Pollen-mediated gene flow of genetically modified crops to their wild relatives can facilitate the spread of transgenes into the ecosystem and alter the fitness of the consequential progeny. A two-year field study was conducted to quantify the gene flow from glufosinate-ammonium resistant (GR) soybean (Glycinemax) to its wild relative, wild soybean (G. soja), and assess the potential weed risk of hybrids resulting from the gene flow during their entire life cycle under field conditions in Korea, where wild soybean is the natural inhabitant. Pollen-mediated gene flow from GR soybeans to wild soybeans ranged from 0.292% (mixed planting) to 0.027% at 8 m distance. The log-logistic model described the gene flow rate with increasing distance from GR soybean to wild soybean; the estimated effective isolation distance for 0.01% gene flow between GR and wild soybeans was 37.7 m. The F1 and F2 hybrids exhibited the intermediate characteristics of their parental soybeans in their vegetative and reproductive stages. Canopy height and stem length of hybrids were close to those of wild soybean, which shows an indeterminate growth; the numbers of flowers, pods, and seeds per hybrid plant were close to those of wild soybean and significantly higher than those of GR soybean. Seed longevity of F2 hybrid plants was also intermediate but significantly greater than that of GR soybean due to high seed dormancy. Our results suggest that transgenes of the GR soybean might disperse into wild populations and persist in the agroecosystem of the genetic origin regions due to the pollen-mediated gene flow and the relatively high fitness of the hybrid progeny.
Keywords: Glufosinate resistance; Relative fitness; Seed longevity; Transgene flow; Weed risk.
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