Pantoea agglomerans is the etiological agent for black spot necrosis on beach peas

Abstract

Pantoea agglomerans was isolated from necrotic spots in the leaves of a beach pea (Lathyrus maritimus L.) that grew on the shorelines of Newfoundland, Canada. The bacterium produced cellulase and amylase and was shown to be a wound parasite. Ultrastructural studies of infected leaves showed bacterial aggregates surrounded by pellicles, within intercellular spaces of the necrotic tissue. The bacterium was adapted to temperate climatic conditions. On a culture medium it grew at 5–37 °C, with optimal growth observed at 10–25 °C. Under natural environmental conditions beach peas may be exposed to seawater. When the bacterium was tested for growth tolerance to NaCl, the NaCl was inhibitory, most noticeably at concentrations above 250 mM. Beyond contributing to mechanical injury of plant tissue and keeping the plant surface moist, it is likely that seawater would hinder, rather than enhance, the survival of the bacterium during the phase of the infection process when it was outside the host plant.Key words: beach pea, host–pathogen, Lathyrus maritimus, Pantoea agglomerans.