Family: Botourmiaviridae

Genus: Rhizoulivirus

Distinguishing features

Rhizouliviruses have a mono-segmented genome, infect fungi, and are phylogenetically distinct from other botourmiaviruses.

Virion

No true virions are associated with rhizouliviruses since their genomes have no capsid protein gene.

Genome organization and replication

The Rhizoctonia solani ourmia-like virus 1Rs (RsOLV1) genome is a (+) RNA molecule of 1 901 nucleotides with 57% GC content. The partial virus genome contains a single ORF from nt positions 1 to 1 851, predicted to encode a polypeptide of 616 amino acids (68.47 kDa) (Marzano et al., 2016). Rhizoctonia solani ourmia-like virus 2, Rhizoctonia solani ourmia-like virus 3 and Rhizoctonia solani ourmia-like virus 4 genomes are longer at 3 223 to 4 557 nt, and contain a single open reading frame (ORF) coding for longer RNA-directed RNA polymerases (RdRP) of 998 to 1 259 aa (Picarelli et al., 2019). The genome of Armillaria mellea ourmia-like virus 1 (AmOlV1) is 3 919 nt in length and contains a single ORF from positions 923 to 3 649, predicted to code for a protein of 908 amino acids (Linnakoski et al., 2021). 

Biology

Most currently known members of this genus are reported from a single host, plant pathogenic fungus Rhizoctonia solani (Marzano et al., 2016, Picarelli et al., 2019). Armillaria mellea ourmia-like virus 1 infects the edible fungus Armillaria mellea (Linnakoski et al., 2021).

Species demarcation criteria

Amino acid sequence identities of putative RdRP proteins between viruses belonging to different species in the genus Rhizoulivirus are less than 90%.