Genus: Rymovirus


Genus: Rymovirus

Distinguishing features

This genus includes three species. Rymoviruses are presumably transmitted by host-adapted populations of eriophyid mite species in a semi-persistent manner. Rymoviruses share a reciprocal monophyletic relationship with members of the genus Potyvirus (French and Stenger 2005).

Virion

Morphology

Virions are flexuous filaments 690–720 nm×11–15 nm in size.

Physicochemical and physical properties

Virion density in CsCl is 1.325 g cm-3 (for ryegrass mosaic virus (RGMV)). Virion Sedimentation coefficient S20,w is 165–166S for most members.

Nucleic acid

Virions contain a single molecule of linear positive-sense ssRNA of about 9.5 kb with a 3′-poly(A) terminus.

Proteins

Rymoviruses encode one type of coat (capsid) protein (CP), with a theoretical Mr of 35,482 Da and an apparent Mr estimated by Western blots of 45 kDa for RGMV.

Genome organization and replication

The complete genome sequences available for isolates of RGMV, Agropyron mosaic virus (AgMV), and Hordeum mosaic virus (HoMV) indicate that rymoviruses have a genome organization and replication strategy similar to other members of the Potyviridae with monopartite genomes (Figure 2.Potyviridae). 

Antigenicity

Particles of most rymoviruses are moderately immunogenic. HoMV and AgMV are serologically related.

Biology

Host range

Most rymoviruses have limited but widespread host ranges within the family Gramineae but some have relatively narrow host ranges.

Transmission

Transmission by eriophyid mites and mechanical transmission have been reported for most members. The eriophyid mites transmitting rymoviruses are different from those transmitting tritimoviruses. The cereal rust mite Abacarus hystrix transmits both RGMV and AgMV, but only the former is efficiently transmitted. No vector is known for HoMV. Recent studies have revealed that host-associated populations of A. hystrix represent a species complex.

Species demarcation criteria

See discussion under family description.

Member species

SpeciesVirus name(s)Exemplar isolateExemplar accession numberExemplar RefSeq numberAvailable sequenceOther isolatesOther isolate accession numbersVirus abbreviationIsolate abbreviation
Agropyron mosaic virusAgropyron mosaic virusND402AY623626NC_005903Complete genomeAgMV
Hordeum mosaic virusHordeum mosaic virusPV81AY623627NC_005904Complete genomeHoMV
Ryegrass mosaic virusryegrass mosaic virusDKY09854NC_001814Complete genomeRGMV

Virus names, the choice of exemplar isolates, and virus abbreviations, are not official ICTV designations.

Derivation of names

Rymovirus: from ryegrass mosaic virus, a member of the type species Ryegrass mosaic virus.