Isolation And Identification Of Biocontrol Bacteria S7 And Y10 And The Disease Prevention Effect On Ginseng Gray Mold

A total of 224 strains,105 bacteria,77 fungi,and 42 actinomycetes were isolated in 10 different soil samples.Among the 59 strains of isolated and purified antibacterial bacteria,32 were bacteria,17 were fungi,and 10 were actinomycetes.Initial screening and rescreening were carried out by the plate confrontation method of the strain and its fermentation concentrate,and finally two strains of highly effective antibacterial S7 and Y10 bacteria with an antibacterial rate of more than 80%were selected.According to the morphological and physiological and biochemical characteristics of 16S rDNA of S7 strain,the homology alignment sequence of ITS rDNA sequence of Y10 strain and the strain phylogenetic tree constructed based on the homology sequence,the S7 strain was preliminarily identified as Bacillus subtilis Trichoderma harzianum.The influence of culture conditions on the bacteriostatic activity of S7 and Y10 strains and their fermentation concentrates showed that the bacteriostatic effect on the ginseng Botrytis cinerea was the strongest under the temperature of 20℃ and neutral conditions,and the bacteriostatic effect was stronger under the condition of strong acid and alkali weak.The antibacterial effect of S7 and Y10 strains on ginseng Botrytis cinerea in different concentrations of PDA medium is more than 50%,indicating that their biocontrol effects are not completely nutrition competition;S7 strain fermentation concentrate is stable to temperature,pH,and ultraviolet light The performance is better,and the range of adaptation is wider.The thermal stability of the Y10 strain fermentation concentrate is weak,but it is stable to pH and ultraviolet.S7 and Y10 strains were tested for defensive enzymes in ginseng tissues using an ice-bath grinding method using a UV spectrophotometer.It was found that the defensive enzyme activity in the ginseng roots in different treatments was significantly higher than that in the control sprayed with sterile water only.Defensive enzyme activity was highest in the root of Botrytis cinerea,followed by Botrytis cinerea+S7 treatment and Botrytis cinerea+Y10 treatment;again,the defensive enzyme activity of S7 strain and Y10 strain treatment.In the mixed treatment of biocontrol fungus and Botrytis cinerea,the defense enzyme activity of the biocontrol fungus was the highest after 24h,followed by the simultaneous control.The defense enzyme activity was the lowest after the biocontrol fungus and the gray fungus.S7 and Y10 strains were used to control the gray mold of ginseng roots by spraying with bacterial suspension,and the disease index was measured by the cross method.It was found that only spraying S7 and Y10 treatments had no disease,and other treatments occurred in varying degrees.Disease.Among the different treatments,the control effect of inoculation with B.cinerea was the highest after 24h,followed by the control effect of simultaneous inoculation,and the control effect of inoculation with B.cinerea was inoculated after 24h.It shows that the preventive effect of S7 and Y10 strains is stronger than the therapeutic effect.