Whole genome sequencing suggests that “non-pathogenicity on banana (NPB)” is the ancestral state of the Ralstonia solanacearum IIB-4 lineage

Abstract

The bacterial wilt pathogens in the Ralstonia solanacearum species complex (RSSC) have broad but finite host ranges. Population genetic surveys of RSSC pathogens show that many sequevars (subspecies groups) are predominantly recovered from wilting solanaceous plants. In contrast, strains in the IIB-4 sequevar have been isolated from plants in over a dozen families. We characterized the natural variation in host range of nineteen IIB-4 strains to explore the molecular determinants of host range within the RSSC. We used Illumina sequencing to assemble draft genomes of 12 strains. Based on whole genome phylogenetic analysis, these IIB-4 strains cluster into five subclades. We quantified virulence of each strain on tomato cv. Moneymaker (Solanaceae), banana cv. Dwarf Cavendish (Musaceae), melon cv. Sweet Granite (Cucurbitaceae), and impatiens cv. Beacon Orange (Balsaminaceae). To enable future meta-analyses that identify genetic factors that drive host-range, the raw virulence data is included as a supplemental table. Overall, the virulence patterns correlated with phylogeny. Strains from Martinique, Dominican Republic, Brazil, as well as multiple strains imported into Florida were highly virulent on tomato, melon, and impatiens. Several strains from Peru were highly virulent on tomato and had moderate-to-low virulence on banana, melon, and impatiens. One strain from Colombia was highly virulent on all hosts. Our findings reinforce the phenotypic plasticity within the Ralstonia solanacearum species complex.