Distinguishing features
Waikaviruses have a monopartite genome encapsidated by three capsid proteins; these viruses are transmitted by aphids or leafhoppers.
Virion
See discussion under family description.
Genome organisation and replication
The genomic organization of waikaviruses is similar to that of sequiviruses. However, small ORFs have been identified near the 3ʹ-end of the RNA or overlapping with the main polyprotein but in a different reading frame (Figure 3.Secoviridae) (Chaouch et al., 2004, Thole and Hull 1996, Firth and Atkins 2008). Some experimental evidence has been presented suggesting that subgenomic RNAs are produced from the 3ʹ-region of the RNA (Reddick et al., 1997). The biological significance of the small open reading frames or of the putative subgenomic RNAs is not known. The genomic RNAs are polyadenylated at their 3ʹ-end. The presence of a 5ʹ-linked VPg has not been confirmed experimentally.
Biology
The natural host range of waikaviruses is usually restricted to species within a few plant families (Bockelman et al., 1982). Waikaviruses are not sap-transmitted. Field transmission is in the semi-persistent manner by aphids or leafhoppers. A virus-encoded helper protein is probably needed. Some waikaviruses are helper viruses for the insect transmission of other viruses: anthriscus yellows virus in the case of parsnip yellow fleck virus (PYFV, genus Sequivirus) (Murant and Gould 1968) and rice tungro spherical virus in the case of rice tungro bacilliform virus (family Caulimoviridae) (this association being responsible for the very damaging rice tungro disease) (Hibino 1983).
Species demarcation criteria
See discussion under family description.
Member species
| Species | Virus name | Isolate | Accession number | RefSeq number | Available sequence | Virus Abbrev. | |
|---|---|---|---|---|---|---|---|
| Anthriscus yellows virus | Anthriscus yellows virus | No entry in Genbank | AYV | ||||
| Bellflower vein chlorosis virus | bellflower vein chlorosis virus | CT1 | KT238881 | NC_027915 | Complete genome | BVCV | |
| Maize chlorotic dwarf virus | maize chlorotic dwarf virus | TN | U67839 | NC_003626 | Complete genome | MCDV | |
| Rice tungro spherical virus | rice tungro spherical virus | Shen | M95497 | NC_001632 | Complete genome | RTSV |
Virus names, the choice of exemplar isolates, and virus abbreviations, are not official ICTV designations.
Related, unclassified viruses
|
Virus name |
Accession number |
Virus abbreviation |
|
blackcurrant waikavirus A |
BCWVA |
|
|
red clover associated virus 1 |
RCaV1 |