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Disease Note.

First Report of Erwinia amylovora on New Host Species in the Genus Sorbus. T. vander Zwet, USDA-ARS, Appalachian Fruit Research Station (AFRS), Kearneysville, WV 25430. Plant Dis. 79:424. Accepted for publication 27 January 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-0424C.

Characteristic shepherd's crook symptoms of fire blight, caused by Erwinia amylovora, were observed in early July of 1994 on a 6-yr-old Chinese mountainash (Sorbus folgneri (C. Schneider) Rehd.) tree at the U.S. National Arboretum in Washington, DC. This tree originated from seed collected from the Shennongjia Forest District in the People's Republic of China. Similar symptoms were also observed on 14 5-yr-old trees of Korean mountainash (Sorbus alnifolia (Siebold & Zucc.) K. Koch), cultivar Red Bird, at the Princeton Nurseries near Allentown, NJ Infected shoots were collected from the diseased trees, and tissues from lesions were plated on nutrient-yeast-dextrose agar with incubation at 26 C. Resulting bacterial colonies were streaked onto selective Crosse-Goodman medium and examined for craters characteristic of those produced by E. amylovora. Analyses of cellular fatty acids showed bacteria from both tree species belonged to the E. amylovora group (1). Pathogenicity tests conducted on immature pear fruit in the laboratory at 26 C and on succulent shoots of potted Jonathan apple in the greenhouse at 28 C resulted in typical fire blight symptoms. This is the first report of these two mountainash species as hosts of E. amylovora (2). The strains from these host plants have been deposited in the AFRS worldwide collection for this pathogen as well as in the American Type Culture Collection in Rockville, Maryland.

References: (I) J. M. Wells et al. J. Phytopathol. 140:31, 1994. (2) T. van der Zwet and H L. Keil, U.S. Dept. Agric Handh. 510, 1979.