Biological Control of Verticillium Wilt in Eggplant Using a Ralstonia solanacearum Non-pathogenic Mutant Strain

Abstract

We previously study, reported that a bacterial wilt disease of eggplant was suppressed by pre-inoculation with a non-pathogenic (phenotypic conversion: PC) mutant of Ralstonia solanacearum. In the present study, we examined the suppression of Verticillium wilt disease in eggplant using a PC mutant for which the biocontrol of other soil-borne diseases had already been achieved. We tested the suppression of Verticillium wilt by pre-inoculation with live bacteria, heat-killed bacteria, and a culture filtrate of the PC mutant, and found that the disease was suppressed when eggplant was inoculated with live bacteria. Biocontrol was increased by inoculation with a high concentration of the PC mutant. However, suppression decreased when the PC mutant-inoculated seedlings were transplanted into soil containing a high concentration (>10⁶ conidia・g^–1) of the pathogen. In cultivations at 20°C and 25°C after PC mutant inoculation, biocontrol was reduced compared with that at 30°C.