Family: Yadokariviridae

Genus: Alphayadokarivirus


Distinguishing features

Members of the genus Alphayadokarivirus form a distinct lineage to that of betayadokariviruses in phylogenetic analysis of the RdRP protein.



The known capsid donors for members of this genus include the unclassified virus yado-nushi virus 1 (YnV1) and Aspergillus foetidus slow virus 1 (AfSV1, genus Victorivirus, family Totiviridae), which partner with yado-kari virus 1 (YkV1) or Aspergillus foetidus slow virus 2 (AfSV2), respectively (Kozlakidis et al., 2013a, Kozlakidis et al., 2013b, Zhang et al., 2016). The heterocapsids show non-enveloped spherical forms of 33–40 nm diameter.

Physicochemical and physical properties

See the description for the family Yadokariviridae.

Nucleic acid

The heterocapsids of YkV1 and AfSV2 encase the replicative form dsRNA. The accumulation ratio of dsRNA of the alphayadokariviruses to that of the capsid donors is approximately 1:1 in the total virus particles fraction, based on the estimation of band intensity on electrophoretic gels (Kozlakidis et al., 2013a, Kozlakidis et al., 2013b, Zhang et al., 2016).


YkV1 replicative form dsRNA is hetero-encapsidated with the CP of unrelated YnV1 (Zhang et al., 2016). YnV1 CP is produced by the specific cleavage at two sites of a polyprotein encoded by the 5′-proximal ORF. Although the trans-encapsidation of AfSV2 dsRNA by co-infected AfSV1 is suggested by virus particle purification, detailed components of these virus particles have not been examined (Kozlakidis et al., 2013a, Kozlakidis et al., 2013b).

Genome organization and replication

All members of the genus have non-segmented monocistronic (+) RNA genomes that encode a polyprotein containing a 2A-like cleavage peptide (Kozlakidis et al., 2013b, Nerva et al., 2016, Zhang et al., 2016, Gilbert et al., 2019, Chiapello et al., 2020, Sahin et al., 2021). Replication likely occurs inside the heterocapsids as described in the section for the family Yadokariviridae. Among the three completely sequenced alphayadokariviruses, one has a poly(A) tail at the 3′-terminus of the genome (Kozlakidis et al., 2013b, Zhang et al., 2016), while the other two do not (Nerva et al., 2016, Zhang et al., 2016).


Members of the genus have been detected in six ascomycetous fungal species, i.e., Rosellinia necatrix, Aspergillus foetidus, A. homomorphus, Penicillium aurantiogriseum, P. digitatum and Picoa juniperi; the hosts being from Japan, Italy, Turkey, Israel, and China (Kozlakidis et al., 2013b, Nerva et al., 2016, Zhang et al., 2016, Gilbert et al., 2019, Sahin et al., 2021). The alphayadokariviruses from A. homomorphus and P. digitatum have been described from publicly available transcriptomic data and have not yet been isolated (Gilbert et al., 2019). One member was discovered from an environmental sample associated with an oomycetous plant pathogen (Plasmopara viticola) in Italy (Chiapello et al., 2020). The biological roles of alphayadokariviruses have been investigated only for YkV1. YkV1 has a beneficial relationship with its partner dsRNA virus but a harmful relationship with the host fungus (see the descriptions for the family Yadokariviridae).

Species demarcation criteria

· Nucleotide and deduced amino acid sequence (≤ 70% RdRP amino acid sequence identity between members of distinct species)
· Genome organization (e.g., coding strategy)
The genus Alphayadokarivirus includes six species, which include seven different viruses.

Related, unclassified viruses

Virus name Accession number Virus abbreviation
Rhizoctonia solani mycovirus 1 KX349063 RsMV1

Virus names and abbreviations are not official ICTV designations