Tuesday, November 14, 2006
186-9
Microbial communities colonizing residues do not differ between Cry3Bb Bt and Non-Bt corn Hybrid in the field.
Kai Xue, Dept. Of Crop & Soil Science,Cornell University, 706 Bradfield Hall, Cornell University, Ithaca, NY 14853, Raquel Serohijos, Maple Hill Apt. A3, 301 Maple Ave, 301 Maple Ave, Ithaca, NY 14850, United States of America, Medha Devare, Cornell University, 611 Bradfield Hall, 611 Bradfield Hall, Ithaca, NY 14853, United States of America, and Janice Thies, "719 Bradfield Hall, Cornell Univ.", Dept. Of Crop & Soil Science, Ithaca, NY 14853, United States of America.
Transgenic Bt corn variety MON863 expresses the Cry3Bb protein, which has insecticidal activity against certain species of corn rootworm. MON863 was released for commercial use in the U.S. in 2003. Despite the rapid adoption of Bt crops by farmers, public concern continues to mount over the potential environmental impacts of these crops. Altered rates of residue decomposition have been highlighted most recently. In this study, we assessed the effects of Bt and non-Bt corn residues on rates of residue decomposition and on associated decomposer communities, but only the latter results are presented here. Litterbags containing cobs, roots, or stalks plus leaves from Bt (MON863), non-Bt without and with insecticide (non-Bt+I) used during plant growth, were placed at the soil surface and at 10 cm depth in field plots with the corresponding crop treatments. After 3.5 months, DNA was extracted from the microbial communities that colonized residues in the litterbags collected from the field. Fungal and bacterial community DNA was amplified with ITS and 16S rDNA primers, respectively. PCR products were digested in separate reactions using the restriction enzymes HhaI and MspI for fungi, and HhaI and Sau96I for bacteria. Terminal restriction fragments were sized and the resulting data analyzed by use of multivariate statistical approaches. There was no detectable difference in either the bacterial or fungal communities colonizing residues from Bt, non-Bt or non-Bt+I corn plants. However, communities colonizing residues placed on the soil surface clearly separated from those on residues placed at 10 cm depth for both bacteria and fungi. The location (planting history of plots) also had a marked effect on bacterial and fungal communities. Combined, these results indicate that differences in microbial community composition observed in our study are driven primarily by environmental factors rather than by any differences between the corn hybrids tested.
Handout (.pdf format, 715.0 kb)