Papaya ringspot virus
| Papaya ringspot virus (PRSV) | |
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| Symptoms of PRSV on Papaya tree (a) and fruit (b) | |
| Virus classification | |
| Group: | Group IV ((+)ssRNA) |
| Order: | Unassigned |
| Family: | Potyviridae |
| Genus: | Potyvirus |
| Species: | Papaya ringspot virus |
| Synonyms | |
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Papaya ringspot virus (PRSV) is a pathogenic plant virus 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.
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.
Hawaiian papaya production has been severely affected twice by PRSV. The virus was introduced to Oahu as early as 1937. The disease was mild for a number of years until it either mutated or a more aggressive strain was introduced around 1950. Within 12 years, the amount of land under papaya production dropped 94%. Production was then moved from Oahu to the Puna region of Hawaii island (the "Big Island") under strict quarantine. In 1971 PRSV was found in home gardens but efforts were taken to prevent its spread. The virus emerged in commercial farms in 1992 and by 1995 production in Puna was impossible. Commercial growers again relocated to the Hamakua coast but with only limited success. Hawaiian papaya production was halved by the end of the decade. Transgenic papaya varieties that are resistant to PRSV entered production in 1998 and resuscitated the industry.
Both pathotypes 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 United States. PRSV-W isolates have been found in the United States, the Caribbean, Mexico, Italy, Germany, Australia, France, India, the Middle East, and South America.
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