Survival, transmission, and taxonomy of Pseudomonas syringae van Hall, the causal organism of bacterial brown spot of bean (Phaseolus vulgaris L.)

Abstract

Pseudomonas syringae van Hall was shown to be transmitted on seed of bean (Phaseolus vulgaris L.). The pathogen survived in bean field soil until April but not until May. Isolates studied were pathogenic to pea, but not to red clover, white dutch clover, ladino clover, alfalfa, or white lupine. Attempts to isolate P. syringae as a pathogen or as an epiphyte from plants in fence lines and wind breaks surrounding diseased bean fields failed. It was concluded that infected seed is a principal source of the bacterial brown spot pathogen in Wisconsin. Routine bacteriological tests including the utilization of 12 carbohydrates, six organic acids, and 30 other diagnostic tests did not differentiate P. syringae and P. pisi Sackett. These two species differed with respect to acrylamide disc-gel electrophoretic protein patterns, electrophoretic peroxidase isozymes, toxin production, and host range. Isolates of P. syringae produced a toxin with characteristics of syringomycin, whereas isolates of P. pisi did not produce such a toxin.