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Disease Note. Archontophoenix alexandrae, a New Host of Pseudomonas solanacearum in Australia. E. Akiew, Plant Pathology Branch, DPI, P.O. Box 1054, Mareeba 4880, Queensland, Australia. F. Hams, Kamerunga Research Station, Redlynch 4872, Queensland, Australia. Plant Dis. 74:615. Accepted for publication 8 February 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0615A. Recently, Alexandra palm trees (Archontophoenix alexandrae
H. Wendl. & Drude) in a commercial palm nursery in Cairns, Queensland,
began dying prematurely. Diseased trees failed to produce seeds
and had wilted, desiccated leaves and vascular tissues with brown
to black discoloration. Copious milky white droplets of bacterial exudate
formed on freshly cut vascular tissues a few hours after cutting.
A steady stream of whitish bacterial ooze emanated from pieces of
discolored vascular tissues that were suspended in water. A gramnegative,
rod-shaped bacterium (0.5 X 1.5 µm) isolated from border
lesions in the trunks of infected trees was found to be pathogenic
to l-yr-old Alexandra palm seedlings. The bacterial isolates were
identified as Pseudomonas solanacearum (Smith) Smith based on the
scheme presented by N. J. Palleroni in Bergey's Manual of Systematic
Bacteriology (1984). The isolates were classified as biovar III on the
basis of their ability to utilize three hexose alcohols (mannitol, sorbitol,
and dulcitol) and to produce acid from three disaccharides (cellobiose,
maltose, and lactose) (1). The bacterium caused symptoms typical
of bacterial wilt in Nicotiana tabacum L., Capsicum annuum L.,
Solanum tuberosum L. S. melongena L., Arachis hypogaea L., and
Lycopersicon esculentum Mill. This is the first report of a member
of the Palmae as a host for P. solanacearum in Australia and elsewhere. |