A diagnostic microarray for the multiplex characterization of strains of the Ralstonia solanacearum species complex

Bacterial wilt caused by the Ralstonia solanacearum species complex (RSSC) is one of the most destructive plant diseases worldwide. RSSC affects a wide range of host species and includes several ecotypes that represent major constraints and are under strict regulation (i.e brown rot or Moka strains). The reliable characterization of epidemiological strains at the ecotype level is a challenge considering such a complexity and is generally achieved by combining several diagnostic protocols. Therefore, we used microarray technology (ArrayTube) to develop a standard protocol that performs in a single reaction a multiplex characterization of RSSC strains, from the phylotype to the ecotype level (17 targeted groups of interest). Based on 27 sequenced genomes of RSSC, probes were designed with a 50-mer length constraint and thoroughly evaluated for any flaws or secondary structures. Validation data performed on target (n=75) and non-target strains (n=12) showed strong intra-repeatability, inter-repeatability, and reproducibility, as well as good specificity, which allowed for the proper detection of the 17 groups of interest (Cellier et al, 2017). This custom microarray represents a significant improvement in the epidemiological monitoring of Rssc strains worldwide, and it has the potential to provide insights for phylogenetic incongruence of Rssc strains based on the host of isolation and may be used to indicate potentially emergent strains.