Genetic Diversity and Host Range Variation of Ralstonia solanacearum Strains Entering North America

Abstract

Each year, large volumes of ornamental and food plant propagative stock are imported into the North America; occasionally, Ralstonia solanacearum is found systemically infecting this plant material. In this study, 107 new R. solanacearum strains were collected over a 10-year period from imported propagative stock and compared with 32 previously characterized R. solanacearum strains using repetitive polymerase chain reaction (rep-PCR) element (BOX, ERIC, and REP) primers. Additional strain comparisons were made by sequencing the endoglucanase and the cytochrome b561 genes. Using rep-PCR primers, populations could be distinguished by biovar and, to a limited extent, country of origin and original host. Similarity coefficients among rep-PCR clusters within biovars were relatively low in many cases, indicating that disease outbreaks over time may have been caused by different clonal populations. Similar population differentiations of R. solanacearum were obtained when comparing strain sequences using either the endoglucanase or cytochrome b561 genes. We found that most of the new biovar 1 strains of R. solanacearum entering the United States were genetically distinct from the biovar 1 strains currently found infecting vegetable production. These introduced biovar 1 strains also had a broader host range and could infect not only tomato, tobacco, and potato but also anthurium and pothos and cause symptoms on banana. All introductions into North America of race 3, biovar 2 strains in the last few years have been linked to geranium production and appeared to be clonal.

Contrasting recombination patterns and demographic histories of the plant pathogen Ralstonia solanacearum inferred from MLSA

“…Adaptation to some particular hosts and capacity to induce latent infections in plant material may have been a key factor for dissemination (and a possible demographic bottleneck). Plant-mediated dissemination was mostly associated with banana, ginger and potato (Buddenhagen, 1986;Coutinho, 2005), and strains intercepted in global surveys on latently infected plant material were mostly of phylotype IIB, not of phylotype I (Norman et al, 2009). This contradiction can, however, be explained by the fact that this survey was largely performed on imports of South America, where IIB strains are prevalent.…”

Genetic mapping of a major dominant gene for resistance to Ralstonia solanacearum in eggplant

“…Moreover, genes or QTLs associated with BW-resistance were reported against non-characterized R. solanacearum strains, whereas strain-and phylotype-specific QTLs were reported for tomato. Among solanaceous-infecting R. solanacearum populations, phylotype I strains are the most prevalent clade found in most Asian eggplant production areas (Horita and Tsuchiya 2001;Ivey et al 2007;Jaunet and Wang 1999;Xu et al 2009) as well as in Africa (Mahbou Somo Toukam et al 2009), America (Ji et al 2007;Norman et al 2009;Sanchez Perez et al 2008), and the Caribbean ). In a previous study, we showed that phylotype I strains display different virulence patterns, called pathoprofiles, on a core collection of tomato, pepper and eggplant representative of the genetic diversity for resistance in these species (Lebeau et al 2011).…”

Diversity of Brazilian biovar 2 strains of Ralstonia solanacearum

“…The Bv2 strains presented in this study all grouped in the phylotype II branch, with one strain in the IIa subpopulation and all the others in the IIb subpopulation, corroborating the result of the multiplex PCR for phylotype determination (results not shown and Table 1). This result reflects the fact that strains from the same geographic origin (i.e., Asia, America, Africa, Indonesia) most likely share a common ancestor (Jeong et al 2007;Ji et al 2007;Norman et al 2009;Wicker et al 2007). The geographic isolation explains the population divergence.…”