gene Flow: Implications for Crop Diversity and Wild Relatives

A number of important transgene flow cases have been reportedin centres of crop origin and diversity. Perhaps most widelyknown is the case of transgene introgression of maize in Oaxaca,Mexico (Quist & Chapela 2001; 2002). The substantial attentionpaid to reports on the status of transgenes in Mexican maize(Quist & Chapela 2001; NAFTA-CEC 2002; Alvarez Morales2002; Quist & Chapela 2002; Cleveland et al. 2005; Ortiz-Garciaet al. 2005) has not translated into follow-up empirical studieson the evolutionary significance of transgenes in maize landracepopulations. Given the occurrence of transgenic introgressionevents in Mexico, concerns have emerged over similar eventstaking place in other important crop plants, including riceand soya in China (Huang et al. 2003). The impendingcommercialisation of GM rice has been met with considerableconcern over gene flow to wild and weedy rice relatives (Lu& Snow 2005), and to non-transgenic commercial varieties.Given these events, and the uncertainties over the significanceof transgenic hybridisation, the introduction of transgenic cropsin their centres of origin and diversification represents a broadconcern with socio-economic and agricultural implications. Someof these impacts, particularly evolutionary implications, may beirreversible. For these reasons, transgenic introductions in centresof origin and diversification merit special consideration.The issue of intellectual property rights (IPRs) on crop cultivarsadds another dimension to the issue of transgene flow. WhileIPRs are in conflict with the age-old practice of seed exchangeamongst local farmers who use landraces, the introduction ofidentifiable transgenic technologies opens up the possibilitythat legal action could be taken against local farmers by thepatent holders. 22See the case of Percy Schmeiser, a canola farmer from Canada (http://www.percyschmeiser.com/)15