Suppression of Bacterial Wilt in Potatoes by Non-pathogenic Ralstonia solanacearum using Bud Pieces and Plants Grown from Bud Pieces

Abstract

The phytopathogen Ralstonia solanacearum undergoes spontaneous phenotypic conversion (PC) from a wild-type pathogenic form to a non-pathogenic form in plants, soil, and broth culture, and after prolonged culture on agar plates. Using a bud piece and the plant grown from the bud piece, we investigated the suppression of bacterial wilt disease by the PC mutant 8266PC in potatoes that cannot be grafted. In plants inoculated with 10⁸ cfu·mL⁻¹ of 8266PC, the effective suppression of bacterial wilt disease was observed. This suppression effect was reduced at high temperatures and a high pathogenic bacterial density. However, we observed a high incidence of biological control (66.7%) even under severe conditions (30°C/27°C and 10⁶ cfu·g⁻¹). Bud pieces inoculated with less than 10⁴ cfu·mL⁻¹ of 8266PC emerged and grew like those grown in sterile distilled water. Consequently, we inoculated bud pieces with 10⁴ cfu·mL⁻¹ of 8266PC, but no suppression effect on bacterial wilt was observed.