Spread of Cryphonectria hypovirus1 into 45 vegetative compatibility types of Cryphonectria parasitica on grafted American chestnut trees

Hogan, E. P.; Griffin, G. J.

doi:10.1046/j.1439-0329.2002.00272.x

Cited by 15 publications

(32 citation statements)

References 27 publications

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“…There have been relatively few studies on the impact of CHV‐1 induced hypovirulence using plant material . To our knowledge, this is the first time that the infectivity of virulent and hypovirulent isolates of C. parasitica has been evaluated on chestnut seedlings although other studies have used cut chestnut stems, naturally infected trees or both .…”

Section: Discussionmentioning

confidence: 99%

“…F1 and other subtypes have been found in some parts of France, Spain, eastern Turkey and Germany . The CHV‐1 virus does not occur naturally in USA but is present in a few locations such as in Virginia where it has been released for the biological control of American chestnut blight, Wisconsin or Maryland . In Europe, several genetic recombinations have contributed to the evolution of the CHV‐1 …”

Section: Discussionmentioning

confidence: 99%

“…Since then, many studies have identified various mycoviruses that could be useful tools for chestnut blight control in North America such as CHV‐1, CHV‐2, CHV‐3 and CHV‐4 although the latter does not cause hypovirulence, as well as CpMyRV‐1, or CpMyRV2, CHV‐1 and CHV‐2 found in Asia, and CHV‐1 in Europe . Hogan and Griffin showed evidence of the spread of CHV‐1 among local VCGs of the fungus after introduction from Europe into Virginia; and Zamora et al . also demonstrated that the effectiveness of subtype F1 (commonly known as French subtype) in north‐western Spain was dependent on the fungus VCG.…”

Section: Introductionmentioning

confidence: 99%

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Hypovirulent effect of theCryphonectria hypovirus 1in British isolates ofCryphonectria parasitica

Romon-Ochoa

Gorton

Lewis

et al. 2019

Pest Management Science

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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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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Hypovirulent effect of theCryphonectria hypovirus 1in British isolates ofCryphonectria parasitica

Romon-Ochoa

Gorton

Lewis

et al. 2019

Pest Management Science

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“…In contrast, based on the laboratory transmission results presented here, the application of two SD strains representing the vic2-1 and vic2-2 alleles should convert field strains representing all possible vic genotypic combinations of the defined six diallelic vic genetic loci. The likelihood for successful conversion by SD strains under field conditions is increased when one considers reports that vic-mediated resistance to hypovirus transmission is lower in infected chestnut tissue than in laboratory transmission assays (7,(32)(33)(34)(35). It is anticipated that the use of SD strains as vectors to effectively deliver hypoviruses into natural C. parasitica populations will enhance efforts to integrate hypovirulence-mediated biological control with increased disease resistance derived from backcross resistance breeding programs for woodland restoration of the American chestnut tree.…”

Section: Discussionmentioning

confidence: 99%

Engineering super mycovirus donor strains of chestnut blight fungus by systematic disruption of multilocus vic genes

Zhang

Nuss

2016

Proc. Natl. Acad. Sci. U.S.A.

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Transmission of mycoviruses that attenuate virulence (hypovirulence) of pathogenic fungi is restricted by allorecognition systems operating in their fungal hosts. We report the use of systematic molecular gene disruption and classical genetics for engineering fungal hosts with superior virus transmission capabilities. Four of five diallelic virus-restricting allorecognition [vegetative incompatibility (vic)] loci were disrupted in the chestnut blight fungus Cryphonectria parasitica using an adapted Cre-loxP recombination system that allowed excision and recycling of selectable marker genes (SMGs). SMG-free, quadruple vic mutant strains representing both allelic backgrounds of the remaining vic locus were then produced through mating. In combination, these super donor strains were able to transmit hypoviruses to strains that were heteroallelic at one or all of the virus-restricting vic loci. These results demonstrate the feasibility of modulating allorecognition to engineer pathogenic fungi for more efficient transmission of virulence-attenuating mycoviruses and enhanced biological control potential.M ycovirus infections have been reported to reduce virulence (hypovirulence) for a wide range of plant pathogenic fungi, providing potential for biological disease control (1-6). For hypovirulence to be effective, the virulence-attenuating viruses must be efficiently transmitted from infected hypovirulent strains to uninfected virulent strains (5, 7). Mycoviruses generally have evolved exclusive intracellular lifestyles (8). With very few exceptions (9), mycovirus infections cannot be initiated by exposure of uninfected hyphae to cell extracts or secretions from infected fungal isolates. Transmission is limited to intracellular mechanisms, vertical transmission through asexual spores, and horizontal transmission through anastomosis (fusion of hyphae).Horizontal mycovirus transmission to uninfected isolates of the same fungal species is complicated by nonself allorecognition genetic systems, termed "heterokaryon" or "vegetative incompatibility" (vic), which operate widely in filamentous fungi (10). Interactions between genetically distinct individuals of the same species result in an incompatible reaction that triggers localized programmed cell death (PCD), forming a line of demarcation, or barrage, along the zone of contact (10-12) and restricting cytoplasmic transmission of viruses and other cytoplasmic elements (1,(13)(14)(15).A negative correlation between vic diversity and virus transmission has been reported for several fungal hosts (1, 16), but has most extensively been demonstrated for the chestnut blight fungus Cryphonectria parasitica infected with virulence-attenuating hypoviruses (7,(17)(18)(19)(20). Genetic analyses have defined six diallelic vic genetic loci for C. parasitica (21). These loci and associated genes were recently identified at the molecular level through a comparative genomics approach (22, 23) ( Table 1). Independent gene disruption analysis of 12 genes associated with these loci (22, 23) ...

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“…The inoculated white strains ( Dodds 1980; Elliston 1985; Hillman et al 1995) and white isolates recovered from the grafts, based on hybridization tests ( Robbins and Griffin 1999) and sequence analysis of cDNA generated from dsRNA of 11 graft isolates ( Griffin, Robbins, Hogan and Farias unpublished), are infected with Cryphonectria hypovirus 1 (CHV1). CHV1 has spread throughout the grafted trees and into 45 vc types of C. parasitica ( Hogan and Griffin 2002). In addition, evaluation of in vitro C. parasitica variants, that resemble in vivo variants observed here in spatial pattern and vc compatibility, was undertaken.…”

Section: Introductionmentioning

confidence: 99%

Incomplete movement of Cryphonectria hypovirus 1 within a vegetative compatibility type of Cryphonectria parasitica in natural cankers on grafted American chestnut trees

Hogan

Griffin²

2002

Forest Pathology

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Summary American chestnut trees, grafted in 1980 from large survivors, were inoculated in 1982 and 1983 with four white (European) hypovirulent strains of Cryphonectria parasitica, infected with C. hypovirus 1 (CHV1); this hypovirus has been shown to be capable of moving rapidly within the mycelium of a vegetative compatibility (vc) type of C. parasitica in blight cankers. Using a 49‐cell lattice plot, 17.8×17.8 cm, the spatial patterns and frequencies of white and pigmented isolates and white and pigmented vc types were investigated within superficial cankers on the grafts located outside the hypovirulent‐strain‐inoculated zone. Four of six cankers assayed contained white isolates, and three of the four had random spatial patterns of white isolates, based on join‐count statistics. Vc tests, using pigmented isolates and pigmented single‐spore colonies of white isolates, indicated that the majority of white and pigmented isolates recovered from each of two cankers assayed were in one vc type. White and pigmented lattice‐plot cells of the same vc type were frequently in contact with each other, indicating incomplete movement of CHV1 within a vc type. Nine and 10 vc types were found in the two cankers; it is hypothesized that small, white vc type areas in each canker may be a source of CHV1 transmission to the major vc types. Based on join‐count statistics, the spatial pattern of the single, major vc type in one canker was non‐random (aggregated), whereas the other canker had a random major vc type pattern. White and pigmented in vitro variants (sectors) of C. parasitica, that resemble white and pigmented in vivo variants in spatial contact and vc compatibility, were intermediate hypovirulent and virulent on forest American chestnuts, and dsRNA positive and negative, respectively. Incomplete movement of CHV1 within a vc type could be a major cause of the prevalence of pigmented isolates in superficial cankers on chestnut trees.

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Spread of Cryphonectria hypovirus1 into 45 vegetative compatibility types of Cryphonectria parasitica on grafted American chestnut trees

Cited by 15 publications

References 27 publications

Hypovirulent effect of theCryphonectria hypovirus 1in British isolates ofCryphonectria parasitica

Hypovirulent effect of theCryphonectria hypovirus 1in British isolates ofCryphonectria parasitica

Engineering super mycovirus donor strains of chestnut blight fungus by systematic disruption of multilocus vic genes

Incomplete movement of Cryphonectria hypovirus 1 within a vegetative compatibility type of Cryphonectria parasitica in natural cankers on grafted American chestnut trees

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