Carbon Allocation And Field Residue Decomposition Dynamics Of Mon863 Bt Corn And Public Perceptions Of Transgenic Crops In China
Transgenic corn variety MON863, released in 2003, expresses the Cry3Bb protein from Bacillus thuringiensis (Bt), which has insecticidal activity against the corn rootworm (CRW). Despite the rapid adoption of Bt crops by farmers, public concern continues to mount over their potential environmental impacts. I assessed the effects of Bt corn and its parental NonBt hybrid on residue decomposition and carbon (C) allocation in field and greenhouse experiments. In the field, lignin concentration of Bt and NonBt corn residues, rates of residue decomposition, residue-colonizing decomposer communities and decomposition of the Cry3Bb protein were evaluated in litterbag studies. None of these variables were significantly different between the two hybrids. Differences observed were driven primarily by environmental factors related to time of sampling. The Cry3Bb protein decomposed nearly completely after 3.5 months in the field, indicating that the protein is unlikely to pose any significant ecological risks. Three greenhouse experiments were conducted to measure the allocation of labeled carbon (13C) in Bt and NonBt corn. There were no significant effects of Bt corn on 13C allocation, total C or lignin content of plant tissues. However, the lignin content of NonBt corn roots was significantly higher than that of Bt corn roots when plants were inoculated with CRW, indicating that induced systemic resistance, rather than presence of the Bt gene, may effect C budgets in agricultural systems where CRW is present. NonBt corn was significantly taller than MON863 Bt corn. This was most likely the result of normal varietal variation as suggested by the differences in growth characteristics observed when Bt and NonBt corn from three maturity groups were compared. A survey was conducted in China to explore the attitude(s) of Chinese consumers towards transgenic crops. Results showed that a large proportion of respondents held neutral positions towards or were unsure about transgenic crops. Respondents' attitudes shifted when provided information about the potential benefits and risks of transgenic crops. These results indicated that the commercial release of Bt rice is likely to encounter resistance from consumers. Future scenario testing indicated that increased public awareness would not necessarily improve consumer acceptance of transgenic rice.
dissertation or thesis