Whole Genome Sequencing Suggests that “Nonpathogenicity 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. Certain IIB-4 lineages have been classified as banana-virulent or “not pathogenic to banana (NPB)”. Prior analysis suggested that the NPB lineage has diverged from the banana-virulent IIB-4 strains. To test this model, we analyzed the phenotypes and phylogeny of a diverse collection of 19 IIB-4 isolates. We used Illumina sequencing to assemble draft genomes of 12 new strains. Based on whole genome phylogenetic analysis, these IIB-4 strains clustered into five subclades. We quantified virulence of each strain on tomato, banana, melon, and impatiens plants. Overall, the virulence patterns correlated with phylogeny. Banana virulence was restricted to the 4/4 IIB-4D subclade (N=4/4 strains) and IIB-4E subclade (N=1/2 strains). Subclades IIB-4D and IIB-4E are sister sublcades and their closest relative, the IIB-4A-C subclade, lacked virulence on banana. Our data support a revised model in which banana virulence is an innovation within the IIB4D/E subclades.

A Meta-analysis of the known Global Distribution and Host Range of theRalstoniaSpecies Complex

“…As a significant caveat, Ralstonia host range can vary between strains that are closely related (i.e. in the same sequevar) [64,190,195,200]. Nevertheless, host range patterns often correlate with phylogeny [195,200].…”

“…To get a better estimate of the diversity of potential hosts for Ralstonia, we did a search of the literature using search terms like "weeds", "host range", and older names for the pathogen (Pseudomonas solanacearum, Burkholderia solanacearum). [189][190][191][192][193] 2022 [194][195][196][197][198] Converting strain metadata into a structured format for data science:…”

“…in the same sequevar) [64,190,195,200]. Nevertheless, host range patterns often correlate with phylogeny [195,200]. Collectively, Phylotype I has a wide host range (123 plant species in 43 botanical families).…”

Characterization ofRalstonia pseudosolanacearumdiversity and screening host resistance to manage bacterial wilt in South Asia

“…Genomic data and phenotypic data should be published in both summarized and raw formats to make the data most valuable for future meta-analysis. For this reason, we recently published raw host-range and whole genome sequence data on 19 phylotype IIB-4 RSSC isolates (Beutler et al 2022). In this study, we quantified wilt incidence on a panel of Solanaceae accessions that have previously been phenotyped against 12 global RSSC isolates and six RSSC isolates from Louisiana, U.S (Lebeau et al 2011; Lewis Ivey et al 2021).…”

A pangenomic atlas reveals that eco-evolutionary dynamics shape plant pathogen type VI secretion systems

“…Pioneering studies on Moko disease by Luis Sequeira and Ivan Buddenhagan demonstrated that the causal pathogens are facultatively transmitted by either soil transmission or contact transmission of insects with sap, similar to BDB (86,87). We and other groups have sequenced isolates from the Sequiera and Buddenhagan collection from the 1960s Moko epidemic (88)(89)(90)(91), and we now know that multiple RSSC lineages were responsible for the epidemic, including T6SS + lineages (IIB-4 and IIB-3) and T6SS null lineages (IIA-6). Further epidemiological research is needed to understand how variation in transmission routes shapes the evolution and behavior of RSSC lineages.…”