title: A built-in mechanism to mitigate the spread of insect-resistance and herbicide-tolerance transgenes into weedy rice populations.
abstract: BACKGROUND
  The major challenge of cultivating genetically modified (GM) rice (Oryza sativa) at the commercial scale is to prevent the spread of transgenes from GM cultivated rice to its coexisting weedy rice (O. sativa f. spontanea). The strategic development of GM rice with a built-in control mechanism can mitigate transgene spread in weedy rice populations.
  
  
  RESULTS
  An RNAi cassette suppressing the expression of the bentazon detoxifying enzyme CYP81A6 was constructed into the T-DNA which contained two tightly linked transgenes expressing the Bt insecticidal protein Cry1Ab and the glyphosate tolerant 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), respectively. GM rice plants developed from this T-DNA were resistant to lepidopteran pests and tolerant to glyphosate, but sensitive to bentazon. The application of bentazon of 2000 mg/L at the rate of 40 mL/m(2), which is approximately the recommended dose for the field application to control common rice weeds, killed all F(2) plants containing the transgenes generated from the Crop-weed hybrids between a GM rice line (CGH-13) and two weedy rice strains (PI-63 and PI-1401).
  
  
  CONCLUSIONS
  Weedy rice plants containing transgenes from GM rice through gene flow can be selectively killed by the spray of bentazon when a non-GM rice variety is cultivated alternately in a few-year interval. The built-in control mechanism in combination of cropping management is likely to mitigate the spread of transgenes into weedy rice populations.
authors.affiliation: State Key Laboratory of Rice Biology, Institute of Insect Sciences, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, China.
authors.forename: Chengyi
authors.initials: C
authors.lastname: Liu
authors.forename: Jingjing
authors.initials: J
authors.lastname: Li
authors.forename: Jianhua
authors.initials: J
authors.lastname: Gao
authors.forename: Zhicheng
authors.initials: Z
authors.lastname: Shen
authors.forename: Bao-Rong
authors.initials: BR
authors.lastname: Lu
authors.forename: Chaoyang
authors.initials: C
authors.lastname: Lin
mesh_terms: D000818:Animals; D001581:Benzothiadiazines / Q000494:pharmacology; D051456:Gene Flow; D006540:Herbicides / Q000494:pharmacology; D007313:Insecta / Q000276:immunology; D012275:Oryza / Q000187:drug effects / Q000235:genetics*; D019076:Transgenes
chemical_list: D001581:Benzothiadiazines; D006540:Herbicides; C002003:bentazone