Biological Control of the Bacterial Wilt of the Tomato ‘Micro-Tom' by Phenotypic Conversion Mutants of Ralstonia solanacearum

抄録

Ralstonia solanacearum causes bacterial wilt in tomatoes and undergoes spontaneous phenotypic conversion (PC) from a wild-type pathogenic to non-pathogenic form. We investigated the suppressions of bacterial wilt disease of the tomato cv. Micro-Tom by using PC mutants. Tomato seedlings were pre-inoculated with a PC mutant suspension and then challenge-inoculated with the wild-type strain. Seedlings pre-inoculated with the selected PC mutant showed suppression of bacterial wilt in both soil and hydroponic tests. We also analyzed the expressions of pathogenesis-related (PR) protein genes in the tomato to elucidate the mechanisms underlying the disease control by the PC mutant. The expressions of basic PR proteins were induced in tomato roots by inoculation with the PC mutant. Our results suggested that an induced defense response is involved in the biological control of bacterial wilt in tomatoes by the PC mutant. In addition, there was no effect on the growth, yield or quality of the tomato plants inoculated with the PC mutant. We also used 18 PC mutants to investigate the suppression of bacterial wilt in tomato plants. Some strains showed effective suppression against the disease. We suspect that the suppression of bacterial wilt in tomatoes by PC mutants could become a practical biological control method.