scholarly journals Dynamics of Cryphonectria hypovirus Infection in Chestnut Blight Cankers

2014 ◽  
Vol 104 (9) ◽  
pp. 918-925 ◽  
Author(s):  
Sarah Franziska Bryner ◽  
Simone Prospero ◽  
Daniel Rigling
Keyword(s):  
Virus Infection ◽  
Cryphonectria Parasitica ◽  
Chestnut Blight ◽  
Seedling Mortality ◽  
Chestnut Blight Fungus ◽  
European Chestnut ◽  
Virulent Strains ◽  
Coppice Forest ◽  
Cryphonectria Hypovirus ◽  
Over Time

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.

scholarly journals Emergence and diversification of a highly invasive chestnut pathogen lineage across southeastern Europe

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Lea Stauber ◽  
Thomas Badet ◽  
Alice Feurtey ◽  
Simone Prospero ◽  
Daniel Croll
Keyword(s):  
Cryphonectria Parasitica ◽  
Chestnut Blight ◽  
Southeastern Europe ◽  
Chestnut Blight Fungus ◽  
The North ◽  
Fitness Advantage ◽  
European Chestnut ◽  
Recent Outbreak ◽  
Single Mating ◽  
European Genotype

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.

scholarly journals Temporal and spatial genetic population structure of Cryphonectria parasitica and its associated hypovirus across an invasive range of chestnut blight in Europe

2021 ◽  
Author(s):  
Marin Ježić ◽  
Janine Melanie Schwarz ◽  
Simone Prospero ◽  
Kiril Sotirovski ◽  
Mihajlo Risteski ◽  
...  
Keyword(s):  
Population Structure ◽  
Cryphonectria Parasitica ◽  
Population Diversity ◽  
Chestnut Blight ◽  
Genetic Population ◽  
Invasive Range ◽  
Temporal And Spatial ◽  
Cryphonectria Hypovirus ◽  
High Diversity ◽  
Over Time

Chestnut blight has spread throughout Europe since the introduction of its causal agent Cryphonectria parasitica over 70 years ago. In our study, we have analysed 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 analyse the spatial and temporal population structure across an invasive range of the pathogen in Europe. Regardless which genetic marker was used, the over 60 year-old Swiss and Croatian populations had a high population diversity, while 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.

scholarly journals 75 years of the chestnut blight fungus Cryphonectria parasitica (Murr.) Barr in Europe

2014 ◽  
pp. 82-85
Author(s):  
László Radócz ◽  
Gábor Görcsös ◽  
Gábor Tarcali ◽  
Gabriella Kovács ◽  
Qin Ling
Keyword(s):  
Biological Control ◽  
Cryphonectria Parasitica ◽  
Vegetative Compatibility ◽  
Chestnut Blight ◽  
Chestnut Blight Fungus ◽  
European Chestnut ◽  
High Prevalence ◽  
History Of ◽  
Short Time ◽  
High Diversity

The chestnut blight fungus Cryphonectria parasitica is a native pathogen in East Asia and has been introduced into North America and Europe. Historical records and population genetic studies revealed at least three major introduction events from Asia into Europe. Nowadays, chestnut blight is present in almost the entire distribution range of European chestnut, i.e. from the Iberian Peninsula to the Caucasus. The C. parasitica population in most countries has been studied in respect to the diversity of vegetative compatibility (vc) types and the occurrence of hypovirulence. The vc type diversity of the different populations varied considerably. Typically, a high diversity of vc types has been found in areas with a long history of chestnut blight and where sexual recombination between divergent genotypes commonly has occurred. On the other hand, newly established populations often showed a low diversity with only one, or a few vc types present. Hypovirulence, i.e. the occurrence of C. parasitica isolates infected by Cryphonectria hypovirus 1 has been found widespread in Europe. Natural dissemination and active biological control applications have lead to a high prevalence of the hypovirus and to the recovery of many chestnut stands. Virulent cankers became hypovirus-infected within a short time and ceased expansion. There is concern that the diversity of vegetative compatibility types could increase in Europe through sexual reproduction between C. parasitica genotypes originating from different introductions. A higher level of vegetative incompatibility would not only hamper hypovirus spread within a population but could also select for lower virulence in CHV-1 and subsequently lead to an erosion of biological control. Recent studies, however, indicate that the vc type barriers are not so restrictive than previously assumed and that so far no evidence for an erosion of biological control system in high diversity populations can be observed.

scholarly journals Hypovirus Virulence and Vegetative Incompatibility in Populations of the Chestnut Blight Fungus

2012 ◽  
Vol 102 (12) ◽  
pp. 1161-1167 ◽  
Author(s):  
Sarah Franziska Bryner ◽  
Daniel Rigling
Keyword(s):  
Biocontrol Agent ◽  
Cryphonectria Parasitica ◽  
Vegetative Compatibility ◽  
Chestnut Blight ◽  
Vegetative Incompatibility ◽  
Tree Disease ◽  
Chestnut Blight Fungus ◽  
Fungal Populations ◽  
Cryphonectria Hypovirus ◽  
High Diversity

Cryphonectria hypovirus 1 hyperparasitizes the chestnut blight fungus Cryphonectria parasitica and acts as a biocontrol agent for this serious tree disease. The virus is transmitted cytoplasmatically between fungal individuals. However, highly virulent viruses strongly debilitate their host and, thus, reduce their own transmission probability. Furthermore, vegetative incompatibility between fungi is an important transmission barrier. Therefore, virulent viruses are expected to be strongly selected against in fungal populations with high levels of vegetative incompatibility, eventually leading to the erosion of biocontrol. To test this prediction, we assessed the virulence of the virus in four European C. parasitica populations with high diversity of vegetative compatibility types and in four populations with low diversity. We expected the degree of virus virulence to be lower in fungal populations with high levels of vegetative incompatibility. However, our results did not reveal such a trend. No significant differences in virus virulence between populations with low versus high diversity of vegetative compatibility types were observed. There was no evidence for an erosion of disease control due to the presence of these transmission barriers. Thus, the findings of this study are promising for the sustainability of Cryphonectria hypovirus 1 as a biocontrol agent for chestnut blight in Europe.

scholarly journals Role of Fresh Dead Wood in the Epidemiology and the Biological Control of the Chestnut Blight Fungus

Plant Disease ◽  
2019 ◽  
Vol 103 (3) ◽  
pp. 430-438 ◽  
Author(s):  
Joana Beatrice Meyer ◽  
Loïc Chalmandrier ◽  
Fabio Fässler ◽  
Christopher Schefer ◽  
Daniel Rigling ◽  
...  
Keyword(s):  
Biological Control ◽  
Dead Wood ◽  
Biocontrol Agent ◽  
Castanea Sativa ◽  
Cryphonectria Parasitica ◽  
Chestnut Blight ◽  
Chestnut Blight Fungus ◽  
Study Sites ◽  
Cryphonectria Hypovirus

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.

scholarly journals Characterization of a Hypovirus-Regulated Septin Cdc11 Ortholog, CpSep1, from the Chestnut Blight Fungus Cryphonectria parasitica

2019 ◽  
Vol 32 (3) ◽  
pp. 286-295 ◽  
Author(s):  
Myeongjin Jo ◽  
Kum-Kang So ◽  
Yo-Han Ko ◽  
Jeesun Chun ◽  
Jung-Mi Kim ◽  
...  
Keyword(s):  
Cryphonectria Parasitica ◽  
Chestnut Blight ◽  
Null Mutant ◽  
Wild Type ◽  
Chestnut Blight Fungus ◽  
Germination Process ◽  
Cryphonectria Hypovirus ◽  
Null Mutants

We identified a protein spot showing downregulation in the presence of Cryphonectria hypovirus 1 and tannic acid supplementation as a septin subunit with the highest homology to the Aspergillus nidulans aspA gene, an ortholog of the Saccharomyces cerevisiae Cdc11 gene. To analyze the functional role of this septin component (CpSep1), we constructed its null mutant and obtained a total of eight CpSep1-null mutants from 137 transformants. All CpSep1-null mutants showed retarded growth, with fewer aerial mycelia and intense pigmentation on plates of potato dextrose agar supplemented with L-methionine and biotin. When the marginal hyphae were examined, hyperbranching was observed in contrast to the wild type. The inhibition of colonial growth was partially recovered when the CpSep1-null mutants were cultured in the presence of the osmostabilizing sorbitol. Conidia production of the CpSep1-null mutants was significantly increased by at least 10-fold more. Interestingly, the conidial morphology of the CpSep1-null mutants changed to circular in contrast to the typical rod-shaped spores of the wild type, indicating a role of septin in the spore morphology of Cryphonectria parasitica. However, no differences in the germination process were observed. Virulence assays using excised chestnut bark, stromal pustule formation on chestnut stems, and apple inoculation indicated that the CpSep1 gene is important in pathogenicity.

scholarly journals Identification of an RNA Silencing Suppressor Encoded by a Symptomless Fungal Hypovirus, Cryphonectria Hypovirus 4

Biology ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 100
Author(s):  
Annisa Aulia ◽  
Kiwamu Hyodo ◽  
Sakae Hisano ◽  
Hideki Kondo ◽  
Bradley I. Hillman ◽  
...  
Keyword(s):  
Rna Silencing ◽  
Expression System ◽  
Cryphonectria Parasitica ◽  
Inhibitory Effect ◽  
Chestnut Blight ◽  
Silencing Suppressor ◽  
Terminal Portion ◽  
Transgenic Expression ◽  
Chestnut Blight Fungus ◽  
Cryphonectria Hypovirus

Previously, we have reported the ability of a symptomless hypovirus Cryphonectria hypovirus 4 (CHV4) of the chestnut blight fungus to facilitate stable infection by a co-infecting mycoreovirus 2 (MyRV2)—likely through the inhibitory effect of CHV4 on RNA silencing (Aulia et al., Virology, 2019). In this study, the N-terminal portion of the CHV4 polyprotein, termed p24, is identified as an autocatalytic protease capable of suppressing host antiviral RNA silencing. Using a bacterial expression system, CHV4 p24 is shown to cleave autocatalytically at the di-glycine peptide (Gly214-Gly215) of the polyprotein through its protease activity. Transgenic expression of CHV4 p24 in Cryphonectria parasitica suppresses the induction of one of the key genes of the antiviral RNA silencing, dicer-like 2, and stabilizes the infection of RNA silencing-susceptible virus MyRV2. This study shows functional similarity between CHV4 p24 and its homolog p29, encoded by the symptomatic prototype hypovirus CHV1.

scholarly journals Effect of the media on morphology of Cryphonectria parasitica (Murr.) Barr isolates and their Vegetative Compatibility Groups

2015 ◽  
pp. 38-42
Author(s):  
Gabriella Kovács ◽  
László Radócz
Keyword(s):  
Cryphonectria Parasitica ◽  
Vegetative Compatibility ◽  
Bark Extract ◽  
Chestnut Blight ◽  
Vegetative Compatibility Groups ◽  
Infested Area ◽  
Chestnut Blight Fungus ◽  
Virulent Strains ◽  
Different Types ◽  
The Media

The most dangerous pathogen for the European and American chestnuts is the blight fungus Cryphonectria parasitica (Murrill) Barr. Short after its introduction a big number of chestnut trees were destroyed on the infested area. The control could be really complicated, because of the numerous vegetative compatibility groups of the fungus. There is a type that carries a mycovirus viz. hypovirus in the cytoplasm. We are able to control effectively this pathogen by using mycovirus-carrying strains (called hypovirulent fungal strains also). In laboratory it is easy to multiply the virulent and the hypovirulent strains of the fungus but do not easy to differentiate colonies visually on simple PDA medium. During our research, we tested different types of media, based on potato and chestnut bark extract respectively. It was observed that on potato medium the virulent strains produce more orange pigments. So it is more easy to differentiate virulent or hypovirulent isolates of chestnut blight fungus based on colony colour and morphology.

scholarly journals Incidence and Diversity of Double-Stranded RNAs Occurring in the Chestnut Blight Fungus, Cryphonectria parasitica, in China and Japan

1998 ◽  
Vol 88 (8) ◽  
pp. 811-817 ◽  
Author(s):  
Tobin L. Peever ◽  
Yir-Chung Liu ◽  
Kerong Wang ◽  
Bradley I. Hillman ◽  
Robert Foglia ◽  
...  
Keyword(s):  
New Jersey ◽  
North America ◽  
North American ◽  
Cryphonectria Parasitica ◽  
Liaoning Province ◽  
Chestnut Blight ◽  
Chestnut Blight Fungus ◽  
China And Japan ◽  
Hybridization Group ◽  
Cryphonectria Hypovirus

Isolates of the chestnut blight fungus, Cryphonectria parasitica, were randomly sampled from 10 subpopulations in China and 8 subpopulations in Japan and screened for the presence of double-stranded (ds) RNA using an immunoblot procedure with a monoclonal antibody specific for dsRNA. The overall incidence of dsRNA in C. parasitica was 2 and 6% in China and Japan, respectively, much lower than the 28% found previously in North American populations. Genetic relatedness of dsRNAs within and among populations in China and Japan was examined using RNA-RNA hybridizations with labeled-dsRNA probes. The majority of Chinese and Japanese dsRNAs were members of a single hybridization group, related to Cryphonectria hypovirus 1 (CHV1) from Europe, and are referred to as CHV1-type dsRNAs. No evidence was obtained for genetic differentiation between CHV1-type dsRNAs sampled in China and Japan. Five Japanese isolates contained two genetically distinct dsRNAs. The larger segments (approximately 12 kilobases [kb]) were members of the CHV1 hybridization group, while the smaller segments (approximately 3 kb) did not hybridize with any known dsRNA from C. parasitica including the 2.7-kb dsRNA from isolate NB631 from New Jersey or dsRNA from isolate RC1 from Michigan. Two small dsRNA segments (approximately 1.8 and 2 kb) from one isolate sampled from Liaoning Province in northeastern China did not hybridize with any of the dsRNA probes tested including several described dsRNAs of similar size from C. parasitica in North America. Three dsRNAs from Anhui Province, China, hybridized to Cryphonectria hypovirus 2 (CHV2)-specific probes and are thus referred to as CHV2-type dsRNAs. Sequence analysis of 1,627 base pairs of these three CHV2-type dsRNAs from Anhui revealed that they were identical to each other in the region sequenced and very closely related to CHV2-NB58, isolated from New Jersey. We speculate that CHV2-NB58 may have been introduced into North America from this part of China. This is the first record of a North American C. parasitica dsRNA that is genetically related to a dsRNA from Asia.

scholarly journals Detection of natural infection of Quercus spp. by the chestnut blight fungus (Cryphonectria parasitica) in Hungary

2002 ◽  
Vol 8 (2) ◽  
Author(s):  
L. Radócz ◽  
I. J. Holb
Keyword(s):  
Natural Infection ◽  
Cryphonectria Parasitica ◽  
Castanea Dentata ◽  
American Chestnut ◽  
Chestnut Blight ◽  
Chestnut Blight Fungus ◽  
European Chestnut ◽  
Total Destruction ◽  
Quercus Spp ◽  
Endothia Parasitica

The chestnut blight fungus Cryphonectria parasitica (Murrill) Barr [syn.: Endothia parasitica (Murr) Anderson] caused almost total destruction of the American chestnut (Castanea dentata) and widely spread on European chestnut (Castanea saliva) in many European countries. In Hungary, because this fungus threatens most of the Hungarian chestnut stands, great efforts have been made to delay its spread. Biological control with Hungarian hypovirulent strains of the pathogen seems to be an effective method for saving the affected chestnut trees. Until 1998 the fungus was detected on Castanea saliva only, then on some trees of young Quercus petrea in mixed chestnut forests, which also showed the typical symptoms of blight (Kőszeg and Zengővárkony). Although blight symptoms are not so serious in Quercus spp. than in Castanea spp., it seems that C. parasitica threatens the young Quercus spp. in Hungary, mainly in heavily infected chestnut forests. This is the first report of C. parasitica cankers on oak in Hungary.

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