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Multiplication of Pseudomonas cepacia in Onion Leaves. Stanley O. Kawamoto, Former Graduate Assistant, Department of Plant Pathology, Cornell University, Ithaca, New York 14850, Senior author is now Research Technician II; James W. Lorbeer, Professor, Department of Plant Pathology, Cornell University, Ithaca, New York 14850. Phytopathology 62:1263-1265. Accepted for publication 12 May 1972. DOI: 10.1094/Phyto-62-1263.

Initial symptom expression in young onion leaf blades injected with different concentrations of Pseudomonas cepacia was delayed from 1 to 5 days as inoculum concentration was decreased from 10⁸ cells/ml to 10³ cells/ml. Concentrations less than 10³ cells/ml failed to induce symptoms. Young leaves were highly susceptible; most mature leaves failed to develop symptoms. The population of P. cepacia increased to more than 10⁹ cells/leaf disc from an initial population level of 10⁴ cells/leaf disc. The initial symptoms of water-soaking and wilting were expressed when the peak population was attained. Bacteria declined in number after appearance of symptoms. None was reisolated once diseased leaves became dry and brittle. Air-dried diseased leaves apparently are not sources of inocula in the field.