The Use of Dry-Leaf Inoculum for Establishment of Common Bacterial Blight of Beans. R. L. Gilbertson, Research Associate, Department of Plant Pathology, University of Wisconsin-Madison 53706. R. E. Rand, E. Carlson, and D. J. Hagedorn. Senior Research Specialist, Research Specialist, and Emeritus Professor, Department of Plant Pathology, University of Wisconsin-Madison 53706. Plant Dis. 72:385-389. Accepted for publication 12 November 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0385.

Inoculum of Xanthomonas campestris pv. phaseoli, causal agent of common bacterial blight of beans, was prepared from dried diseased bean leaves collected from greenhouse- or field-grown plants. Viable colony-forming units in the dry-leaf inoculum were quantified on general and selective media. Pathogenic strains of X. c. pv. phaseoli were recovered from dry-leaf inoculum stored for up to 6 yr. The efficacy of dry-leaf inoculum for establishing common blight epidemics in the field was compared to that of an aqueous cell suspension in tests with a susceptible and resistant bean cultivar. Dry-leaf inoculum was applied to seed at planting or to plants at two stages of growth. Symptom severities in plants inoculated with the dry-leaf inoculum were similar to those of plants inoculated with aqueous cell suspensions. Symptom severity varied with inoculation method, but the expected cultivar reaction to the disease was observed after inoculation with dry-leaf inoculum or the aqueous cell suspension. Dry-leaf inoculum provides a simple, rapid, and effective technique for inoculating beans with X. c. pv. phaseoli, particularly where laboratory facilities are limited.