Screening And Compound Biocontrol Effect Of An Antagonistic Bacterium Against Potato Black Scurf And Scab Disease

Potato black scurf（Rhizoctonia solani）and scab（Streptomyces scabies）have a serious impact on the yield and quality of potato.The effect of conventional methods to control these two diseases is not ideal,and biological control has become a research hotspot.It has been reported that the screening and biocontrol of antagonistic bacteria against a single disease,but there is no report on the antagonistic bacteria and the compound effect of antagonistic bacteria on the two diseases.A single strain is susceptible to various environmental factors,and the control effect is unstable.The combination of biocontrol bacteria can combine strains with different antibacterial effects,complement each other,and improve the control effect.The purpose of this study was to screen out the biocontrol strains with good inhibitory effect on potato black scurf and scab,and to combine the strain with other antagonistic strains.Through pot experiment,the control effect and biocontrol effect on potato black scurf and scab were explored,which provided theoretical basis for the development of biocontrol agents.The test results are as follows:1.A strain BKS76 with good antagonistic effect against R.solani and S.scabies wa s screened by plate confrontation method.The strain BKS76 was identified as Bacillus a xarquiensis by systematic identification.Its inhibition diameter against S.scabies reached32.3 mm,and the inhibition rate against R.solani was 59.3%.2.In order to improve the antibacterial ability of BKS76,the suitable fermentation conditions of strain BKS76 were determined by measuring the OD₆₀₀value of the fermentation broth of strain BKS76 and its inhibitory effect on the two pathogens.The results showed that the optimum fermentation conditions were 6%inoculation amount,160 r/min,30℃and p H 6 for40 h.3.The strain BKS76 was compounded with the strains BKS51 and TK78 which had the best inhibitory effect on S.scabies and R.solani respectively,and three compoundin g combinations were set up,namely BKS76-BKS51,BKS76-TK78 and BKS76-BKS51-T K78.The appropriate ratio was determined by the inhibitory effect of different ratio com binations on the two pathogens.The results showed that the best ratio of the three group s was equal ratio mixing.4.The control effect of strain BKS76 and its compound on two diseases of potato was studied by pot experiment.The results showed that the control effect of BKS76 on black scurf was 42.32%-44.88%,and the control effect on scab was 36.51%-46.31%.The combination of BKS76-TK78-BKS51 was the best,and the control effect on black scurf was 55.14%-57.38%,and the control effect on scab was 56.56%-65.31%.5.The biocontrol effect of antagonistic strain BKS76 and its compound was studied.The results showed that strain BKS76 could produce siderophore and glucanase.The strain BKS76and its compound had obvious growth promoting effect on potato,which could significantly promote the morphological indexes of potato plants and increase the biomass,and also increase the weight of potato tubers.BKS76-BKS51-TK78 compound high-dose treatment had the best growth-promoting effect on potato plant morphological indexes.The plant height,stem diameter,lateral length,lateral root number and stolon in tuber growth period were 37.9 cm,8.9 mm,28.2cm,26.8 and 5.7,respectively,which were 21.86%,25.35%,49.21%,40.31%and 50.00%higher than CK blank control.This treatment can increase the weight of potato tubers by29.56%compared with CK.6.BKS76 and its combination could improve the enzyme activity,defense enzyme a ctivity and bacterial diversity of potato rhizosphere soil.The high-dose treatment of BKS76-BKS51-TK78 compound could significantly increase the activities of SOD,POD,PPO,CAT and urease,phosphatase,catalase and invertase in the tuber growth period compare d with CK,which increased by 42.38%,49.47%,30.79%,42.85%and 51.70%,59.45%,47.26%,44.08%,respectively.Compared with CK,this treatment increased the relative ab undance of Firmicutes and Acidobacteria.The treatment increased the relative abundance of Firmicutes,Acidobacteria etc.compared to CK.