Impact of crop management on intraspecific diversity of Pseudomonas corrugata in bulk soil.

The genetic structure of Pseudomonas corrugata populations was investigated in bulk soil to evaluate the impact of crop management on the intraspecific diversity of this bacterium stimulated in plant rhizosphere. As these bacteria are rare in bulk soil, an immunotrapping assay was developed to isolate them from soils located in Grignon (France), where adjacent plots with similar soil features were cultivated under maize/wheat crop rotation or continuous wheat cropping. Genomic fingerprinting of 291 isolates was performed using repetitive sequence-based polymerase chain reaction (ERIC-PCR). Most of these isolates (236 out of 291) were assigned to P. corrugata on the basis of an amplified ribosomal DNA restriction analysis (ARDRA) with 12 restriction enzymes. Data were analyzed by Pearson's chi-squared tests and genetic diversity was evaluated with specific indices for richness and evenness. Comparison of richness or evenness diversity indices (global diversity) showed no significant difference, whereas ERIC-PCR fingerprinting data (intraspecific diversity) showed that the genetic structure of P. corrugata was significantly affected by crop management.