Bacterial Leaf Spot of Hibiscus rosa-sinensis Incited by Pseudomonas syringae pv. hibisci. J. B. Jones, GCREC, University of Florida, Bradenton. A. R. Chase, AREC, University of Florida, Apopka; B. C. Raju, Yoder Brothers, Alva, FL; and J. W. Miller, Division of Plant Industry, Gainesville, FL. Plant Dis. 70: 441-443. Accepted for publication 14 October 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-441.

Strains of Pseudomonas syringae that cause leaf spot of Hibiscus rosa-sinensis in Florida were found to be physiologically and pathogenically distinct from P. syringae pv. syringae (P. s. syringae). Strains isolated from hibiscus utilized l(+)tartrate but not dl-lactate and did not produce syringomycin or antimetabolites against Escherichia coli. Four of five strains of P. s. syringae were positive for the latter two tests, and all strains of P. s. syringae were negative for growth on l (+)tartrate and positive for growth on dl-lactate. On the basis of biochemical and pathogenicity tests, the bacterium was also distinct from two other P. syringae pathovars. We propose that the strains isolated from H. rosa-sinensis be designated P. s. hibisci. Cultivars of H. rosa-sinensis varied in susceptibility to this pathovar.