Effects of five chemicals on inhibitory activity and carbon metabolism of Ralstonia solanacearum

Tobacco bacterial wilt caused by Ralstonia solanacearum is one of the important diseases in tobacco production, which seriously affects the yield and quality of tobacco leaves. In order to screen out efficient chemical agents for controlling tobacco bacterial wilt, the inhibitory activity of zhongshengmycin, oxytetracycline, benziothiazolinone, kasugamycin and chlorobromoisocyanuric acid on R. solanacearum was determined by plate colony counting method. The Biolog GEN III Microplate was used to investigate the carbon metabolism and chemical susceptibility of R. solanacearum under the stress of the above five chemicals. The results showed that R. solanacearum was restrained by all the five chemicals, and their antibacterial activity from strong to weak was zhongshengmycin > oxytetracycline > benziothiazolinone > kasugamycin > chlorobromoisocyanuric acid with EC₅₀ values of 0.24, 0.74, 2.84, 7.95 and 273.99 mg/L, respectively. The Biolog GEN III carbon metabolism showed that all the 71 carbon sources such as monosaccharides and amino acids in the Biolog GEN III Microplate could be metabolized by R. solanacearum. However, under chemical stress, the metabolism of carbon sources by R. solanacearum was inhibited to varying degrees, with amino acids, hexoic acids, carboxylic acids, esters and fatty acid carbohydrates being the most significantly inhibited. As the concentration of the tested chemicals increased, R. solanacearum reduced the metabolic intensity of 65, 18, 60, and 7 carbon sources in the Biolog GEN III Microplate under 6 mg/L of zhongshengmycin, 8 mg/L of oxytetracycline, 30 mg/L of kasugamycin and 5738 mg/L of chlorbromoisocyanuric acid stress, and increased 6, 53, 10, and 60 carbon sources, respectively. Under the stress of 8 mg/L benziothiazolinone, the metabolic intensity of 71 carbon sources of R. solanacearum decreased. In addition, the susceptibility of R. solanacearum to 23 chemicals in the Biolog GEN III Microplate differed at different concentrations of the five chemicals stress and without chemical treatment, with greater sensitivity to low pH and less sensitivity to low concentrations of NaCl. This study can provide a reference for the selection and efficient utilization of chemical control agents to tobacco bacterial wilt.