Update on gene transfer biotechnology of papaya

Abstract

Papaya ringspot virus (PRSV) is the most devastating disease of papayas worldwide. For 15 years, since 1998, genetically engineered, PRSV resistant Hawaii papayas, 'Rainbow', 'SunUp', and 'Laie Gold' have been sold locally and 'Rainbow' has been exported to the western US. Following deregulation, it has been exported for eight years to Canada and for three years, on a very small scale, to Japan. Markets like Hong Kong that do not differentiate between non-transgenic products and genetically engineered organisms (GMOs) also import Hawaii GMO papayas. At least fifteen research groups attempted to develop GMO papayas, mostly for PRSV resistance. A majority of the papayas were resistant to their specific PRSV strains; however at least initially China is the only other country to have commercialized transgenic virus resistant papaya. Activity in GMO projects is reduced because of negative publicity and lack of funding, but several projects continue: delayed ripening in Malaysia and the Philippines (field testing); PRSV and Papaya leaf distortion mosaic virus (PLDMV) broad resistance with single, double, and super-constructs in Taiwan; PRSV resistance construct development in Pune, India; multiplication of transgenic plants for PRSV resistance testing in Hainan, China; transformation of papaya for PRSV resistance with a gene from a papaya relative, Vasconcellea pubescens; and the final stages of deregulation of a second PRSV resistant papaya for Florida in the US.