The Dialectic of Pro-Poor Papaya - The Oxford Topic of Food, Politics, and Society - page 757

Inthesameyear(1986),plantvirologistDennisGonsalvesatCornellUniversitybegan
a project to use pathogen-derived resistance against viruses that affect fruits and vegeta-
bles—principallypapaya,butalsocucumber,watermelon,andsquash.Gonsalves'swork
was given additional real-world relevance by the anticipated likelihood that papaya
ringspot virus would island-hop in Hawaii to affect the main papaya-growing Puna dis-
trictontheBigIsland.Giventhesensitivitiesthatwouldeventuallyarisearoundutiliz-
ing the new transgenic technology in an important food crop, an attractive aspect of the
PDRapproachisthatnoactualproteinisexpressedbytheplant—themereintroduction
of viral DNA into the genome of the papaya plant is enough to shut down viral replica-
tion and thereby prevent infection by the virus.
Gonsalves and his team utilized the newly invented “gene gun” (rather than
Agrobacterium )tointroducetheviruscoatproteingenesintopapaya,togetherwith
new techniques for tissue-culturing transformed plants. The first papaya varieties to be
geneticallyengineeredinthiswayweretheHawaiianred-leshed“Sunset,”whichwas
subsequentlycrossedtotheconsumer-preferredandBigIsland-adaptedyellowleshed
“Kapoho” variety. The resulting transgenic lines demonstrated extremely robust resis-
tance to Hawaiian strains of PRSV. By the end of 1992, the Cornell team began to con-
duct field trials of one of the new papaya varieties at Waimanalo on Oahu island, where
PRSV was first discovered many decades earlier. Giving particular urgency to the proj-
ect, PRSV was indeed discovered in the main papaya-growing Puna region of Hawaii
in the same year, and the virus began to spread rapidly. Despite an eradication program
involving the destruction of thousands of infected papaya trees, within five years the
entire growing region was severely affected and the industry under threat of destruction.
Introduction of Virus-resistant
Transgenic Papaya in Hawaii
In1995alarge-scaleieldtrialofnewtransgenicyellow-leshedF1hybrid“Rainbow”
papaya variety was begun in Puna, Hawaii—resistant papayas were planted in a
virus-infested area, with non-transgenic varieties surrounding the test site as controls.
The reported results were striking: while the susceptible papaya varieties withered under
the pressure of virus infection, the transgenic variety demonstrated near-total resis-
tance,evenwhenphysicallyinoculatedwiththevirus.Yieldsoftheresistant“Rainbow”
varietyweremorethan2,200kg/ha(morethanthreetimestheindustryaverage),as
compared to negligible 56 kg/ha for susceptible “Sunset” variety ater full infection
(Ferreiraet al.2002).Becausethetrialwasundertakenintheprimarypapaya-growing
region, local farmers were able to visit and see evidence of the success of transgenic
papaya at first hand in the field.
Meanwhile,Hawaii'spapayaindustrywassuferingacrisis,andfull-scalecollapse
threatened: by 1998 commercial production had fallen to about half the 1992 level, and