Papaya ringspot virus

Papaya ringspot virus (PRSV) is a plant pathogenic virus^[1] in the genus Potyvirus and the virus family Potyviridae.

The virus is a non-enveloped, flexous rod-shaped particle that is between 760-800 nm long and 12 nm in diameter. It is transmitted between plants by mechanical activities like pruning and by numerous aphid species such as Myzus persicae . No seed transmission has been detected.^[2]

There are two major types of this virus that are serologically indistinguishable and are so closely genetically related that they are now considered the same virus species. The type that gave the virus its name are the Type P isolates (PRSV-P). This type infects papaya and several members of the melon family (Cucurbitaceae). The other type, Type W isolates (PRSV-W), does not infect papaya. Isolates of PRSV-W do infect cucurbits such as watermelon, cucumber, and squash and were originally known as Watermelon mosaic virus 1'.'^[3][4]

Both types are distributed worldwide. PRSV-P, for example, is known to be present in the Middle East, Africa, South and Central American. It has also been found in China, France, Germany, India, Italy, Mexico, Taiwan, and the USA. PRSV-W isolates have been found in the USA, the Caribbean, Mexico, Italy, Germany, Australia, France, India, the Middle East, and South America.

This virus produces two types of inclusions visible under a light microscope with proper staining of epidemal strips^[5]. One inclusion is the typical cylidrical inclusion (CI) which is considered diagnostic for the potyvirus group,^[6] and the other is called the amorphous inclusion (AI). The presence of both inclusions can be diagnostic for this virus.^[7]

PRSV-W

In squash, watermelon and other cucurbits, PRSV-W causes mottling and distortion of leaves and fruit. (Symptoms and Inclusions of PRSV-W in Squash) PRSV-W is considered to be one of the limiting factors in the growing of cucurbits in Florida ^[8].

PRSV-W should not be confused with Watermelon mosaic virus 2^[9], another potyvirus that infects cucurbits around the world, including Florida, and which is now known simple as Watermelon mosaic virus (WMV). PRSV has a different host range, different serological properties, and no nucleotide sequence homology with WMV^[10]. WMV also has different cytoplasmic inclusion bodies that can differentiate it from PRSV-W.

Polyclonal and monoclonal antibodies have been made for both of the CI and AI proteins as well as for the capsid protein of PRSV-W ^[11].

References

1. ^ About Plant Viruses
2. ^ Description of Plant Viuses :Papaya ringspot virus
3. ^ Webb & Scott, Phytopathology 55: 895, 1965
4. ^ Purcifull & Hiebert, Phytopathology 69: 112, 1979 (http://www.apsnet.org/phyto/PDFS/1979/Phyto69n02_112.pdf)
5. ^ How to Stain for Plant Virus Inclusions
6. ^ Potyvirus Cylindical Inclusions
7. ^ Inclusions of PRSV
8. ^ Webb, S., Hiebert, E., and Kucharek, T.A. 2003. Identity and distribution of viruses infecting cucurbits in Florida. Phytopathology 93:S89.
9. ^ Watermelon Mosaic Virus Photos
10. ^ Description of Plant Viruses: Watermelon mosaic virus 2
11. ^ Baker, C.A , H. Lecoq, and D.E. Purcifull. 1991. Serological and Biological Variability among Papaya Ringspot Virus Type-W Isolates in Florida. Phytopathology 81: 722-728.(http://www.apsnet.org/phyto/PDFS/1991/Phyto81n07_722.pdf)

External links

• Description of Plant Viruses:Papaya ringspot virus
• Plant Viruses Online:Papaya ringspot virus
• Plant viruses Online:Watermelon mosaic virus 1
• ICTVdB - The Universal Virus Database:Papaya ringspot potyvirus
• ICTVdB - The Universal Virus Database:Watermelon mosaic virus 1
• Family Groups - The Baltimore Method
• Crop Knowledge Master:Papaya ringspot virus (P strain)