Population biology of the chestnut blight fungus, Cryphonectria parasitica

1995 ◽  
Vol 73 (S1) ◽  
pp. 311-319 ◽  
Author(s):  
Michael G. Milgroom
Keyword(s):  
Gene Flow ◽  
North America ◽  
Population Biology ◽  
Random Mating ◽  
Cryphonectria Parasitica ◽  
Vegetative Compatibility ◽  
Chestnut Blight ◽  
Vegetative Compatibility Groups ◽  
Chestnut Blight Fungus ◽  
Endothia Parasitica

Interest in the population biology of the chestnut blight fungus Cryphonectria parasitica has been motivated largely by the potential for biological control of chestnut blight with fungal viruses that cause hypovirulence. Earlier studies gave valuable insights into the correlation between diversity of vegetative compatibility groups and transmission of hypovirulence viruses. However, inferences about evolutionary processes affecting populations were not possible because vegetative compatibility groups are not genetically defined. Using restriction fragment length polymorphism markers, however, progress has been made in studying the origin of C. parasitica in North America, gene flow among populations, dispersal within populations, and recombination and the mating system. Cryphonectria parasitica populations in North America are genetically more similar to populations in Japan than in China, which is consistent with previous speculations that this fungus was introduced from Japan. Populations in China and Japan are quite different, suggesting little or no gene flow between these areas. Restricted gene flow and genetic drift are probably the dominant evolutionary forces shaping North American populations, with approximately 20% of gene diversity due to differences among populations (GST = 0.20). Two populations of C. parasitica in Michigan and one population in Italy are primarily clonal in structure. In contrast, sexual reproduction appears to be common in populations in eastern North America, although most of these populations deviate significantly from random mating. Deviations from random mating are most likely due to self-fertilization (uniparental inbreeding), restricted dispersal of male gametes, and mating between individuals that are more closely related genetically than would be expected by chance (biparental inbreeding). Aggregations of similar genotypes in space suggest that populations of C. parasitica may be structured into genetic neighborhoods by restricted dispersal. Future research efforts in this system will explore isolation by distance and address questions of hypovirulence virus coevolution with its fungal host. Key words: Cryphonectria parasitica, Endothia parasitica, chestnut blight, genetic neighbourhoods, inbreeding.

Spatial pattern analysis of vegetative compatibility groups in the chestnut blight fungus, Cryphonectria parasitica

1991 ◽  
Vol 69 (7) ◽  
pp. 1407-1413 ◽  
Author(s):  
Michael G. Milgroom ◽  
William L. MacDonald ◽  
Mark L. Double
Keyword(s):  
Average Distance ◽  
Cryphonectria Parasitica ◽  
Mantel Test ◽  
Vegetative Compatibility ◽  
Chestnut Blight ◽  
Spatial Pattern Analysis ◽  
Vegetative Compatibility Groups ◽  
Clear Cut ◽  
Chestnut Blight Fungus ◽  
Endothia Parasitica

Vegetative compatibility groups were determined for 914 isolates of the chestnut blight fungus, Cryphonectria (Endothia) parasitica, collected over a 5-year period from American chestnut trees in eight regenerating clear-cut plots. We tested the hypothesis that the average distance between individuals in the same vegetative compatibility group is not different from the average distance between individuals with vegetative compatibility assigned at random. Nonrandom patterns were detected in all plots at least once during the study, indicating that vegetative compatibility groups were often aggregated. However, when multiple occurrences of vegetative compatibility groups on the same tree were eliminated from the analysis, there was only one test (out of 98 in total) in which the null hypothesis was rejected. We conclude that nonrandom patterns of vegetative compatibility groups are due primarily to multiple occurrences of vegetative compatibility groups on the same trees. Nearly half of all new cankers detected once the epidemic got started were in the same vegetative compatibility groups as cankers previously resident on the same tree. These data are consistent with the hypothesis that populations of C. parasitica are partly clonal in structure. Key words: Endothia parasitica, hypovirulence, Mantel test, matrix comparison, spatial autocorrelation.

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 Some new findings of Cryphonectria parasitica (Murrill) M. E. Barr in the Czech Republic

2010 ◽  
Vol 46 (No. 1) ◽  
pp. 19-24 ◽  
Author(s):  
L. Jankovský ◽  
D. Palovčíková ◽  
P. Haltofová
Keyword(s):  
Czech Republic ◽  
Cryphonectria Parasitica ◽  
Climatic Conditions ◽  
Vegetative Compatibility ◽  
Chestnut Blight ◽  
The Czech Republic ◽  
Vegetative Compatibility Groups ◽  
Ornamental Tree ◽  
New Information ◽  
New Findings

This study provides new information on the distribution of the chestnut blight agent Cryphonectria parasitica and its vegetative compatibility groups (VCGs) in the Czech Republic. This study has revealed the presence of the disease in six localities. The VCG tests showed that each locality was represented by a single distinct VCG, which was different from the others collected in the country. The tests with 31 European testers of C. parasitica VCGs (EU-1 to EU-31) had assigned Czech isolates to VCGs EU-1, EU-4, EU-12, EU-13, EU-15, and EU-19. Moreover, the study showed that in the Czech Republic chestnut blight attacks young trees, not exceeding 35 years of age, and that climatic conditions in the country are suitable for C. parasitica. As two of the diseased localities were ornamental tree nurseries, one might expect its further spread over the country as a result of plant trade. The origin of infection remains unknown in all the localities where C. parasitica was detected.  

scholarly journals Hyperparasites Influence Population Structure of the Chestnut Blight Pathogen, Cryphonectria parasitica

2013 ◽  
Vol 103 (12) ◽  
pp. 1280-1286 ◽  
Author(s):  
Joshua C. Springer ◽  
Anita L. Davelos Baines ◽  
Dennis W. Fulbright ◽  
Matthew T. Chansler ◽  
Andrew M. Jarosz
Keyword(s):  
Population Structure ◽  
North America ◽  
Asexual Reproduction ◽  
Population Level ◽  
Cryphonectria Parasitica ◽  
Chestnut Blight ◽  
Chestnut Blight Fungus ◽  
History Of ◽  
Fungal Populations ◽  
Pathogen Populations

Vegetative compatibility (VC) is commonly used to characterize structure and diversity in fungal populations. In the chestnut blight fungus, Cryphonectria parasitica, high VC diversity is hypothesized to be responsible for the failure of hyperparasitic mycoviruses to spread through pathogen populations in North America. To test this hypothesis, we assessed VC diversity at three recovering sites in Michigan where mycoviruses had invaded and compared them with four epidemic population sites where mycoviruses were absent. VC diversity was assessed for samples collected in 1996 and 2009, which allowed us to determine how C. parasitica populations changed with time. Twelve VC types were found in 1996 while 29 were found in 2009; 75% of types overlapped between the sample dates. Sites where mycoviruses were present had unique VC structures with the exception of the recovering population site at County Line where the main VC group was also detected at two epidemic sites. With one exception, epidemic sites contained more VC groups and displayed higher population level diversity than recovering sites. Mating-type analyses of blight populations revealed that two of three recovering populations were significantly skewed for MAT2 suggesting asexual reproduction, while epidemic sites with a long history of blight infection had ratios near 50:50 suggesting sexual reproduction. We propose that selection in the largely asexual C. parasitica populations at two recovering sites favors the most-fit fungal genotype by mycovirus combination and results in reduced diversity relative to the sexually reproducing pathogen populations at epidemic sites.

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 DNA fingerprinting and analysis of population structure in the chestnut blight fungus, Cryphonectria parasitica.

Genetics ◽  
1992 ◽  
Vol 131 (2) ◽  
pp. 297-306 ◽  
Author(s):  
M G Milgroom ◽  
S E Lipari ◽  
W A Powell
Keyword(s):  
Population Structure ◽  
Null Hypothesis ◽  
Random Mating ◽  
Population Sample ◽  
Cryphonectria Parasitica ◽  
The Other ◽  
Chestnut Blight ◽  
Dna Fingerprints ◽  
Restriction Fragments ◽  
Chestnut Blight Fungus

Abstract We analyzed DNA fingerprints in the chestnut blight fungus, Cryphonectria parasitica, for stability, inheritance, linkage and variability in a natural population. DNA fingerprints resulting from hybridization with a dispersed moderately repetitive DNA sequence of C. parasitica in plasmid pMS5.1 hybridized to 6-17 restriction fragments per individual isolate. In a laboratory cross and from progeny from a single perithecium collected from a field population, the presence/absence of 11 fragments in the laboratory cross and 12 fragments in the field progeny set segregated in 1:1 ratios. Two fragments in each progeny set cosegregated; no other linkage was detected among the segregating fragments. Mutations, identified by missing bands, were detected for only one fragment in which 4 of 43 progeny lacked a band present in both parents; no novel fragments were detected in any progeny. All other fragments appeared to be stably inherited. Hybridization patterns did not change during vegetative growth or sporulation. However, fingerprint patterns of single conidial isolates of strains EP155 and EP67 were found to be heterogenous due to mutations that occurred during culturing in the laboratory since these strains were first isolated in 1976-1977. In a population sample of 39 C. parasitica isolates, we found 33 different fingerprint patterns with pMS5.1. Most isolates differed from all other isolates by the presence or absence of several fragments. Six fingerprint patterns each occurred twice. Isolates with identical fingerprints occurred in cankers on the same chestnut stems three times; isolates within the other three pairs were isolated from cankers more than 5 m apart. The null hypothesis of random mating in this population could not be rejected if the six putative clones were removed from the analysis. Thus, a rough estimate of the clonal fraction of this population is 6 in 39 isolates (15.4%).

scholarly journals Biologische Bekämpfung des Kastanienrindenkrebses auf der Alpennordseite der Schweiz|Biological control of chestnut blight north of the Swiss Alps

2007 ◽  
Vol 158 (11) ◽  
pp. 342-348
Author(s):  
Ursula Heiniger
Keyword(s):  
Biological Control ◽  
Castanea Sativa ◽  
Cryphonectria Parasitica ◽  
Vegetative Compatibility ◽  
Swiss Alps ◽  
Chestnut Blight ◽  
Biologische Bekämpfung ◽  
Chestnut Blight Fungus ◽  
Low Rate

Since 1986 several isolated stands of chestnut (Castanea sativa) located north of the Swiss Alps have been infected with the chestnut blight fungus (Cryphonectria parasitica). At all sites (1–3), the diversity of the vegetative compatibility types was low. To control the disease, the hypovirus CHV1 was introduced at seventeen sites in five cantons. In total, 571 cankers were treated with local C. parasitica isolates containing CHV1. Re-inspection of the cankers one to two years after treatment demonstrated that the percentage of active cankers was significantly reduced in three cantons. Re-isolations of C. parasitica showed that the hypovirus persisted in 33% to 75% of the treated cankers and was disseminated to new cankers at a low rate. The difficulties and the potential of hypovirus treatment of small chestnut stands are discussed.

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