Screening Of Antagonistic Strains And Bactericide For Bacterial Stem And Root Rot Of Sweet Potato

Bacterial Stem and Root Rot of Sweet Potato is a newly discovered bacterial disease caused by Dickeya dadantii in China recent years.The disease is extremely harmful and can infect sweet potatos' leaves,stems and roots.The typical symptom of the disease is that the base of the sweet potato stem becomes black,rotten and soft,and the infected leaves turn yellow.The vascular bundles invaded by the stems and roots are dark brown,and the roots are taupe rot and smelly.In this paper,the biological characteristics of bacterial stem and root rot of sweet potato pathogens were studied,and the bactericides which inhibited bacterial stem and root rot of sweet potato and their control methods were screened,and the antagonistic strains which inhibited bacterial stem and root rot of sweet potato were screened indoors.It laid a foundation for further research on the control methods of bacterial stem and root rot of sweet potato.The main findings are as follows(In this paper,BSRRSP is used to refer to bacterial stem and root rot of sweet potato):1.Biological characteristics of BSRRSP pathogen: D.dadantii is a Gram-negative bacterium,and belongs to facultative anaerobic bacteria.The suitable growth temperature range was 18 °C~42 °C,and the lethal temperature was 70 °C.The growth pH range was 4~9,and citrate could be utilized.Different strains had different utilization of carbon sources,and none of the three strains could utilize nitrite.2.Screening of effective bactericides for BSRRSP: 10 kinds of bactericides were screened by effective indoor bactericides to inhibit Dickeya dadantii,such as 72%agricultural streptomycin,0.3% tetramycin,3% thiazolone and 6% chloramphenicol.The five bactericides with different action mechanisms were used in the subsequent pot experiment.Different application methods of the effective bactericide and the concentration of the experiment were used.It was found that 72% of the agricultural streptomycin was soaked in different concentrations for 10 min and 30 min.There was no significant difference in the control effect on BSRRSP,and the control effect was above 80%.The five kinds of bactericides had no control effect on bacterial stem and root rot of sweet potato.The suitable concentrations of the five bactericides were sprayed when the sweet potato seedlings were cut,6% spring leimycin 500× was the best,20% thiazole zinc 250×,72% agricultural streptomycin 2000 × control effect was not effective.3.Screening and identification of antagonistic strains of BSRRSP: isolated from soils harvested from healthy sweet potato and BSRRSP and infected with sweet potato roots,and screened 23 antagonistic strains which inhibited Bacterial Stem and Root Rot of Sweet Potato by plate sputum culture method in vitro(some of the strains could induce root rot),5 strains of antagonistic strains which had antagonistic effectson bacterial stem and root rot of sweet potato and did not cause the root rot of sweet potato were screened out,and 4 strains of antagonistic bacteria were Bacillus amyloliquefaciens.The other strain was Bacillus subtilis.