Current Knowledge of Viruses Infecting Papaya and Their Transgenic Management

Abstract

Papaya (Carica papaya L.), native to the South American continent, is an important horticultural crop cultivated across the tropical and subtropical regions of the globe. Papaya is rich source of vitamin-C and globally it is ranked fourth in total fruit production, next only to bananas, oranges and mangoes. India is the leading producer of papaya and both India and Brazil put together account for more than 50 % of global papaya production. Multiple pests and pathogens are known to inflict damage to papaya, of which viral diseases are the most damaging ones. Of all the viral diseases, papaya ring spot virus (PRSV) belonging to the Potyviridae family is most important one, followed by the viruses belonging to the Geminiviridae family causing leaf curl disease in papaya. Other viral diseases of papaya are Papaya meleira virus (PMeV), Papaya mosaic virus (PapMV), Papaya lethal yellowing virus (PLYV) and several other viruses are known to infect papaya, but may not be of economical significance. Management of viral diseases in papaya is very crucial to accomplish a good harvest, and of all the management practices, genetic engineering papaya for virus resistance is most promising and successful. The PRSV resistant transgenic papaya varieties “SunUp” and “Rainbow” developed by the University of Hawaii and extensively cultivated in the Hawaii islands of United States is the most successful field application of transgenic technology. Since there is significant sequence variation in the PRSV strains from different parts of the world and many more diverse range of viruses are known to infect papaya, there is an urgent need to develop region specific virus resistant papaya.