Twenty-nine cultures of
Erwinia milletiae (Kawakami & Yoshida 1920) Magrou 1937 were isolated from galls on
Wistaria floribunda DC. which were collected in several areas of the Shizuoka prefecture, Japan. Seven cultures of
E. herbicola (Lühnis 1911) Dye 1964 were isolated from the surface of leaves of
Citrus spp. and
W. floribunda DC. The physiological and pathogenicity characters of these cultures were compared. Cultures of
E. milletiae were pathogenic on only 2 plant species out of 48 tested, namely
W. floribunda DC. and
W. brachybotrys Sieb. & Zucc. on which outgrowths were formed on growing stems 10 to 14 days after inoculation. These outgrowths developed into galls about 5 mm in diameter 1 month after inoculation, 20 to 30 mm 1 year after inoculation and 50 to 60 mm 2 years after inoculation. Gall formation was also induced on the thick roots, crowns, trunks, leaf-petioles, and midribs of leaflets of the plants following wound inoculation. No culture of
E. herbicola was pathogenic in any plants tested, although one culture (EH2) induced a confluent necrosis in citrus leaf tissues when inoculated by the infiltration technique. Physiological and biochemical characters of
E. herbicola showed that this species is quite heterogeneous since out of 71 tests with seven cultures, 18 gave variable results. In contrast, the cultures of
E. milletiae were consistently homogeneous in their physiological and cultural properties, variations being detected in only 3 tests. The characters of
E. milletiae were closely similar to those of
E. herbicola, falling within the range of diversity of the latter. Therefore, we consider that on the basis of pathogenicity to
Wistaria floribunda DC. and
W. brachybotrys Sieb. & Zucc.,
E. milletiae should be classified as a pathovar of
E. herbicola under the scientific name of
E. herbicola pv.
milletiae (Kawakami & Yoshida 1920) nov. comb. Culture EM1 is proposed as the neopathotype strain of the bacterium and has been lodged in Plant Diseases Division Culture Collection, DSIR, Auckland, New Zealand and National Collection of Plant Pathogenic Bacteria, Plant Pathology Laboratory, Ministry of Agriculture, Fisheries and Food, Harpenden, England.
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