Papaya

Abstract

Papaya ( Carica papaya L.) is currently the fastest growing tropical fruit crop in the world. It is a tree‐like, herbaceous, short‐lived perennial plant 3–8 m in height native to tropical America. It is cultivated on farms as well as backyard gardens worldwide in tropical and subtropical regions within 32 degrees latitude north and south of the equator. Fruits can be harvested as early as 9 months after sowing and are anywhere from 255 g to 6 kg, depending on the variety. Papaya is grown largely for its nutritious fresh fruit which contains relatively high amounts of vitamins A, C, and E as well as calcium, potassium, and iron, but also for by‐products such as papain, a proteinase found in the latex of unripe fruit used to tenderize meat and in pharmaceutical industries. Transgenic varieties “Rainbow” and “SunUp” were developed in Hawaii to be resistant to papaya ringspot virus (PRSV), the most devastating disease threatening papaya production worldwide. Development and commercialization of the transgenic papaya in Hawaii serves as a model for successful biotechnology application to specialty crop improvement. Advances in transformation and development of transgenic papaya and the prospects of commercialization in various countries are also discussed.

Papaya ringspot virus‐P: characteristics, pathogenicity, sequence variability and control

“…Although other laboratories have engineered resistance against PRSV using the CP (Bau et al ., 2003; Cheng et al ., 1996; Davis and Ying, 2004; Lines et al ., 2002) or the replicase (Chen et al ., 2001a) genes of PRSV, we will emphasize here the Hawaii transgenic papaya case because the resultant Rainbow and SunUp cultivars are the only transgenic papayas to be deregulated and commercialized, and to be sold and consumed in the mainland US and Canada (Gonsalves, 1998, 2006; Gonsalves et al ., 2004b, 2007a; Suzuki et al ., 2007; Tripathi et al ., 2006).…”

“…By 1997, approvals from all three agencies were granted and in April 1998, licence agreements from all parties were obtained, allowing the commercial cultivation of papaya 55‐1 or its derivatives in the State of Hawaii. The deregulation of Hawaiian transgenic papaya has been previously reviewed (Gonsalves, 1998; Gonsalves et al ., 2007a; Suzuki et al ., 2007). At present, transgenic papaya is widely sold in Hawaii and exported to the mainland US and Canada.…”

“…An overview on the control of PRSV by development of genetically engineered virus resistance in papaya has been included as it is the most successful approach to combat PRSV and it has been commercially implemented in Hawaii. However, PRSV remains a threat to the economic production of papaya and cucurbits worldwide (Fermin and Gonsalves, 2003; Fermin et al ., 2004; Fuchs and Gonsalves, 2007; Gonsalves, 1998, 2006; Gonsalves and Fermin, 2004; Gonsalves and Ferreira, 2003; Gonsalves et al ., 2004a,b, 2006, 2007a,b; Suzuki et al ., 2007; Tripathi et al ., 2006).…”

“…The devastating nature of PRSV on commercial crops is exemplified by the near destruction of the Hawaiian papaya industry in the 1990s (Ferreira et al ., 2002; Gonsalves, 1998, 2006; Gonsalves et al ., 2006, 2007a). This pathogen profile reviews the current knowledge on the biology of PRSV, pathogenesis, genome, isolate/sequence diversity and development of disease control strategies.…”

Current achievements and future directions in genetic engineering of European plum (Prunus domestica L.)

“…Secondly, and perhaps most significantly, transformation may provide for genetic improvements that would otherwise be impossible using traditional breeding. A clear example are the transgenic papaya varieties ‘Rainbow’ and ‘SunUp’ resistant to papaya ringspot virus (PRSV), the most devastating disease threatening papaya production worldwide (Gonsalves et al 2009 ). There is not natural source of PRSV resistance in the papaya germplasm, and genetic transformation allowed the production of PRSV resistant cultivars fast enough to fight against an emergent disease in Hawaii during the 90 s.…”