Major concern in commercialization of GM crops is:
Ecological risk assessment of genetically modified crops prioritizes likelihood and consequence of transgene movement into natural populations. Pollen dispersal by wind or pollinators can fertilize compatible wild relatives growing near fields, introducing transgene into weedy gene pool. If trait confers selective advantage such as herbicide tolerance allowing survival in managed landscapes or insect resistance increasing fitness, introgressed individuals may increase frequency. Concerns include loss of genetic diversity, altered ecosystem interactions, and development of weeds difficult to control. Factors influencing gene flow include flowering synchrony, compatibility, and distance isolation. Regulatory dossiers require outcrossing rate estimation using trap plants and molecular markers. While low yield or poor germination are agronomic issues evaluated during variety testing, gene flow to weedy relatives remains primary environmental concern shaping buffer zone requirements, stewardship plans, and public debate about commercial cultivation of GM crops in centers of origin. Isolation distances of 200 meters for canola and 50 meters for maize recommended by OECD to limit cross-pollination to below 0.1 percent threshold. Monitoring includes PCR detection of transgene in wild relative seed lots. Socio-economic concerns include coexistence of organic and GM farming systems. Scientific consensus recognizes gene flow as manageable through biological containment and good agricultural
Ref: Dale Plant Biotech J 2002 gene flow; Ellstrand Annu Rev Ecol Syst 2003; NCBI NBK131103 biosafety; https://www.ncbi.nlm.nih.gov/books/NBK131103/