Screening Of Antagonistic Bacteria Against Steptomyces Scabies And Preliminary Study On Its Biocontrol Mechanism

In recent years,the damage of scab disease in the main potato producting areas in China has gradually increased.However,the existing methods have poor control effects and cannot effectively reduce the damage of scab disease.It has caused serious economic losses to the potato industry in China and restricted the potato industry develop.Potato scab disease is a soil-borne disease caused by a variety of Steptomyces spp.,which is difficult to control by conventional methods.Biological control is an effective way to prevent soil-borne diseases and has gradually become a research hotspot.The purpose of the study is to screen scab bacteria-resistant strains with high antagonistic effects,and to study the control effect and mechanism of antagonistic bacteria through pot experiments,to provide bacteria resources for the development of biocontrol agents,and also to provide the prevention and treatment of the theoretical foundation for potato scab disease.The test results are as follows:1.Through plate confrontation,oxford cup method and safety test,the antagonistic strains BKS51 and BKS104 were screened.They have obvious antagonistic effects against Steptomyces scabies,and the bacteriostatic diameters reached 37.0 mm and 43.3 mm,respectively.2.Using spectrophotometry to measure the OD value of the antagonist at 600 nm and the bacteriostatic diameter of the scab bacteria to determine the best fermentation and culture conditions for the antagonistic bacteria.The results showed that the best fermentation conditions for strain BKS51 were inoculation of 8%～10%,and fermentation and culture at 160 r/min,30℃,p H 5～7 for 48～72 h is the best fermentation conditions for strain BKS104 It is inoculated with inoculum of 8%～10%,and fermented for 48～72 h under the conditions of 140 r/min,30℃,and p H 5～7.3.The results of potted plant control experiments show that the strains BKS51 and BKS104 have good control effects on potato scab disease,and the control effect increases with the increase of the inoculation amount.The control effect of BKS51 with different inoculation amounts is 48.76%～73.09%.,The control effect of BKS104 with different inoculation amount is 57.15%～81.15%.4.Clarify the classification status of BKS51 and BKS104 through morphology,physiology,biochemistry and molecular biology identification.The results showed that the bacterial colony of the strain BKS51 was round,milky white and opaque,with fold-like protrusions on the surface,dull,irregular edges,no pigment production,and spores.The bacterial colony of the strain BKS104 is round,milky white,opaque,the colony is moist,the surface is shiny,the edges are neat,there is no pigment production,and it contains spores.Based on the results of physiological,biochemical and molecular biology identification,the strain BKS51 was identified as Bacillus amyloliquefaciens;and BKS104 was identified as Bacillus velezensis.5.Preliminary study on the biological control mechanism of strains BKS51 and BKS104,the results showed that strain BKS104 can produce siderophore,and strains BKS51 and BKS104 can produce cellulase;after the two strains are applied to the soil,the quantity first decreases and then stabilizes.It indicates that both strains can colonize the potato rhizosphere soil;both strains BKS51 and BKS104 have significant growth-promoting effect on potato,which not only significantly promote the morphological indicators of potato plants and increase the biomass,but also increase the weight of potato tubers.Strains BKS51 and BKS104 can increase the number of potato rhizosphere microorganisms;suitable inoculation of antagonistic bacteria can increase the activities of soil urease,acid phosphatase,invertase,catalase and polyphenol oxidase.6.Through high-throughput sequencing of rhizosphere soil bacterial groups,the results showed that a total of 31 bacterial phylum and 514 bacterial genus were detected in the seedling stage,and 34 bacterial phylum and 520 genus were detected in the tuber growth stage.The application of two antagonistic bacteria can increase the bacterial population diversity of potato rhizosphere soil.The two antagonistic bacteria can significantly increase the abundance of Pseudomonas with nitrogen fixation and biocontrol effects and Flavobacterium with soil remediation ability in rhizosphere soil.