ABSTRACT
The term papaya ringspot (PRS) was first coined by Jensen in 1949 to describe a papaya disease in Hawaii. The inevitable entry of Papaya ringspot virus (PRSV) into the Puna district on Hawaii Island was discovered during the first week of May in a papaya field in Pahoa, 1-3 miles from the major papaya growing areas in Puna (Hawaii). Diseases such as papaya mosaic (caused by Papaya mosaic virus (PapMV)) and watermelon mosaic (caused by Watermelon mosaic virus-1) were shown recently to be caused by PRSV. The PRSV causes a major disease of papaya and cucurbits and is found in all areas of the world where papaya and cucurbits are cultivated. The primary host range of PRSV is limited to papaya (Caricaceae) and cucurbits (Cucurbitaceae), with Chenopium amaranticolor and C. quinoa (Chenopodiaceae) serving as local lesion hosts. The virus is grouped into the papaya infecting biotype (PRSV-p) which affects papaya and/or cucurbits, and the cucurbit infecting biotype (PRSV-w) which affects cucurbits only. PRSV belongs to family Potyviridae, genus potyvirus and is an aphid-transmissible RNA virus that commonly infects papaya, causing serious disease and economic loss. Virions of PRSV are rod-shaped and flexuous measuring 760-800 × 12 nm with a monopartite single-stranded positive sense RNA as its genome. Like other potyviruses, PRSV is transmitted in a nonpersistent manner by several species of aphids. Genetically engineered papaya has been used to successfully control the disease caused by PRSV in Hawaii. The virus, PRSV, is transmitted non-persistently by aphid vectors and does not multiply in the vector. The disease cycle can start with aphids feeding on infected papaya for as little as 15 s and subsequently feeding on a healthy papaya. There is no incubation period. The virus does not persist in the vector so transmission to another plant has to occur rather rapidly (Gonsalves et al. 2010).
