| Virus Group IV|
| Potyvirus, Potato virus Y, Papaya ringspot virus, Wheat streak mosaic vi, Wheat spindle streak mo|
The Potyviridae are a family of viruses that encompasses more than 30% of known plant viruses, many of which are of great agricultural significance. Currently, 190 species are placed in this family, divided among eight genera.
Based on the amino acid sequences of their coat proteins, potyviruses are now divided into eight genera. All but the Bymovirus genus are single-stranded particles.
Potyvirus is the largest genus in the family, with more than 100 known species. These viruses are 720–850 nm in length and are transmitted by aphids. They can also be easily transmitted by mechanical means.
The species in the genus Macluravirus are 650–675 nm in length and are also transmitted by aphids.
The plant viruses in the genus Ipomovirus are transmitted by whiteflies and they are 750–950 nm long.
Tritimovirus and the Rymovirus viruses are 680–750 nm long and are transmitted by eriophydid mites. (The rymoviruses are closely related to the potyviruses and may eventually be merged with the potyviruses.)
The Bymovirus genome consists of two particles instead of one (275 and 550 nm) and these viruses are transmitted by the chytrid fungus, Polymyxa graminis.
They are nonenveloped, flexuous filamentous, rod-shaped particles. The diameter is around 12–15 nm, with a length of 200–300 nm.
Genomes are linear and not segmented, bipartite, around 85–12kb in length, consisting of positive-sense RNA, which is surrounded by a protein coat made up of a single viral encoded protein called a capsid. All induce the formation of virus inclusion bodies called cylindrical inclusions (‘pinwheels’) in their hosts. These consist of a single protein (about 70 kDa) made in their hosts from a single viral genome product.
Viral replication is cytoplasmic. Entry into the host cell is achieved by penetration. Replication follows the positive-stranded RNA virus replication model. Positive-stranded RNA virus transcription is the method of transcription. Translation takes place by −1 ribosomal frameshifting. The virus exits the host cell by tubule-guided viral movement. Plants serve as the natural host. The virus is transmitted via a vector (insects). Transmission routes are vector and mechanical.