Abstract Insertion sequence (IS) elements of organisms have the ability to move into genes or DNA sequences as a single unit, implying that these elements play an important role in the evolution of the organisms. A new IS (ISRso21) was isolated and characterized from Ralstonia solanacearum strain FJAT-1458. Sequence analysis indicated that the ISRso21 was closely related to the members of ISL3 family. The results of insertion sites polymorphism of ISRso21 showed that the frequency of positive strains isolated from Northern of Fujian Province was higher than that isolated from other areas. There was significant difference in the distribution of ISRso21 among R. solanacearum isolated from different geography. Therefore, the present of ISRso21 in R. solanacearum strains might be associated with geographic origin. Moreover, the different insertion sites of ISRso21 in R. solanacearum genome were associated with the different pathogenicity. The results indicated that genomic rearrangements of phenotype conversion transcriptional regulator A (phcA) which was inserted by ISRso21, might play a major role in the control of pathogenicity. In upstream of phcA gene of R. solanacearum, the inserted detection rate of ISRso21 in all strains was 4.71%. The detection rates in avirulent strains and virulent strains were 28.57% and 0.00%, respectively. The insertion of ISRso21 in diaminopimelate decarboxylase gene might make the R. solanacearum strains adapt betterly to the environment. The different insertion sites of ISRso21 in the R. solanacearum strains need to be furtherly investigated, which can provide an alternative way to reveal the pathogenicity of R. solanacearum.
