ENZYMATIC RELATEDNESS AMONGST PHYTOPATHOGENIC CORYNEFORM BACTERIA AND ITS POTENTIAL USE FOR THEIR IDENTIFICATION

API ZYM and other experimental enzymatic API-galleries (aminopeptidases, esterases, osidases) were tested on 197 strains representing 16 phytopathogenic coryneform species. It was our aim to evaluate the utility of these tests in the identification of members of this group. The data were subjected to a numerical analysis. At the 71% similarity level, eight phenons were distinguished. Phenon A consisted of Clavibacter michiganense subsp. sepedonicum, a homogeneous phenon with an internal similarity of 82%. The phena B and C comprised the other subspecies of Clavibacter michiganense i. e. Clavibacter michiganense subsp. insidiosum, Clavibacter michiganense subsp. nebraskense, Clavibacter michiganense subsp. tessellarius and Clavibacter michiganense subsp. michiganense. Phenon C moreover, also comprised Curtobacterium species. The 4 pathovars of Curtobacterium flaccumfaciens were related to some Clavibacter michiganense subspecies; they could not be differentiated by API ZYM tests. Phenon G harboured Rhodococcus and Clavibacter xyli strains. In phenon H, eleven coryneforms isolated from Lolium rigidum clustered together with Clavibacter rathayi and Clavibacter tritici. Rhodococcus species (phenon G) and the group of 'grass coryneforms' (phenon H) were only distantly related to the other phena of phytopathogenic coryneforms. According to the enzymatic tests strains of the following taxa were scattered over at least two phenons: Clavibacter michiganense subsp. michiganense, subsp. insidiosum, and subsp. nebraskense; Curtobacterium flaccumfaciens pv. flaccumfaciens and Arthrobacter ilicis. For the differentiation of phytopathogenic coryneforms beta-galactosidase, beta-xylosidase and alpha-mannosidase seem to be the best differentiating features.