Ralstonia solanacearum CMI1000, MOLK2 and1609

Ralstonia solanacearum is a phytopathogenic beta-proteobacterium capable of infecting a large number of plant species. Genoscope has sequenced the genomes of three strains with very different host ranges. The first genome sequenced was that of a strain with a wide host range, CMI1000. It is organized in two replicons, a chromosome of 3.7 Mb and a megaplasmid of 2.1 Mb, with very similar GC% (about 67%). About 10 genome equivalents were assembled using a sequential strategy in order to limit the problems caused by repetitive sequences. This assembly benefited from end sequencing of BAC clones with an average insert size of 100 kb. The resulting sequence was subjected to a finishing phase, and the final sequence was over 99% validated by comparison with experimentally obtained restriction enzyme fingerprints on a minimum tiling path of BAC clones. Annotation was carried out by Christian Boucher’s group at the Laboratoire Interactions Plantes-Microorganismes (access to the annotated sequence).

The genomes of Molk2 (a strain of race 2, isolated from a banana tree) and 1609 (a race 3 strain, isolated from potato) have genomes which are comparable to that of CMI1000 (about 6 Mb, GC% estimated at 67%). They are being sequenced at Genoscope at depths of 6.2X and 7.3X respectively. Three libraries are being used for each project: two libraries of plasmid clones with average insert sizes of 3 and 10 kb, and a library of miniBACs with an average insert size of 25 kb. After a first assembly, finishing will only be carried out on regions of special interest, in each genome