Wide genetic diversity of Ralstonia solanacearum strains affecting tomato in Trinidad, West Indies

Abstract

The genetic diversity of Ralstonia solanacearum causing bacterial wilt of tomato in Trinidad was assessed using the hierarchical phylotyping scheme and rep-PCR DNA fingerprinting. Seventy-one isolates were collected in 2003 on infected tomato crops in the four main vegetable cropping areas of Trinidad (North, Central, South-East and South). Two phylotypes were present, with phylotype II being much more prevalent (66%) than phylotype I (34%). Phylotype II strains consisted mainly of sequevar 7 in Central and South-East, and sequevar 35 in North, South-East and South. This is the first report of sequevar 7 outside southeastern USA. In contrast, no 'brown rot' (phylotype IIB ⁄ 1, race 3 biovar 2) or emerging strains of phylotype IIB ⁄ 4NPB were identified. Rep-PCR data were used to assess population genetic structure. No significant clustering by geographical distance was found, suggesting regular gene flow among cropping areas (via waterways, plant or soil). However, the population from Central was significantly differentiated from the others, containing only phylotype II ⁄ seq 7 strains, with a high degree of clonality, suggesting a possible recent introduction from abroad. The South population was less aggressive and more genetically diverse, suggesting horizontal gene transfers within the population, even among isolates of different phylotypes. Phylotype I and phylotype II populations differed slightly in clonality levels, with indications of more frequent recombination events within phylotype I populations. Possible factors influencing genetic diversity and distribution within the island are discussed.

Phylotype and sequevar variability of Ralstonia solanacearum in Brazil, an ancient centre of diversity of the pathogen

“…Most Brazilian isolates of R. solanacearum (84%) belonged to phylotype II, although phylotype I isolates were also detected. The occurrence of isolates corresponding to more than one phylotype has been reported in different countries and is usually attributed to effective dispersal processes (Sanchez Perez et al ., ; Ramsubhag et al ., ). Overall, the percentages of phylotypes I, IIA and IIB isolates in Brazil were similar to those reported in other Latin American countries.…”

“…The diversity of R . solanacearum in South America and in the Caribbean has been studied in Venezuela (García et al ., ), Colombia (Cardozo et al ., ), Uruguay (Siri et al ., ), French Guiana (Deberdt et al ., ), Brazil (Pinheiro et al ., ; Santana et al ., ; Garcia et al ., ; Albuquerque et al ., ), Martinique (Wicker et al ., ) and Trinidad and Tobago (Ramsubhag et al ., ). In Brazil, the most recent study (Albuquerque et al ., ) was conducted using banana and potato isolates obtained from small areas.…”

New Multilocus Variable-Number Tandem-Repeat Analysis (MLVA) Scheme for Fine-Scale Monitoring and Microevolution-Related Study of Ralstonia pseudosolanacearum Phylotype I Populations

“…However, all these studies focused only on large scales and did not pay particular attention to how microevolution acted on the field scale. Until now, field-scale studies focusing on RSSC genetic diversity were achieved only with markers with poor interlaboratory portability (RAPD [50], REP-PCR [51,53], and AFLP [54,55]). In this study, we decided to develop a new MLVA scheme, as VNTR loci have already proved their use in field-scale microevolution studies of plant-pathogenic bacterial epidemics, e.g., for local populations of Xanthomonas citri pv.…”

“…Until now, only two studies have addressed the population genetic structure on a local scale. The first one was conducted in India by using RAPD markers (50), and the second was performed on Trinidad Island by using repetitive sequence-based PCR (REP-PCR) (51). Unfortunately, the low repeatability and reproducibility with RAPD markers make the results difficult to interpret, and REP-PCR portability between laboratories remains problematic (6).…”

Plant-derived Antibacterial Metabolites Suppressing Tomato Bacterial Wilt Caused by Ralstonia solanacearum

“…of more than 50 botanical families that represent more than 200 plant species, including tomato, potato, eggplant, pepper, peanut, tobacco, banana, groundnut, olive, and ginger (Genin, 2010;Ramsubhag et al, 2012;Vu et al, 2013).…”