Analysis and Modeling of Time–Dose–Mortality ofMelanoplus sanguinipes, Locusta migratoria migratorioides,andSchistocerca gregaria(Orthoptera: Acrididae) fromBeauveria, Metarhizium,andPaecilomycesIsolates from Madagascar

Nowierski, Robert M.; Zeng, Zheng; Jaronski, Stefan T.; Delgado, F.X.; Swearingen, Will D.

doi:10.1006/jipa.1996.0039

Cited by 68 publications

(78 citation statements)

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“…Many workers have characterized the host range of different isolates in attempts to characterize strains on the basis of pathogenicity (28). Most of the information on why isolates attack some hosts and not others is concerned with the effects of different host components on adhesion and germination (35).…”

Section: Discussionmentioning

confidence: 99%

Developmental and Transcriptional Responses to Host and Nonhost Cuticles by the Specific Locust Pathogen Metarhizium anisopliae var. acridum

2005

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Transcript patterns elicited in response to hosts can reveal how fungi recognize suitable hosts and the mechanisms involved in pathogenicity. These patterns could be fashioned by recognition of host-specific topographical features or by chemical components displayed or released by the host. We investigated this in the specific locust pathogen Metarhizium anisopliae var. acridum. Only host (Schistocerca gregaria) cuticle stimulated the full developmental program of germination and differentiation of infection structures (appressoria). Cuticle from beetles (Leptinotarsa decimlineata) repressed germination while cuticle from hemipteran bugs (Magicicada septendecim) allowed germination but only very low levels of differentiation, indicating that the ability to cause disease can be blocked at different stages. Using organic solvents to extract insects we identified a polar fraction from locusts that allowed appressorial formation against a flat plastic (hydrophobic) surface. Microarrays comprising 1,730 expressed sequence tags were used to determine if this extract elicits different transcriptional programs than whole locust cuticle or nonhost extracts. Of 483 differentially regulated genes, 97% were upregulated. These included genes involved in metabolism, utilization of host cuticle components, cell survival and detoxification, and signal transduction. Surprisingly, given the complex nature of insect epicuticle components and the specific response of M. anisopliae var. acridum to locusts, very similar transcript profiles were observed on locust and beetle extracts. However, the beetle extract cluster was enriched in genes for detoxification and redox processes, while the locust extract upregulated more genes for cell division and accumulation of cell mass. In addition, several signal transduction genes previously implicated in pathogenicity in plant pathogens were only upregulated in response to locust extract, implying similarities in the regulatory circuitry of these pathogens with very different hosts.Many fungal insect pathogens, such as Metarhizium anisopliae, infect host cuticles via spores that adhere and germinate to form a series of infection structures during penetration. In the presence of nutrients and water, conidia of M. anisopliae form germ tubes. The germ tube continues undifferentiated hyphal growth on a soft surface or if nutrient quality and quantity is not conducive to differentiation. On a host cuticle, however, apical elongation terminates and the germ tube swells distally to form an appressorium, a major site of adhesion and for production of enzymes that help breach host cuticle and establish a nutritional relationship with the host (33, 38). The formation of appressoria by strains of M. anisopliae var. anisopliae with a broad host range can also be induced efficiently by a hard hydrophobic surface (i.e., polystyrene) in the presence of low levels of complex nitrogenous nutrients. However, pathogens with a narrow host range such as M. anisopliae var. acridum (specific for acridids) germinate...

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Section: Discussionmentioning

confidence: 99%

Developmental and Transcriptional Responses to Host and Nonhost Cuticles by the Specific Locust Pathogen Metarhizium anisopliae var. acridum

2005

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“…All TCM trends in Fig. 3a to e fit very well in the TCM model (9,20). No significant heterogeneity was detected for each of the fitted TCM relationships (P Ն 0.14 in Hosmer-Lemeshow tests for the goodness of fit).…”

Section: Resultsmentioning

confidence: 73%

“…The robust TCM modeling analysis, which elucidated not only the effects of conidial concentration and posttreatment time but also the interaction of both variables (9,20), clearly differentiated the LC 50 and LT 50 trends of BbV28 and BbW in the three bioassays on S. litura larvae. Such trends between the two fungal strains were similar when conidia were sprayed only on the larvae for cuticle infection but differed significantly when conidia were sprayed on leaves for ingestion or on both larvae and leaves for cuticle and per os infections.…”

Section: Discussionmentioning

confidence: 99%

“…Time-concentration-mortality (TCM) data from each bioassay were fitted to a TCM model by correcting the daily mortality for each treatment with the control mortality (9,20). The modeling analysis was performed with updated DPS software (30), resulting in estimates of parameters for the effects of conidial concentration, postspray time length (in days), and their interaction on larval mortality.…”

Section: Methodsmentioning

confidence: 99%

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Integration of Insecticidal Protein Vip3Aa1 into Beauveria bassiana Enhances Fungal Virulence to Spodoptera litura Larvae by Cuticle and Per Os Infection

Ying

Chen

et al. 2010

Appl Environ Microbiol

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The entomopathogenic fungus Beauveria bassiana acts slowly on insect pests through cuticle infection. Vegetative insecticidal proteins (Vip3A) of Bacillus thuringiensis kill lepidopteran pests rapidly, via per os infection, but their use for pest control is restricted to integration into transgenic plants. A transgenic B. bassiana strain (BbV28) expressing Vip3Aa1 (a Vip3A toxin) was thus created to infect the larvae of the oriental leafworm moth Spodoptera litura through conidial ingestion and cuticle adhesion. Vip3Aa1 (ϳ88 kDa) was highly expressed in the conidial cytoplasm of BbV28 and was detected as a digested form (ϳ62 kDa) in the larval midgut 18 and 36 h after conidial ingestion. The median lethal concentration (LC 50 ) of BbV28 against the second-instar larvae feeding on cabbage leaves sprayed with conidial suspensions was 26.2-fold lower than that of the wild-type strain on day 3 and 1.1-fold lower on day 7. The same sprays applied to both larvae and leaves for their feeding reduced the LC 50 of the transformant 17.2-and 1.3-fold on days 3 and 7, respectively. Median lethal times (LT 50 s) of BbV28 were shortened by 23 to 35%, declining with conidial concentrations. The larvae infected by ingestion of BbV28 conidia showed typical symptoms of Vip3A action, i.e., shrinkage and palsy. However, neither LC 50 nor LT 50 trends differed between BbV28 and its parental strain if the infection occurred through the cuticle only. Our findings indicate that fungal conidia can be used as vectors for spreading the highly insecticidal Vip3A protein for control of foliage feeders such as S. litura.

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“…For example, LD 50 of Metarhizium spp. in Locusta migratoria migratorioides is from 60 to 300 conidia per grasshopper (Nowierski et al, 1996). Therefore, the use of fungi to control the lesser mealworm in poultry houses in Brazil will require further field studies to determine the cost-benefit ratio of each strategy and the virulence of the fungus (or conversely, susceptibility of the host).…”

Section: Discussionmentioning

confidence: 99%

Selection for entomopathogenic fungi and LD50 of Metarhizium anisopliae (Metsch.) Sorok. for the Lesser Mealworm Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae)

Chernaki-Leffer¹,

Sosa-Gòmez

Almeida³

2007

Rev. Bras. Cienc. Avic.

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The pathogenicity of insect-pathogenic hyphomycetous isolates to the lesser mealworm Alphitobius diaperinus (Panzer) was tested in this study. Thirty isolates of Beauveria bassiana (Balsamo) Vuillemin, Paecilomyces amoenoroseus (Hennings), P. fumosoroseus (Wize) Brown & Smith, P. lilacinus (Thom) Samson, P. tenuipes (Petch) Samson, Metarhizium anisopliae (Metschnikoff) Sorokin, and M. anisopliae var. acridum were initially screened by sprinkling dry conidia onto adult A. diaperinus or by allowing adults to walk on Petri dishes with sporulating fungal isolates. The two most virulent isolates, CNPSo-Ma352 (M. anisopliae) and CNPSo-Ma356 (M. anisopliae), killed 30% and 26.7% of the dry-conidia treated adults, respectively. These two isolates were selected for LD 50 bioassays. LD 50 of CNPSo-Ma352 was 4.5 x 10 4 conidia per larva, and 2.1 x 10 5 conidia per adult, and for strain CNPSo-Ma356, LD 50 was 2.2 x 10 4 conidia per larva and 1.3 x 10 5 conidia per adult. Larvae were 5-6 times more susceptible than adults. A larger number of conidia required to cause 50% mortality in insect evaluates, suggesting the reduced susceptibility of A. diaperinus to entomopathogenic fungi. Nevertheless, these and other strains of fungus offer an alternative method for controlling of lesser mealworm in poultry houses when associated to integrated management.

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Analysis and Modeling of Time–Dose–Mortality ofMelanoplus sanguinipes, Locusta migratoria migratorioides,andSchistocerca gregaria(Orthoptera: Acrididae) fromBeauveria, Metarhizium,andPaecilomycesIsolates from Madagascar

Cited by 68 publications

References 0 publications

Developmental and Transcriptional Responses to Host and Nonhost Cuticles by the Specific Locust Pathogen Metarhizium anisopliae var. acridum

Developmental and Transcriptional Responses to Host and Nonhost Cuticles by the Specific Locust Pathogen Metarhizium anisopliae var. acridum

Integration of Insecticidal Protein Vip3Aa1 into Beauveria bassiana Enhances Fungal Virulence to Spodoptera litura Larvae by Cuticle and Per Os Infection

Selection for entomopathogenic fungi and LD50 of Metarhizium anisopliae (Metsch.) Sorok. for the Lesser Mealworm Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae)

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