Potential gene flow from genetically modified oilseed rape (Brassica napus) to its relatives

Abstract

Both greenhouse and field studies to evaluate gene flow from GM Brassica napus to its relatives were conducted in the Exprimental Farm Station of Soeul National University, Suwon, Korea. The greenhouse study was conducted for setting up basic experimental conditions and then field studies were conducted to quantify the potential gene flow from GM Brassica napus to its relatives under different pollination conditions. Simple sequence repeats (SSR) and herbicide resistance (glufosinate-ammonium) markers were used for confirming F1 hybrids resulted from outcrossing between GM B. napus and its relatives. The experimental data clearly demonstrated the possibility of gene flow from GM B. napus to its relatives such as B. napus and B. juncea in the field condition, but showed no gene flow to Raphanus sativus. Under simulated favorite pollination by synchronizing flowering time and placing honeybee hive, the potential gene flow from GM B. napus to its relatives was evaluated. To MS relatives, it was estimated to be 32.48% and 21.95% to MS B. napus and MS B. juncea, respectively, at 2 m distance, and decreased with increasing distance, reaching 0.3% and 0.25%, respectively, at 128 m distance. In contrast, to male fertile (MF) relatives, the potential gene flow was estimate to be 2.33% and 0.076% to MF B. napus and MF B. juncea, respectively, at 2 m distance and decreased to 0.007% for MF B. napus at 75 m and 0.025% for MF B. juncea at 16 m distance. Therefore, the gene flow rates to MS relatives at 2 m distance were 16 times for B. napus and 288 times for B. juncea greater than the gene flow rate to FM relatives, suggesting big difference between the maximum potential gene flow and the practical gene flow. The three-parameter log-logistic model well described gene flows against distance, indicating that the suitability of the equations for prediction of gene flow rate at a specified distance. Isolation distances between GM B. napus and its GM relatives were then recommended based on the model and the tolerable threshold (0.01%) made by EU. The isolation distance for less than 0.01% gene flow from GM B. napus was esimted to be 2710 m and 254 m for MS B. napus and B. juncea, respectively, and 122.5 m and 23.7 m for MF B. napus and B. juncea, respectively. Our studies would provide informative reference values and scientific basis for risk assessment of gene flow from GM B. napus to its relatives under Korean climatic condition. The modeled equation will also provide scientific evidence for the determination of isolation distance and the regulation of GM crops cultivation.