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ABSTRACT
The papaya crop is severely affected by papaya ringspot virus (PSRV) worldwide. This review focuses on efforts to control the destructiveness of the disease caused by PSRV in Hawaii, starting from the use of cross protection to parasite-derived resistance with transgenic papaya expressing the PSRV coat protein gene. A chronology of the research effort is given and related to the development of technologies and the pressing need to control PSRV in Hawaii. The development of commercial virus-resistant transgenic papaya provides a tangible approach to control PSRV in Hawaii. Moreover, the development of transgenic papaya by other laboratories and employment of a mechanism of effective technology transfer to different countries hold promise for control of PSRV worldwide.
KEY WORDS: pathogen-derived resistance, socioeconomic impact, technology transfer, transformation, cross protection
INTRODUCTION
This review covers our efforts to develop control of papaya ringspot virus (PRSV) in papaya, with primary focus on Hawaii. The review traces the evolution of research to control PRSV, the use of transgenic papaya, and its recent commercialization. It is not meant to be an in-depth review of either PRSV or alternate measures in use worldwide to control PRSV in papaya. The information, which is presented chronologically, points out the people involved, interactions of technologies, timing of actions as related to disease occurrence, potentials, and hurdles that must be overcome to use transgenic plants, all in the context of controlling a widespread and severe disease.
THE PAPAYA
Papaya (Carica papaya L.) is an important fruit crop grown widely in tropical and subtropical lowland regions (31). It is largely consumed as a fresh dessert fruit, and the green fruit is often used as salad. Papain is also recovered from the latex of green fruit. The tree is widely planted in home gardens because it is relatively easy to grow from seed; the first mature fruits can be harvested nine months after sowing seeds, and fruit is produced continuously year-round. Although delicious and rich in vitamins A and C (31), the fruit is fragile, a characteristic limiting large-scale exportation to countries in temperate regions. Improvements in postharvest and shipping technologies should enhance commercialization of this crop. In total production, papaya ranks above strawberries and below grapefruit (31). The FAO estimated that about 5.7...