CHARACTERIZATION OF STREPTOMYCETES CAUSING DEEP-PITTED SCAB OF POTATO IN QUEBEC, CANADA

Nine streptomycete strains that cause deep-pitted scab of potato were characterized by performing 138 physiological and morphological tests. A numerical analysis revealed that the deep-pitted scab-inducing organisms were related to strains belonging to cluster 1 of Williams et al. (Streptomyces albidoflavus). The levels of similarity between the deep-pitted scab-inducing strains and strains of Streptomyces scabies and Streptomyces acidiscabies were low (52 and 54%, respectively). The fatty acid profiles of the deep-pitted scab-inducing organisms differed considerably from those of S. scabies and S. acidiscabies. The deep-pitted scab-inducing bacteria were characterized by the predominance in their profiles of the 15:0 anteiso, 15:0 iso, 16:0 iso, 16:0, and 17:0 anteiso acids. The results of physiological characterization experiments, a fatty acid analysis, and whole-cell protein electrophoresis showed that the deep-pitted scab-inducing strains characterized in this study formed a relatively homogeneous group. These pathogenic strains could also be differentiated from S. scabies by their high cellulolytic and proteolytic activities.