Crown Gall of Stone Fruit II. Identification and Nomenclature of Agrobacterium Isolates

Twenty-seven local isolates of Agrobacterium and twenty-three isolates supplied by other laboratories were compared by biochemical tests, serology, protein patterns following gel electrophoresis, and by pathogenicity. All isolates fell into two distinct biotypes and this was supported by their serological reactions and by their protein patterns. Biotype 1 contained tumour-inducing, root-proliferating, and non-pathogenic forms; biotype 2 contained both these pathogenic forms but no non-pathogens. We believe the present division of the genus into species based on pathogenicity is untenable. If the genus is to be retained, we propose that it should consist of one species, A. radiobacter, with pathogenicity indicated by a varietal epithet and the biotype specified.