Gram-negative, nonsporeforming rods with rounded ends, 0.3 to 0.7 by 1.0 to 1.8 pm, occurring singly or in pairs; motile by means of one to five polar flagella. Rather slow-growing, gray-white, smooth, glistening, raised and circular or slightly irregular to undulate colonies are produced on nutrient agar; levan negative or levan positive on nutrient-sucrose (5%) agar; produces a weak, blue-green fluorescent, diffusible pigment on King’s B medium; some strains produce a brown diffusiblepigment. Metabolism is respiratory. Oxidase negative, catalase positive. Acid is produced from D-( +)-galactose, glucose, D-( +)-ribose, sucrose (slow), D-( +)- xylose, and mannitol; no acid is produced from maltose, D-( +)-raffinose, erythritol, or salicin; alkali is produced from L-( +)-tartrate; esculin, arginine, gelatin, and starch are not hydrolyzed; generally, arbutin and casein are not hydrolyzed. Nitrates are not reduced. H2S is not produced from cysteine. No growth occurs in nutrient broth at 37°C or with 5% NaC1. Hypersensitivity is produced in tobacco leaves. The deoxyribonucleicacid contains 60 mol% guanine plus cytosine (3). Causes galls and wartlike excrescences on various species of Oleaceae and N. oleander L. Gall-forming isolates produce indolyl-acetic acid and cytokinin-like substances in vitro.

The following pathovars of P. syringae subsp. savastanoi are recognized: pathovar oleae, causing parenchymatic galls on various species of the Oleaceae (15, 16); pathovar nerii, causing parenchymaticgalls or wartlike excrescences on N. oleander L. and various species of the Oleaceae (14); and pathovar fraxini, causing wartlike excrescences on F. excelsior L. and 0.europea L. (2, 5 , 13).