Biological Activites of Toxin Produced by Tomato Canker Bacterium, Clavibacter michiganensis subsp. michiganensis, against Tomato Plant and Its Callus Cells.

Abstract

Clavibacter michiganensis subsp. michiganensis, causal agent of bacterial canker of tomato, produces phytotoxic glycopeptide which causes wilting on tomato cuttings. In order to select toxin-tolerant callus cells and to produce resistant tomato plants, the biological activities of a crude toxin against tomato plants and callus cells were compared with the pathogenic effects of the bacterium. In callus cells co-cultured with the bacterium, susceptible cultivars had a higher percentage of dead cells than resistant cultivars, which showed apparent differences in resistance. Similar responses were obtained with callus cells treated with a crude toxin precipitated with 30 to 40% saturation of ammonium sulfate. These results paralleled closely inoculation tests to whole plants. In tomato cuttings treated with unheated and heated (120°C, 5min) toxin transpiration rates decreased to 20 to 30% and wilting symptoms occurred both in the resistant and the susceptible cultivars, although the activity of heated toxin was attenuated. This result suggests that heat-labile component(s), such as protein(s), may be associated in the toxin activity, in addition to the heat-stable components, such as polysaccharides.