F Wang et al. Plant Biotechnology Journal (2006) Vol.4 p 667 – 676
“A large-scale field study of transgene flow from cultivated rice (Oryza sativa) to common wild rice (O. rufipogon) and barnyard grass (Echinochloa crusgalli)”
Pollen mediated gene flow is known to vary with distance between source and receptor, with family closeness and with timing. In this study a large area of land was planted with GM and non-GM rice at various times to ensure some synchronisation of flowering. In this experiment the GM rice was herbicide tolerant.
The maximum transgene flow was between 11% and 18% when source and receptor were within 1 metre. Probability of flow decreased rapidly with distance reaching 0.01% at 150 to 250 metres. Probability was related to wind speed; greater transport distances were detected in areas with higher wind speeds.
Gene flow to barnyard grass, grown amongst the GM rice for 5 successive years, could not be detected.
The rates of gene flow reported here are unusually high; the result of careful control to test maximum probabilities in the field. Rates were above 1% even at 20 metres.
Resistance to herbicide need not be the result of transgene flow from the GM plant. Repeated application of just one type of herbicide will create selection pressure in native weeds and encourage the development of resistance. Evidence for this is summarised in: TRENDS in Plant Science Vol.11 No.7 July 2006 p 324-328. The increased use of GM crops will encourage the intensive regular use of specific herbicides.