*Article Ralstonia solanacearum* **Facing Spread-Determining Climatic Temperatures, Sustained Starvation, and Naturally Induced Resuscitation of Viable but Non-Culturable Cells in Environmental Water**

**Belén Álvarez 1,2,† , María M. López <sup>1</sup> and Elena G. Biosca 2,\***


**Abstract:** *Ralstonia solanacearum* is a bacterial phytopathogen affecting staple crops, originally from tropical and subtropical areas, whose ability to survive in temperate environments is of concern under global warming. In this study, two *R. solanacearum* strains from either cold or warm habitats were stressed by simultaneous exposure to natural oligotrophy at low (4 ◦C), temperate (14 ◦C), or warm (24 ◦C) temperatures in environmental water. At 4 ◦C, the effect of temperature was higher than that of oligotrophy, since *R. solanacearum* went into a viable but non-culturable (VBNC) state, which proved to be dependent on water nutrient contents. Resuscitation was demonstrated *in vitro* and *in planta*. At 14 ◦C and 24 ◦C, the effect of oligotrophy was higher than that of temperature on *R. solanacearum* populations, displaying starvation-survival responses and morphological changes which were stronger at 24 ◦C. In tomato plants, starved, cold-induced VBNC, and/or resuscitated cells maintained virulence. The strains behaved similarly regardless of their cold or warm areas of origin. This work firstly describes the natural nutrient availability of environmental water favoring *R. solanacearum* survival, adaptations, and resuscitation in conditions that can be found in natural settings. These findings will contribute to anticipate the ability of *R. solanacearum* to spread, establish, and induce disease in new geographical and climatic areas.

**Keywords:** bacterial wilt; global warming; environmental stress; VBNC; pathogenicity
