Abstract
Reactions of tobacco leaf tissues infiltrated with either wild types or induced mutants of Xanthomonas campestris pv. oryzae were investigated. Leaf areas infiltrated with high concentration levels (more than 107 cells/ml) of virulent strains developed yellowing discoloration followed by necrosis of hypersensitive-like reaction (HLR) by 96hr after infiltration. The development of necrosis was much delayed with weakly virulent mutants and no necrotic lesions developed with avirulent mutants. Virulent revertants induced from avirulent mutant regained inductivity of necrosis, suggesting that close relationship exists between the virulence to rice and necrosis inductivity to an uncongenial plant of tobacco. Population changes in tobacco leaf tissues were different between virulent and avirulent strains, that is, the population sharply decreased accompanied with development of necrosis in the former, while it was remained constant or gradually declined in the latter.
