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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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2
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Stauber L, Croll D, Prospero S. Temporal changes in pathogen diversity in a perennial plant-pathogen-hyperparasite system. Mol Ecol 2022; 31:2073-2088. [PMID: 35122694 PMCID: PMC9540319 DOI: 10.1111/mec.16386] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Revised: 01/26/2022] [Accepted: 01/31/2022] [Indexed: 11/27/2022]
Abstract
Hyperparasites can affect the evolution of pathosystems by influencing the stability of both pathogen and host populations. However, how pathogens of perennial hosts evolve in the presence of a hyperparasite has rarely been studied. Here, we investigated temporal changes in genetic diversity of the invasive chestnut blight pathogen Cryphonectria parasitica in the presence of its parasitic mycovirus Cryphonectria hypovirus 1 (CHV1). The virus reduces fungal virulence and represents an effective natural biocontrol agent against chestnut blight in Europe. We analysed genome‐wide diversity and CHV1 prevalence in C. parasitica populations in southern Switzerland that were sampled twice at an interval of about 30 years. Overall, we found that both pathogen population structure and CHV1 prevalence were retained over time. The results suggest that recent bottlenecks have influenced the structure of C. parasitica populations in southern Switzerland. Strong balancing selection signals were found at a single vegetative incompatibility (vic) locus, consistent with negative frequency‐dependent selection imposed by the vegetative incompatibility system. High levels of mating among related individuals (i.e., inbreeding) and genetic drift are probably at the origin of imbalanced allele ratios at vic loci and subsequently low vc type diversity. Virus infection rates were stable at ~30% over the study period and we found no significant impact of the virus on fungal population diversity. Consequently, the efficacy of CHV1‐mediated biocontrol was probably retained.
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Affiliation(s)
- Lea Stauber
- Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Birmensdorf, Switzerland.,Laboratory of Evolutionary Genetics, Institute of Biology, University of Neuchâtel, Switzerland.,Department of Environmental Sciences, University of Basel, Switzerland
| | - Daniel Croll
- Laboratory of Evolutionary Genetics, Institute of Biology, University of Neuchâtel, Switzerland
| | - Simone Prospero
- Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Birmensdorf, Switzerland
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Owashi Y, Aihara M, Moriyama H, Arie T, Teraoka T, Komatsu K. Population Structure of Double-Stranded RNA Mycoviruses That Infect the Rice Blast Fungus Magnaporthe oryzae in Japan. Front Microbiol 2020; 11:593784. [PMID: 33193269 PMCID: PMC7664462 DOI: 10.3389/fmicb.2020.593784] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 09/28/2020] [Indexed: 11/28/2022] Open
Abstract
Various viruses infect Magnaporthe oryzae (syn. Pyricularia oryzae), which is a well-studied fungus that causes rice blast disease. Most research has focused on the discovery of new viruses and the hypovirulence-associated traits conferred by them. Therefore, the diversity and prevalence of viruses in wild fungal populations have not been explored. We conducted a comprehensive screening of M. oryzae mycoviruses from various regions in Japan using double-stranded RNA (dsRNA) electrophoresis and RT-PCR assays. We detected three mycoviruses, Magnaporthe oryzae virus 2 (MoV2), Magnaporthe oryzae chrysovirus 1 (MoCV1), and Magnaporthe oryzae partitivirus 1 (MoPV1), among 127 of the 194 M. oryzae strains screened. The most prevalent virus was MoPV1 (58.8%), which often co-infected in a single fungal strain together with MoV2 or MoCV1. MoV2 and MoCV1 were found in 22.7 and 10.8% of strains, respectively, and they were usually distributed in different regions so that mixed-infection with these two mycoviruses was extremely rare. The predominance of MoPV1 in M. oryzae is supported by significant negative values from neutrality tests, which indicate that the population size of MoPV1 tends to increase. Population genetic analyses revealed high nucleotide diversity and the presence of phylogenetically diverse subpopulations among the MoV2 isolates. This was not the case for MoPV1. Furthermore, studies of a virus-cured M. oryzae strain revealed that MoV2 does not cause any abnormalities or symptoms in its host. However, a leaf sheath inoculation assay showed that its presence slightly increased the speed of mycelial growth, compared with virus-free mycelia. These results demonstrate that M. oryzae in Japan harbors diverse dsRNA mycovirus communities with wide variations in their population structures among different viruses.
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Affiliation(s)
- Yuta Owashi
- Laboratory of Plant Pathology, Graduate School of Agriculture, Tokyo University of Agriculture and Technology (TUAT), Fuchu, Japan.,Western Region Agricultural Research Center, National Agriculture and Food Research Organization, Fukuyama, Japan
| | - Mitsuhiro Aihara
- Laboratory of Plant Pathology, Graduate School of Agriculture, Tokyo University of Agriculture and Technology (TUAT), Fuchu, Japan
| | - Hiromitsu Moriyama
- Laboratory of Plant Pathology, Graduate School of Agriculture, Tokyo University of Agriculture and Technology (TUAT), Fuchu, Japan
| | - Tsutomu Arie
- Laboratory of Plant Pathology, Graduate School of Agriculture, Tokyo University of Agriculture and Technology (TUAT), Fuchu, Japan
| | - Tohru Teraoka
- Laboratory of Plant Pathology, Graduate School of Agriculture, Tokyo University of Agriculture and Technology (TUAT), Fuchu, Japan
| | - Ken Komatsu
- Laboratory of Plant Pathology, Graduate School of Agriculture, Tokyo University of Agriculture and Technology (TUAT), Fuchu, Japan
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Kolp M, Double ML, Fulbright DW, MacDonald WL, Jarosz AM. Spatial and temporal dynamics of the fungal community of chestnut blight cankers on American chestnut (Castanea dentata) in Michigan and Wisconsin. FUNGAL ECOL 2020. [DOI: 10.1016/j.funeco.2020.100925] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Aulia A, Andika IB, Kondo H, Hillman BI, Suzuki N. A symptomless hypovirus, CHV4, facilitates stable infection of the chestnut blight fungus by a coinfecting reovirus likely through suppression of antiviral RNA silencing. Virology 2019; 533:99-107. [PMID: 31146252 DOI: 10.1016/j.virol.2019.05.004] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 05/14/2019] [Accepted: 05/14/2019] [Indexed: 01/10/2023]
Abstract
Field-collected US strain C18 of Cryphonectria parasitica, the chestnut blight fungus, was earlier reported to be infected by a double-stranded RNA virus, mycoreovirus 2 (MyRV2). Next-generation sequencing has revealed co-infection of C18 by a positive-strand RNA virus, hypovirus 4 (CHV4). The current molecular and genetic analyses showed interesting commensal interactions between the two viruses. CHV4 facilitated the stable infection and enhanced vertical transmission of MyRV2, which was readily lost during subculturing and showed reduced vertical transmission in single infections. Deletion of a key antiviral RNA silencing gene, dcl2, in isolate C18 increased stability of MyRV2 in single infections. The ability of CHV4 to facilitate stable infection with MyRV2 appears to be associated with the inhibitory effect of CHV4 on RNA silencing via compromising the induction of transcriptional up-regulation of dcl2. These results suggest that natural infection of isolate C18 by MyRV2 in the field was facilitated by CHV4 co-infection.
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Affiliation(s)
- Annisa Aulia
- Institute of Plant Science and Resources (IPSR), Okayama University, Kurashiki, 710-0046, Japan; Graduate School of Environmental and Life Science, Okayama University, Okayama, 700-8530, Japan
| | - Ida Bagus Andika
- Institute of Plant Science and Resources (IPSR), Okayama University, Kurashiki, 710-0046, Japan
| | - Hideki Kondo
- Institute of Plant Science and Resources (IPSR), Okayama University, Kurashiki, 710-0046, Japan
| | - Bradley I Hillman
- Plant Biology and Pathology, Rutgers University, New Brunswick, NJ, 08901, USA
| | - Nobuhiro Suzuki
- Institute of Plant Science and Resources (IPSR), Okayama University, Kurashiki, 710-0046, Japan.
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Meyer JB, Chalmandrier L, Fässler F, Schefer C, Rigling D, Prospero S. Role of Fresh Dead Wood in the Epidemiology and the Biological Control of the Chestnut Blight Fungus. PLANT DISEASE 2019; 103:430-438. [PMID: 30632896 DOI: 10.1094/pdis-05-18-0796-re] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The invasive fungus Cryphonectria parasitica, the causal agent of chestnut blight, is able to survive and sporulate on the bark of fresh dead Castanea sativa wood for at least 2 years. Here, we experimentally investigated the role of fresh dead wood in the epidemiology of chestnut blight, specifically in the spread of the hyperparasitic virus Cryphonectria hypovirus 1, which acts as biocontrol agent of C. parasitica. A total of 152 artificially initiated, virulent bark cankers in four chestnut stands were treated with virus-infected asexual spores originating either from sporulating dead wood or from a spore suspension. Molecular markers for both the virus and the fungal carrier were used to examine the spread of the applied biocontrol virus. Fourteen months after treatment, 42 to 76% of the conidial spray-treated cankers and 50 to 60% of the cankers exposed to a sporulating dead stem had been virus infected by the applied hypovirulent conidia in all four study sites. Virus infection reduced canker expansion and promoted canker healing (callusing). Thus, fresh chestnut dead wood may play an important role in supporting the successful spread of natural hypovirulence in chestnut forests. Further, combined with the application of virus-infected conidial suspensions, it may help promote the establishment of artificially released hypoviruses in chestnut stands to control chestnut blight.
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Affiliation(s)
- Joana Beatrice Meyer
- Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), CH-8903 Birmensdorf, Switzerland
| | - Loïc Chalmandrier
- Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), CH-8903 Birmensdorf, Switzerland; Landscape Ecology, Institute of Terrestrial Ecosystems, ETH Zürich, Switzerland; and Department of Botany, University of Wyoming, Laramie, WY 82071-2000, U.S.A
| | - Fabio Fässler
- Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), CH-8903 Birmensdorf, Switzerland
| | - Christopher Schefer
- Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), CH-8903 Birmensdorf, Switzerland
| | - Daniel Rigling
- 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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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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Murolo S, De Miccolis Angelini RM, Faretra F, Romanazzi G. Phenotypic and Molecular Investigations on Hypovirulent Cryphonectria parasitica in Italy. PLANT DISEASE 2018; 102:540-545. [PMID: 30673478 DOI: 10.1094/pdis-04-17-0517-re] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Chestnut blight is caused by the fungus Cryphonectria parasitica. As one of the most ecologically important diseases of Castanea spp., C. parasitica can rapidly kill trees. In Europe, mitigation of disease severity took place spontaneously through colonization of C. parasitica by mycoviruses, which reduced the virulence of the fungus. In the framework of a survey, 138 C. parasitica isolates were identified, and virulent/hypovirulent phenotypes were determined through morphological properties and pathogenicity tests. For a pool of four hypovirulent isolates, dsRNA was extracted, cDNA synthesized, and a library subjected to next-generation sequencing. The bioinformatics analysis allowed detecting and reconstructing the complete genome of Cryphonectria hypovirus 1 (CHV-1), denoted as CHV-1 Marche. When compared with the available genomes of other hypoviruses that affected the virulence of C. parasitica, available in databases, CHV-1 Marche showed some nucleotide diversity. The approach used in this study was effective to explore the virome inside a pool of hypovirulent C. parasitica isolates. Next-generation sequencing allowed us to exclude the presence of any other ssRNA and dsRNA viruses infecting the fungus and determine CHV-1 as the only responsible of hypovirulence of C. parasitica in the analyzed samples.
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Affiliation(s)
- Sergio Murolo
- Department of Agricultural, Food and Environmental Sciences, Marche Polytechnic University, Ancona, Italy
| | | | - Francesco Faretra
- Department of Soil, Plant and Food Sciences, University of Bari, Italy
| | - Gianfranco Romanazzi
- Department of Agricultural, Food and Environmental Sciences, Marche Polytechnic University, Ancona, Italy
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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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