Genetic and Pathogenic Characterization of Bacterial Wilt Pathogen, Ralstonia pseudosolanacearum (Ralstonia solanacearum Phylotype I), on Roses in Korea

The purpose of this study was to analyze the genetic and pathogenic characteristics of Ralstonia pseudosolanacearum in roses in Korea, and to examine the similarities and differences between Korean isolates and the first-reported European strains. Between 2017 and 2019, seventeen isolates from rose plants were identified as R. pseudosolanacearum using Ralstonia-specific primers. All 17 isolates were identified as race 1 using race-specific primers, and were confirmed as biovar 3 due to their ability to utilize carbon sources. Multiplex PCR using phylotype discriminating specific primers identified the 17 isolates as phylotype I. Sequevar comparison with reference sequevars using the sequences of the egl, mutS, and fliC genes, and only the egl gene, revealed that the strains evaluated in this study corresponded to sequevar I-33. The pathogenicity in roses differed depending on the rose cultivars. The different methods used for the genetic characterization of R. pseudosolanacearum indicate that the 17 rose bacterial wilt isolates had the same genetic characteristics. The lack of genetic variation in these isolates indicates their recent introduction from other countries (likely European countries). Therefore, appropriate quarantine and control measures should be taken in order to avoid further increases in the pathogenicity and/or secondary host range of R. pseudosolanacearum through genetic mutation.