The Green Fence of Chinese Hibiscus (Hibiscus rosa-sinensis L.) Prevents Pollen Dispersal of Transgenic Rice (Oryza sativa)

Abstract

Transgene escape mediated by pollen dispersal is one of the preeminent concerns about genetically modified crops, including rice. In this study, the rice pollen donor of non-glutinous Oryza sativa ssp. japonica cv. ‘Tainung 67’ [TNG 67] had a greater potential of pollen flow, which was shown by the greater quantity, germination rate, and viability of pollen, than the other rice pollen donor of transgenic AAN. The pollen-mediated gene flow was detected by the frequency of outcrossed seeds in a “checker-board pattern” and alternating row arrangement of rice pollen donor (TNG 67 or AAN) and pollen recipient (glutinous rice ‘TNG 73’) in the fields. We conducted field experiments to assess rice pollen dispersal with or without a “green” fence of Chinese hibiscus, Hibiscus rosa-sinensis L., of approximately 2 m in height and 0.6 m in thickness. Without a green fence, the outcrossing rate of TNG 73 seeds decreased with increasing distance from the pollen donor, from 1.68% at 1 m to 0.01% at 35 m, with no outcrossing beyond 40 m. The outcrossing rate varied with the direction of pollen donor, from 0.05% in the northeastern direction to 0.78% in the southern direction, which was caused by prevailing wind direction. With the green fence, no seeds of TNG 73 were outcrossed. Since a buffer zone of at least 40 m is needed to prevent outcrossing of rice by pollen dispersal in an open field, planting of Chinese hibiscus around the rice field as a green fence would be an effective measure for preventing transgene escape mediated by pollen flow.