Abstract
The phytopathogen Ralstonia solanacearum undergoes spontaneous phenotype conversion (PC) from a wild-type pathogenic form to a non-pathogenic form in plants, soil, broth culture, and after prolonged culture on agar plates. We investigated the suppression of bacterial wilt disease of eggplant using a PC mutant (E-PCstr). We also tested varietal differences in suppression of bacterial wilt disease by E-PCstr using 12 susceptible commercial eggplant cultivars. At primary inoculation, eggplant seedlings were inoculated with 20 mL cell suspensions (106, 108 cfu·mL−1 of live and heat-killed E-PCstr). Seven days after primary inoculation, the seedlings were challenge inoculated with 20 mL of bacterial suspension (107 cfu·mL−1 of the pathogenic strain 8238rif which is a spontaneous mutant from the wild type strain 8238 and resistant to rifampicin). In seedlings inoculated with 108 cfu·mL−1 of live E-PCstr, effective suppression of bacterial wilt disease was observed. In the suppressed seedlings, E-PCstr colonized and vertical movement of 8238rif was limited. There were varietal differences in suppression of the bacterial wilt disease induced by E-PCstr, and a correlation between the suppression of and resistance to bacterial wilt disease was observed among the eggplant cultivars.
