CHARACTERIZATION OF STREPTOMYCETES CAUSING RUSSET SCAB IN QUEBEC

Strains of actinomycetes causing russet scab on potato tubers were dif ferent from Streptomyces scabies and S. acidiscabies. The russet scab- inducing organisms were characterized by a bright yellow mycelium on y east malt extract (YME) which turned brown with age, and by aerial myc elium forming flexuous spore chains which appeared as a gray mass on t he colonies. The organisms utilized L-arabinose, D-fructose, D-glucose , D-mannitol, raffinose, rhamnose, sucrose, and D-xylose. They degrade d xanthine and xylan, but did not produce melanin. The russet scab-ind ucing organisms should be placed in the genus Streptomyces, since they possessed the typical morphology, biosynthesized similar fatty acids, and produced LL-diaminopimelic acid in their cell walls, characterist ic of Streptomyces species. A high level of similarity (78%) was found between the russet scab-inducing organisms and members of the cluster S. aureofaciens, indicating that both groups may be included in the s ame Streptomyces cluster.