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Plant host effects on rhizosphere bacterial communities and pathogen suppression.
B. E. ARENZ (1), J. M. Bradeen (1), L. K. Otto-Hansen (1), J. C. Anderson (1), L. L. Kinkel (1). (1) University of Minnesota, St. Paul, MN, U.S.A.

This study explored the influence of plant species on bacterial rhizosphere community composition, structure, and function (pathogen suppressive activity). Soil was collected from 6 agricultural and natural habitats with differing plant species histories, sieved, homogenized, and evaluated for edaphic characteristics. Subsequently, 2 grasses, <i>Andropogon gerardii</i> (Ag) and <i>Secale cereale</i> (Sc) were planted individually into each soil and maintained in a greenhouse for 14 weeks. DNA was extracted from both pre- and post-plant soils, amplified with bacterial rDNA-specific primers, and sequenced via 454 pyrosequencing. Suppressive activity against 3 plant pathogens was evaluated in vitro. Pre-plant samples from different locations supported distinctive bacterial communities, which remained distinct following planting. Both Ag and Sc significantly increased bacterial diversity compared to pre-plant soil communities. Groups that decreased in relative abundance after planting included the Flavobacteriaceae, Sphingobacteriales, Sphingomonodaceae, and Burkholderiales, indicating that the grass rhizosphere or the greenhouse environment is less favorable to these groups. In vitro tests of pre-plant communities were significantly different in <i>Streptomyces</i> spp., total bacterial, and inhibitor densities and inhibition zone size, (all; p<0.0001). Microbial community composition remained significantly different among distinct soils despite increases in diversity induced by Ag and Sc. <p><p>Keywords: NA

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