Submitted to: Food and Nutrition Bulletin
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2005
Publication Date: 12/26/2005
Citation: Sakuanrungsirikul, S., Sarindu, N., Prasartsee, V., Chaikiatiyos, S., Siriyan, R., Sriwatanakul, M., Lekananon, P., Kitprasert, C., Boonsong, P., Kosiyachinda, P., Fermin, G., Gonsalves, D. 2005. Update on the development of virus-resistant papaya: Virus-resistant transgenic papaya for people in rural communities of Thailand. Food and Nutrition Bulletin. 26(4):422-426. Interpretive Summary: Papaya is one of the most important and preferred crops in rural communities of Thailand. However, papaya ringspot virus (PRSV) has severely affected papaya in Thailand since the mid 1970s and has affected the availability of papaya to these rural communities. Efforts to use biotechnology to control PRSV in Thailand were started in 1995 through a collaborative effort with Thailand Department of Agriculture and Cornell University. In 1997, transgenic papaya resistant to strains of PRSV were transferred to the research station in Tha Pra in Northeast Thailand. Greenhouse and confined field experiments showed that the transgenic papaya was resistant to PRSV and greatly outperformed nontransgenic papaya when both types of plants were exposed to PRSV. The transgenic papaya is being studied further with the aim of eventually commercializing the transgenic papaya. This transgenic papaya could have a major impact in making papaya more available to people of rural communities who use papaya as a daily food source.
Technical Abstract: Papaya (Carica papaya L.) is one of the most important and preferred crops in rural communities in Thailand. Papaya ringspot virus (PRSV) is a serious disease of papaya throughout Thailand. Efforts to control the virus by various methods either have not been successful or have not resulted in sustainable control. In 1995, collaborative research by the Department of Agriculture of Thailand and Cornell University to develop transgenic papaya resistant to PRSV was initiated. Two local Thai cultivars were transformed by microprojectile bombardment with the use of a nontranslatable coat protein gene of PRSV from Khon Kaen. Numerous kanamycin-resistant plants were regenerated and were inoculated with the PRSV Khon Kaen isolate for selection of resistant lines. Since 1997, promising R0 transgenic lines have been transferred to the research station at Thapra for subsequent screenhouse tests and selection of the most PRSV-resistant lines. In selection set 1, three R3 lines initially derived from Khaknuan papaya showed excellent resistance to PRSV (97% to 100%) and had a yield of fruit 70 times higher than nontransgenic Khaknuan papaya. In selection set 2, one R3 line initially derived from Khakdam papaya showed 100% resistance. Safety assessments of these transgenic papayas have so far found no impact on the surrounding ecology. No natural crossing between transgenic and nonmodified papaya was observed beyond a distance of 10 m from the test plots. Analysis of the nutritional composition found no differences in nutrient levels in comparison with the nonmodified counterparts. Molecular characterization by Southern blotting revealed three copies of the transgene presented; however, no coat protein product was expressed. Data on additional topics, such as the effects of feeding the transgenic papaya to rats and the stability of the gene inserts, are currently being gathered.