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Urzo MLR, Guinto TD, Eusebio-Cope A, Budot BO, Yanoria MJT, Jonson GB, Arakawa M, Kondo H, Suzuki N. Metatranscriptomic Sequencing of Sheath Blight-Associated Isolates of Rhizoctonia solani Revealed Multi-Infection by Diverse Groups of RNA Viruses. Viruses 2024; 16:1152. [PMID: 39066314 PMCID: PMC11281561 DOI: 10.3390/v16071152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2024] [Revised: 07/10/2024] [Accepted: 07/11/2024] [Indexed: 07/28/2024] Open
Abstract
Rice sheath blight, caused by the soil-borne fungus Rhizoctonia solani (teleomorph: Thanatephorus cucumeris, Basidiomycota), is one of the most devastating phytopathogenic fungal diseases and causes yield loss. Here, we report on a very high prevalence (100%) of potential virus-associated double-stranded RNA (dsRNA) elements for a collection of 39 fungal strains of R. solani from the rice sheath blight samples from at least four major rice-growing areas in the Philippines and a reference isolate from the International Rice Research Institute, showing different colony phenotypes. Their dsRNA profiles suggested the presence of multiple viral infections among these Philippine R. solani populations. Using next-generation sequencing, the viral sequences of the three representative R. solani strains (Ilo-Rs-6, Tar-Rs-3, and Tar-Rs-5) from different rice-growing areas revealed the presence of at least 36 viruses or virus-like agents, with the Tar-Rs-3 strain harboring the largest number of viruses (at least 20 in total). These mycoviruses or their candidates are believed to have single-stranded RNA or dsRNA genomes and they belong to or are associated with the orders Martellivirales, Hepelivirales, Durnavirales, Cryppavirales, Ourlivirales, and Ghabrivirales based on their coding-complete RNA-dependent RNA polymerase sequences. The complete genome sequences of two novel RNA viruses belonging to the proposed family Phlegiviridae and family Mitoviridae were determined.
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Affiliation(s)
- Michael Louie R. Urzo
- Microbiology Division, Institute of Biological Sciences, College of Arts and Sciences, University of the Philippines Los Baños, Los Baños 4031, Laguna, Philippines; (M.L.R.U.); (T.D.G.)
| | - Timothy D. Guinto
- Microbiology Division, Institute of Biological Sciences, College of Arts and Sciences, University of the Philippines Los Baños, Los Baños 4031, Laguna, Philippines; (M.L.R.U.); (T.D.G.)
| | - Ana Eusebio-Cope
- Fit-for-Future Genetic Resources Unit, Rice Breeding Innovations Department, International Rice Research Institute (IRRI), University of the Philippines Los Baños, Los Baños 4031, Laguna, Philippines
| | - Bernard O. Budot
- Institute of Weed Science, Entomology, and Plant Pathology, College of Agriculture and Food Science, University of the Philippines Los Baños, Los Baños 4031, Laguna, Philippines;
| | - Mary Jeanie T. Yanoria
- Traits for Challenged Environments Unit, Rice Breeding Innovations Department, International Rice Research Institute (IRRI), University of the Philippines Los Baños, Los Baños 4031, Laguna, Philippines; (M.J.T.Y.); (G.B.J.)
| | - Gilda B. Jonson
- Traits for Challenged Environments Unit, Rice Breeding Innovations Department, International Rice Research Institute (IRRI), University of the Philippines Los Baños, Los Baños 4031, Laguna, Philippines; (M.J.T.Y.); (G.B.J.)
| | - Masao Arakawa
- Faculty of Agriculture, Meijo University, Nagoya 468-8502, Japan;
| | - Hideki Kondo
- Plant-Microbe Interactions Group, Institute of Plant Science and Resources (IPSR), Okayama University, Chuo 2-20-1, Kurashiki 710-0046, Japan
| | - Nobuhiro Suzuki
- Plant-Microbe Interactions Group, Institute of Plant Science and Resources (IPSR), Okayama University, Chuo 2-20-1, Kurashiki 710-0046, Japan
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Northrup GR, White A, Parratt SR, Rozins C, Laine AL, Boots M. The evolutionary dynamics of hyperparasites. J Theor Biol 2024; 582:111741. [PMID: 38280543 DOI: 10.1016/j.jtbi.2024.111741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 12/14/2023] [Accepted: 01/16/2024] [Indexed: 01/29/2024]
Abstract
Evolutionary theory has typically focused on pairwise interactions, such as those between hosts and parasites, with relatively little work having been carried out on more complex interactions including hyperparasites: parasites of parasites. Hyperparasites are common in nature, with the chestnut blight fungus virus CHV-1 a well-known natural example, but also notably include the phages of important human bacterial diseases. We build a general modeling framework for the evolution of hyperparasites that highlights the central role that the ability of a hyperparasite to be transmitted with its parasite plays in their evolution. A key result is that hyperparasites which transmit with their parasite hosts (hitchhike) will be selected for lower virulence, trending towards hypermutualism or hypercommensalism. We examine the impact on the evolution of hyperparasite systems of a wide range of host and parasite traits showing, for example, that high parasite virulence selects for higher hyperparasite virulence resulting in reductions in parasite virulence when hyperparasitized. Furthermore, we show that acute parasite infection will also select for increased hyperparasite virulence. Our results have implications for hyperparasite research, both as biocontrol agents and for their role in shaping community ecology and evolution and moreover emphasize the importance of understanding evolution in the context of multitrophic interactions.
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Affiliation(s)
- Graham R Northrup
- Center for Computational Biology, College of Engineering, University of California, Berkeley, CA, USA.
| | - Andy White
- Maxwell Institute for Mathematical Sciences, Heriot-Watt University, Edinburgh, UK; Department of Mathematics, Heriot-Watt University, Edinburgh, UK
| | - Steven R Parratt
- Department of Ecology, Evolution and Behaviour, University of Liverpool, Liverpool, UK
| | - Carly Rozins
- Department of Science and Technology Studies, Division of Natural Science, York University, Toronto, Ontario, Canada
| | - Anna-Liisa Laine
- Research Centre for Ecological Change, Organismal and Evolutionary Biology Research Programme, University of Helsinki, Finland; Department of Evolutionary Biology and Environmental Studies, University of Zurich, Switzerland
| | - Mike Boots
- Department of Integrative Biology, University of California Berkeley, CA, USA; Center for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn Campus, UK
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3
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Ahmad F, Tomada S, Poonsiri T, Baric S. Molecular genetic variability of Cryphonectria hypovirus 1 associated with Cryphonectria parasitica in South Tyrol (northern Italy). Front Microbiol 2024; 15:1291542. [PMID: 38476955 PMCID: PMC10927965 DOI: 10.3389/fmicb.2024.1291542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2023] [Accepted: 01/25/2024] [Indexed: 03/14/2024] Open
Abstract
Cryphonectria hypovirus 1 (CHV-1) has been widely studied and used as a biocontrol agent because of its ability to infect the chestnut blight fungus, Cryphonectria parasitica, and to reduce its virulence. Knowledge about the hypovirus, its presence, and diversity is completely lacking in South Tyrol (northern Italy), which may obstruct biocontrol measures for chestnut blight based on CHV-1. This work aimed to study the occurrence of CHV-1 infecting C. parasitica in South Tyrol and to perform a genetic characterization of the hypovirus. In South Tyrol, CHV-1 was found to occur in 29.2% of the fungal isolates investigated, varying in frequency between different regions and chestnut stands. Twenty-three haplotypes based on partial cDNA (complementary DNA) sequences of open reading frame (ORF)-A and 30 haplotypes based on partial cDNA sequences of ORF-B were identified among 47 and 56 hypovirulent fungal isolates, respectively. Phylogenetic analysis showed that all the haplotypes belonged to the Italian subtype of CHV-1 and that they were closely related to the populations of Italy, Switzerland, Croatia and Slovenia. Evidence of recombination was not found in the sequences and point mutations were the main source of diversity. Overall, this study indicated that the prevalence of CHV-1 in South Tyrol is low compared to many other central and western European populations and determined a need to actively impose biocontrol measures. Using sequence analysis, we identified some variants of interest of CHV-1 that should be studied in detail for their potential use in biocontrol.
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Affiliation(s)
- Farooq Ahmad
- Laboratory for Phytopathology, Faculty of Agricultural, Environmental and Food Sciences, Free University of Bozen-Bolzano, Bolzano, Italy
| | - Selena Tomada
- Laboratory for Phytopathology, Faculty of Agricultural, Environmental and Food Sciences, Free University of Bozen-Bolzano, Bolzano, Italy
| | - Thanalai Poonsiri
- Department of Pathobiology, Faculty of Science, Mahidol University, Bangkok, Thailand
| | - Sanja Baric
- Laboratory for Phytopathology, Faculty of Agricultural, Environmental and Food Sciences, Free University of Bozen-Bolzano, Bolzano, Italy
- Competence Centre for Plant Health, Free University of Bozen-Bolzano, Bolzano, Italy
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Romon-Ochoa P, Smith O, Lewis A, Kupper Q, Shamsi W, Rigling D, Pérez-Sierra A, Ward L. Temperature Effects on the Cryphonectria hypovirus 1 Accumulation and Recovery within Its Fungal Host, the Chestnut Blight Pathogen Cryphonectria parasitica. Viruses 2023; 15:1260. [PMID: 37376560 DOI: 10.3390/v15061260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 05/24/2023] [Accepted: 05/25/2023] [Indexed: 06/29/2023] Open
Abstract
Biological control of Cryphonectria parasitica fungus, the causal agent of chestnut blight, by virus infection (hypovirulence) is an effective control strategy against chestnut blight in Europe and some parts of North America. The most studied mycovirus is the Cryphonectria hypovirus 1 (CHV1) type species of the Hypoviridae family. In this study, the CHV1 virus was studied within some highly infected British isolates of Cryphonectria parasitica, gained in the past through co-culture transmissions. The effects of six temperatures (5-30 °C, in 5 °C steps) on six infected isolates (three with viral strain E-5, and other three with viral strain L-18) and their respective negative non-infected controls, three isogenic virulent fungal isolates, were examined. Experiments were performed with the nine isolate types with three replicates on potato dextrose agar (PDA) with cellophane sheets per isolate and temperature. A recently developed rapid, specific, quantitative reverse transcription PCR (RT-qPCR) screening method was used. This enabled quantifying the concentration (nanograms per microliter or copy numbers) of the virus within each isolate repetition. The presence of the virus had a significant negative effect between 20 and 25 °C on the C. parasitica growth rate, which was anyway highly influenced by and positively correlated with the temperature. The temperature clearly determined the virus accumulation and its recovery from cold or heat, and the virus optimum temperature was estimated at 15-25 °C.
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Affiliation(s)
- Pedro Romon-Ochoa
- Forest Research, Plant Pathology Department, Alice Holt Research Station, Surrey GU104LH, UK
| | - Olivia Smith
- Forest Research, Plant Pathology Department, Alice Holt Research Station, Surrey GU104LH, UK
| | - Alex Lewis
- Forest Research, Tree Health Diagnostics and Advisory Service (THDAS), Alice Holt, Surrey GU104LH, UK
| | - Quirin Kupper
- Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zuercherstrasse 111, 8903 Birmensdorf, Switzerland
| | - Wajeeha Shamsi
- Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zuercherstrasse 111, 8903 Birmensdorf, Switzerland
| | - Daniel Rigling
- Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zuercherstrasse 111, 8903 Birmensdorf, Switzerland
| | - Ana Pérez-Sierra
- Forest Research, Tree Health Diagnostics and Advisory Service (THDAS), Alice Holt, Surrey GU104LH, UK
| | - Lisa Ward
- Forest Research, Plant Pathology Department, Alice Holt Research Station, Surrey GU104LH, UK
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Canker Development and Biocontrol Potential of CHV-1 Infected English Isolates of Cryphonectria parasitica Is Dependent on the Virus Concentration and the Compatibility of the Fungal Inoculums. Viruses 2022; 14:v14122678. [PMID: 36560682 PMCID: PMC9785502 DOI: 10.3390/v14122678] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 11/23/2022] [Accepted: 11/26/2022] [Indexed: 12/05/2022] Open
Abstract
Biological control of Cryphonectria parasitica fungus, causal agent of chestnut blight, by virus infection (hypovirulence) has been shown to be an effective control strategy against chestnut blight in Europe and some parts of North America. The most studied mycovirus is the Cryphonectria hypovirus 1 (CHV-1) type species of the Hypoviridae family. To efficiently provide biocontrol, the virus must be able to induce hypovirulence in its fungal host in chestnut trees. Here, two different CHV-1 subtype I virus strains (E-5 and L-18), gained by transmissions, were tested for their hypovirulence induction, biocontrol potential, and transmission between vegetatively compatible (VCG) and incompatible fungal isolate groups in sweet chestnut seedlings and branches. Both strains of CHV-1 showed great biocontrol potential and could protect trees by efficiently transmitting CHV-1 by hyphal anastomosis between fungal isolates of the same VCG and converting virulent to hypovirulent cankers. The hypovirulent effect was positively correlated with the virus concentration, tested by four different reverse-transcription PCRs, two end-point and two real-time methods, one of which represents a newly developed real-time PCR for the detection and quantification of CHV-1.
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6
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Microsatellite Analysis Revealing High Genetic Diversity of the Chestnut Blight Fungus in South Tyrol (Northern Italy). FORESTS 2022. [DOI: 10.3390/f13020344] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Cryphonectria parasitica, which causes chestnut blight, is one of the most important pathogens of forest trees. In Europe, mycovirus-mediated biocontrol is the most efficient method to control the disease but can be impeded by the lack of information about the population structure of the fungus within a region. In particular, sexual reproduction and the new introduction of the pathogen can complicate biocontrol strategies. For this reason, this study aimed to determine the population structure of C. parasitica, which causes chestnut blight, in the northern Italian region of South Tyrol, using eleven multilocus microsatellite markers. Fifty-one haplotypes were found across South Tyrol, belonging to three divergent clusters. Recombinant genotypes demonstrated that sexual reproduction occurs across the different clusters. The most dominant genotypes in the region were also the most dominant in neighboring areas, such as Switzerland, northern Italy and France. All of the clusters from South Tyrol were related to the Italian genotype pool and are thought to have been introduced from northern Italian and other European populations due to naturally occurring gene flow or human-mediated introduction. At least three separate introduction events of C. parasitica might have happened in South Tyrol that could be separated by time. This study demonstrated a high genetic diversity of C. parasitica in South Tyrol and helped to shed light on the sexual reproduction and introduction events in the local populations.
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Kupper Q, Cornejo C. A Multiplex PCR Approach to Determine Vegetative Incompatibility Genotypes and Mating Type in Cryphonectria parasitica. Methods Mol Biol 2022; 2536:435-446. [PMID: 35819619 DOI: 10.1007/978-1-0716-2517-0_25] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
This chapter presents a genotyping assay that uses DNA isolated from axenic cultures of Cryphonectria parasitica, which discriminates the six known diallelic vic loci and the two mating idiomorphs (MAT gene) based on (i) modified primer, labeled with a fluorescent dye, (ii) multiplex polymerase chain reaction (multiplex-PCR), and (iii) capillary electrophoresis system. Alternatively, we show that the same primer set is suitable for conventional PCR of each vic locus and MAT gene using nonmodified primer and agarose gel electrophoresis.
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Affiliation(s)
- Quirin Kupper
- Swiss Federal Research Institute WSL, Birmensdorf, Switzerland
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8
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Ježić M, Schwarz JM, Prospero S, Sotirovski K, Risteski M, Ćurković-Perica M, Nuskern L, Krstin L, Katanić Z, Maleničić E, Poljak I, Idžojtić M, Rigling D. Temporal and Spatial Genetic Population Structure of Cryphonectria parasitica and Its Associated Hypovirus Across an Invasive Range of Chestnut Blight in Europe. PHYTOPATHOLOGY 2021; 111:1327-1337. [PMID: 33417482 DOI: 10.1094/phyto-09-20-0405-r] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Chestnut blight has spread throughout Europe since the introduction of its causal agent, Cryphonectria parasitica, >70 years ago. In our study, we analyzed the diversity of vegetative compatibility (vc) and microsatellite genotypes of C. parasitica, as well as sequence diversity of Cryphonectria hypovirus 1 (CHV1) in six populations from Switzerland, Croatia, and North Macedonia. Resampling of local populations that were already investigated more than a decade ago allowed us to analyze the spatial and temporal population structure across an invasive range of the pathogen in Europe. Regardless of which genetic marker was used, the >60-year-old Swiss and Croatian populations had high population diversity, whereas more recent North Macedonian populations were mostly clonal. These diversity differences between the investigated populations remained stable over time. A high diversity of CHV1 was observed in all three countries, with North Macedonian strains forming a separate cluster from strains obtained in other countries. No correlation between vc diversity and CHV1 prevalence was observed, suggesting a well-established and maintained natural hypovirulence in all countries, further corroborated by an observed increase in genetic diversity of Croatian C. parasitica populations over time, without collapse of CHV1 prevalence.
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Affiliation(s)
- Marin Ježić
- University of Zagreb, Faculty of Science, Department of Biology, Division of Microbiology, Zagreb, Croatia
| | | | - Simone Prospero
- Swiss Federal Research Institute WSL, 8903 Birmensdorf, Switzerland
| | - Kiril Sotirovski
- Ss Cyril and Methodius University in Skopje, Hans Em Faculty of Forest Sciences, Landscape Architecture and Environmental Engineering, 1000 Skopje, North Macedonia
| | - Mihajlo Risteski
- Ss Cyril and Methodius University in Skopje, Hans Em Faculty of Forest Sciences, Landscape Architecture and Environmental Engineering, 1000 Skopje, North Macedonia
| | - Mirna Ćurković-Perica
- University of Zagreb, Faculty of Science, Department of Biology, Division of Microbiology, Zagreb, Croatia
| | - Lucija Nuskern
- University of Zagreb, Faculty of Science, Department of Biology, Division of Microbiology, Zagreb, Croatia
| | - Ljiljana Krstin
- University J. J. Strossmayer of Osijek, Department of Biology, 31000 Osijek, Croatia
| | - Zorana Katanić
- University J. J. Strossmayer of Osijek, Department of Biology, 31000 Osijek, Croatia
| | - Ema Maleničić
- University of Zagreb, Faculty of Science, Department of Biology, Division of Microbiology, Zagreb, Croatia
| | - Igor Poljak
- University of Zagreb, Faculty of Forestry and Wood Technology, Department of Forest Genetics, Dendrology and Botany, 10000 Zagreb, Croatia
| | - Marilena Idžojtić
- University of Zagreb, Faculty of Forestry and Wood Technology, Department of Forest Genetics, Dendrology and Botany, 10000 Zagreb, Croatia
| | - Daniel Rigling
- Swiss Federal Research Institute WSL, 8903 Birmensdorf, Switzerland
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Khalifa ME, MacDiarmid RM. A Mechanically Transmitted DNA Mycovirus Is Targeted by the Defence Machinery of Its Host, Botrytis cinerea. Viruses 2021; 13:v13071315. [PMID: 34372522 PMCID: PMC8309985 DOI: 10.3390/v13071315] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Revised: 07/03/2021] [Accepted: 07/05/2021] [Indexed: 12/11/2022] Open
Abstract
Eukaryotic circular single-stranded DNA (ssDNA) viruses were known only to infect plants and vertebrates until the discovery of the isolated DNA mycovirus from the fungus Sclerotinia sclerotiorum. Similar viral sequences were reported from several other sources and classified in ten genera within the Genomoviridae family. The current study reports two circular ssDNA mycoviruses isolated from the phytopathogen Botrytis cinerea, and their assignment to a newly created genus tentatively named Gemydayirivirus. The mycoviruses, tentatively named botrytis gemydayirivirus 1 (BGDaV1) and BGDaV2, are 1701 and 1693 nt long and encode three and two open reading frames (ORFs), respectively. Of the predicted ORFs, only ORF I, which codes for a replication initiation protein (Rep), shared identity with other proteins in GenBank. BGDaV1 is infective as cell-free purified particles and confers hypovirulence on its natural host. Investigation revealed that BGDaV1 is a target for RNA silencing and genomic DNA methylation, keeping the virus at very low titre. The discovery of BGDaV1 expands our knowledge of the diversity of genomoviruses and their interaction with fungal hosts.
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Affiliation(s)
- Mahmoud E. Khalifa
- The New Zealand Institute for Plant and Food Research Limited, Auckland 1025, New Zealand;
- Botany and Microbiology Department, Faculty of Science, Damietta University, Damietta 34517, Egypt
- Correspondence:
| | - Robin M. MacDiarmid
- The New Zealand Institute for Plant and Food Research Limited, Auckland 1025, New Zealand;
- School of Biological Sciences, The University of Auckland, Auckland 1010, New Zealand
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Stauber L, Badet T, Feurtey A, Prospero S, Croll D. Emergence and diversification of a highly invasive chestnut pathogen lineage across southeastern Europe. eLife 2021; 10:e56279. [PMID: 33666552 PMCID: PMC7935491 DOI: 10.7554/elife.56279] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2020] [Accepted: 02/17/2021] [Indexed: 12/18/2022] Open
Abstract
Invasive microbial species constitute a major threat to biodiversity, agricultural production and human health. Invasions are often dominated by one or a small number of genotypes, yet the underlying factors driving invasions are poorly understood. The chestnut blight fungus Cryphonectria parasitica first decimated the North American chestnut, and a more recent outbreak threatens European chestnut stands. To unravel the chestnut blight invasion of southeastern Europe, we sequenced 230 genomes of predominantly European strains. Genotypes outside of the invasion zone showed high levels of diversity with evidence for frequent and ongoing recombination. The invasive lineage emerged from the highly diverse European genotype pool rather than a secondary introduction from Asia or North America. The expansion across southeastern Europe was mostly clonal and is dominated by a single mating type, suggesting a fitness advantage of asexual reproduction. Our findings show how an intermediary, highly diverse bridgehead population gave rise to an invasive, largely clonally expanding pathogen.
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Affiliation(s)
- Lea Stauber
- Swiss Federal Institute for Forest, Snow and Landscape Research (WSL)BirmensdorfSwitzerland
- Laboratory of Evolutionary Genetics, Institute of Biology, University of NeuchâtelNeuchâtelSwitzerland
| | - Thomas Badet
- Laboratory of Evolutionary Genetics, Institute of Biology, University of NeuchâtelNeuchâtelSwitzerland
| | - Alice Feurtey
- Laboratory of Evolutionary Genetics, Institute of Biology, University of NeuchâtelNeuchâtelSwitzerland
- Plant Pathology, Institute of Integrative Biology, ETH ZürichZürichSwitzerland
| | - Simone Prospero
- Swiss Federal Institute for Forest, Snow and Landscape Research (WSL)BirmensdorfSwitzerland
| | - Daniel Croll
- Laboratory of Evolutionary Genetics, Institute of Biology, University of NeuchâtelNeuchâtelSwitzerland
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Romon-Ochoa P, Gorton C, Lewis A, van der Linde S, Webber J, Pérez-Sierra A. Hypovirulent effect of the Cryphonectria hypovirus 1 in British isolates of Cryphonectria parasitica. PEST MANAGEMENT SCIENCE 2020; 76:1333-1343. [PMID: 31603609 DOI: 10.1002/ps.5644] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 10/01/2019] [Accepted: 10/02/2019] [Indexed: 06/10/2023]
Abstract
BACKGROUND Chestnut blight, caused by Cryphonectria parasitica, is controlled in many European countries by the naturally occurring mycovirus Cryphonectria hypovirus 1 (CHV-1). During surveys of recently identified chestnut blight outbreak in England, CHV-1 was detected in several individuals of the pathogen isolated from affected trees. We investigated two of these CHV-1-infected isolates (L-6 and Db-1) as potential biocontrol agents for deployment in the UK comparing their virulence against virus-free (M1275) and hypovirulent (M784) European isolates by inoculating sweet chestnut seedlings. RESULTS Both the European CHV-1 M784 hypovirulent isolate and UK L-6 isolate formed significantly smaller lesions in sweet chestnut seedling bark than the other three isolates (Db-1, and virulent isolates FTC121 and M1275). The highest virus concentration was detected in isolate M784, followed by L-6, with the lowest concentration in isolate Db-1. White colony colouration indicative of hypovirulence was common in colonies re-isolated from smaller lesions, and the same isolates also tended to be slower growing in culture, have a higher virus concentration, and caused less epicormic growth and fewer stromata to be present in plants. L-6 and Db-1 virus sequences, respectively, matched the virus haplotype E-5 detected previously in Switzerland and a mutation of the same subtype I haplotype. CONCLUSION Isolate L-6 could potentially act as biocontrol for chestnut blight outbreaks in the UK but further laboratory and field experiments are needed. © 2019 Crown copyright. Pest Management Science © 2019 Society of Chemical Industry.
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Affiliation(s)
- Pedro Romon-Ochoa
- Forest Research, Tree Health Diagnostics and Advisory Service (THDAS), Farnham, UK
| | - Caroline Gorton
- Forest Research, Tree Health Diagnostics and Advisory Service (THDAS), Farnham, UK
| | - Alex Lewis
- Forest Research, Tree Health Diagnostics and Advisory Service (THDAS), Farnham, UK
| | - Sietse van der Linde
- Forest Research, Tree Health Diagnostics and Advisory Service (THDAS), Farnham, UK
| | - Joan Webber
- Forest Research, Tree Health Diagnostics and Advisory Service (THDAS), Farnham, UK
| | - Ana Pérez-Sierra
- Forest Research, Tree Health Diagnostics and Advisory Service (THDAS), Farnham, UK
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12
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Rigling D, Borst N, Cornejo C, Supatashvili A, Prospero S. Genetic and Phenotypic Characterization of Cryphonectria hypovirus 1 from Eurasian Georgia. Viruses 2018; 10:v10120687. [PMID: 30513977 PMCID: PMC6315935 DOI: 10.3390/v10120687] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 11/30/2018] [Accepted: 11/30/2018] [Indexed: 01/18/2023] Open
Abstract
Cryphonectria hypovirus 1 (CHV-1) infects the chestnut blight fungus Cryphonectria parasitica and acts as a biological control agent against this harmful tree disease. In this study, we screened the recently characterized C. parasitica population in Eurasian Georgia for the presence of CHV-1. We found 62 CHV-1 infected C. parasitica isolates (9.3%) among a total of 664 isolates sampled in 14 locations across Georgia. The prevalence of CHV-1 at the different locations ranged from 0% in the eastern part of the country to 29% in the western part. Sequencing of two specific regions of the viral genome one each in ORFA and ORFB revealed a unique CHV-1 subtype in Georgia. This subtype has a recombinant pattern combining the ORFA region from the subtype F2 and the ORFB region from subtype D. All 62 viral strains belonged to this Georgian CHV-1 subtype (subtype G). The CHV-1 subtype G strongly reduced the parasitic growth of C. parasitica isolates from Georgia, with a more severe effect on the European genepool compared to the Georgian genepool. The CHV-1 subtype detected in Georgia provides a valuable candidate for biological control applications in the Caucasus region.
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Affiliation(s)
- Daniel Rigling
- WSL Swiss Federal Research Institute, Zürcherstrasse 111, 8903 Birmensdorf; Switzerland.
| | - Nora Borst
- WSL Swiss Federal Research Institute, Zürcherstrasse 111, 8903 Birmensdorf; Switzerland.
| | - Carolina Cornejo
- WSL Swiss Federal Research Institute, Zürcherstrasse 111, 8903 Birmensdorf; Switzerland.
| | - Archil Supatashvili
- Vasil Gulisashvili Forestry Institute, Agricultural University of Georgia, 0186 Tbilisi, Georgia.
| | - Simone Prospero
- WSL Swiss Federal Research Institute, Zürcherstrasse 111, 8903 Birmensdorf; Switzerland.
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Rigling D, Prospero S. Cryphonectria parasitica, the causal agent of chestnut blight: invasion history, population biology and disease control. MOLECULAR PLANT PATHOLOGY 2018; 19:7-20. [PMID: 28142223 PMCID: PMC6638123 DOI: 10.1111/mpp.12542] [Citation(s) in RCA: 189] [Impact Index Per Article: 31.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 12/19/2016] [Accepted: 01/26/2017] [Indexed: 05/25/2023]
Abstract
Chestnut blight, caused by Cryphonectria parasitica, is a devastating disease infecting American and European chestnut trees. The pathogen is native to East Asia and was spread to other continents via infected chestnut plants. This review summarizes the current state of research on this pathogen with a special emphasis on its interaction with a hyperparasitic mycovirus that acts as a biological control agent of chestnut blight. TAXONOMY Cryphonectria parasitica (Murr.) Barr. is a Sordariomycete (ascomycete) fungus in the family Cryphonectriaceae (Order Diaporthales). Closely related species that can also be found on chestnut include Cryphonectria radicalis, Cryphonectria naterciae and Cryphonectria japonica. HOST RANGE Major hosts are species in the genus Castanea (Family Fagaceae), particularly the American chestnut (C. dentata), the European chestnut (C. sativa), the Chinese chestnut (C. mollissima) and the Japanese chestnut (C. crenata). Minor incidental hosts include oaks (Quercus spp.), maples (Acer spp.), European hornbeam (Carpinus betulus) and American chinkapin (Castanea pumila). DISEASE SYMPTOMS Cryphonectria parasitica causes perennial necrotic lesions (so-called cankers) on the bark of stems and branches of susceptible host trees, eventually leading to wilting of the plant part distal to the infection. Chestnut blight cankers are characterized by the presence of mycelial fans and fruiting bodies of the pathogen. Below the canker the tree may react by producing epicormic shoots. Non-lethal, superficial or callusing cankers on susceptible host trees are usually associated with mycovirus-induced hypovirulence. DISEASE CONTROL After the introduction of C. parasitica into a new area, eradication efforts by cutting and burning the infected plants/trees have mostly failed. In Europe, the mycovirus Cryphonectria hypovirus 1 (CHV-1) acts as a successful biological control agent of chestnut blight by causing so-called hypovirulence. CHV-1 infects C. parasitica and reduces its parasitic growth and sporulation capacity. Individual cankers can be therapeutically treated with hypovirus-infected C. parasitica strains. The hypovirus may subsequently spread to untreated cankers and become established in the C. parasitica population. Hypovirulence is present in many chestnut-growing regions of Europe, either resulting naturally or after biological control treatments. In North America, disease management of chestnut blight is mainly focused on breeding with the goal to backcross the Chinese chestnut's blight resistance into the American chestnut genome.
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Affiliation(s)
- Daniel Rigling
- Swiss Federal Institute for ForestSnow and Landscape Research (WSL)Birmensdorf8903Switzerland
| | - Simone Prospero
- Swiss Federal Institute for ForestSnow and Landscape Research (WSL)Birmensdorf8903Switzerland
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Nuskern L, Tkalec M, Ježić M, Katanić Z, Krstin L, Ćurković-Perica M. Cryphonectria hypovirus 1-Induced Changes of Stress Enzyme Activity in Transfected Phytopathogenic Fungus Cryphonectria parasitica. MICROBIAL ECOLOGY 2017; 74:302-311. [PMID: 28160056 DOI: 10.1007/s00248-017-0945-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Accepted: 01/22/2017] [Indexed: 06/06/2023]
Abstract
Cryphonectria parasitica is a phytopathogenic fungus introduced from Eastern Asia to North America and to Europe, where it causes chestnut blight, a devastating disease of chestnut trees. The disease can be biologically controlled utilising the mycovirus Cryphonectria hypovirus 1 (CHV1), which changes the physiology of the host, reducing its virulence towards chestnut. We measured fungal growth in vitro and activities of glutathione S-transferase, catalase and superoxide dismutase, enzymes involved in oxidative stress response, to elucidate the effects of CHV1 infection on the host. Six CHV1 strains of different subtypes and three fungal isolates were used in different combinations to better represent natural conditions, where higher genetic diversity of both fungus and virus is expected. The infection with different CHV1 strains decreased in vitro growth rate of infected fungal isolates and increased activity of their stress enzymes in most of the studied fungus/virus combinations, indicating increased oxidative stress following CHV1 infection. All our field CHV1 strains belong to the Italian subtype, but while strain M56-1 had equal or even stronger effect on its fungal host than prototypic strain EP713 of French subtype F1, strain B11 had no effect. Thus, the severity of the observed effects depended on a particular virus strain, fungal isolate, and the combination of the two, rather than solely on the virus subtype. Since previous research showed discordance between accumulation of mRNA and stress-related proteins in CHV1 infected C. parasitica, our results emphasise the importance of enzymes' activity measurements as an invaluable extension of transcriptomic and proteomic analyses.
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Affiliation(s)
- Lucija Nuskern
- Department of Biology, Faculty of Science, University of Zagreb, Marulicev trg 9a, 10000, Zagreb, Croatia
| | - Mirta Tkalec
- Department of Biology, Faculty of Science, University of Zagreb, Marulicev trg 9a, 10000, Zagreb, Croatia
| | - Marin Ježić
- Department of Biology, Faculty of Science, University of Zagreb, Marulicev trg 9a, 10000, Zagreb, Croatia
| | - Zorana Katanić
- Department of Biology, University of Josip Juraj Strossmayer in Osijek, Ulica cara Hadrijana 8A, 31000, Osijek, Croatia
| | - Ljiljana Krstin
- Department of Biology, University of Josip Juraj Strossmayer in Osijek, Ulica cara Hadrijana 8A, 31000, Osijek, Croatia
| | - Mirna Ćurković-Perica
- Department of Biology, Faculty of Science, University of Zagreb, Marulicev trg 9a, 10000, Zagreb, Croatia.
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Meyer JB, Gallien L, Prospero S. Interaction between two invasive organisms on the European chestnut: does the chestnut blight fungus benefit from the presence of the gall wasp? FEMS Microbiol Ecol 2015; 91:fiv122. [PMID: 26472577 DOI: 10.1093/femsec/fiv122] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/30/2015] [Indexed: 11/13/2022] Open
Abstract
The impact of invasive fungal pathogens and pests on trees is often studied individually, thereby omitting possible interactions. In this study the ecological interaction between the chestnut blight fungus Cryphonectria parasitica and the chestnut gall wasp Dryocosmus kuriphilus was investigated. We determined if abandoned galls could be colonized by C. parasitica and thereby act as an entry point and a source of pathogen inoculum. Moreover we assessed the identity and diversity of other gall-colonizing fungal species. A total of 1973 galls were randomly sampled from 200 chestnut trees in eight Swiss stands. In a stand C. parasitica was isolated from 0.4-19.2% of the galls. The incidence of C. parasitica on the galls and the fungal diversity significantly increased with the residence time of D. kuriphilus in a stand. All but one C. parasitica cultures were virulent. The predominant fungus isolated from galls was Gnomoniopsis castanea whose abundance influenced negatively that of C. parasitica. This study shows that D. kuriphilus galls can be colonized by virulent strains of the chestnut blight fungus C. parasitica. This can have effects on the chestnut blight incidence even in chestnut stands where the disease is successfully controlled by hypovirulence. The gall wasp presence influences also the fungal species composition on chestnut trees.
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Affiliation(s)
- Joana B Meyer
- Swiss Federal Institute for Forest, Snow and Landscape Research WSL, CH-8903 Birmensdorf, Switzerland
| | - Laure Gallien
- Swiss Federal Institute for Forest, Snow and Landscape Research WSL, CH-8903 Birmensdorf, Switzerland
| | - Simone Prospero
- Swiss Federal Institute for Forest, Snow and Landscape Research WSL, CH-8903 Birmensdorf, Switzerland
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16
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Bardin M, Ajouz S, Comby M, Lopez-Ferber M, Graillot B, Siegwart M, Nicot PC. Is the efficacy of biological control against plant diseases likely to be more durable than that of chemical pesticides? FRONTIERS IN PLANT SCIENCE 2015; 6:566. [PMID: 26284088 PMCID: PMC4515547 DOI: 10.3389/fpls.2015.00566] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Accepted: 07/09/2015] [Indexed: 05/18/2023]
Abstract
The durability of a control method for plant protection is defined as the persistence of its efficacy in space and time. It depends on (i) the selection pressure exerted by it on populations of plant pathogens and (ii) on the capacity of these pathogens to adapt to the control method. Erosion of effectiveness of conventional plant protection methods has been widely studied in the past. For example, apparition of resistance to chemical pesticides in plant pathogens or pests has been extensively documented. The durability of biological control has often been assumed to be higher than that of chemical control. Results concerning pest management in agricultural systems have shown that this assumption may not always be justified. Resistance of various pests to one or several toxins of Bacillus thuringiensis and apparition of resistance of the codling moth Cydia pomonella to the C. pomonella granulovirus have, for example, been described. In contrast with the situation for pests, the durability of biological control of plant diseases has hardly been studied and no scientific reports proving the loss of efficiency of biological control agents against plant pathogens in practice has been published so far. Knowledge concerning the possible erosion of effectiveness of biological control is essential to ensure a durable efficacy of biological control agents on target plant pathogens. This knowledge will result in identifying risk factors that can foster the selection of strains of plant pathogens resistant to biological control agents. It will also result in identifying types of biological control agents with lower risk of efficacy loss, i.e., modes of action of biological control agents that does not favor the selection of resistant isolates in natural populations of plant pathogens. An analysis of the scientific literature was then conducted to assess the potential for plant pathogens to become resistant to biological control agents.
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Affiliation(s)
- Marc Bardin
- Plant Pathology Unit, Institut National de la Recherche Agronomique, UR407, Montfavet, France
| | - Sakhr Ajouz
- Plant Pathology Unit, Institut National de la Recherche Agronomique, UR407, Montfavet, France
| | - Morgane Comby
- Plant Pathology Unit, Institut National de la Recherche Agronomique, UR407, Montfavet, France
| | - Miguel Lopez-Ferber
- Laboratoire de Génie de l’Environnement Industriel, Ecole des Mines d’Alès, Institut Mines-Telecom, Alès, France
| | - Benoît Graillot
- Laboratoire de Génie de l’Environnement Industriel, Ecole des Mines d’Alès, Institut Mines-Telecom, Alès, France
- Natural Plant Protection,Arysta LifeScience Group, Pau, France
| | - Myriam Siegwart
- Plantes et Systèmes de Culture Horticoles Unit, Institut National de la Recherche Agronomique, UR1115, Avignon, France
| | - Philippe C. Nicot
- Plant Pathology Unit, Institut National de la Recherche Agronomique, UR407, Montfavet, France
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17
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Pautasso M, Schlegel M, Holdenrieder O. Forest health in a changing world. MICROBIAL ECOLOGY 2015; 69:826-842. [PMID: 25502075 DOI: 10.1007/s00248-014-0545-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Accepted: 11/27/2014] [Indexed: 06/04/2023]
Abstract
Forest pathology, the science of forest health and tree diseases, is operating in a rapidly developing environment. Most importantly, global trade and climate change are increasing the threat to forest ecosystems posed by new diseases. Various studies relevant to forest pathology in a changing world are accumulating, thus making it necessary to provide an update of recent literature. In this contribution, we summarize research at the interface between forest pathology and landscape ecology, biogeography, global change science and research on tree endophytes. Regional outbreaks of tree diseases are requiring interdisciplinary collaboration, e.g. between forest pathologists and landscape ecologists. When tree pathogens are widely distributed, the factors determining their broad-scale distribution can be studied using a biogeographic approach. Global change, the combination of climate and land use change, increased pollution, trade and urbanization, as well as invasive species, will influence the effects of forest disturbances such as wildfires, droughts, storms, diseases and insect outbreaks, thus affecting the health and resilience of forest ecosystems worldwide. Tree endophytes can contribute to biological control of infectious diseases, enhance tolerance to environmental stress or behave as opportunistic weak pathogens potentially competing with more harmful ones. New molecular techniques are available for studying the complete tree endobiome under the influence of global change stressors from the landscape to the intercontinental level. Given that exotic tree diseases have both ecologic and economic consequences, we call for increased interdisciplinary collaboration in the coming decades between forest pathologists and researchers studying endophytes with tree geneticists, evolutionary and landscape ecologists, biogeographers, conservation biologists and global change scientists and outline interdisciplinary research gaps.
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Affiliation(s)
- Marco Pautasso
- Forest Pathology & Dendrology, Institute of Integrative Biology (IBZ), ETH Zurich, 8092, Zurich, Switzerland,
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18
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Ghabrial SA, Castón JR, Jiang D, Nibert ML, Suzuki N. 50-plus years of fungal viruses. Virology 2015; 479-480:356-68. [PMID: 25771805 DOI: 10.1016/j.virol.2015.02.034] [Citation(s) in RCA: 454] [Impact Index Per Article: 50.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 01/31/2015] [Accepted: 02/19/2015] [Indexed: 10/23/2022]
Abstract
Mycoviruses are widespread in all major taxa of fungi. They are transmitted intracellularly during cell division, sporogenesis, and/or cell-to-cell fusion (hyphal anastomosis), and thus their life cycles generally lack an extracellular phase. Their natural host ranges are limited to individuals within the same or closely related vegetative compatibility groups, although recent advances have established expanded experimental host ranges for some mycoviruses. Most known mycoviruses have dsRNA genomes packaged in isometric particles, but an increasing number of positive- or negative-strand ssRNA and ssDNA viruses have been isolated and characterized. Although many mycoviruses do not have marked effects on their hosts, those that reduce the virulence of their phytopathogenic fungal hosts are of considerable interest for development of novel biocontrol strategies. Mycoviruses that infect endophytic fungi and those that encode killer toxins are also of special interest. Structural analyses of mycoviruses have promoted better understanding of virus assembly, function, and evolution.
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Affiliation(s)
- Said A Ghabrial
- Plant Pathology Department, University of Kentucky, Lexington, KY, USA.
| | - José R Castón
- Department of Structure of Macromolecules, Centro Nacional Biotecnologıa/CSIC, Campus de Cantoblanco, Madrid, Spain
| | - Daohong Jiang
- State Key Lab of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei Province, PR China
| | - Max L Nibert
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, USA
| | - Nobuhiro Suzuki
- Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama, Japan
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19
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Detection and genetic characterisation of a novel mycovirus in Hymenoscyphus fraxineus, the causal agent of ash dieback. INFECTION GENETICS AND EVOLUTION 2014; 28:78-86. [DOI: 10.1016/j.meegid.2014.09.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Revised: 08/29/2014] [Accepted: 09/01/2014] [Indexed: 12/11/2022]
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20
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Bryner SF, Prospero S, Rigling D. Dynamics of Cryphonectria hypovirus infection in chestnut blight cankers. PHYTOPATHOLOGY 2014; 104:918-925. [PMID: 24601984 DOI: 10.1094/phyto-03-13-0069-r] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Virulent strains of the chestnut blight fungus Cryphonectria parasitica cause lethal bark cankers on chestnut trees. Infection of C. parasitica with Cryphonectria hypovirus 1 in Europe biologically controls this disease, leading to nonlethal and inactive cankers. Unexpectedly, virus-free C. parasitica strains have been isolated from inactive cankers. In this study, we compared the virulence of virus-infected and virus-free C. parasitica strains isolated from either inactive or active cankers on chestnut seedlings and sprouts. In the seedling experiment, we assessed canker growth and seedling mortality. In the sprout experiment, we also assessed canker growth and made fungal reisolations to determine virus infection and immigration of foreign vegetative compatibility (vc) types over a period of 13 years in a coppice forest. Overall, the virulence of virus-free C. parasitica strains isolated from inactive versus active cankers did not differ. Significant differences were only attributed to virus infection. Virus infection and fungal strain composition in cankers changed over time. Foreign vc types immigrated into cankers and virus-free cankers became virus-infected within a few years. Most of the cankers were callused over time and became inactive. However, we observed that the virus did not always persist in these cankers. This study demonstrates that virus spread occurs effectively in European chestnut forests and that this biocontrol system is highly dynamic.
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21
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Gross A, Hosoya T, Queloz V. Population structure of the invasive forest pathogen Hymenoscyphus pseudoalbidus. Mol Ecol 2014; 23:2943-60. [PMID: 24819666 DOI: 10.1111/mec.12792] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Revised: 04/29/2014] [Accepted: 04/30/2014] [Indexed: 12/21/2022]
Abstract
Understanding the genetic diversity and structure of invasive pathogens in source and in introduced areas is crucial to the revelation of hidden biological features of an organism, to the reconstruction of the course of invasions and to the establishment of effective control measures. Hymenoscyphus pseudoalbidus (anamorph: Chalara fraxinea) is an invasive and highly destructive fungal pathogen found on common ash Fraxinus excelsior in Europe and is native to East Asia. To gain insights into its dispersal mechanisms and history of invasion, we used microsatellite markers and characterized the genetic structure and diversity of H. pseudoalbidus populations at three spatial levels: (i) between Europe and Japan, (ii) in Europe and (iii) at the epidemic's front in Switzerland. Phylogenetic and network analysis demonstrated that individuals from both regions are conspecific. However, populations from Japan harboured a higher genetic diversity and were genetically differentiated from European ones. No evident population structure was found among the 1208 European strains using Bayesian and multivariate clustering analysis. Only the distribution of genetic diversity in space, pairwise population differentiation (GST) and the spatial analysis of principal components revealed a faint geographical pattern around Europe. A significant allele deficiency in most European populations pointed to a recent genetic bottleneck, whereas no pattern of isolation by distance was found. Our data suggest that H. pseudoalbidus was introduced just once by at least two individuals. The potential source region of H. pseudoalbidus is vast, and further investigations are required for a more accurate localization of the source population.
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Affiliation(s)
- Andrin Gross
- Forest Pathology and Dendrology, Institute of Integrative Biology (IBZ), ETH Zurich, Universitätsstrasse 16, Zurich, 8092, Switzerland
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22
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Peters FS, Busskamp J, Prospero S, Rigling D, Metzler B. Genetic diversification of the chestnut blight fungus Cryphonectria parasitica and its associated hypovirus in Germany. Fungal Biol 2013; 118:193-210. [PMID: 24528641 DOI: 10.1016/j.funbio.2013.11.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Revised: 11/06/2013] [Accepted: 11/20/2013] [Indexed: 10/25/2022]
Abstract
Chestnut blight in south-western Germany was first reported in 1992 and is since expanding in distribution. Here we investigated the invasion history of Cryphonectria parasitica and its associated hypovirus. For this, we characterized 284 isolates collected between 1992 and 2012 for hypovirulence, vegetative compatibility (vc), mating type, and microsatellite haplotype. A total of 27 haplotypes and 15 vc types were observed, although the C. parasitica population analyzed is currently dominated to 50 % by one haplotype and to 64 % by the vc type EU-2. Structure analysis indicated two divergent genetic pools. Over 66 % of the haplotypes belonged to a pool probably originating from northern Italy. Further diversification is expected due to ongoing sexual recombination, but also to new migration and additional introductions. Cryphonectria hypovirus 1 (CHV-1) was found in four of five C. parasitica populations from Baden-Württemberg. Genetic analysis of the 35 CHV-1 isolates obtained revealed that they all belong to the German subtype, although they have clearly diverged from the first German hypovirus isolated in 1992. Our study suggests that C. parasitica has been introduced into Germany several times from two different gene pools, whereas the hypovirus most probably has a single origin.
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Affiliation(s)
- Franziska S Peters
- FVA Forest Research Institute of Baden-Württemberg (FVA-BW), Dept. Forest Protection, Wonnhaldestr. 4, D-79100 Freiburg, Germany.
| | - Johanna Busskamp
- FVA Forest Research Institute of Baden-Württemberg (FVA-BW), Dept. Forest Protection, Wonnhaldestr. 4, D-79100 Freiburg, Germany.
| | - Simone Prospero
- WSL Swiss Federal Research Institute, Zürcherstrasse 111, CH-8903 Birmensdorf, Switzerland.
| | - Daniel Rigling
- WSL Swiss Federal Research Institute, Zürcherstrasse 111, CH-8903 Birmensdorf, Switzerland.
| | - Berthold Metzler
- FVA Forest Research Institute of Baden-Württemberg (FVA-BW), Dept. Forest Protection, Wonnhaldestr. 4, D-79100 Freiburg, Germany.
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23
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Prospero S, Lutz A, Tavadze B, Supatashvili A, Rigling D. Discovery of a new gene pool and a high genetic diversity of the chestnut blight fungus Cryphonectria parasitica in Caucasian Georgia. INFECTION GENETICS AND EVOLUTION 2013; 20:131-9. [PMID: 23994123 DOI: 10.1016/j.meegid.2013.08.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Revised: 08/08/2013] [Accepted: 08/12/2013] [Indexed: 11/24/2022]
Abstract
In this study, we investigated the population genetic structure and possible origins of the plant pathogen Cryphonectria parasitica in Caucasian Georgia, a region within the centre of origin of the host species Castanea sativa. A total of 427 C. parasitica isolates from nine populations were genotyped at 10 microsatellite loci. A high genetic diversity was detected, but the overall Georgian population was dominated by three haplotypes which were present in most individual populations. Two of them have not been previously found in Europe. Bayesian clustering analysis and principal component analysis could not identify their source population, neither in Asia nor in North America. On the other hand, one haplotype is frequent in Central Europe and probably naturally invaded Caucasian Georgia from neighbouring Turkey. Seventy-three haplotypes were unique to specific populations, and 66 of them were represented by a single isolate. Allele patterns suggest that most of these haplotypes emerged locally through sexual recombination between haplotypes of the Georgian and the central European gene pool. Due to the high incidence of haplotypes not otherwise present in Europe, Caucasian Georgia represents an additional source of diversity for the European C. parasitica population.
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Affiliation(s)
- S Prospero
- Swiss Federal Institute for Forest, Snow and Landscape Research WSL, CH-8903 Birmensdorf, Switzerland.
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24
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Bryner SF, Rigling D, Brunner PC. Invasion history and demographic pattern of Cryphonectria hypovirus 1 across European populations of the chestnut blight fungus. Ecol Evol 2012; 2:3227-41. [PMID: 23301186 PMCID: PMC3539014 DOI: 10.1002/ece3.429] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Revised: 10/09/2012] [Accepted: 10/13/2012] [Indexed: 01/16/2023] Open
Abstract
We reconstructed the invasion history of the fungal virus Cryphonectria hypovirus 1 (CHV-1) in Europe, which infects the chestnut blight fungus Cryphonectria parasitica. The pattern of virus evolution was inferred based on nucleotide sequence variation from isolates sampled across a wide area in Europe at different points in time. Phylogeny and time estimates suggested that CHV-1 was introduced together with its fungal host to Europe and that it rapidly colonized the central range along the south facing slopes of the Alps and the north-east facing slopes of the Dinaric Alps. These central populations were the source for two waves of simultaneous invasions toward the southern Balkans and Turkey, as indicated by migration rates. Our results showed that the evolutionary scenarios for CHV-1 and C. parasitica were spatially congruent. As infection with CHV-1 reduces the pathogenicity of C. parasitica toward the chestnut tree, CHV-1 invasions of the newly established C. parasitica populations probably prevented the development of devastating chestnut blight epidemics in Europe. We propose that in this, and supposedly in other pathosystems, geographic, vegetation-related, demographic, economic, and political factors may help explain the correlated invasion pattern of a parasite and its host.
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Affiliation(s)
- Sarah F Bryner
- WSL Swiss Federal Research Institute CH-8903, Birmensdorf, Switzerland
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