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Impact of Genetically Modified Crops on Soil- and Plant-Associated Microbial Communities

^a Department of Soil Science, University of Saskatchewan, Saskatoon, SK, Canada S7N 5A8
^b Department of Land Resource Science, University of Guelph, Guelph, ON, Canada N1G 2W1

View larger version (29K): [in a new window]   Fig. 1. Yearly global hectareage of genetically modified crops (James, 2003).

View larger version (24K): [in a new window]   Fig. 2. Potential sites of interaction between transgenes and soil microbial community. HT, herbicide tolerance gene.

View larger version (24K): [in a new window]   Fig. 3. Principal component analysis (PCA) of fatty acid methyl esters (FAMEs) obtained from the rhizosphere soil of canola cultivars grown at Eyebrow and Melfort, Saskatchewan, in 1998. Each symbol is the average of four replicates at one field site (n = 4). Closed symbols represent conventional varieties: triangles, Excel replicates; squares, Fairview replicates; diamonds, Hyola replicates; circles, 45A71 replicates. Open symbols represent genetically modified varieties: triangles, Exceed replicates; squares, Innovator replicates; diamonds, Invigor replicates; circles, Quest replicates. Error bars represent the standard error of the mean. Percent variation and P values are marked in parentheses. Reproduced with permission from Dunfield and Germida (2001).

View larger version (36K): [in a new window]   Fig. 4. Principal component analysis (PCA) of community-level physiological profiles (CLPP) obtained for microbial communities from fallow soil and rhizosphere microbial communities of canola varieties grown at Watson, Saskatchewan, sampled in May, June, July, August, and October 1999 and April 2000. Closed circles represent fallow soil (n = 4). Closed triangles represent conventional variety, Excel (n = 4). Open squares represent genetically modified variety, Quest (n = 4). Error bars represent the standard error of the mean. Percent variation explained by each PC is marked in parentheses. P values have been included when a significant variety effect is present, as determined by analysis of variance (ANOVA). Reproduced with permission from Dunfield and Germida (2003).

View larger version (24K): [in a new window]   Fig. 5. Principal component analysis (PCA) of the relative species compositions (based on identification by fatty acids) of cultured rhizobacteria from the non-transgenic control (DES), transgenic control plant line (DC1), and transgenic lines (DL4 and DL5) in five samplings. The clustering of the species patterns was based on PCs 1 and 2, explaining 28 and 16% of the variance, respectively. Reproduced with permission from Heuer et al. (2002).