Detection of gene flow from GM to non-GM watermelon in a field trial

Gene flow from genetically modified (GM) crops to conventional non-GM crops is a serious concern for protection of conventional and organic farming. Gene flow from GM watermelon developed for rootstock use, containing cucumber green mottle mosaic virus (CGMMV)-coat protein (CP) gene, to a non-GM isogenic control variety 'Chalteok' and grafted watermelon 'Keumcheon' was investigated in a small scale field trial as a pilot study. Hybrids between GM and non-GM watermelons were screened from 1304 'Chalteok' seeds and 856 'Keumcheon' seeds using the duplex PCR method targeting the CGMMV-CP gene as a marker. Hybrids were found in all pollen recipient plots. The gene flow frequencies were greater for 'Chalteok' than for 'Keumcheon'; with 75% outcrossing in the 'Chalteok' plot at the closest distance (0.8 m) to the GM plot. A much larger scale field trial is necessary to identify the isolation distance between GM and non-GM watermelon, as the behaviors of insect pollinators needs to be clarified in Korea.