Influence of gene flow from GM to non-GM soybeans by the size of the pollen donor

Abstract

The use of genetically modified (GM) crops has increased continuously over the world, and concerns about the potential risks of GM crops have also risen. Although, until now, GM crops have not been cultivated commercially in Korea, it is necessary to develop technology for the safe evaluation of GM crops. In this study, we investigated the influence of gene flow from GM to non-GM soybeans by the size of the pollen donor. In the experimental design, GM soybeans were placed in the center as a pollen donor and non-GM soybeans were placed in four directions as the pollen receivers. Three sizes of pollen donor were designed as $90cm{\times}90cm$, $180cm{\times}180cm$, and $360cm{\times}360cm$. A total 22,719 seeds were collected from non-GM soybeans, and 14 hybrids were finally obtained through herbicide resistance screening and PCR analysis. The highest hybridization rate was 0.78% at a distance of 15 cm from a $360cm{\times}360cm$ GM pollen donor, and the farthest distance of hybridization was 180 cm from a GM pollen donor which was $360cm{\times}360cm$ in size. Ten hybrids were found among the 14 hybrids at the $360cm{\times}360cm$ pollen donor size, 3 hybrids at $180cm{\times}180cm$, 1 hybrid at $90cm{\times}90cm$. From these results, it could be concluded that with the larger pollen donor size, more hybridization occurred in soybeans.

Fig. 1. Diagrammatic representation of experimental design for gene fow. Genetically modifed (GM) soybeans were planted in center (black circle) as pollen source. non-GM soybeans (white circle) were planted in four directions beside GM soybeans.

Fig. 2. The experimental design of the field trial. Genetically modified (GM) soybeans were planted in center (black rectangles) as pollen source. non-GM soybeans were planted in four directions beside GM soybeans. The size of GM pollen source was 90 cm × 90 cm (A), 180 cm × 180 cm (B), and 360 cm × 360 cm (C). (D) is photograph of the experimental field trial.

Fig. 3. The example of sampling point for gene flow. Gray squares indicate the soybeans from which fruits were collected for screening hybrids.

Fig. 4. Part of hybrid detection by PCR analysis. bar gene was used to detect hybrid and lectin gene used as control gene. GM, genetically modifed. * means non-specifc band.

Table 1. Frequency of out-crossing rates evaluated from surviving progeny in East and West sites.

Table 2. Frequency of out-crossing rates evaluated from surviving progeny in North and South sites.