Sensitivity of Ralstonia solanacearum to four fungicides and synergistic toxicity of combinatory fungicides.

To screen the effective fungicides inhibiting tobacco bacterial wilt, streptomycin was used as the control agent, and the sensitivities of Ralstonia solanacearum to fungicides fluazinam, SYP-14288, benziothiazolinone and kasugamycin were determined by Bioscreen C growth curve tester. The synergistic interactions between fluazinam and nano sulfur, nano copper, nano silver at nine combination ratios were tested respectively by the Wadley method. The results showed that the average EC₅₀ values of SYP-14288 and fluazinam against R. solanacearum were 0.037 8 and 0.305 0 μg/mL, the distribution ranges of EC₅₀ were 0.018 7-0.053 4 μg/mL and 0.147 1-0.890 4 μg/mL respectively. The average EC₅₀ values of streptomycin, benziothiazolinone and kasugamycin against R. solanacearum were 0.546 3, 2.429 9 and 9.927 3 μg/mL, indicating that fluazinam and SYP-14288 could effectively inhibit the growth of R. solanacearum, and their control effects were better than that of streptomycin. The sensitivity baselines of R. solanacearum to the five fungicides all obeyed normal distribution with continuous single peak curves, which could be used for monitoring the strains resistant to R. solanacearum in tobacco fields. The EC₅₀ of the combined fluazinam and nano fungicides at different ratios were all lower than that of single nano fungicide. The combination of fluazinam and nano sulfur at a volume ratio of 1:40 had a synergistic coefficient of 1.60. The additive effect was the most obvious when fluazinam and nano copper were mixed at the ratio of 80:1(EC₅₀=0.142 2 μ g/mL). There was an additive effect by mixing fluazinam and nano silver at 1:20, and the synergistic coefficient was 1.41. [ABSTRACT FROM AUTHOR]