title: Limited fitness advantages of crop-weed hybrid progeny containing insect-resistant transgenes (Bt/CpTI) in transgenic rice field.
abstract: BACKGROUND
  The spread of insect-resistance transgenes from genetically engineered (GE) rice to its coexisting weedy rice (O. sativa f. spontanea) populations via gene flow creates a major concern for commercial GE rice cultivation. Transgene flow to weedy rice seems unavoidable. Therefore, characterization of potential fitness effect brought by the transgenes is essential to assess environmental consequences caused by crop-weed transgene flow.
  
  
  RESULTS
  Field performance of fitness-related traits was assessed in advanced hybrid progeny of F(4) generation derived from a cross between an insect-resistant transgenic (Bt/CpTI) rice line and a weedy strain. The performance of transgene-positive hybrid progeny was compared with the transgene-negative progeny and weedy parent in pure and mixed planting of transgenic and nontransgenic plants under environmental conditions with natural vs. low insect pressure. Results showed that under natural insect pressure the insect-resistant transgenes could effectively suppress target insects and bring significantly increased fitness to transgenic plants in pure planting, compared with nontransgenic plants (including weedy parent). In contrast, no significant differences in fitness were detected under low insect pressure. However, such increase in fitness was not detected in the mixed planting of transgenic and nontransgenic plants due to significantly reduced insect pressure.
  
  
  CONCLUSIONS
  Insect-resistance transgenes may have limited fitness advantages to hybrid progeny resulted from crop-weed transgene flow owning to the significantly reduced ambient target insect pressure when an insect-resistant GE crop is grown. Given that the extensive cultivation of an insect-resistant GE crop will ultimately reduce the target insect pressure, the rapid spread of insect-resistance transgenes in weedy populations in commercial GE crop fields may be not likely to happen.
authors: Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Department of Ecology and Evolutionary Biology, Fudan University, Shanghai, China.
authors: Xiao
authors: X
authors: Yang
authors: Feng
authors: F
authors: Wang
authors: Jun
authors: J
authors: Su
authors: Bao-Rong
authors: BR
authors: Lu
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000378:metabolism; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics; D018556:Crops, Agricultural / Q000235:genetics*; D003433:Crosses, Genetic; D004731:Endotoxins / Q000235:genetics; D004777:Environment; D051456:Gene Flow; D005818:Genetic Engineering / Q000379:methods; D006460:Hemolysin Proteins / Q000235:genetics; D006824:Hybridization, Genetic; D007313:Insecta; D008957:Models, Genetic; D012275:Oryza / Q000235:genetics*; D030821:Plants, Genetically Modified / Q000235:genetics; D015203:Reproducibility of Results; D012306:Risk; D019076:Transgenes
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis