The Classification, Identification and Nomenclature of Agrobacteria

Abstract

In order to devise a scheme for the identification and differentiation of agrobacteria, 50 strains of Agrobacterium , mostly those maintained in the National Collection of Plant Pathogenic Bacteria, were separated into four clusters when subjected to numerical taxonomic analysis. For the two major clusters, regardless of the phytopathogenic effect of the strains, we would adopt the species names A. tumefaciens and A. rhizogenes. A third cluster merits the use of the specific name A. rubi whilst a hitherto unrecognized fourth cluster of yellow‐pigmented isolates may constitute a fourth species in the genus. The species name A. radiobacter is rejected as this species is synonymous with A. tumefaciens and the latter, being the type species of the genus, takes priority. To indicate the phytopathogenic effect of strains within our four Agrobacterium clusters we would use the terms: saprophytic state, tumourigenic state and rhizogenic state. Revised descriptions, without regard to phytopathogenic effect, are given for A. tumefaciens, A. rhizogenes and A. rubi.