Strategies For Production of Marker-Free Transgenic Crops

The realization of generation marker-free transgenic plants for commercialization would simplify the regulatory process and improve consumer acceptance to remove gene sequences that are not serving a purpose in the final plant variety. For scientific purposes, eliminating the marker genes from the final plant would permit the use of experimental marker genes that have not undergone extensive biosafety evaluations or that may generate negative pleiotropic effects in the plants. Furthermore, it would permit the recycling of useful marker genes for recurrent transformation of transgenic plants if they were eliminated prior to the next round of transformation. Although a number of strategies have been described for generating marker-free transgenic plants, all are more difficult to implement or are less efficient than procedures which leave the marker genes in the plant. Presently, sufficient data has been accumulated to indicate that cotransformation of non-selected genes with selectable marker genes followed by rounds of segregation will create marker-free plants.