Detection of double‐stranded RNA and virus‐like particles in Australian isolates of <i>Pythium irregulare</i>

Gillings, Michael R.; Tesoriero, L.; Gunn, L. V.

doi:10.1111/j.1365-3059.1993.tb01466.x

Cited by 41 publications

(19 citation statements)

References 32 publications

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“…The incidence and variability of mycoviruses has most commonly been determined based on the presence of dsRNAs, which have been found in many common filamentous fungi with incidences ranging from a few per cent to 100% (Table 3). All four phyla of the true fungi, Chytridiomycota, Zygomycota, Ascomycota and Basidiomycota, act as hosts to mycoviruses, as do plant pathogenic oomycetes such as Phytophthora (Hacker et al ., 2005; Tooley et al ., 1989) and Pythium (Gillings et al ., 1993). Mycoviruses are distinct from those viruses that use fungi as vectors because mycoviruses are able to replicate within the fungal host (Rochon et al ., 2004).…”

Section: Diversity and Incidence Of Mycovirusesmentioning

confidence: 99%

Mycoviruses of filamentous fungi and their relevance to plant pathology

Pearson

Beever

Boine

et al. 2009

Molecular Plant Pathology

439

342

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Mycoviruses (fungal viruses) are reviewed with emphasis on plant pathogenic fungi. Based on the presence of virus-like particles and unencapsidated dsRNAs, mycoviruses are common in all major fungal groups. Over 80 mycovirus species have been officially recognized from ten virus families, but a paucity of nucleic acid sequence data makes assignment of many reported mycoviruses difficult. Although most of the particle types recognized to date are isometric, a variety of morphologies have been found and, additionally, many apparently unencapsidated dsRNAs have been reported. Until recently, most characterized mycoviruses have dsRNA genomes, but ssRNA mycoviruses now constitute about one-third of the total. Two hypotheses for the origin of mycoviruses of plant pathogens are discussed: the first that they are of unknown but ancient origin and have coevolved along with their hosts, the second that they have relatively recently moved from a fungal plant host into the fungus. Although mycoviruses are typically readily transmitted through asexual spores, transmission through sexual spores varies with the host fungus. Evidence for natural horizontal transmission has been found. Typically, mycoviruses are apparently symptomless (cryptic) but beneficial effects on the host fungus have been reported. Of more practical interest to plant pathologists are those viruses that confer a hypovirulent phenotype, and the scope for using such viruses as biocontrol agents is reviewed. New tools are being developed based on host genome studies that will help to address the intellectual challenge of understanding the fungal-virus interactions and the practical challenge of manipulating this relationship to develop novel biocontrol agents for important plant pathogens.

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Section: Diversity and Incidence Of Mycovirusesmentioning

confidence: 99%

Mycoviruses of filamentous fungi and their relevance to plant pathology

Pearson

Beever

Boine

et al. 2009

Molecular Plant Pathology

439

342

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“…dsRNA elements observed in fungal isolates can be quite diverse in terms of the size and number of molecules, and several dsRNAs of different sizes infecting the same fungus might correspond to multipartite viral genomes, to mixed infections, or even to defective products of virus replication (14,33). Because of char-acteristics like their persistence in infected hosts or the efficient transmission of mycoviruses to spores, the polymorphic dsRNA profiles detected in fungi have been proposed as markers for distinguishing isolates of different origins within a species (15,21,48). These dsRNA profiles have been associated with a geographical structure in some fungal species (31,54), but often this is not the case (42,49).…”

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confidence: 99%

Prevalence and Diversity of Viruses in the Entomopathogenic Fungus Beauveria bassiana

Herrero

Dueñas

Quesada‐Moraga

et al. 2012

Appl Environ Microbiol

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bViruses have been discovered in numerous fungal species, but unlike most known animal or plant viruses, they are rarely associated with deleterious effects on their hosts. The knowledge about viruses among entomopathogenic fungi is very limited, although their existence is suspected because of the presence of virus-like double-stranded RNA (dsRNA) in isolates of several species. Beauveria bassiana is one of the most-studied species of entomopathogenic fungi; it has a cosmopolitan distribution and is used as a biological control agent against invertebrates in agriculture. We analyzed a collection of 73 isolates obtained at different locations and from different habitats in Spain and Portugal, searching for dsRNA elements indicative of viral infections. The results revealed that the prevalence of viral infections is high; 54.8% of the isolates contained dsRNA elements with viral characteristics. The dsRNA electropherotypes of infected isolates indicated that virus diversity was high in the collection analyzed and that mixed virus infections occurred in fungal isolates. However, a hybridization experiment indicated that dsRNA bands that are similar in size do not always have similar sequences. Particular virus species or dsRNA profiles were not associated with locations or types of habitats, probably because of the ubiquity and efficient dispersion of this fungus as an airborne species. The sequence of one of the most common dsRNA elements corresponded to the 5.2-kbp genome of a previously undescribed member of the Totiviridae family, termed B. bassiana RNA virus 1 (BbRV1).

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“…An isolate of Pythium irregulare , associated with infected Canadian cucumber plants, harboured virions which measured 28 nm in diameter and contained dsRNA (Klassen et al ., 1991). Associated with Australian wheat, another isolate of Pythium irregulare was found to hold dsRNA but these VLPs measured 45 nm in diameter (Gillings et al ., 1993). dsRNA but no VLPs were reported to occur in Pythium butleri (Buck, 1986).…”

Section: Introductionmentioning

confidence: 99%

Different pathotypes of the sunflower downy mildew pathogen Plasmopara halstedii all contain isometric virions†

Heller-Dohmen

Göpfert

Hammerschmidt

et al. 2008

Molecular Plant Pathology

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Eight pathotypes of Plasmopara halstedii were screened to investigate the occurrence of virions and the potential viral influence on the pathogenicity of the sunflower downy mildew pathogen. In 23 of 26 P. halstedii isolates derived from eight countries in Europe, North America and South America, virions were detected by transmission electron microscopy. By contrast, there were no ultrastructural indications of virus-like particles in eight other related Oomycetes. The virions of representative P. halstedii isolates were morphologically and biochemically characterized and compared among each other. Regardless of their host's pathotypes, the geographical origin of the isolate and the sensitivity towards the fungicide metalaxyl, the viral characters obtained were uniform. The virions were isometric and measured approximately 37 nm in diameter. One polypeptide of c. 36 kDa and two segments of single-stranded RNA (3.0 and 1.6 kb) were detected. Both viral RNA segments were detected by capillary electrophoresis in the three remaining P. halstedii isolates where virions were undetectable by transmission electron microscopy. Virus-specific primers for the 1.6 kb-segment were synthesized and used to determine and compare a partial sequence of the viral coat protein among virions of different P. halstedii pathotypes. In all tested isolates, fragments of 0.7 kb were amplified which were directly sequenced. Sequence variation was insignificant. As both less aggressive and more aggressive P. halstedii isolates contained virions, the presence or absence of virions could not explain the diverse aggressiveness of the downy mildew pathogen towards sunflower. Moreover, the results indicated that pathogenicity of P. halstedii was not related to variation in morphological or biochemical characters of the virions.

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Detection of double‐stranded RNA and virus‐like particles in Australian isolates of Pythium irregulare

Cited by 41 publications

References 32 publications

Mycoviruses of filamentous fungi and their relevance to plant pathology

Mycoviruses of filamentous fungi and their relevance to plant pathology

Prevalence and Diversity of Viruses in the Entomopathogenic Fungus Beauveria bassiana

Different pathotypes of the sunflower downy mildew pathogen Plasmopara halstedii all contain isometric virions†

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