Asparagus virus 1
Asparagus virus 1 (AV-1) is one of the nine known viruses that affects asparagus plants. It is in the "Potyviridae" family. Initially reported by G. L Hein in 1960, it is a member of the genus Potyvirus and causes no distinct symptoms in asparagus plants. The only known plant that can get AV-1 is asparagus plants. It is spread by aphids vectors, which means that aphids do not cause the AV-1, but they do spread it. Morphology. The virus consists of a capsid. The virus capsid is not enveloped. Capsid / nucleocapsid is elongated with helical symmetry. The  capsid is filamentous, flexuous with a clear modal length with a length of 740 nm and a width of 13 nm. Axial canal is indistinct, the basic helix is obscure. Physicochemical and physical properties. There is one sedimenting component(s) found in purified preparations. The sedimentation coefficient is 146 S20w. A260/A280 ratio is 1.24. The thermal inactivation point (TIP) is at 50-55 °C. The longevity in vitro (LIV) is 2–11 days. Although the titer is dependent on the host, the decimal exponent (DEX) of the dilution endpoint is usually around 3-4. Nucleic acid. The MR of the  genome constitutes 6% of the virus by weight. The genome is monopartite, only one particle size is recovered of linear, positive-sense, single-stranded RNA. Proteins. Proteins constitute around 94% of the virus by weight. The viral genome encodes structural proteins and non-structural proteins. Lipids. Lipids are not reported. Antigenicity. The virus is serologically related to bean yellow mosaic, lettuce mosaic, and turnip mosaic viruses. The virus does not show serological relationships to beet mosaic, iris mild mosaic, and potato Y viruses. Diagnostics and reference collections. Asparagus virus 1 occurs naturally in asparagus plants that often are infected with  tobacco streak, Asparagus 2, or cucumber mosaic viruses. Few, if any, symptoms are caused. Asparagus 1 virus is readily separated from the others because its host range is limited and it causes only necrotic local lesions in Chenopodium quinoa and no symptoms in Cucumis sativus, Phaseolus vulgaris, or Nicotiana tabacum. Transmission and vector relationships. The virus is transmitted by mechanical inoculation. It is not transmitted by contact between hosts, by seeds nor by pollen. The virus is transmitted by arthropods of the order Hemiptera, family Aphididae; Aphis craccivora, Myzus persicae. The principal natural vector(s) are Myzus persicae. The virus is  not transmitted by Aphis gossypii, Macrosiphum euphorbiae. The virus is transmitted in a non-persistent manner. Experimental hosts and symptoms. Under the experimental conditions, susceptibility to being infected by the viruses is found in several families. Susceptible host species are found in the Alliaceae, Amaranthaceae, Asparagaceae, Chenopodiaceae, Tetragoniaceae. The following species were susceptible to experimental virus infection: Allium tuberosum, Asparagus officinalis, Chenopodium album, Chenopodium amaranticolor, Chenopodium capitatum, Chenopodium quinoa, Gomphrena globosa, Tetragonia tetragonioides. Experimentally infected hosts mainly show symptoms of necrotic local lesions. Experimentally infected insusceptible hosts. Families containing insusceptible hosts: Species inoculated with the virus that do not show  signs of susceptibility: Maintenance and propagation hosts. The most commonly used maintenance and propagation host species are Asparagus officinalis, Chenopodium amaranticolor, C. quinoa, Tetragonia tetragonioides. Histopathology. The virus can be best detected in leaves, stems, roots, and mesophyll of the infected plant. Virions are found in the cytoplasm. Cytopathology. Inclusions are present in infected cells. Inclusion bodies in the host cell are found in the cytoplasm. Cytoplasmic inclusions are pinwheels. Inclusions do not contain mature virions. Geographical distribution. The virus is probably distributed worldwide (wherever asparagus is grown commercially).