The genotypic diversity of Pseudomonas brassicacearum populations isolatedfrom roots of Arabidopsis thaliana: influence of plant genotype

Pseudomonas brassicacearum is a newly described bacterial species isolated from the rhizosphere of Arabidopsis thaliana. The P. brassicacearum populat ions were isolated from the rhizosphere of two ecotypes of A. thaliana (Was silewskija (WS) and Columbia (COL)), a mutant of Columbia impaired in starc h metabolism (pgm mutant), and a genetically distant plant (wheat), grown i n a French eutric cambisol (Mereville). The strains were isolated on semi-s elective media. Their diversity was assessed using repetitive extragenic pa lindromic (REP)-PCR profiling and their affiliation to the P. brassicacearu m species using ARDRA and siderotyping. A total of 379 strains isolated in two experiments were clustered into 68 REP-genotypes. Statistical analysis showed that the genetic structure of the P. brassicacearum populations was homogeneous for strains isolated from different plants of the same genotype within the same experiment, but significantly differed across the four tes ted plant genotypes. Comparison of the REP-genotype distributions showed th at some bacterial genotypes were poorly represented, whereas others were st rongly stimulated by plant roots. (C) 2001 Federation of European Micro bio logical Societies. Published by Elsevier Science B.V. All rights reserved.