Articles
Gene flow from commercial transgenic papaya fields into feral populations in Hawaii
Article number
1124_5
Pages
33 – 40
Language
English
Abstract
Commercial release of transgenic papaya cultivars ‘Rainbow’ and ‘SunUp’ in 1998 protected Hawaii’s papaya industry from Papaya ringspot virus. In addition to providing genetically engineered (GE) virus resistance, the transgenes also provided unique genetic markers for tracking movement of papaya seeds and gametes within and beyond agricultural fields.
Beginning a decade after the first release of ‘Rainbow’, our project surveyed the occurrence of the beta-glucuronidase (GUS) marker transgene in feral papaya populations on the islands of Oahu (2010) and Hawaii (2011). Feral papaya plants were defined as plants that were apparently established and growing without human assistance.
In total, 623 feral plants were sampled in wide-ranging surveys, and GUS assays of apical leaf tissues determined that 22% of all plants were transgenic.
GE incidence was greater among feral plants in regions growing GE papayas commercially, compared with incidence in other districts (34 vs. 12% on Oahu and 49 vs. 13% on Hawaii). Oahu’s small but widely dispersed GE production fields resulted in a higher average gene flow (26% of feral plants were GE), relative to that on the island of Hawaii (19%), where a much larger field area of GE papayas is confined to a relatively small geographic region of the island.
GUS assays of 12-seed samples harvested from each of 119 non-GE feral hermaphrodite plants detected no evidence of pollination by GE sources.
In contrast, 16% of 128 non-GE feral female plants had fruit containing at least one GUS-positive seed, indicating cross-pollination with GE plants had occurred.
This finding supports previous research indicating that hermaphrodite Hawaiian solo papaya plants self-pollinate before anthesis, which greatly reduces the possibility of effective cross-pollination.
Beginning a decade after the first release of ‘Rainbow’, our project surveyed the occurrence of the beta-glucuronidase (GUS) marker transgene in feral papaya populations on the islands of Oahu (2010) and Hawaii (2011). Feral papaya plants were defined as plants that were apparently established and growing without human assistance.
In total, 623 feral plants were sampled in wide-ranging surveys, and GUS assays of apical leaf tissues determined that 22% of all plants were transgenic.
GE incidence was greater among feral plants in regions growing GE papayas commercially, compared with incidence in other districts (34 vs. 12% on Oahu and 49 vs. 13% on Hawaii). Oahu’s small but widely dispersed GE production fields resulted in a higher average gene flow (26% of feral plants were GE), relative to that on the island of Hawaii (19%), where a much larger field area of GE papayas is confined to a relatively small geographic region of the island.
GUS assays of 12-seed samples harvested from each of 119 non-GE feral hermaphrodite plants detected no evidence of pollination by GE sources.
In contrast, 16% of 128 non-GE feral female plants had fruit containing at least one GUS-positive seed, indicating cross-pollination with GE plants had occurred.
This finding supports previous research indicating that hermaphrodite Hawaiian solo papaya plants self-pollinate before anthesis, which greatly reduces the possibility of effective cross-pollination.
Authors
R. Manshardt, D. Bishaw, K. Pitz, C.N. Stewart
Keywords
Carica papaya L., GUS transgene, pollen drift, organic production, bioconfinement, coexistence
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