"What makes our study unique is that we evaluated AMF colonization in 14 different lines of Bt and non-Bt corn under consistent experimental conditions in a greenhouse using locally collected agricultural field soil as the AMF inoculum," said Cheeke.
"The use of whole soil in this study allowed each Bt and non-Bt corn line to interact with a community of soil organisms, making this study more ecologically relevant than other greenhouse studies that use a single species of AMF," she adds.
Interestingly, the authors found that colonization of plant roots by symbiotic soil fungi was lower in the genetically modified Bt corn than in the control lines. However, there was no difference in root biomass or shoot biomass between the two types of corn at the time of harvest.
Cheeke and co-authors also determined that the Bt-protein itself is not directly toxic to the fungi since AMF colonization of vegetable soybeans did not differ for those grown in soil previously containing Bt vs. non-Bt corn.
Together these findings contribute to the growing body of knowledge examining the unanticipated effects of Bt crop cultivation on non-target soil organisms. Examining non-target effects of genetically engineered crops on symbiotic soil organisms becomes even more important as acreage devoted to the cultivation of Bt crops continues to increase globally.
"In 2011, 88% of the corn cultivated in the United States was genetically modified to express insect resistance, herbicide tolerance, or some combination of stacked traits," Cheeke commented. "Globally, genetically modified corn is cultivated in at least 16 different countries."
Cheeke notes that the next step is to understand the ecological significance of this study. "In greenhouse studies Bt corn had lower levels AMF colonization, so now it is important to see i
|Contact: Richard Hund|
American Journal of Botany