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Going with the flow -- are designer genes good movers?
The possibility of gene flow from crops to related wild plants to create superweeds is often raised by anti-GM campaigners. However, it is not confined to GM varieties: it can happen with any crop plant if conditions are right; the GM debate has raised our awareness of this. So, we need to ask three questions. Firstly, are there related wild species in the area in which the crop is grown? Secondly, does hybridisation actually occur? Thirdly, if it does, what are the consequences? With the first of these questions already answered positively, Chen et al., (Kyongsan, South Korea; Kunming and Shanghai, PR China: pp. 67-73) set out to answer the second. They established large experimental plots in which a GM rice (Oryza sativa) variety carrying a herbicide tolerance gene was grown in the presence of 'weedy' rice (O. sativa spontanea). They also established plots of GM rice adjacent to plots of wild rice (O. rufipogon). The GM rice was used as the pollen donor and seeds were collected from the weedy and wild plants. Germination of seeds in the presence of the herbicide revealed some tolerant progeny. The presence of the herbicide-tolerance gene in those hybrid progeny was detected by PCR and the heterozygote nature of the tolerant plants was established by the detection of particular repeat sequences. The frequencies of the hybrids were low: a maximum of 0.046 % for crop rice to weedy rice and a maximum of 2.19 % for crop rice to wild rice. Nevertheless these data demonstrate that gene flow does indeed occur although it is not known whether the herbicide-tolerance trait makes the recipient species more competitive. This reinforces the view that all crop varieties carrying new genetic traits, whether GM or 'conventionally' bred, need to be evaluated for the possibility of out-crossing and, if it does occur, of the possible ecological consequences.
Professor J. A. BryantUniversity of Exeter, UK
j.a.bryant{at}exeter.ac.uk
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