Family: Botourmiaviridae

Genus: Betascleroulivirus

Distinguishing features

Betasclerouliviruses have a mono-segmented genome and infect fungi. Some members of the genus have been identified in association with grapevine leaves infected with the oomycete Plasmopara viticola. Betasclerouliviruses are phylogenetically distinct from other botourmiaviruses.

Virion

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

Genome organization and replication

The Pyricularia oryzae ourmia-like virus 2 (PoOLV2) genome is a (+) RNA molecule of 1 671 nucleotides with 54% GC content. The complete genome sequence has a 5′ non-coding region (NCR) of 304 nt and a 3′-NCR of 266 nt. The full-length virus genome contains a single open reading frame (ORF) from positions 305 to 1 405, predicted to encode a polypeptide of 366 amino acids (41.42 kDa) that has similarity to the RNA-directed RNA polymerase (RdRP) of other betasclerouliviruses (Ohkita et al., 2019). Botrytis cinerea ourmia-like virus 10 has a genome of 2 430 nt with an ORF coding for a RdRP of 615 aa and has a long 3′-NCR of 536 nt (Ruiz-Padilla et al., 2021). Plamospara viticola lesion-associated betasclerouliviruses have genomes of 2 135 to 2 548 nt and encode RdRPs of 606 to 649 aa (Chiapello et al., 2020).

Biology

PoOLV2 infects the plant pathogenic fungus Pyricularia oryzae (Ohkita et al., 2019). Botrytis cinerea ourmia-like virus 10 was identified in Botrytis cinerea isolated from grapevine (Ruiz-Padilla et al., 2021). Plamospara viticola lesion associated betasclerouliviruses were identified in grapevine leaves showing lesions due to infection with downy mildew (oomycete Plasmopara viticola) (Chiapello et al., 2020).

Species demarcation criteria

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