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Production of Basal Soft Rot Symptom and Maceration of Carnation Tissue by Pseudomonas caryophylli and Corynebacterium species. Chelston W. D. Brathwaite, Graduate Assistant, Department of Plant Pathology, Cornell University, Ithaca, New York 14850; Robert S. Dickey, Professor, Department of Plant Pathology, Cornell University, Ithaca, New York 14850. Phytopathology 60:1040-1045. Accepted for publication 4 February 1970. DOI: 10.1094/Phyto-60-1040.

A species of Corynebacterium was commonly isolated from the basal soft rot tissue of carnation plants infected by Pseudomonas caryophylli. Carnation plants root-inoculated with P. caryophylli and, 1 week later, with Corynebacterium sp. wilted more rapidly than plants inoculated with P. caryophylli alone or simultaneously with the two organisms. When wilting occurred, all plants inoculated first with P. caryophylli and later with Corynebacterium sp. developed extensive root discoloration and rotting, while plants inoculated simultaneously with the two bacteria exhibited less extensive root rot; only a few plants inoculated with P. caryophylli alone showed any discernible root discoloration. Corynebacterium sp. alone caused no visible effect on the plants. Carnation leaf tissue was rapidly macerated when incubated in phosphate buffer (pH 7.0, 0.1 m) containing both P. caryophylli and Corynebacterium sp.; maceration commenced 30 hr after inoculation and reached a maximum value at 66 hr. The initiation and amount of maceration was affected by the inoculum concentration of cells of Corynebacterium sp. but not by P. caryophylli. Maceration was more rapid when tissue was inoculated with P. caryophylli and later inoculated with Corynebacterium sp. than when the sequence of inoculation was reversed. Tissue incubated with Corynebacterium sp. alone was slightly macerated 72 hr after inoculation, while tissue incubated with P. caryophylli alone was not macerated after 7 days.