Screening Of Antagonistic Bacteria Against Four Diseases Of Potato And Optimization Of Fermentation Conditions

In order to search for antagonistic strains of potato Fusarium wilt,Verticillium wilt,nevoid and late blight,92 strains ofbacteria were isolated and screened from soil samples of Inner Mongolia by screening spores,which were divided into 7 genera.Bacillus,Paenibacillus,Lysobacter,Psendomonas,Brevibacillus,Ochrobactrum and Enterobacter,respectively.The most dominant genus was Bacillus,including 67 strains,accounting for 73%of the total bacterial species.19 strains could inhibit potato Fusarium wilt,Verticillium wilt,black nevoid and late blight,and 9 belong to Bacillus,6 strains belong to Paenibacillus,2 strains belong to Lysobacter,1 strain belongs to Psendomonas,1 belongs to Brevibacillus.Plate stand-off test showed that P01 had the best inhibitory effect on potato late blight H5 had the best inhibitory effect on potato wilt,black nevoid and late blight,P16 had the best inhibitory effect on potato wilt and verticillium wilt,and P01 had the best inhibitory effect on potato blight and Verticillium wilt.Both black nevoid disease and late blight had inhibitory effect.Most of the strains with good biocontrol effect had the ability of fixing nitrogen,dissolving inorganic phosphorus and producing iron carrier.In order to achieve the best biomass,single factor experiment and orthogonal experiment were used to optimize the fermentation conditions of the four strains with the best antagonistic effect The results showed that the best formula of P01 strain was 10 g/L tryptone,5 g/L yeast extract,10 g/L sodium chloride,8 g/L sucrose,10 g/L maltose,6 g/L casein and lg/L magnesium sulfate.The optimum culture conditions were pH 7.2,fermentation temperature 28?,fermentation time 52 h,fermentation speed 180 r min,inoculum size 250 ?L/50 mL.The best formula of P16 strain was tryptone 10 g/L,yeast extract 5 g/L,sodium chloride 10 g/L,sucrose 8 g/L,glucose 6 g/L,peptone 8 g/L,magnesium sulfate 2.5 g/L.The best culture conditions of pH 8.0,28 ?fermentation temperature,fermentation time 35 h,fermentation speed 160 r/min,inoculation amount including 250 ?L/50 mL.The best formula of H5 strain was tryptone 10 g/L,yeast extract 5 g/L,sodium chloride 10 g/L,sucrose 8g/L,glucose 8 g/L,peptone 10 g/L,magnesium sulfate 1.5 g/L.The best culture conditions of pH 8.0,30?fermentation temperature,fermentation time 24 h,fermentation speed 180 r/min,inoculation amount including 250 ?L/50 mL.The best formula for K16 strain was 10 g/L tryptone,5 g/L yeast extract,10 g/L sodium chloride,8g/L sucrose,6 g/L glucose,8 g/L casein,2 g dipotassium phosphate.The best culture conditions of pH 7.2,30?fermentation temperature,fermentation time 47 h,fermentation speed 180 r/min,inoculation amount including 150 ?L/50 mL.