Family: Botourmiaviridae


María A. Ayllón, Massimo Turina, Jiatao Xie, Luca Nerva, Shin-Yi Lee Marzano, Livia Donaire and Daohong Jiang

The citation for this ICTV Report chapter is the summary published as Ayllón et al., (2020):
ICTV Virus Taxonomy Profile: BotourmiaviridaeJournal of General Virology, 101, 454–455. 

Corresponding author: María A. Ayllón (
Edited by: F. Murilo Zerbini and Peter Simmonds
Posted: February 2020, updated September 2021
PDF: ICTV_Botourmiaviridae.pdf (2020 version)


The family Botourmiaviridae includes viruses infecting plants and filamentous fungi with positive-sense single-stranded RNA genomes (Table 1. Botourmiaviridae). The genus Ourmiavirus was previously unassigned to a family and was the subject of a previous ICTV Report chapter and Virus Taxonomy Profile (Turina et al., 2017). The family includes six genera: Ourmiavirus, Botoulivirus, Magoulivirus, Penoulivirus, Rhizoulivirus and Scleroulivirus. Members of the genus Ourmiavirus are plant viruses with non-enveloped bacilliform virions composed of a single coat protein. The genome consists of three segments, each one encoding a single protein. Virions possess a unique structure with a series of discrete lengths from 30 to 62 nm. The RNA-directed RNA polymerase has closest similarity to that of invertebrate viruses related to viruses of the family Narnaviridae; the movement protein is similar to the movement proteins of tombusviruses; the coat protein shows limited similarity to the coat proteins of several plant and animal viruses. Members of the other three genera are non-encapsidated fungal viruses with a genome of 2,000–3,400 nucleotides. Virus full-length genomes contain a unique open reading frame encoding an RNA-directed RNA polymerase with closest similarity to that of ourmiaviruses. 

Table 1Botourmiaviridae Characteristics of members of family Botourmiaviridae




Ourmia melon virus VE9 (RNA1: EU770623; RNA2:EU770624; RNA3: EU770625), species Ourmia melon virus, genus Ourmiavirus


Ourmiavirus: bacilliform (18 nm × 30–62 nm) with a 23.8 kDa coat protein. Members of other genera are not encapsidated 


Positive-sense RNA; monopartite (Botoulivirus, Magoulivirus, Penoulivirus, Rhizoulivirus and Scleroulivirus) (2–3 kb) or tripartate (Ourmiavirus) (2.8; 1.1; 0.97 kb)


Cytoplasmic; virion assembly is coupled to active replication


From genomic RNA; each genomic segment is monocistronic

Host Range

Plants and fungi


Realm Riboviria, kingdom Orthornavira, phylum Lenarviricota, class Miaviricetes, order Ourlivirales; the family Botourmiaviridae includes six genera (Ourmiavirus Botoulivirus, Magoulivirus, Penoulivirus, Rhizoulivirus and Scleroulivirus) and 35 species



The bacilliform virions of ourmiaviruses constitute a series of particles with conical ends (apparently hemi-icosahedra) and cylindrical bodies 18 nm in diameter. The bodies of the particles are composed of a series of double disks, the most common particle having two disks (particle length 30 nm), a second common particle having three disks (particle length 37 nm) with rarer particles having four disks (particle length 45.5 nm) or six disks (particle length 62 nm) (Figure 1. Botourmiaviridae). There is no envelope (Figure 2. Botourmiaviridae). 

Figure 1. Botourmiaviridae.  Diagram of virion surface of a member of the genus Ourmiavirus, showing arrangement and number of double disks and conical ends in particles of different length. Each row of five triangles represents a double disk. 


Figure 2. Botourmiaviridae Virion morphology. (A, B, C) Negative-contrast electron micrographs (uranyl acetate) of purified particles of Ourmia melon virus. The bar represents 100 nm. (D, E) Features of the two commonest particle types, enhanced by photographic superimposition. 

Physicochemical and physical properties

For members of the genus Ourmiavirus the Mr of virions and their sedimentation coefficients are not known. The buoyant density in CsCl of all particle sizes is 1.375 g cm−3. The particles are stable at pH 7. Thermally, ourmiaviruses are relatively stable; infectivity is retained in crude sap after heating for 10 min at 70 °C but not 80 °C, and is retained after at least one freeze–thaw cycle. The particles are stable after CsCl density gradient centrifugation, treatment with Triton X-100, and treatment with chloroform but not n-butanol. 

Nucleic acid

Ourmiaviruses have a genome comprised of three linear, positive-sense, ssRNA molecules. Members of the other three genera have a monosegmented genome. In Ourmia melon virus (OuMV), the three RNAs are 2,814, 1,064 and 974 nt, similar to those of other members of the genus (Rastgou et al., 2009). In Botrytis ourmia-like virus (BOLV) (genus Botoulivirus) the RNA is 2,903 nt (Donaire et al., 2016); members of the genera Botoulivirus , Magoulivirus, Penoulivirus, Rhizoulivirus and Scleroulivirus have similar genomes. The genome of Magnaporthe oryzae ourmia-like virus 1 (MOLV1) isolate Guy11, a representative isolate of the genus Magoulivirus, is polyadenylated at the 3′-end (Illana et al., 2017); this is not observed for members of other genera. 


The single structural protein or coat protein (CP) of Ourmia melon virus is 23.8 kDa and is encoded by RNA3. 


None reported. 


None reported. 

Genome organization and replication

In members of the family Botourmiaviridae, each genomic RNA has one ORF (Figure 3. Botourmiaviridae). RNA1 of Ourmiavirus or the unique RNA of the other three genera encodes a protein carrying the highly conserved core domain GDD typical of an RNA-directed RNA polymerase (RdRP) (Rastgou et al., 2009, Donaire et al., 2016, Illana et al., 2017, Marzano et al., 2016, Marzano and Domier 2016). Ourmia melon virus encodes a 23.8 kDa CP (encoded by RNA3) and the two non-structural proteins RdRP (97.5 kDa, encoded by RNA1) and the movement protein (MP, 31.6 kDa, encoded by RNA2) (Crivelli et al., 2011). Similarly-sized proteins are predicted to be encoded by members of the species, Epirus cherry virus and Cassava virus C (Rastgou et al., 2009). For botourmiaviruses infecting fungi, the single ssRNA segment encoding RdRP is sufficient for replication (Wang et al., 2020). 


Figure 3. Botourmiaviridae Schematic genome organization of representative isolates of the six genera of the family Botourmiaviridae showing the size of each RNA and the positions and coding capacity of the ORFs. CP, coat protein; MP, movement protein; RdRP, RNA-directed RNA Polymerase. 

A protein fusion of the CP to GFP localizes specifically to the nucleolus (Rossi et al., 2014) but there is no direct evidence of the CP in the nucleus during infection (Rossi et al., 2015). Synthesis of CP from actively replicating RNA3 is necessary for both virion assembly and systemic infection of the host (Crivelli et al., 2011). There is no evidence for the presence of subgenomic RNAs or the production of additional proteins by ribosomal readthrough or frameshifting. The MP may undergo post-translational modification. Alanine scanning mutagenesis of conserved residues in the MP showed their importance in determining symptoms, movement, and formation of tubular  structures that may play a role in cell-to-cell movement (Margaria et al., 2016). Details of replication are not known except that CP interferes with the plant silencing defense only in the context of virus infection (Rossi et al., 2015). 

The 81.88 kDa RdRP of Botrytis ourmia-like virus is encoded by the monosegmented genomic RNA (Donaire et al., 2016), and predicted to be similar for members of the other five genera. Mycoviruses can survive inside their fungal hosts without capsid or movement proteins, hence, it is assumed that members of genera Botoulivirus, Magoulivirus, Penoulivirus, Rhizoulivirus and Scleroulivirus may require only the RdRP for their replication. 


Ourmia melon virus can easily be mechanically transmitted to a wide range of dicotyledonous plants (about 40 host species in 15 families have been reported), usually inducing systemic ringspots, mosaic and necrosis, with local lesions on some hosts. Tissue tropism is controlled by the KR-rich region at the amino terminus of the CP (Rossi et al., 2015). No vector has been identified but several species of weeds around infected fields are commonly infected, suggesting horizontal transmission of the virus. However, experimental transmission has not been obtained with several aphid species, the whiteflies Trialeurodes vaporariorum and Bemisia tabaci, or the mite Tetranychus urticae. Attempts at transmission through soil or irrigation water have been unsuccessful. Experimental seed transmission rates are 1–2% in Nicotiana benthamiana and N. megalosiphon. Members of different species in the genus Ourmiavirus occur in geographically diverse areas and on widely different hosts, though there are experimental hosts in common. Members of the other five genera in the family infect fungi in different genera such as Botrytis, Sclerotinia, Magnaporthe, Rhizoctonia, Epiccocum, Neofusicoccum, Acremonium, Phaeoacremonium, Cladosporium, Penicillium, Entoleuca, Colletotrichum, Pyricularia, Phoma, Aspergillus, Phomosis, or have been associated with soybean leaves (Donaire et al., 2016, Illana et al., 2017, Marzano et al., 2016, Marzano and Domier 2016, Wang et al., 2020, Nerva et al., 2019b, Nerva et al., 2019a, Velasco et al., 2019, Guo et al., 2019, Ohkita et al., 2019, Zhou et al., 2020, Gilbert et al., 2019, Li et al., 2019, Hrabáková et al., 2017). 

Sclerotinia sclerotiorum ourmia-like virus 4 (SsOLV4) has been found in cytoplasm and mitochondria, and the infectious clone of this mycovirus could transfer among S. sclerotiorum strains via hyphal anastomosis, suggesting that only the RdRP-coding RNA segment is sufficient for transmission (Wang et al., 2020). 


Virions of Ourmia melon virus (i.e. the assembled coat protein) are good immunogens, as are the tubular structures associated with the MP. Antisera to these proteins do not react in Western blots to proteins in extracts of plants infected with members of either of the other two virus species in the genus Ourmiavirus

Derivation of names

Botoulivirus: from Botrytis and ourmia-like

Botourmiaviridae: from Botrytis and ourmia-like

Ourmiavirus: from Ourmia (Urmia, Orumieh), a city in north-western Iran where the Ourmia melon virus was first found

Magoulivirus: from Magnaporthe and ourmia-like

Penoulivirus: from Penicillium and ourmia-like

Rhizoulivirus: from Rhizoctonia and ourmia-like

Scleroulivirus: from Sclerotinia and ourmia-like

Genus demarcation criteria

The genus Ourmiavirus is clearly separated from the other five genera based on host (plants rather than fungi), the number of genomic segments (three segments rather than one segment) and the presence of a MP and a CP (only for Ourmiavirus). The demarcation criteria for the other five genera that include members infecting fungi, (Botoulivirus, Scleroulivirus, Magoulivirus, Penoulivirus, and Rhizoulivirus) is based on differences in RdRP amino acid sequence. Members of different genera in the family Botourmiaviridae have less than 70 % identity in alignment of the complete RdRP amino acid sequence. 

Relationships within the family

There are six recognized genera within the family Botourmiaviridae. Phylogenetic relationships of conserved regions in the RpRP gene of different genera and species in the family Botourmiaviridae are depicted in Figure 4. Botourmiaviridae. Members of the family form a monophyletic bootstrap supported group, as do each of the six genera. 

Figure 4. Botourmiaviridae Phylogenetic tree of members of the family Botourmiaviridae. A maximum likelihood phylogenetic tree was constructed based on the multiple amino acid sequence alignment of the RNA-directed RNA polymerase (RdRP) using IQ-TREE (version 1.6.11) (Nguyen et al., 2015, Trifinopoulos et al., 2016) with the best-fit model “VT+F+I+G4” and 1,000 replicates ultrafast bootstrap (Minh et al., 2013). Viruses classified in the genera Mitovirus, Narnavirus and Levivirus were used as outgroups. This phylogenetic tree and corresponding sequence alignment are available to download from the Resources page

Relationships with other taxa

Viruses of the genus Ourmiavirus are exceptional, having particles of unique morphology and a unique combination of phylogenetic affinities for the three different genomic RNAs. The MP encoded by RNA2 has clear similarities with the MPs of viruses in the family Tombusviridae (Rastgou et al., 2009). The CP shows distant affinities with the CPs of sobemo, tombus- and luteoviruses (plant viruses) and nodaviruses (animal viruses) (Rastgou et al., 2009). The RdRP encoded by RNA1 has affinity with the RdRP of ourmia-like viruses from invertebrate hosts (Shi et al., 2016)