Complex transmission of partiti-, ambi- and ourmiaviruses in the forest pathogen Heterobasidion parviporum.

Utilizing Heterobasidion partitivirus 13 strain an1 (HetPV13-an1) and 15 strain pa1 (HetPV15-pa1) in co-infection is considered a potential biocontrol approach against Heterobasidion root and butt rot. Both partitiviruses mediate debilitating effects in most Heterobasidion host isolates and are generally transmitted efficiently between host strains. In this investigation, we conducted transmission experiments in the laboratory (in vitro) using several H.

Virus transmission frequencies in the pine root rot pathogen Heterobasidion annosum.

The combined use of Heterobasidion partitiviruses 13 and 15 (HetPV13-an1 and HetPV15-pa1) is considered a promising biocontrol approach against Heterobasidion root and butt rot. In a previous study, the transmission frequency of HetPV15-pa1 was found to be higher from a double partitivirus-infected donor than from a single partitivirus-infected donor. In this study, we included a wider array of recipient isolates to assess whether the phenomenon is widespread across different host strains and conducted transmission experiments on artificial media (in vitro) using a total of 45 different H.

Diversity and impact of single-stranded RNA viruses in Czech populations.

comprises some of the most devastating pathogens of conifers. Exploring virocontrol as a potential strategy to mitigate economic losses caused by these fungi holds promise for the future. In this study, we conducted a comprehensive screening for viruses in 98 .

, a novel ribovirian phylum for viruses with viroid-like properties.

Fungi harbor a vast diversity of mobile genetic elements (MGEs). Recently, novel fungal MGEs, tentatively referred to as 'ambiviruses,' were described. 'Ambiviruses' have single-stranded RNA genomes of about 4-5 kb in length that contain at least two open reading frames (ORFs) in non-overlapping ambisense orientation.

Discovery and Identification of Viruses Infecting Oomycetes.

This chapter describes protocols suitable for the detection and identification of RNA viruses infecting oomycetes (so-called water molds of Kingdom Heterokonta, Stramenopila), focusing on species of Phytophthora and exemplified by P. fragariae. The protocol includes laboratory procedures for oomycete cultivation and total RNA extraction from harvested mycelia, followed by instructions on suitable parameters given for sequencing companies on ribosomal RNA depletion, cDNA library preparation, and total RNA-sequencing (RNA-Seq).

Detection of single nucleotide polymorphisms in virus genomes assembled from high-throughput sequencing data: large-scale performance testing of sequence analysis strategies.

Recent developments in high-throughput sequencing (HTS) technologies and bioinformatics have drastically changed research in virology, especially for virus discovery. Indeed, proper monitoring of the viral population requires information on the different isolates circulating in the studied area. For this purpose, HTS has greatly facilitated the sequencing of new genomes of detected viruses and their comparison.

Mycoviruses as a part of the global virome: Diversity, evolutionary links and lifestyle.

Knowledge of mycovirus diversity, evolution, horizontal gene transfer and shared ancestry with viruses infecting distantly related hosts, such as plants and arthropods, has increased vastly during the last few years due to advances in the high throughput sequencing methodologies. This also has enabled the discovery of novel mycoviruses with previously unknown genome types, mainly new positive and negative single-stranded RNA mycoviruses ((+) ssRNA and (-) ssRNA) and single-stranded DNA mycoviruses (ssDNA), and has increased our knowledge of double-stranded RNA mycoviruses (dsRNA), which in the past were thought to be the most common viruses infecting fungi. Fungi and oomycetes (Stramenopila) share similar lifestyles and also have similar viromes.

Bunyaviruses Affect Growth, Sporulation, and Elicitin Production in .

is an important oomycetous plant pathogen with numerous host plant species, including garden strawberry ( × ) and silver birch (). also hosts mycoviruses, but their phenotypic effects on the host oomycete have not been studied earlier. In the present study, we tested polyethylene glycol (PEG)-induced water stress for virus curing and created an isogenic virus-free isolate for testing viral effects in pair with the original isolate.

High Diversity of Novel Viruses in the Tree Pathogen Revealed by High-Throughput Sequencing of Total and Small RNA.

, an oomycete pathogen causing root and trunk rot of different tree species in Asia, was shown to harbor a rich diversity of novel viruses from different families. Four isolates collected from in a semi-natural montane forest site in Vietnam were investigated for viral presence by traditional and next-generation sequencing (NGS) techniques, i.e.

Phenotypic Recovery of a Isolate Infected by a Debilitation-Associated Virus Is Related to Altered Host Gene Expression and Reduced Virus Titer.

The fungal genus includes forest pathogenic species hosting a diverse group of partitiviruses. They include the host debilitating Heterobasidion partitivirus 13 strain an1 (HetPV13-an1), which was originally observed in a slowly growing strain 94233. In this study, a relatively fast-growing sector strain 94233-RC3 was isolated from a highly debilitated mycelial culture of 94233, and its gene expression and virus transcript quantities as well as the genomic sequence of HetPV13-an1 were examined.

Going Viral: Virus-Based Biological Control Agents for Plant Protection.

The most economically important biotic stresses in crop production are caused by fungi, oomycetes, insects, viruses, and bacteria. Often chemical control is still the most commonly used method to manage them. However, the development of resistance in the different pathogens/pests, the putative damage on the natural ecosystem, the toxic residues in the field, and, thus, the contamination of the environment have stimulated the search for saferalternatives such as the use of biological control agents (BCAs).

Discovery and Community Dynamics of Novel ssRNA Mycoviruses in the Conifer Pathogen .

species are highly destructive basidiomycetous conifer pathogens of the Boreal forest region. Earlier studies have revealed dsRNA virus infections of families and in strains, and small RNA deep sequencing has also identified infections of members in these fungi. In this study, the virome of was examined for the first time by RNA-Seq using total RNA depleted of rRNA.

RNA-Dependent RNA Polymerase from Heterobasidion RNA Virus 6 Is an Active Replicase In Vitro.

Heterobasidion RNA virus 6 (HetRV6) is a double-stranded (ds)RNA mycovirus and a member of the recently established genus within the family . The purpose of the study was to determine the biochemical requirements for RNA synthesis catalyzed by HetRV6 RNA-dependent RNA polymerase (RdRp). HetRV6 RdRp was expressed in and isolated to near homogeneity using liquid chromatography.

Towards the Forest Virome: High-Throughput Sequencing Drastically Expands Our Understanding on Virosphere in Temperate Forest Ecosystems.

Thanks to the development of HTS technologies, a vast amount of genetic information on the virosphere of temperate forests has been gained in the last seven years. To estimate the qualitative/quantitative impact of HTS on forest virology, we have summarized viruses affecting major tree/shrub species and their fungal associates, including fungal plant pathogens, mutualists and saprotrophs. The contribution of HTS methods is extremely significant for forest virology.

Viral diversity in Phytophthora cactorum population infecting strawberry.

Eighty-eight Phytophthora cactorum strains isolated from crown or leather rot of strawberry in 1971-2019 were screened for viruses using RNA-seq and RT-PCR. Remarkably, all but one isolate were virus-infected, most of them harbouring more than one virus of different genera or species. The most common virus occurring in 94% of the isolates was the Phytophthora cactorum RNA virus 1 (PcRV1) resembling members of Totiviridae.

The virome from a collection of endomycorrhizal fungi reveals new viral taxa with unprecedented genome organization.

Mutualistic plant-associated fungi are recognized as important drivers in plant evolution, diversity, and health. The discovery that mycoviruses can take part and play important roles in symbiotic tripartite interactions has prompted us to study the viromes associated with a collection of ericoid and orchid mycorrhizal (ERM and ORM, respectively) fungi. Our study, based on high-throughput sequencing of transcriptomes (RNAseq) from fungal isolates grown in axenic cultures, revealed in both ERM and ORM fungi the presence of new mycoviruses closely related to already classified virus taxa, but also new viruses that expand the boundaries of characterized RNA virus diversity to previously undescribed evolutionary trajectories.

Mixed infection by a partitivirus and a negative-sense RNA virus related to mymonaviruses in the polypore fungus Bondarzewia berkeleyi.

Virus communities of forest fungi remain poorly characterized. In this study, we detected two new viruses co-infecting an isolate of the polypore fungus Bondarzewia berkeleyi using high-throughput sequencing. One of them was a putative new partitivirus designated as Bondarzewia berkeleyi partitivirus 1 (BbPV1), with two linear dsRNA genome segments of 1928 and 1863 bp encoding a putative RNA-dependent RNA polymerase (RdRP) of 591 aa and a putative capsid protein of 538 aa.

Complete genome sequence of a novel toti-like virus from the plant-pathogenic oomycete Phytophthora cactorum.

This report describes the complete genome sequence of a double-stranded RNA (dsRNA) virus infecting the oomycetous plant pathogen Phytophthora cactorum. The virus genome consists of a single dsRNA segment of 5699 bp with two open reading frames predicted to overlap with each other and encoding a putative capsid protein of 705 aa and an RNA-dependent RNA polymerase of 779 aa. Sequence comparisons indicated that this virus, designated as "Phytophthora cactorum RNA virus 1" (PcRV1), shares the highest sequence similarity with the unclassified Pythium splendens RNA virus 1 (58% RdRp aa sequence identity).

Virus population structure in the ectomycorrhizal fungi Lactarius rufus and L. tabidus at two forest sites in Southern Finland.

Lactarius fungi belong to the Russulaceae family and have an important ecological role as ectomycorrhizal symbionts of coniferous and deciduous trees. Two Lactarius species, L. tabidus and L.

Multiple virus infections on Heterobasidion sp.

Heterobasidion viruses have previously been shown to affect each other's transmission and phenotypic effects on their hosts in a complex way. In this work, Heterobasidion parviporum strains hosting five coinfecting viruses simultaneously were constructed and used as donors in transmission experiments. They showed that viruses move more frequently between the mycelia of the same species than between the mycelia of H.

Mitoviruses in the conifer root rot pathogens Heterobasidion annosum and H. parviporum.

Mitoviral infections are highly common among fungi, but so far only one mitovirus has been described in Heterobasidion spp. conifer pathogens. Here, the occurrence of further mitoviruses was investigated using a previously published RNA-Seq dataset for de novo contig assembly.

Viruses of fungi and oomycetes in the soil environment.

Soils support a myriad of organisms hosting highly diverse viromes. In this minireview, we focus on viruses hosted by true fungi and oomycetes (members of Stamenopila, Chromalveolata) inhabiting bulk soil, rhizosphere and litter layer, and representing different ecological guilds, including fungal saprotrophs, mycorrhizal fungi, mutualistic endophytes and pathogens. Viruses infecting fungi and oomycetes are characterized by persistent intracellular nonlytic lifestyles and transmission via spores and/or hyphal contacts.

Alphapartitiviruses of Wood Decay Fungi Affect Each Other's Transmission and Host Growth.

spp. root rot fungi are highly destructive forest pathogens of the northern boreal forests, and are known to host a diverse community of partitiviruses. The transmission of these mycoviruses occurs horizontally among host strains via mycelial anastomoses.