Containment and mitigation of transgene flow from crops

Two general approaches are used to deal with transgene flow: containment of the transgenes within the transgenic crop; or transgenic mitigation of the effects of the primary transgenic trait should it escape. Most containment mechanisms severely restrict gene flow only in one direction. Gene flow (leakage) is inevitable even in that direction, allowing spread through the population of undesired species, unless mitigated. Limitations to containing transgene flow Several molecular mechanisms have been proposed to contain transgenes by preventing introgression to relatives via pollen. These containment strategies can either suppress gene outflow from the crop, or protect the crop from inflow from wild or weedy relatives.1 The proposals to integrate the transgene in the plastid or mitochondrial genomes do not preclude the relative from pollinating the crop and then acting as the recurrent pollen parent. Claims of no paternal inheritance of plastome-encoded traits have been not substantiated, indeed maternal inheritance is leaky. Tobacco and other species typically transmit transplastomic traits via pollen at a frequency of 10–3–10–4 in laboratory experiments. A large-scale field experiment utilized a Setaria italica (foxtail millet) with chloroplast-inherited atrazine resistance (bearing a nuclear dominant red leaf base marker) crossed with five different male sterile yellow- o