Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 8/6/2011
Publication Date: 8/10/2011
Citation: Gealy, D.R., Burgos, N.R. 2011. Gene flow and herbicide resistance: Lessons learned from herbicide-resistant rice systems. American Phytopathological Society Annual Meeting. August 6-10, 2011. Honolulu, Hawaii. Pesticide Resistance in Agriculture-A Global Issue. Interpretive Summary:
Technical Abstract: Gene flow in plants is a process whereby genes are exchanged between members of the same or closely related species via pollen and become established in new populations. This natural process has long been an issue in breeding and the seed industry, but interest has increased since the deployment of pesticide-resistant crop systems in areas infested by weedy/wild relatives of the crop. Imidazolinone (IMI) herbicide-resistant (HR) genes imbedded in traditional cultivars or in commercial hybrids of rice are examples of such systems, which are now widely grown and have been highly successful in the US. The types of rice and weedy rice can affect outcrossing rates in this self-pollinated species. Outcrossing has ranged from <0.001% to >1.0% as shown using SSR analyses, and occurs primarily between plants separated by < 2 m. Outcrossing was detected at 300 m in a field scale experiment. Some bottlenecks that restrict gene flow between rice and weedy rice have been identified. However, repeated applications of IMI herbicides to rice fields over time result in powerful selective advantages to weedy rice plants once they have acquired HR genes. Planting time, humidity and temperature during flowering, and other environmental factors also affect outcrossing and gene flow. Reports of HR weedy rice in farm fields are increasing. The degree to which HR genes have introgressed into weedy rice populations via gene flow from IMI rice, and approaches to mitigating this process are under investigation.