Family: Botourmiaviridae

Genus: Gammascleroulivirus

Distinguishing features

Gammasclerouliviruses have a mono-segmented genome. Members of the genus have been identified in association with grapevine leaves affected by infection with the oomycete Plasmopara viticola, and are phylogenetically distinct from other botourmiaviruses. The genome of Magnaporthe oryzae botourmiavirus 6 is polyadenilated at the 3′-end (Liu et al., 2020).

Virion

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

Genome organization and replication

The Plasmopara viticola lesion associated ourmia-like virus 49 (PvaOLV49) genome is a (+) RNA molecule of 2 412 nucleotides with 54% GC content. The complete genome sequence has a 5′ non-coding region (NCR) of 50 nt and a 3′-NCR of 408 nt. The virus genome contains a single open reading frame (ORF) from nt positions 51 to 2 004, predicted to encode a polypeptide of 650 amino acids (72.54 kDa) that has similarity to the RNA-directed RNA polymerases (RdRP) of other gammasclerouliviruses (Chiapello et al., 2020). Plasmopara viticola lesion associated ourmia-like virus 50 (PVaOLV50) has a genome of 2 408 nt with a single ORF coding for an RdRP of 637 aa (Chiapello et al., 2020). The Magnaporthe oryzae botourmiavirus 6 genome is 2 385 nt in length, including a 1 989 nt unique putative ORF from nt positions 28 to 2016, encoding an RdRp of 662 amino acids (Liu et al., 2020).

Biology

PvaOLV49 and Plasmopara viticola lesion associated ourmia-like virus 50 (PVaOLV50) have been identified in grapevine leaves affected by infection with the plant pathogenic oomycete Plasmopara viticola (Chiapello et al., 2020). Magnaporthe oryzae botourmiavirus 6 has been found associated with leaves showing symptoms of infection with Magnaporthe oryzae (Liu et al., 2020).

Species demarcation criteria

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