Numerical Taxonomic Analysis of Agrobacterium

SUMMARY: Ninety-two biochemical, physiological and nutritional characters of 70 Agro-bacterium strains and a few representatives of the genera Rhizobium, Pseudomonas, Erwinia, Achromobacter, Klebsiella and Escherichia were subjected to computer analysis. Sixty-five agrobacteria fell into two distinct clusters. All authentic 3-keto-lactose-positive Agrobacterium tumefaciens and A. radiobacter strains grouped in one rather heterogeneous cluster, whereas the atypical 3-ketolactose-negative tumour-inducing agrobacteria, and the named A. rhizogenes strains, grouped in a very tight cluster. Agrobacterium rubi and two other 3-ketolactose-negative tumour-inducing strains were not placed in either cluster. Two other strains were misnamed. Diagnostic characters are presented for distinguishing clusters and groups. The present division of the genus into species is based on phytopathogenicity and does not reflect the natural relationships amongst the agrobacteria.