Genetic diversity of tumorigenic bacteria associated with crown gall disease of raspberry in Serbia

During the last 3 years, crown gall disease was observed in some young raspberry plantations throughout Serbia, causing considerable economic losses. Based on biochemical and physiological tests, PCR targeting the 23S rRNA gene, and 16S rRNA and recA gene sequence analysis, at least two different species were identified as causal agents of disease. Out of 14 strains isolated from raspberry tumors, 12 were identified as tumorigenic Rhizobium rhizogenes, one belonged to Agrobacterium tumefaciens genomic species G8, while the remaining strain formed a separate phylogenetic lineage within A. tumefaciens species complex, different from all known genomic species. All strains investigated harbored nopaline-type of Ti plasmid and showed identical pathogenic properties by inoculating several test plants. However, they were divided into two genetic groups based on PCR-RFLP analysis of Ti plasmid virA-virB2 region. Furthermore, total of nine unique ERIC-PCR profiles were identified among the strains studied. Although strains of R. rhizogenes exhibited similar ERIC-PCR profiles, they were differentiated into six distinct genetic groups. Based on the fact that some genetic groups were composed of strains originating from different geographic areas, it can be assumed that they have a common origin and were probably disseminated by movement of infected plant material