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Comparative study of emerging Ralstonia pseudosolanacearum strains

David Norman: Univ of Florida MREC

<div><em>Ralstonia pseudosolanacearum</em> (Rps), previously known as <em>R. solanacearum </em>phylotype I, one of the causal agents of Bacterial Wilt that was confirmed to be infecting blueberry in multiple counties in Florida in 2016. Unexpectedly, the population structure of strains infecting blueberry is not clonal, instead it includes Rps and <em>R. solanacearum</em> (Rs) phylotype IIA strains, which makes detection and analysis of host range more difficult. In the Netherlands, a new Rps strain that infects roses has been isolated and characterized; this strain is virulent and has been found in several countries through Europe. Since 2013, Rps strains have been commonly found on mandevilla production in Florida. We hypothesized that the emerging Rps strains infecting new hosts in Florida are related to the strain infecting roses in Europe and their host range could be determined by differences in their type 3 effector sets. In order to test this hypothesis, we sequenced the genomes of three Rps strains from mandevilla, blueberry and rose (P781, P824, and PD7123 respectively) and we are in the process of comparing their genomes. We are currently evaluating host range of the three strains. Preliminary results show that neither the blueberry (P824) nor the rose (PD7123) Rps strains infect mandevilla plants when wound inoculated and the rose strain is very virulent on southern highbush blueberry.</div>