Family: Alphaflexiviridae

Genus: Sclerodarnavirus

 

Distinguishing features

There is a single species in the genus, Sclerotinia sclerotiorum debilitation-associated RNA virus represented by Sclerotinia sclerotiorum debilitation-associated RNA virus, a capsid-less mycovirus. Despite the lack of capsid, phylogenetic analysis of the replication-associated protein (Rep) places it within the Alphaflexiviridae family (Xie et al., 2006)

Virion 

Morphology

None. 

Physicochemical and physical properties

No information. 

Nucleic acid

A single linear molecule of positive-sense RNA of 5470 nt with a polyadenylated tract at the 3′-terminus (Figure 1. Sclerodarnavirus). 

Proteins

No information available. 

Carbohydrates

Not applicable. 

Genome organization and replication

There is a single ORF encoding a Rep protein of 193 kDa (Figure 1. Sclerodarnavirus). 

Figure 1. Sclerodarnavirus.  Sclerotinia sclerotiorum debilitation-associated RNA virus genome organization. Mtr, methyltransferase; Hel, helicase; RdRP, RNA-directed RNA polymerase. 

Biology

Sclerotinia sclerotiorum debilitation-associated RNA virus was discovered in the plant pathogenic fungus Sclerotinia sclerotiorum and appears to cause debilitation (hypovirulence). 

Derivation of names

Sclerodarna: from Sclerotinia sclerotiorum debilitation-associated RNA virus, the type species of the genus. 

Species demarcation criteria

Since there is currently only a single species in the genus, species demarcation criteria are not yet defined, but , as delineated for other genera in the family, members of distinct species may have less than 72% nt identity (or 80% aa identity) between Rep genes.