Two New Hosts of Pseudomonas syringae pv. tagetis. N. H. Rhodehamel, Department of Plant Pathology, USDA-ARS, Department of Plant Pathology, University of Wisconsin, Madison 53706. R. D. Durbin, USDA-ARS, Department of Plant Pathology, University of Wisconsin, Madison 53706. Plant Dis. 73:368. Accepted for publication 27 February 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0368E.
Pseudomonas syringae pv. tagetis (Hellmers) Young, Dye, & Wilkie
causes necrotic leaf spots and a striking apical chlorosis of several
Compositae: African marigold (Tagetes erecta L.), French marigold (T.
patula L.), sunflower (Helianthus annuus L.), Jerusalem artichoke (H.
tuberosus L.), common ragweed (Ambrosia artemisiifolia L.), and
dandelion (Taraxacum officinale Weber) (I). In the spring of 1988 we
isolated bacteria from two other species having identical symptoms.
They were growing in proximity to diseased Jerusalem artichoke along
an abandoned railroad line in western Dane County, Wisconsin.
Bacteria, obtained in nearly pure culture from the necrotic leaf spots,
resembled P. s. pv. tagetis in symptom expression, physiological
characteristics, and RFLP profiles. These new hosts, compass plant
(Silphium perfoliatum L.) and another sunflower species (H. salicifolius
A. Dietr.), are classified within the Compositae tribes Asteraceae and
Heliantheae, respectively, consistent with the idea that the natural hosts
of the pathogen are limited to members of the Compositae.