1994 Volume 60 Issue 1 Pages 13-19
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.