Biotechnology

One of the most virulent diseases to strike a papaya tree or shrub is “Papaya Ringspot Virus”. Once this virus secures a foothold in a field, it can lead to financial ruin and abandonment of the acreage in a matter of two growing seasons.

Figure A

Healthy papaya fields in the Puna District, Hawaii, 1992

Figure B

Severely PRV-infected abandoned papaya fields in the Puna District, Hawaii, 1994

Papaya ringspot is characterized by “. . . a yellowing and stunting of the crown of papaya trees, a mottling of the foliage. . ., shoe-stringing of younger leaves. . ., water-soaked streaking of the stalks. . ., and small darkened rings on the surface of fruit. . .” (State of Hawaii DOA). The leaf canopy of a papaya tree decreases as the disease gains a stronger foothold; as a result, the number, size, and quality of the papayas produced decreases.

By 1995, Hawaii’s papaya industry was faced with economic ruin due to the ringspot virus. 95% of the state’s papaya was grown in the Puna District, and the ringspot virus was decimating field after field. Fortunately, research had already begun in the direction of developing a papaya that was resistant to ringspot disease, as it had previously been detected on Oahu and Maui. By the time ringspot disease was discovered in the Puna District, a field trial of transgenic papaya had been established on Oahu (a transgenic papaya has had its genome altered by the transfer of a gene from another species; in this case, a ringspot resistant gene).
The success of the transgenic papaya was beyond any of the researchers’ wildest dreams.

Figure C

This picture shows a solid block of PRV-resistant Rainbow papaya growing well even though it was planted in the middle of a severely-infected field.

The positive impacts of the use of this biotechnology are the development of a PRV-resistant strain of papaya, the resulting continuation and growth of Hawaii’s papaya industry, and a safe and affordable product for consumers. Interestingly enough, the Hawaiian papaya industry has kept both transgenic and non-transgenic species of papaya in production. The transgenic papaya allows for planting in previously unusable infected acreage, and is sold both domestically and to countries where there are no restrictions against bio-engineered produce. The non-transgenic papaya market is a much smaller industry, but allows the Hawaiian Islands to continue to export their papayas to countries that restrict bio-engineered produce, most notably Japan. Japan accounts for 20% of Hawaii’s export market. On a side note, Canada accounts for 11% of Hawaii’s export market and approved the import of transgenic papaya in January 2003.

This biotechnology has been implemented since 1992 in the countries of Brazil, Jamaica, Thailand, Bangladesh, and several East African countries through a technology transfer program. “. . . [S]tudents or scientists [come] to the host institution (at that time, Cornell University) to develop a transgenic papaya that would be useful in their countries” (APS). As there are varying strains of papaya ringspot virus specific to different nations, this has allowed for development of a transgenic papaya (using papayas from the individual countries) that will be able to resist the particular strain of a particular country.

I could find no health concerns relating specifically to transgenic papaya, and only the concern of durability of the ringspot virus resistance (of which there has been no breakdown noted in transgenic papaya).

Works Cited

“Papaya Ringspot Virus”, State of Hawaii Department of Agriculture, New Pest Advisory No. 02-03, May 2002, http://hawaii.gov/hdoa/pi/ppc/npa-1/npa02-03_prvmaui.pdf

“Transgenic Virus Resistant Papaya: From Hope to Reality for Controlling Papaya Ringspot Virus in Hawaii, The American Phytopathological Society, APSnet, Feature Story July-August 2004, http://www.apsnet.org/ONLINE/FEATURE/RINGSPOT/

All pictures are copied from the aforementioned APSnet feature story