Production of antibacterial substance, and changes in peroxidase and polyphenoloxidase activities in tobacco plants inoculated with avirulent isolate of Pseudomonas solanacearum

The substances obtained from the leaf, stem and root of tobacco plants inoculated with avirulent and virulent isolates of Pseudomonas solanacearum were at and on TLC plate, respectively. Both substances showed antibacterial activities not only on P. solanacearum but also on Erwinia carotovora subsp. carotovora and Escherichia coli in vitro. However, the antibacterial substances were not detectable from the filtrate of the autoclaves tobacco sap medium, in which the avirulent or virulent bacterium was cultured for 3 days. Peroxidase and poly phenoloxidase activities and their isozyme patterns did not differ significantly between plants treated with the virulent and avirulent isolates, or between the susceptible cultivar BY 4 and the resistant cultivar NC 82. However, activities of the two enzymes were increased in leaves of the susceptible cultivar BY 4 treated with either the virulent or the avirulent isolate.