Flower‐visiting insects and their potential impact on transgene flow in rice

Abstract

Summary1. Rice is one of the most important crops in the world. Several transgenic varieties of rice have been developed, and some have recently entered pre-production trials. One concern with genetically modified (GM) crops is transgene escape, but prior studies suggest this risk is low for rice because it is self-pollinated and the dispersal of pollen by wind is limited. 2. Little is known about the impact of pollen transport by insects. We characterized the insects visiting rice plants during anthesis and considered the effects of insect pollination on gene flow. 3. We conducted a 2-year nationwide survey in China and identified more than 510 insect species that visited rice flowers. Honeybees, hoverflies and several other species carried large amounts of pollen. The European honeybee Apis mellifera visited rice flowers regularly with daily foraging activity peaking between 12.00 and 13.00 h. 4. We monitored 20 European honeybee colonies located 100-1000 metres away from rice fields in mixed agricultural landscapes and found the honeybees carried viable pollen at least 500 m away from the rice pollen source. 5. We used four GM rice lines as pollen donors, their non-GM parental varieties as pollen recipients and the European honeybee as the pollinator in field-cage experiments to assess whether honeybees increase the frequency of gene flow in rice. Results from screening over 1Á5 million germinated offspring seeds over a 3-year study period showed that honeybees significantly increase transgene flow in rice. 6. Synthesis and applications. Our results indicate that a remarkably high diversity of insects visit rice flowers in China and that hundreds of species including honeybees carry large amounts of rice pollen. European honeybees carry viable pollen over long distances, forage on rice flowers regularly and increase the frequency of transgene flow. Insects mediate gene flow in rice more than previously assumed, and this should be taken into consideration during the ecological risk assessment of transgene flow in self-pollinated and/or anemophilous crops.

Ingestion of Bt rice pollen does not reduce the survival or hypopharyngeal gland development of Apis mellifera adults

“…Apis mellifera has also been selected as surrogate species in nontarget risk assessments of insect-resistant, genetically engineered plants [5,[8][9][10] because honey bees consume pollen [11][12][13] and because the pollen produced by most insect-resistant, genetically engineered plants contains insecticidal Cry proteins. The honey bee has previously been used to assess the nontarget effects of Bt cotton [14][15][16][17] and maize [18][19][20], but it has rarely been used for Bt rice [8], although many studies have demonstrated that honey bees collect rice pollen as a food source during rice anthesis [21].…”

Fitness correlates of crop transgene flow into weedy populations: a case study of weedy rice in China and other examples

“…Notably, Pu et al. () also reported insect‐mediated pollination in rice, where increased frequency of transgene flow was detected.…”

Integrated pest management for sustainable rice cultivation: a holistic approach

“…This has been largely due to continuing debate over their potential long-term effects and difficulties in managing adaptation by target organisms, particularly in tropical regions where cropping is more intensive (Sudianto et al, 2013;Pu et al, 2014) and in developing nations where farms are small (usually >2 ha) and where area-wide resistance management would be consequently difficult (Teetes, 1994).…”