaAbstract:An attempt to find a correlation between the kinetic and thermodynamic terms (e.g. activation energy, pre-exponential factor, isosteric heat, entropy, etc.) of the chemisorption process involved in a commercial Optical Brightener/pulp system is presented. A linear inter-relationship between the kinetic and thermodynamic characteristics of the system was found. Based on the coefficients obtained in the thermodynamic investigation of the adsorption process, it was possible to calculate the kinetic coefficient of the surface inhomogeneity. The use of both a model employing uniformly inhomogeneous surfaces and an approach involving all the kinetic and thermodynamic data was confirmed by the results obtained.
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thermodynamic aspects of the adsorption of an Optical Brightener on pulp
The Journal of Chemical Thermodynamics, 2008Co-Authors: Greta Radeva, Stefka Veleva, Eva ValchevaAbstract:Abstract Optical Brighteners Tinopal UP and Leucophor AP are used in additional treatment of bleached softwood kraft pulp under different conditions. The present paper describes the applicability of Temkin adsorption isotherm to characterize the thermodynamic equilibrium reached in chemisorption of an Optical Brightener on pulp’s uniformly non-homogeneous surface. It is found that this is an endothermic process. The entropy factors dominate the developing non-homogeneity and hence the variation of the Gibbs’s free energy as well.
Loy E Volkman - One of the best experts on this subject based on the ideXlab platform.
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Comparative pathogenesis of Helicoverpa zea S nucleopolyhedrovirus in noctuid larvae.
The Journal of general virology, 2020Co-Authors: Jan O Washburn, James F Wong, Loy E VolkmanAbstract:We used a recombinant of Helicoverpa zea S nucleopolyhedrovirus containing the hsp70/lacZ reporter cassette (HzSNPV-hsp70/lacZ) to quantify mortality relationships and to elucidate early pathogenesis in two permissive hosts, Heliothis virescens and Helicoverpa zea, and one semi-permissive host, Trichoplusia ni. Fourth instar T. ni were highly resistant to fatal infection both by oral injection of occlusions and by intrahaemocoelic injection of budded virus, indicating the presence of both midgut and systemic mechanisms of resistance. In bioassays, newly moulted (4(0)) H. zea were significantly more susceptible than 4(0) H. virescens to fatal infection, but mortality levels were the same for larval cohorts inoculated 16 h after the moult (4(16)). Developmental resistance was stronger in H. zea and in both hosts, partially reversed by administration of the Optical Brightener M2R. In both species, developmental resistance was correlated with a reduced ability of HzSNPV to establish and/or maintain primary midgut infections. In time-course experiments using a dosage of 15 occlusions ( approximately LD(90)), lacZ expression marking the onset of primary and secondary infection was first observed in midgut columnar and tracheal cells at 4 and 12 h, respectively. Inoculation of 4(0) larvae resulted in approximately twofold more foci in H. zea larvae than in H. virescens, but H. zea larvae sloughed infected midgut cells at a faster rate. For both heliothines, interaction of occlusion-derived virus with primary cellular targets within the midgut epithelium was critical to the outcome of infection and a key process underlying acquisition of developmental resistance.
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Comparative pathogenesis of Helicoverpa zea S nucleopolyhedrovirus in noctuid larvae
Journal of General Virology, 2001Co-Authors: Jan O Washburn, James F Wong, Loy E VolkmanAbstract:We used a recombinant of Helicoverpa zea S nucleopolyhedrovirus containing the hsp70/lacZ reporter cassette (HzSNPV-hsp70/lacZ) to quantify mortality relationships and to elucidate early pathogenesis in two permissive hosts, Heliothis virescens and Helicoverpa zea, and one semi-permissive host, Trichoplusia ni. Fourth instar T. ni were highly resistant to fatal infection both by oral injection of occlusions and by intrahaemocoelic injection of budded virus, indicating the presence of both midgut and systemic mechanisms of resistance. In bioassays, newly moulted (40) H. zea were significantly more susceptible than 40 H. virescens to fatal infection, but mortality levels were the same for larval cohorts inoculated 16 h after the moult (416). Developmental resistance was stronger in H. zea and in both hosts, partially reversed by administration of the Optical Brightener M2R. In both species, developmental resistance was correlated with a reduced ability of HzSNPV to establish and/or maintain primary midgut infections. In time-course experiments using a dosage of 15 occlusions (∼LD90), lacZ expression marking the onset of primary and secondary infection was first observed in midgut columnar and tracheal cells at 4 and 12 h, respectively. Inoculation of 40 larvae resulted in approximately twofold more foci in H. zea larvae than in H. virescens, but H. zea larvae sloughed infected midgut cells at a faster rate. For both heliothines, interaction of occlusion-derived virus with primary cellular targets within the midgut epithelium was critical to the outcome of infection and a key process underlying acquisition of developmental resistance.
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midgut based resistance of heliothis virescens to baculovirus infection mediated by phytochemicals in cotton
Journal of Insect Physiology, 2000Co-Authors: Kelli Hoover, Jan O Washburn, Loy E VolkmanAbstract:Abstract The decrease in susceptibility to polyhedrosis disease when Heliothis virescens larvae feed on cotton is profound, limiting the utility of baculoviruses for controlling noctuids on this important crop. We observed that the mortalities of H. virescens larvae challenged with a reporter-gene construct of Autographa californica M nucleopolyhedrovirus (AcMNPV-hsp70/lacZ) and fed either lettuce or artificial diet were ≈2.5-fold higher than that of cotton-fed insects. This decrease in susceptibility on cotton was observed following oral but not intrahemocoelic inoculation of virus, and it was negatively correlated with levels of foliar peroxidase. The rates of development of both infected and uninfected larvae also were correlated negatively with levels of foliar peroxidase, and hence, were significantly lower for insects fed cotton. When Calcofluor White M2R, an Optical Brightener reported to enhance the retention of AcMNPV-infected midgut cells, was included in inoculum administered orally to larvae, mortality levels were equivalent regardless of diet. These results suggest that sloughing of infected midgut cells occurred at a higher rate in insects that fed on cotton compared to the other two diets, and that midgut cell sloughing is the mechanism whereby susceptibility to mortal infection by AcMNPV-hsp70/lacZ is decreased on cotton. This conclusion is consistent with previous reports that ingestion of cotton can generate reactive oxygen species within the midgut lumen that may damage midgut epithelial cells. As far as we know, this is the first study to link resistance intrinsic to the physiology of the insect (e.g., developmental resistance) and resistance conferred by host plant chemistry to a single mechanism, i.e., midgut cell sloughing.
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evidence that the stilbene derived Optical Brightener m2r enhancesautographa californicam nucleopolyhedrovirus infection oftrichoplusia niandheliothis virescensby preventing sloughing of infected midgut epithelial cells
Biological Control, 1998Co-Authors: Jan O Washburn, Bruce A Kirkpatrick, Eric J Haasstapleton, Loy E VolkmanAbstract:Abstract Previous reports have shown that the stilbene-derived Optical Brightener M2R increases mortality and hastens death of larval lepidopterans orally challenged with baculoviruses. The mechanism of viral enhancement, however, has not been elucidated. We used a reporter gene recombinant ofAutographa californicaMNPV (AcMNPV-hsp70/lacZ) to investigate the enhancing effects of M2R on pathogenesis, mortality and time to death in larvae ofTrichoplusia ni,andHeliothis virescensinoculated as newly molted fourth instars (40s) and at various hours after molting (e.g., 16 h = 416). For both hosts, M2R significantly reduced the time to death by AcMNPV. In 40-inoculated larvae, M2R accelerated infection of tracheal cells, but overall the effects on pathogenesis were minor, and no significant increase in mortality over controls was observed. Among infected M2R-treated 416H. virescens,there were significantly more foci per insect compared to controls, and first lacZ expression was detected in the midgut epithelium at 6 h postinoculation (hpi). In contrast, no lacZ signals were detected in the midgut epithelia of control insects at any time point, and first lacZ expression was observed in the tracheal system at 14 hpi. When we compared virus-induced mortality inH. virescensinoculated at various times during the fourth instar, we found that M2R treatment enhanced mortality levels progressively for larvae inoculated later during the instar. Our results suggested that inT. niandH. virescens,M2R enhanced AcMNPV pathogenesis by blocking the sloughing of infected primary target cells in the midgut, thereby countering developmental resistance and increasing mortality.