Scale effect on rice pollen‐mediated gene flow: implications in assessing transgene flow from genetically engineered plants

Abstract

Transgene flow from genetically engineered (GE) crops to non-GE varieties and wild relatives via pollen-mediated gene flow (PMGF) may create food and environmental biosafety concerns. Assessing the level of PMGF from GE crops is required before commercialization. Whether the level of PMGF estimated at relatively small scales can sufficiently represent the actual scenario at large production scales remains unresolved. Here, we estimated average PMGF frequencies from three insect-resistant GE rice lines to their non-GE counterparts at four scales ranging from 9 to 576 m 2 , having the number of GE to non-GE plants constantly at the ratio of 8:1. Based on nearly 1.3 million examined seedlings from non-GE rice plots, very low frequencies (<0.1%) of transgene flow were detected. The highest frequencies were found in plots at the smallest scales. Scale had a significantly negative effect on the frequency of PMGF in rice, with decreased gene flow at increased scale. An extended PMGF model could well represent the experimental data. Field experiments at relatively small scales combined with mathematical modelling could provide useful prediction on the level of rice transgene flow at large production scales. This is probably applicable for other crop species with wind-and self-pollination.Scale effect on rice gene flow J. Rong et al.

Outcrossing Potential between U.S. Blackhull Red Rice and Indica Rice Cultivars

“…Using transgenic insecticide-resistant rice lines from indica-based hybrid breeding systems as a pollen source, OC rates to non-IR rice was , 0.28% at 0.2 m in one study (Rong et al 2007), and 0.0815% in a related study in which a pollen source area of 1 m 2 was imbedded in the center of a 3 by 3-m non-IR plot area (Rong et al 2012). Brownbeard rice and the indica cultivar, MG-63 exhibited substantial overlap in flowering and outcrossing in China .…”

“…Indica rice and U.S. red rice also appear to be better adapted to projected changes in global climate (Ziska and McClung 2008;Ziska et al 2010Ziska et al , 2012. Indica cultivars such as ' , which are commonly used as parents in hybrid rice systems because of their strong outcrossing and hybridization potential, have been investigated in gene flow studies with weedy and wild rice in Asia (Chen et al 2004;Rong et al 2007Rong et al , 2012. Cultivated indica rice has been closely linked evolutionarily with U.S. weedy red rice biotypes (Londo and Schaal 2007;Reagon et al 2010), which may improve the potential for outcrossing and gene flow between these groups.…”

Assessment of the pollen-mediated transgene flow from the plants of herbicide resistant wheat to conventional wheat (Triticum aestivum L.)

“…In our experiment the enlargement of the transgenic pollen donor area from 0.75 to 7.00 m 2 did not significantly affect the average frequency of gene flow, particularly at a distance of 5 m. This observation is in agreement with the results of Rong et al (2007), who showed that transgene flow frequencies were not obviously influenced by the size of GM subplots of rice, predominantly self-pollinated cereal crop. Recent studies on rice involved four field scales ranging from 9 to 576 m 2 revealed that the highest frequencies were found in plots at the smallest scales and that the scale had a significantly negative effect, with decreased gene flow at increased scale in rice (Rong et al 2012). When the plot size of a pollen donor becomes large, the extent of gene flow may rapidly decrease due to the exponential decrease of pollen density, in contrast the increase in the plot size of a pollen recipient would reduce of unwanted transgenic pollen as well (Rong et al 2010).…”

“…Usually the direct measurement of gene flow from a GM crop to non-GM varieties is considered to be impractical and extremely expensive for biosafety assessment at the commercial production scale. However the main challenges for such assessment are to find out whether the gene flow frequency been measured on the basis of a small field experimental scale represents the actual scenario of transgene flow at the large scales of commercial production (Rong et al 2012). Based on the empirical regression model Gustafson et al (2005) predicted that the effect of source field size in the wheat pollen-mediated gene flow would be minimal (\0.1 %).…”

Transgenic cry1Ab/vip3H+epsps Rice with Insect and Herbicide Resistance Acted No Adverse Impacts on the Population Growth of a Non-Target Herbivore, the White-Backed Planthopper, Under Laboratory and Field Conditions

“…Except for the assessment by , little information on the ecological safety of transgenic rice with the fused genes of cry1Ab/vip3H + epsps has been documented. In addition, various reports on the risk evaluations of gene flow have been conducted for transgenic rice lines with herbicide resistance (Lu and Yang 2009;Rong et al 2012). However, the information about the ecological assessments on non-target arthropods has been seldom reported.…”