Application of the maximum threshold distances to reduce gene flow frequency in the coexistence between genetically modified (GM) and non-GM maize.

On the coexistence of genetically modified (GM) and non-GM maize, the isolation distance plays an important role in controlling the transgenic flow. In this study, maize gene flow model was used to quantify the MTD 0.1% and MTD 1% in the main maize-planting regions of China; those were the maximum threshold distance for the gene flow frequency equal to or lower than 1% and 0.1%. The model showed that the extreme MTD 1% and MTD 0.1% were 187 and 548 m, respectively. The regions of northern China and the coastal plain, including Hainan crop winter-season multiplication base, showed a significantly high risk for maize gene flow, while the west-south of China was the largest low-risk areas. Except for a few sites, the isolation distance of 500 m could yield a seed purity of better than 0.1% and meet the production needs of breeder seeds. The parameters of genetic competitiveness ( cp ) were introduced to assess the effects of hybrid compatibility between the donor and recipient. The results showed that hybrid incompatibility could minimize the risk. When cp  = 0.05, MTD 1% and MTD 0.1% could be greatly reduced within 19 m and 75 m. These data were helpful to provide scientific data to set the isolation distance between GM and non-GM maize and select the right place to produce the hybrid maize seeds.