Family: Botourmiaviridae

Genus: Deltascleroulivirus

Distinguishing features

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

Virion

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

Genome organization and replication

The Botrytis cinerea ourmia-like virus 5 (BcOLV5) genome is a (+) RNA molecule of 3 376 nucleotides with 41% GC content. The complete genome sequence has a 5′ non-coding region (NCR) of 124 nt and a long 3′-NCR of 1 035 nt. The virus genome contains a single open reading frame (ORF) from nt positions 125 to 2 341, predicted to encode a polypeptide of 738 amino acids (83.82 kDa) that has similarity to the RNA-directed RNA polymerase (RdRP) of other penouliviruses. The predicted RdRP of BcOLV5 contains the conserved domains of the RdRP of (+) RNA (motifs I-VIII), including the highly conserved core domain GDD (motif VI) (Ruiz-Padilla et al., 2021). Plasmopara viticola lesion associated ourmia-like virus 64 and Plasmopara viticola lesion associated ourmia-like virus 80 have genomes of 2 697 and 3 000 nt, with a single ORF coding for a RdRP of 722 and 737 aa, respectively (Chiapello et al., 2020).

Biology

BcOLV5 infects the plant pathogenic fungus Botrytis cinerea (Ruiz-Padilla et al., 2021). Plasmopara viticola lesion associated ourmia-like virus 64 and Plasmopara viticola lesion associated ourmia-like virus 80 have been identified in grapevine leaves affected by infection with the plant pathogenic 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 Deltascleroulivirus are less than 90%.