Family: Potyviridae
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 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 (Figure1.Rymovirus) and replication strategy similar to other members of the Potyviridae with monopartite genomes (Figure 2.Potyviridae).
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| Figure 1.Rymovirus Schematic diagram of the ryegrass mosaic virus (RMV) genome. The polyprotein ORF is indicated by the large open box divided into putative mature proteins. The pretty interesting Potyviridae protein (PIPO) is represented by a small box. The untranslated regions (UTR) are represented by lines on each end of the large ORF. Activities of mature proteins are postulated by analogy with genus Potyvirus. Conventions are as for the potyvirus genome organization map (Figure 2.Potyviridae). Not to scale. |
Biology
Host range
Most rymoviruses have limited, but widespread host ranges within the family Poaceae, whereas 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.
Antigenicity
Particles of most rymoviruses are moderately immunogenic. HoMV and AgMV are serologically related.
Species demarcation criteria
See discussion under family description.