Advances in the eco-safety researches of transgenic Bt maize
转Bt基因玉米的生态安全性研究进展

Along with the large-scale release of transgenic crops, their possible ecological risks have been paid an increasing attention. The research on eco-safety of transgenic Bt maize was commented from the following two aspects: (1) Effect of Bt toxin produced by transgenic Bt maize on soil eco-systemResearches on the persistence of purified Bt toxin in soil showed that it could be adsorbed by or bound on soil surface-active particles rapidly, and remained its larvicidal activity. The adsorbed or bound toxin had a higher resistance to degradation than the free one. Other researches with root exudates and crop residues showed that the Bt toxin from transgenic Bt maize tissue bio-degraded faster than the purified toxin, while that in root exudates and from Bt maize biomass remained its larvicidal activity for at least 180 days. The plant component of Bt crops may be varied as a result of exogenous Bt gene transferring. A study showed that Bt maize had a higher lignin content than its isogenic non-Bt maize. Thus, the slower decomposition of the Bt maize biomass may result in a longer persistence of the Bt toxin in soil, and thereby, may enhance its hazard to non-target organisms, and result in the selection and enrichment of toxin-resistant target insects. Till now, there are some researches indicating that the population level and species composition of soil microorganisms were varied after transgenic Bt crops release, but there also have some researches showing that the toxin released from Bt maize roots and biomass appeared to have no deleterious effect on earthworms, nematodes, and microorganisms in soil.(2) Effect of Bt maize pollen on non-target insectsWhether the non-target insects hazard from the Bt toxin expressed in Bt maize pollen is associated with Bt maize pollen (the type, amount and toxicity of its produced protein), feeding plants (their distribution and proportion in cornfield, and the deposition of pollen on them) , and non-target insects (their instars, and the susceptibility of their larvae to the Bt protein). Most researches showed that the only transgenic maize pollen that consistently affected monarch larvae was from Cry1Ab event 176 hybrids, but the pollen from Cry1Ab (events Bt11 and Mon 810), Cry1 F, and experimental Cry 9C hybrids had no acute effects on monarch butterfly larvae in field settings. In comparison with the threats posed to insects by the application of pesticides and other farming practices, the widespread release of Bt maize may have huge benefits for environment, monarch butterfly and other insects survival. At present, the researches on the effect of Bt maize pollen on non-target insects are turned from describing assessment into quantitative characterization, and the results are acceptable. Due to the complexity and heterogeneity of soil, the effects of Bt protein on it are still not studied profoundly. However, with the advance in recent methodology, especially the introduction of molecular biological techniq