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Resistance

Resistance of Phaseolus Line WBR 133 to Pseudomonas syringae. Margaret E. Daub, Department of Plant Pathology, University of Wisconsin, Madison 53706; D. J. Hagedorn, Department of Plant Pathology, University of Wisconsin, Madison 53706. Phytopathology 69:946-951. Accepted for publication 9 March 1979. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-946.

Phaseolus line WBR 133 has a high degree of resistance to Pseudomonas syringae, causal agent of bacterial brown spot of bean. Histologic leaf imprint, diffusive resistance porometric, and scanning electron microscopic studies showed no differences between WBR 133 and Tenderwhite, a susceptible cultivar, that would affect penetration of the bacteria into the leaf. In vivo multiplication of the pathogen showed large differences between the two hosts. Bacteria multiplied exponentially in the susceptible host to reach a final concentration of about 5 × 10⁶ cells per square centimeter of leaf, compared with 5 × 10⁴ cells in resistant plants. Resistance was decreased by high temperature, high light intensity, and short day length.