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Pseudomonas caryophylli in Carnation. IV. Unidentified Bacteria Isolated from Carnation. Robert S. Dickey, Professor, Departments of Plant Pathology, Cornell University, Ithaca, New York 14850; Paul E. Nelson, Professor, Departments of Plant Pathology, The Pennsylvania State University, University Park 16802 Phytopathology 60:647-653. Accepted for publication 3 November 1969. DOI: 10.1094/Phyto-60-647.

Standard indexing procedures were used to isolate the unidentified bacteria from healthy carnation seed, leaves, and stems. The unidentified bacteria were isolated more frequently from stems than from seeds or leaves, and were isolated more frequently from older leaves than from younger upper leaves. The bacterial contaminants became associated with the basal stem tissues during rooting of cuttings, and subsequent development of the bacteria was related to plant growth. The distribution of bacteria was continuous in the portion of the stem immediately above the roots, and was random and discontinuous in the remainder of the plant. The bacteria occurred with almost equal frequency in nodal and internodal stem areas, and were isolated from the epidermis, cortical, vascular, and pith tissues of the stems. The occurrence and distribution of the unidentified bacteria in carnation stems were not affected by soil moisture. Culture-indexing alone detected only about 50% of the cuttings that contained unidentified bacteria. Subirrigation of stock plants and indexing cuttings immediately after they were removed from stock plants resulted in fewer cuttings contaminated with bacteria, but the height at which the cuttings were removed from the stock plant had no effect. None of a selected group of isolates of unidentified bacteria caused any discernible symptoms when inoculated into side shoots of carnations. However, one of these isolates caused a more rapid development of symptoms when shoots were inoculated simultaneously with the isolate and the pathogen, Pseudomonas caryophylli, than with the pathogen alone. This isolate had been isolated from a wilted carnation plant infected by P. caryophylli.