Family: Botourmiaviridae

Genus: Betabotoulivirus

Distinguishing features

Betabotuliviruses 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. Betabotuliviruses are phylogenetically distinct from other botourmiaviruses.

Virion

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

Genome organization and replication

The Entoleuca ourmia-like virus 1 (EnOLV1) genome is a (+) RNA molecule of 3 412 nucleotides with 47 % GC content. The genome has a 5′ non-coding region (NCR) of 322 nt and a 3′ NCR of 534 nt. The virus genome contains a single open reading frame (ORF) from positions 323 to 2 878, predicted to encode a polypeptide of 851 amino acids (97.5 kDa) that has similarity to the RNA-directed RNA polymerases (RdRPs) of other betabotouliviruses. The predicted RdRP of EnOLV1 shows homology with the conserved region in the polymerase protein of other ourmia-like viruses (Velasco et al., 2019). Phaeoacremonium minimum ourmia-like virus 3 has a genome of 2 876 nt with a single ORF coding for a RdRP of 694 aa (Nerva et al., 2019b). Plamospara viticola lesion-associated betabotouliviruses comprise genomes of 2 259 to 2 895 nt in length with an ORF coding for a RdRP of 530 to 694 aa (Chiapello et al., 2020).

Biology

EnOLV infects the plant pathogenic fungus Entoleuca (Velasco et al., 2019). Phaeoacremonium minimum ourmia-like virus 3 was identified in samples of esca symptomatic grapevine plants (Nerva et al., 2019b). Plamospara viticola lesion associated betabotouliviruses were identified in grapevine leaves affected by 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 Betabotoulivirus are less than 90%.