Abstract
Avirulent strains of Erwinia carotovora subsp. carotovora CGE234M403 and CGE10M2 obtained by mutagenesis using ethylmethanesulfonate, suppressed soft rot of cabbage leaf efficiently. The degree of soft rot suppression correlated with the ratio of the cell concentration of avirulent strain to virulent strain. Only living cell of avirulent strains showed soft rot suppressiveness. Whereas heat-killed bacteria and supernatant broth excluding bacteria did not show soft rot suppresiveness. The strain CGE10M2 suppressed the growth of wild strains of Erwinia which were susceptible to the bacteriocin produced by CGE10M2. On the other hand, the strain CGE234M403 showed strong suppression activity to even some virulent strains which were resistant to the bacteriocin. Therefore, although antibacterial activity of bacteriocins may contribute to disease suppression, other factor(s) may play a part in the soft rot suppression mechanisms.
