The Effect Of Papaya Ringspot Virus On Production And Future Means Of Possible Control

Papaya production in most parts of the world has been devastated by the papaya ringspot virus (PRV). This disease costs the papaya industry millions of dollars each year. PRV is transmitted by aphids and causes water-soaked lesions and stunted growth of stems and petioles. Infected leaves are mottled and with severe infection become disfigured. The fruit surface develops ringspots and the fruits are reduced in size, ripen prematurely and become non-marketable. Cultural practices, such as windbreaks, intercropping and regular insect pest control, can at best only delay the outbreak of the disease in the area. Cross protection in which mild virus isolates are used to infect susceptible cultivars has shown variable success. By inserting the coat protein (CP) gene of a PRV strain into papayas, plants can be developed that are immunized to the virus. Papayas have recently been genetically engineered with the CP gene from a virulent Hawaiian strain of PRV. The PRV-CP transgenic plants are resistant to the Hawaiian viral strain but susceptible to PRV strains from other geographical regions, including the Caribbean. The University of the Virgin Islands, in cooperation with the University of Puerto Rico and Cornell University, is working to bioengineer resistance to a Caribbean strain of PRV into papaya cultivars grown in the region.