Rhizobium tumorigenes sp. nov., a novel plant tumorigenic bacterium isolated from cane gall tumors on thornless blackberry

Four plant tumorigenic strains 932, 1019, 1078(T) and 1081 isolated from cane gall tumors on thornless blackberry (Rubus sp.) were characterized. They shared low sequence identity with related Rhizobium spp. based on comparisons of 16S rRNA gene (≤98%) and housekeeping genes atpD, recA and rpoB (<90%). Phylogenetic analysis indicated that the strains studied represent a novel species within the genus Rhizobium, with Rhizobium tubonense CCBAU 85046(T) as their closest relative. Furthermore, obtained average nucleotide identity (ANI) and in silico DNA–DNA hybridization (DDH) values calculated for whole-genome sequences of strain 1078(T) and related Rhizobium spp. confirmed the authenticity of the novel species. The ANI-Blast (ANIb), ANI-MUMmer (ANIm) and in silico DDH values between strain 1078(T) and most closely related R. tubonense CCBAU 85046(T) were 76.17%, 84.11% and 21.3%, respectively. The novel species can be distinguished from R. tubonense based on phenotypic and chemotaxonomic properties. Here, we demonstrated that four strains studied represent a novel species of the genus Rhizobium, for which the name Rhizobium tumorigenes sp. nov. is proposed (type strain 1078(T) = DSM 104880(T) = CFBP 8567(T)). R. tumorigenes is a new plant tumorigenic species carrying the tumor-inducing (Ti) plasmid.