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Tepa-Yotto GT, Douro-Kpindou OK, Koussihouédé PSB, Adjaoké AM, Winsou JK, Tognigban G, Tamò M. Control Potential of Multiple Nucleopolyhedrovirus (SfMNPV) Isolated from Fall Armyworm in Nigeria (West Africa). INSECTS 2024; 15:225. [PMID: 38667355 PMCID: PMC11049893 DOI: 10.3390/insects15040225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 03/14/2024] [Accepted: 03/19/2024] [Indexed: 04/28/2024]
Abstract
The fall armyworm (FAW) Spodoptera frugiperda (Lepidoptera, Noctuidae) has now become an invasive pest of global concern. The pest was first detected in Central and Western Africa in early 2016. Sustainable management options explored by stakeholders during early FAW invasion in Africa included the use of biopesticides and biological control. The current study aimed to compare the susceptibility of FAW larvae to SfMNPV with the assumption that the virus isolated from FAW populations in Africa has higher virulence compared with an isolate from Argentina (SfMNPV-ARG). We also hypothesized that host plant plays a role in SfMNPV efficacy and that cannibalism mediates horizontal and vertical transmission of the virus. This work provides pioneering data on the virulence of the new SfMNPV isolate from Nigeria (SfMNPV-KA1), which proved more effective than its exotic counterpart from Argentina (SfMNPV-ARG). The host plant effect made a significant difference between maize and onion with more FAW death in the larvae fed with contaminated onion 5 days post treatment. The study demonstrates and discusses the effect of cannibalism on virus transmission.
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Affiliation(s)
- Ghislain T. Tepa-Yotto
- Biorisk Management Facility (BIMAF), International Institute of Tropical Agriculture (IITA-Benin), Cotonou 08-01000, Benin; (O.K.D.-K.); (P.S.B.K.); (J.K.W.); (M.T.)
- Ecole de Gestion et de Production Végétale et Semencière (EGPVS), Université Nationale d’Agriculture (UNA), Kétou 43, Benin
| | - Ouorou Kobi Douro-Kpindou
- Biorisk Management Facility (BIMAF), International Institute of Tropical Agriculture (IITA-Benin), Cotonou 08-01000, Benin; (O.K.D.-K.); (P.S.B.K.); (J.K.W.); (M.T.)
| | - Précieux Sèna Bonaventure Koussihouédé
- Biorisk Management Facility (BIMAF), International Institute of Tropical Agriculture (IITA-Benin), Cotonou 08-01000, Benin; (O.K.D.-K.); (P.S.B.K.); (J.K.W.); (M.T.)
| | - Abissi Marc Adjaoké
- Ecole Doctorale des Sciences Agronomiques et de l’Eau (EDSAE), Université Nationale d’Agriculture (UNA), Kétou 43, Benin; (A.M.A.); (G.T.)
| | - Jeannette K. Winsou
- Biorisk Management Facility (BIMAF), International Institute of Tropical Agriculture (IITA-Benin), Cotonou 08-01000, Benin; (O.K.D.-K.); (P.S.B.K.); (J.K.W.); (M.T.)
| | - Ghislain Tognigban
- Ecole Doctorale des Sciences Agronomiques et de l’Eau (EDSAE), Université Nationale d’Agriculture (UNA), Kétou 43, Benin; (A.M.A.); (G.T.)
| | - Manuele Tamò
- Biorisk Management Facility (BIMAF), International Institute of Tropical Agriculture (IITA-Benin), Cotonou 08-01000, Benin; (O.K.D.-K.); (P.S.B.K.); (J.K.W.); (M.T.)
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2
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Erdos Z, Studholme DJ, Sharma MD, Chandler D, Bass C, Raymond B. Manipulating multi-level selection in a fungal entomopathogen reveals social conflicts and a method for improving biocontrol traits. PLoS Pathog 2024; 20:e1011775. [PMID: 38527086 PMCID: PMC10994555 DOI: 10.1371/journal.ppat.1011775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 04/04/2024] [Accepted: 03/09/2024] [Indexed: 03/27/2024] Open
Abstract
Changes in parasite virulence are commonly expected to lead to trade-offs in other life history traits that can affect fitness. Understanding these trade-offs is particularly important if we want to manipulate the virulence of microbial biological control agents. Theoretically, selection across different spatial scales, i.e. between- and within-hosts, shapes these trade-offs. However, trade-offs are also dependent on parasite biology. Despite their applied importance the evolution of virulence in fungal parasites is poorly understood: virulence can be unstable in culture and commonly fails to increase in simple passage experiments. We hypothesized that manipulating selection intensity at different scales would reveal virulence trade-offs in a fungal pathogen of aphids, Akanthomyces muscarius. Starting with a genetically diverse stock we selected for speed of kill, parasite yield or infectivity by manipulating competition within and between hosts and between-populations of hosts over 7 rounds of infection. We characterized ancestral and evolved lineages by whole genome sequencing and by measuring virulence, growth rate, sporulation and fitness. While several lineages showed increases in virulence, we saw none of the trade-offs commonly found in obligately-killing parasites. Phenotypically similar lineages within treatments often shared multiple single-nucleotide variants, indicating strong convergent evolution. The most dramatic phenotypic changes were in timing of sporulation and spore production in vitro. We found that early sporulation led to reduced competitive fitness but could increase yield of spores on media, a trade-off characteristic of social conflict. Notably, the selection regime with strongest between-population competition and lowest genetic diversity produced the most consistent shift to early sporulation, as predicted by social evolution theory. Multi-level selection therefore revealed social interactions novel to fungi and showed that these biocontrol agents have the genomic flexibility to improve multiple traits-virulence and spore production-that are often in conflict in other parasites.
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Affiliation(s)
- Zoltan Erdos
- Centre for Ecology and Conservation, University of Exeter, Penryn, United Kingdom
| | | | - Manmohan D. Sharma
- Centre for Ecology and Conservation, University of Exeter, Penryn, United Kingdom
| | - David Chandler
- School of Life Sciences, The University of Warwick, Coventry, United Kingdom
| | - Chris Bass
- Centre for Ecology and Conservation, University of Exeter, Penryn, United Kingdom
| | - Ben Raymond
- Centre for Ecology and Conservation, University of Exeter, Penryn, United Kingdom
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MacDonald P, Myers JH, Cory JS. Warmer temperatures reduce the transmission of a virus in a gregarious forest insect. Ecology 2023; 104:e4159. [PMID: 37632353 DOI: 10.1002/ecy.4159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 06/22/2023] [Accepted: 07/17/2023] [Indexed: 08/28/2023]
Abstract
Understanding how climate warming will influence species interactions is a key question in ecology and predicting changes in the prevalence of disease outbreaks is particularly challenging. Ectotherms are likely to be more influenced by climatic changes as temperature governs their growth, feeding, development, and behavior. We test the hypothesis that pathogen transmission and host mortality will increase at warmer temperatures using a cyclic forest insect, the western tent caterpillar (WTC), Malacosoma californicum pluviale, and its baculovirus. The virus causes population declines at peak host density. WTC are gregarious and clustering is predicted to increase the risk of within family infection; however, how temperature influences this has not been examined. We investigated the impact of temperature on different components of the transmission process in order to pinpoint the possible mechanisms involved. In the laboratory, leaf consumption increased linearly with rising temperature between 15 and 30°C. Insects died more rapidly from virus infection as temperature increased, but this did not translate into differences in the production of viral transmission stages. To examine the influence of temperature on virus transmission, we created a temperature difference between two greenhouses containing potted red alder trees, Alnus rubra. The cooler greenhouse (mean 19.5°C) was roughly similar to ambient temperatures in the field, while the warmer greenhouse was 10°C higher (mean 29°C). As predicted, both larval movement and feeding were higher at the warmer temperature, while the likelihood of the preinfected, inoculum larvae dying on the tents was twice as high in the cooler greenhouse. This resulted in increased virus mortality and a higher transmission parameter under cooler conditions. Therefore, we suggest that, contrary to our prediction, the reduced movement of infected larvae at colder temperatures increased the risk of infection in these gregarious insects and had a greater impact on virus transmission than the increased activity of the susceptible larvae in warmer conditions. Long-term population data from the field, however, show no relationship between temperature and infection levels, suggesting that local changes in virus transmission might not scale up to population infection levels.
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Affiliation(s)
- Paul MacDonald
- Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Judith H Myers
- Biodiversity Centre, University of British Columbia, Vancouver, British Columbia, Canada
| | - Jenny S Cory
- Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada
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4
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Relationships between the fecundity of bark beetles and the presence of antagonists. Sci Rep 2022; 12:7573. [PMID: 35534596 PMCID: PMC9085876 DOI: 10.1038/s41598-022-11630-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Accepted: 04/27/2022] [Indexed: 11/20/2022] Open
Abstract
Although previous research has documented the occurrence of antagonists of bark beetles, the studies have only evaluated individual antagonists and have not assessed the overall effect of all antagonists on adult beetles. In this study, we determined which body-cavity antagonists were associated with a reduction in the fecundity and maternal gallery lengths of two important species of bark beetles: Ips typographus on Norway spruce and I. cembrae on European larch. We evaluated these relationships under natural conditions by collecting maternal females in galleries and examining their internal organs. The antagonists in the I. typographus hemolymph had significant negative associations with fecundity and gallery length. These antagonists were mainly nematodes and parasitoids in the hemocoel. In contrast, a positive association between gregarine presence and I. typographus fecundity was found. No antagonist that was likely to significantly alter I. cembrae fecundity or maternal gallery length was proven. Our study provides the first comprehensive assessment of antagonists that may have the potential impact on reduction the fecundity and thereby mass occurrence of these bark beetles.
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Deschodt PS, Cory JS. Resource limitation has a limited impact on the outcome of virus-fungus co-infection in an insect host. Ecol Evol 2022; 12:e8707. [PMID: 35342581 PMCID: PMC8928876 DOI: 10.1002/ece3.8707] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 02/11/2022] [Accepted: 02/14/2022] [Indexed: 11/10/2022] Open
Abstract
Infection by pathogens is strongly affected by the diet or condition of the prospective host. Studies that examine the impact of diet have mainly focused on single pathogens; however, co-infections within a single host are thought to be common. Different pathogen groups might respond differently to resource availability and diverse infections could increase the costs of host defense, meaning the outcome of mixed infections under varying dietary regimes is likely to be hard to predict. We used the generalist cabbage looper, Trichoplusia ni and two of its pathogens, the DNA virus T. ni nucleopolyhedrovirus (TniSNPV) and the entomopathogenic fungus, Beauveria bassiana to examine how nutrient reduction affected the outcome of mixed pathogen infection. We challenged insects with a low or high effective dose of virus, alone or combined with a single dose of fungus. We manipulated food availability after pathogen challenge by diluting artificial diet with cellulose, a non-nutritious bulking agent, and examined its impact on host and pathogen fitness. Reducing diet quantity did not alter overall or pathogen-specific mortality. In all cases, TniSNPV-induced mortality was negatively affected by fungus challenge. Similarly, B. bassiana-induced mortality was negatively affected by TniSNPV challenge, but only at the higher virus dose. Dietary dilution mainly affected B. bassiana speed of kill when mixed with a high dose of TniSNPV, with an increase in the duration of fungal infection when cellulose was low (high quantity). One pathogen dominated the production of transmission stages in the cadavers and co-infection did not affect the yield of either pathogen. There was no evidence that co-infections were more costly to the survivors of pathogen challenge. In conclusion, dietary dilution did not determine the outcome of mixed pathogen infection, but it had more subtle effects, that differed between the two pathogens and could potentially alter pathogen recycling and host-pathogen dynamics.
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Affiliation(s)
- Pauline S Deschodt
- Department of Biological Sciences Simon Fraser University Burnaby British Columbia Canada
| | - Jenny S Cory
- Department of Biological Sciences Simon Fraser University Burnaby British Columbia Canada
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6
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Rovenolt FH, Tate AT. The Impact of Coinfection Dynamics on Host Competition and Coexistence. Am Nat 2022; 199:91-107. [DOI: 10.1086/717180] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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7
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Raymond B, Erdos Z. Passage and the evolution of virulence in invertebrate pathogens: Fundamental and applied perspectives. J Invertebr Pathol 2021; 187:107692. [PMID: 34798134 DOI: 10.1016/j.jip.2021.107692] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 11/11/2021] [Accepted: 11/12/2021] [Indexed: 01/05/2023]
Abstract
Understanding the ecological and genetic factors that determine the evolution of virulence has broad value for invertebrate pathology. In addition to helping us understand the fundamental biology of our study organisms this body of theory has important applications in microbial biocontrol. Experimental tests of virulence theory are often carried out in invertebrate models and yet theory rarely informs applied passage experiments that aim to increase or maintain virulence. This review summarizes recent progress in this field with a focus on work most relevant to biological control: the virulence of invertebrate pathogens that are 'obligate killers' and which require cadavers for the production of infectious propagules. We discuss recent theory and fundamental and applied experimental evolution with bacteria, fungi, baculoviruses and nematodes. While passage experiments using baculoviruses have a long history of producing isolates with increased virulence, studies with other pathogens have not been so successful. Recent passage experiments that have applied evolution of virulence frameworks based on cooperation (kin selection) have produced novel methods and promising mutants with increased killing power. Evolution of virulence theory can provide plausible explanations for the varied results of passage experiments as well as a predictive framework for improving artificial selection.
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Affiliation(s)
- Ben Raymond
- Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn, TR10 9FE, UK.
| | - Zoltan Erdos
- Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn, TR10 9FE, UK
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REPEAT SPILLOVER OF BEAK AND FEATHER DISEASE VIRUS INTO AN ENDANGERED PARROT HIGHLIGHTS THE RISK ASSOCIATED WITH ENDEMIC PATHOGEN LOSS IN ENDANGERED SPECIES. J Wildl Dis 2021; 56:896-906. [PMID: 33600597 DOI: 10.7589/2018-06-154] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Accepted: 02/19/2020] [Indexed: 11/20/2022]
Abstract
Conservation efforts for the orange-bellied parrot (Neophema chrysogaster), one of the world's most critically endangered bird species, have been hampered by beak and feather disease virus (BFDV) spillover infection. To understand the vulnerability of orange-bellied parrots to potential reservoirs of infection we investigated geographic versus taxonomic structure in 160 full-genome and 319 partial Rep gene BFDV sequences from captive and wild orange-bellied parrots and other wild parrot species in Australia. We found that Australian BFDV populations are structured by host taxonomy. By identifying genetic stratification of BFDV in reservoir hosts we characterized three separate recent incursions of BFDV into orange-bellied parrots from other wild parrots, which demonstrates the susceptibility of critically endangered species to multiple threats of pathogen re-emergence. Our study highlighted how loss of endemic circulating BFDV in orange-bellied parrots precipitated repeated spillover into an immunologically naïve population, causing significant disease.
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Das S, Smith K, Sarker S, Peters A, Adriaanse K, Eden P, Ghorashi SA, Forwood JK, Raidal SR. Assessing circovirus gene flow in multiple spill-over events. Virus Genes 2019; 55:802-814. [PMID: 31463770 DOI: 10.1007/s11262-019-01702-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2019] [Accepted: 08/19/2019] [Indexed: 11/29/2022]
Abstract
The establishment of viral pathogens in new host environments following spillover events probably requires adaptive changes within both the new host and pathogen. After many generations, signals for ancient cross-species transmission may become lost and a strictly host-adapted phylogeny may mimic true co-divergence while the virus may retain an inherent ability to jump host species. The mechanistic basis for such processes remains poorly understood. To study the dynamics of virus-host co-divergence and the arbitrary chances of spillover in various reservoir hosts with equal ecological opportunity, we examined structural constraints of capsid protein in extant populations of Beak and feather disease virus (BFDV) during known spillover events. By assessing reservoir-based genotype stratification, we identified co-divergence defying signatures in the evolution BFDV which highlighted primordial processes of cryptic host adaptation and competing forces of host co-divergence and cross-species transmission. We demonstrate that, despite extensive surface plasticity gathered over a longer span of evolution, structural constraints of the capsid protein allow opportunistic host switching in host-adapted populations. This study provides new insights into how small populations of endangered psittacine species may face multidirectional forces of infection from reservoirs with apparently co-diverging genotypes.
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Affiliation(s)
- Shubhagata Das
- School of Animal and Veterinary Sciences, Charles Sturt University, Boorooma Street, Wagga Wagga, NSW, 2650, Australia
| | - Kate Smith
- School of Biomedical Sciences, Charles Sturt University, Boorooma Street, Wagga Wagga, NSW, 2650, Australia
| | - Subir Sarker
- Department of Physiology, Anatomy and Microbiology, School of Life Sciences, La Trobe University, Melbourne, 3086, Australia
| | - Andrew Peters
- School of Animal and Veterinary Sciences, Charles Sturt University, Boorooma Street, Wagga Wagga, NSW, 2650, Australia
| | - Katherine Adriaanse
- Healesville Sanctuary, Zoos Victoria, Badger Creek Road, Healesville, VIC, 3777, Australia
| | - Paul Eden
- Healesville Sanctuary, Zoos Victoria, Badger Creek Road, Healesville, VIC, 3777, Australia
| | - Seyed A Ghorashi
- School of Animal and Veterinary Sciences, Charles Sturt University, Boorooma Street, Wagga Wagga, NSW, 2650, Australia
| | - Jade K Forwood
- School of Biomedical Sciences, Charles Sturt University, Boorooma Street, Wagga Wagga, NSW, 2650, Australia
| | - Shane R Raidal
- School of Animal and Veterinary Sciences, Charles Sturt University, Boorooma Street, Wagga Wagga, NSW, 2650, Australia.
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Rosenheim JA, Booster NA, Culshaw-Maurer M, Mueller TG, Kuffel RL, Law YH, Goodell PB, Pierce T, Godfrey LD, Hunter WB, Sadeh A. Disease, contagious cannibalism, and associated population crash in an omnivorous bug, Geocoris pallens. Oecologia 2019; 190:69-83. [PMID: 31049659 DOI: 10.1007/s00442-019-04407-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Accepted: 04/24/2019] [Indexed: 11/29/2022]
Abstract
Disease and cannibalism are two strongly density-dependent processes that can suppress predator populations. Here we show that California populations of the omnivorous predatory bug Geocoris pallens are subject to infection by a pathogen, as yet unidentified, that elicits elevated expression of cannibalism. Laboratory experiments showed that the pathogen is moderately virulent, causing flattened abdomens, elevated nymphal mortality, delayed development, and reduced body size of adult females. Infection furthermore increases the expression of cannibalism. Field populations of Geocoris spp. declined strongly in association with sharp increases in the expression of egg cannibalism by adult G. pallens. Increased cannibalism was accompanied by a strongly bimodal distribution of cannibalism expression, with some females (putatively uninfected) expressing little cannibalism and others (putatively infected) consuming most or all of the eggs present. Highly cannibalistic females did not increase their consumption of Ephestia cautella moth eggs, suggesting that the high cannibalism phenotype reflected a specific loss of restraint against eating conspecifics. Highly cannibalistic females also often exhibited reduced egg laying, consistent with a virulent pathogen; less frequently, more cannibalistic females exhibited elevated egg laying, suggesting that cannibalism might also facilitate recycling of nutrients in eggs. Elevated cannibalism was not correlated with reduced prey availability or elevated field densities of G. pallens. Geocoris pallens population crashes appear to reflect the combined consequences of direct virulence-adverse pathogen effects on the infected host's physiology-and indirect virulence-mortality of both infected and uninfected individuals due to elevated cannibalism expression by infected individuals.
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Affiliation(s)
- Jay A Rosenheim
- Department of Entomology and Nematology, University of California, Davis, Davis, CA, 95616, USA.
| | - Nicholas A Booster
- Department of Entomology and Nematology, University of California, Davis, Davis, CA, 95616, USA
| | - Michael Culshaw-Maurer
- Department of Entomology and Nematology, University of California, Davis, Davis, CA, 95616, USA
| | - Tobias G Mueller
- Department of Entomology and Nematology, University of California, Davis, Davis, CA, 95616, USA
| | - Randall L Kuffel
- Department of Entomology and Nematology, University of California, Davis, Davis, CA, 95616, USA
| | - Yao-Hua Law
- Department of Entomology and Nematology, University of California, Davis, Davis, CA, 95616, USA
| | | | - Treanna Pierce
- Department of Entomology and Nematology, University of California, Davis, Davis, CA, 95616, USA
| | - Larry D Godfrey
- Department of Entomology and Nematology, University of California, Davis, Davis, CA, 95616, USA
| | - Wayne B Hunter
- U.S. Horticultural Research Laboratory, USDA Agricultural Research Service, Fort Pierce, FL, 34945, USA
| | - Asaf Sadeh
- Department of Natural Resources, Institute of Plant Sciences, Agricultural Research Organization (Volcani Center), Rishon LeTsion, 7505101, Israel.
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11
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Escasa SR, Harrison RL, Mowery JD, Bauchan GR, Cory JS. The complete genome sequence of an alphabaculovirus from Spodoptera exempta, an agricultural pest of major economic significance in Africa. PLoS One 2019; 14:e0209937. [PMID: 30735528 PMCID: PMC6368282 DOI: 10.1371/journal.pone.0209937] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 12/13/2018] [Indexed: 12/03/2022] Open
Abstract
Spodoptera exempta nucleopolyhedrovirus (SpexNPV) is a viral pathogen of the African armyworm, Spodoptera exempta (Lepidoptera: Noctuidae), a significant agricultural pest of cereal crops in Africa. SpexNPV has been evaluated as a potential insecticide for control of this pest and has served as the subject of research on baculovirus pathology and transmission. Occlusion bodies (OBs) of SpexNPV isolate 244.1 were examined, and the nucleotide sequence of the genome was determined and characterized. SpexNPV-244.1 OBs consisted of irregular polyhedra with a size and appearance typical for alphabaculoviruses. Virions within the polyhedra contained 1–8 nucleocapsids per unit envelope. The SpexNPV-244.1 genome was comprised of a 129,528 bp circular sequence, in which 139 ORFs were annotated. Five homologous regions (hrs) consisting of a variable number of 28-bp imperfect palindromes were identified in the genome. The genome sequence contained the 38 core genes of family Baculoviridae, as well as three ORFs unique to the SpexNPV sequence and one ORF that was apparently acquired by horizontal gene transfer with a betabaculovirus ancestor. Phylogenetic inference with core gene amino acid sequence alignments placed SpexNPV-244.1 in a lineage containing alphabaculoviruses of Spodoptera frugiperda and Spodopotera exigua which in turn is part of a larger group of alphabaculoviruses from the subfamily Noctuinae in the lepidopteran family Noctuidae. Kimura-2-parameter pairwise nucleotide distances indicated that SpexNPV-244.1 represented a different and previously unlisted species in the genus Alphabaculovirus. Gene parity plots indicated that the gene order of SpexNPV-244.l was extensively collinear with that of Spodoptera exigua NPV (SeMNPV). These plots also revealed a group of 17 core genes whose order was conserved in other alpha- and betabaculoviruses.
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Affiliation(s)
- Shannon R. Escasa
- Laboratory for Molecular Ecology, Great Lakes Forestry Centre and Biology Department, Algoma University, Sault Ste, Marie, Ontario, Canada
| | - Robert L. Harrison
- Invasive Insect Biocontrol and Behavior Laboratory, Beltsville Agricultural Research Center, USDA Agricultural Research Service, Beltsville, Maryland, United States of America
- * E-mail: (RLH); (JSC)
| | - Joseph D. Mowery
- Electron and Confocal Microscopy Unit, Beltsville Agricultural Research Center, USDA Agricultural Research Service, Beltsville, Maryland, United States of America
| | - Gary R. Bauchan
- Electron and Confocal Microscopy Unit, Beltsville Agricultural Research Center, USDA Agricultural Research Service, Beltsville, Maryland, United States of America
| | - Jenny S. Cory
- Department of Biological Sciences, Simon Fraser University, University Boulevard, Burnaby, British Columbia, Canada
- * E-mail: (RLH); (JSC)
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Wilson K, Sheldon BC, Gaillard JM, Sanders NJ, Hoggart SPG, Newton E. And the winner of the inaugural Sidnie Manton Award is…. J Anim Ecol 2018; 87:527-529. [PMID: 29652093 DOI: 10.1111/1365-2656.12825] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Kenneth Wilson
- Lancaster Environment Centre, Lancaster University, Lancaster, UK
| | - Ben C Sheldon
- Department of Zoology, Edward Grey Institute, University of Oxford, Oxford, UK
| | - Jean-Michel Gaillard
- CNRS, UMR 5558 "Biométrie et Biologie Evolutive", Université de Lyon, Villeurbanne, France
| | - Nathan J Sanders
- Rubenstein School of Environment and Natural Resources, University of Vermont, Burlington, VT, USA
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13
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Ben‐Ami F. The virulence-transmission relationship in an obligate killer holds under diverse epidemiological and ecological conditions, but where is the tradeoff? Ecol Evol 2017; 7:11157-11166. [PMID: 29299290 PMCID: PMC5743645 DOI: 10.1002/ece3.3532] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 08/30/2017] [Accepted: 09/13/2017] [Indexed: 01/07/2023] Open
Abstract
Parasite virulence is a leading theme in evolutionary biology. Modeling the course of virulence evolution holds the promise of providing practical insights into the management of infectious diseases and the implementation of vaccination strategies. A key element of virulence modeling is a tradeoff between parasite transmission rate and host lifespan. This assumption is crucial for predicting the level of optimal virulence. Here, I test this assumption using the water flea Daphnia magna and its castrating and obligate-killing bacterium Pasteuria ramosa. I found that the virulence-transmission relationship holds under diverse epidemiological and ecological conditions. In particular, parasite genotype, absolute and relative parasite dose, and within-host competition in multiple infections did not significantly affect the observed trend. Interestingly, the relationship between virulence and parasite transmission in this system is best explained by a model that includes a cubic term. Under this relationship, parasite transmission initially peaks and saturates at an intermediate level of virulence, but then it further increases as virulence decreases, surpassing the previous peak. My findings also highlight the problem of using parasite-induced host mortality as a "one-size-fits-all" measure of virulence for horizontally transmitted parasites, without considering the onset and duration of parasite transmission as well as other equally virulent effects of parasites (e.g., host castration). Therefore, mathematical models may be required to predict whether these particular characteristics of horizontally transmitted parasites can direct virulence evolution into directions not envisaged by existing models.
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Affiliation(s)
- Frida Ben‐Ami
- School of ZoologyGeorge S. Wise Faculty of Life SciencesTel Aviv UniversityTel AvivIsrael
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Shikano I, McCarthy EM, Elderd BD, Hoover K. Plant genotype and induced defenses affect the productivity of an insect-killing obligate viral pathogen. J Invertebr Pathol 2017; 148:34-42. [PMID: 28483639 DOI: 10.1016/j.jip.2017.05.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Revised: 04/22/2017] [Accepted: 05/04/2017] [Indexed: 11/18/2022]
Abstract
Plant-mediated variations in the outcomes of host-pathogen interactions can strongly affect epizootics and the population dynamics of numerous species, including devastating agricultural pests such as the fall armyworm. Most studies of plant-mediated effects on insect pathogens focus on host mortality, but few have measured pathogen yield, which can affect whether or not an epizootic outbreak occurs. Insects challenged with baculoviruses on different plant species and parts can vary in levels of mortality and yield of infectious stages (occlusion bodies; OBs). We previously demonstrated that soybean genotypes and induced anti-herbivore defenses influence baculovirus infectivity. Here, we used a soybean genotype that strongly reduced baculovirus infectivity when virus was ingested on induced plants (Braxton) and another that did not reduce infectivity (Gasoy), to determine how soybean genotype and induced defenses influence OB yield and speed of kill. These are key fitness measures because baculoviruses are obligate-killing pathogens. We challenged fall armyworm, Spodoptera frugiperda, with the baculovirus S. frugiperda multi-nucleocapsid nucleopolyhedrovirus (SfMNPV) during short or long-term exposure to plant treatments (i.e., induced or non-induced genotypes). Caterpillars were either fed plant treatments only during virus ingestion (short-term exposure to foliage) or from the point of virus ingestion until death (long-term exposure). We found trade-offs of increasing OB yield with slower speed of kill and decreasing virus dose. OB yield increased more with longer time to death and decreased more with increasing virus dose after short-term feeding on Braxton compared with Gasoy. OB yield increased significantly more with time to death in larvae that fed until death on non-induced foliage than induced foliage. Moreover, fewer OBs per unit of host tissue were produced when larvae were fed induced foliage than non-induced foliage. These findings highlight the potential importance of plant effects, even at the individual plant level, on entomopathogen fitness, which may impact epizootic transmission events and host population dynamics.
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Affiliation(s)
- Ikkei Shikano
- Department of Entomology and Center for Chemical Ecology, Pennsylvania State University, University Park, PA 16802, USA.
| | | | - Bret D Elderd
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Kelli Hoover
- Department of Entomology and Center for Chemical Ecology, Pennsylvania State University, University Park, PA 16802, USA
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Cory JS. Evolution of host resistance to insect pathogens. CURRENT OPINION IN INSECT SCIENCE 2017; 21:54-59. [PMID: 28822489 DOI: 10.1016/j.cois.2017.04.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2017] [Revised: 04/17/2017] [Accepted: 04/19/2017] [Indexed: 06/07/2023]
Abstract
Insect pathogens are widely used as a tool for sustainable pest management. Their complex mode of action was thought to make them immune to the evolution of resistance; however, several examples of field-based resistance to the bacterium Bacillus thuringiensis and a granulovirus have been recorded. Here I review the scenarios where resistance has evolved and discuss the likelihood of it occurring in other entomopathogens. I highlight recent research on the factors which might influence the evolution of resistance to insect pathogens, including the role of pathogen diversity, host nutrition and transgenerational effects.
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Affiliation(s)
- Jenny S Cory
- Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada.
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Lacanobia oleracea nucleopolyhedrovirus (LaolNPV): A new European species of alphabaculovirus with a narrow host range. PLoS One 2017; 12:e0176171. [PMID: 28426736 PMCID: PMC5398697 DOI: 10.1371/journal.pone.0176171] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 04/06/2017] [Indexed: 11/26/2022] Open
Abstract
During an insect sampling program in alfalfa crops near Montpellier, France in 2011, Lacanobia oleracea larvae were collected that died due to nucleopolyhedrovirus infection (LaolNPV). This virus was subjected to molecular and biological characterization. The virus was a multiple nucleocapsid NPV that showed similar restriction profiles to Mamestra configurata NPV-A (MacoNPV-A) but with significant differences. Polypeptide analysis demonstrated similar proteins in occlusion bodies and occlusion derived virions, to those observed in NPVs from Mamestra spp. Terminal sequencing revealed that the genome organization shared similarity with that of MacoNPV-A. The most homologous virus was MacoNPV-A 90/2 isolate (95.63% identity and 96.47% similarity), followed by MacoNPV-A 90/4 strain (95.37% and 96.26%), MacoNPV-B (89.21% and 93.53%) and M. brassicae MNPV (89.42% and 93.74%). Phylogenetic analysis performed with lef-8, lef-9, polh and a concatenated set of genes showed that LaolNPV and the Mamestra spp. NPVs clustered together with HaMNPV, but with a closer genetic distance to MacoNPV-A strains. The Kimura 2-parameter (K-2-P) distances of the complete genes were greater than 0.05 between LaolNPV and the MbMNPV/MacoNPV-B/HaMNPV complex, which indicates that LaolNPV is a distinct species. K-2-P distances were in the range 0.015–0.050 for comparisons of LaolNPV with MacoNPV-A strains, such that additional biological characteristics should be evaluated to determine species status. While MacoNPV-A was pathogenic to seven lepidopteran species tested, LaolNPV was only pathogenic to Chrysodeixis chalcites. Given these findings, Lacanobia oleracea nucleopolyhedrovirus should be considered as a new species in the Alphabaculovirus genus.
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MetaGaAP: A Novel Pipeline to Estimate Community Composition and Abundance from Non-Model Sequence Data. BIOLOGY 2017; 6:biology6010014. [PMID: 28218638 PMCID: PMC5372007 DOI: 10.3390/biology6010014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 01/06/2017] [Accepted: 02/07/2017] [Indexed: 02/01/2023]
Abstract
Next generation sequencing and bioinformatic approaches are increasingly used to quantify microorganisms within populations by analysis of ‘meta-barcode’ data. This approach relies on comparison of amplicon sequences of ‘barcode’ regions from a population with public-domain databases of reference sequences. However, for many organisms relevant ‘barcode’ regions may not have been identified and large databases of reference sequences may not be available. A workflow and software pipeline, ‘MetaGaAP,’ was developed to identify and quantify genotypes through four steps: shotgun sequencing and identification of polymorphisms in a metapopulation to identify custom ‘barcode’ regions of less than 30 polymorphisms within the span of a single ‘read’, amplification and sequencing of the ‘barcode’, generation of a custom database of polymorphisms, and quantitation of the relative abundance of genotypes. The pipeline and workflow were validated in a ‘wild type’ Alphabaculovirus isolate, Helicoverpa armigera single nucleopolyhedrovirus (HaSNPV-AC53) and a tissue-culture derived strain (HaSNPV-AC53-T2). The approach was validated by comparison of polymorphisms in amplicons and shotgun data, and by comparison of predicted dominant and co-dominant genotypes with Sanger sequences. The computational power required to generate and search the database effectively limits the number of polymorphisms that can be included in a barcode to 30 or less. The approach can be used in quantitative analysis of the ecology and pathology of non-model organisms.
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Redman EM, Wilson K, Cory JS. Trade-offs and mixed infections in an obligate-killing insect pathogen. J Anim Ecol 2016; 85:1200-9. [PMID: 27155461 PMCID: PMC4988505 DOI: 10.1111/1365-2656.12547] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Accepted: 04/24/2016] [Indexed: 02/01/2023]
Abstract
Natural populations of pathogens are frequently composed of numerous interacting strains. Understanding what maintains this diversity remains a key focus of research in disease ecology. In addition, within-host pathogen dynamics can have a strong impact on both infection outcome and the evolution of pathogen virulence, and thus, understanding the impact of pathogen diversity is important for disease management. We compared eight genetically distinguishable variants from Spodoptera exempta nucleopolyhedrovirus (SpexNPV) isolated from the African armyworm, Spodoptera exempta. NPVs are obligate killers, and the vast majority of transmission stages are not released until after the host has died. The NPV variants differed significantly in their virulence and could be clustered into two groups based on their dose-response curves. They also differed in their speed of kill and productivity (transmission potential) for S. exempta. The mixed-genotype wild-type (WT) SpexNPV, from which each variant was isolated, was significantly more virulent than any individual variant and its mean mortality rate was within the fastest group of individual variants. However, the WT virus produced fewer new infectious stages than any single variant, which might reflect competition among the variants. A survival analysis, combining the mortality and speed of kill data, confirmed the superiority of the genetically mixed WT virus over any single variant. Spodoptera exempta larvae infected with WT SpexNPV were predicted to die 2·7 and 1·9 times faster than insects infected with isolates from either of the two clusters of genotypes. Theory suggests that there are likely to be trade-offs between pathogen fitness traits. Across all larvae, there was a negative linear relationship between virus yield and speed of kill, such that more rapid host death carried the cost of producing fewer transmission stages. We also found a near-significant relationship for the same trend at the intervariant level. However, there was no evidence for a significant relationship between the induced level of mortality and transmission potential (virus yield) or speed of kill.
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Affiliation(s)
- Elizabeth M Redman
- Molecular Ecology and Biocontrol Group, NERC Centre for Ecology and Hydrology, Mansfield Road, Oxford, OX1 3SR, UK
| | - Kenneth Wilson
- Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, UK
| | - Jenny S Cory
- Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, V5A 1S6, BC, Canada
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