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Genetic relatedness and virulence of a novel Ralstonia pseudosolanacearum (Ralstonia solanacearum phylotype I) isolated from Rosa spp.

Maria Bergsma-Vlami: NVWA

<div>A novel <em>R</em><em>. pseudosolanacearum </em>causing disease in rose has been recently reported. Plants suffered from chlorosis, stunting, wilting and necrosis. Isolates obtained from rose were identified as phylotype I from the '<em>Ralstonia solanacearum</em> species complex' (RSSC), actually reclassified as <em>R. pseudosolanacearum. </em>At the proteomic level, these isolates were accurately identified by MALDI-TOF MS. MLSA positioned these isolates in a distinct clade in phylotype I, exhibiting a clonal structure, when compared with a set of 250 RSSC isolates of worldwide origin. Representative <em>R. pseudosolanacearum</em> isolates from rose were assessed for their virulence in two rose cultivars and in solanaceous crops. Significant differences were observed in susceptibility between the two rose cultivars. Additionally, a temperature dependency in susceptibility was observed for both cultivars irrespective of the mode of inoculation. The solanaceous crops showed to be susceptible to the <em>R</em>. <em>pseudosolanacearum</em> isolates from rose. Interestingly, both rose cultivars were able to harbor symptomless infections with other RSSC isolates than those isolated from rose. Our results demonstrated that latent infections in rose do occur even at temperatures as low as 20°C. This latency poses high risks for the entire floricultural industry as latently infected rose plants might be distributed over various continents, including areas where climatic conditions are optimal for the pathogen.</div>