Tomato Early Blight Of Biological Function Research Of Antibacterial Selection And Antagonism

Tomato early blight is one of the hazards tomato pathogen of tomato growth and great harm for it. With the planting tomato in our country increases, the scope and extent of the dangers of early blight are also gradually increasing. Resistance to pathogens caused by the abuse of chemical pesticides increased, it is difficult to control. In this paper, by screening out early blight from antagonistic bacteria and research on the biological control of early blight.In this study, the antagonistic strain suppress early blight of tomato strongly which screen from the four strains that had been saved in our lab. The screened antagonistic strain was identified by using morphological, physiological, biochemical tests and16S rRNA gene phylogenetic analysis; The fermentation of screened antagonistic strain was centrifuged and forages the cell with ultrasonic disruption and centrifuge the solution; Make the antagonistic experiment with the supernatant of fermentation of screened antagonistic strain and of the solution which was produced by cell disruption; Measure the diameter of inhibition zone respectively; Use antagonistic experiment to detect the activity of antagonistic substances in different temperature gradient, the pH level and span of UV exposure time respectively; Culture the of pathogen in the PDA medium which contain filtered fermentation brotof screened antagonistic strain; Detect the mycelium of morphology and spore germination; In the pot experiment, spraying the fermentation of screened antagonistic strain to the leaves of tomato, then detect the efficiency of the biocontrol.When cultivated with plant fungal pathogen Early blight on PDA plate, antagonist strain H show strong ability to suppress the growth of the pathogen. Its inhibition zone diameter is17.75mm. The strain was identified as Bacillus subtilis by using morphological, physiological, biochemical tests, In addition,16S rRNA gene and phylogenetic analysis illustrated that the antagonistic strain H exhibits high levels of similarity to known Bacillus subtilis.The supernatant of fermentation of antagonistic strain H show strongly suppression but the solution of cell disruption was not. The fermentation which was hydrolysised with Proteinase K and Trypsin can not suppress the growth of fungi. When the temperature is from25℃to40℃, The antibacterial activity of antibacterial substances is best, the temperature at70℃or80℃, only showed a weak antifungal activity. When the pH is9, the antifungal activity of antagonistic substances is strong. Expose in the ultraviolet during4hour, the activity of the antagonistic substances is the same as the control group. If the time of exposure is more than4hours, the activity of the antagonistic substances is declined.At30℃the fermentation broth can significantly inhibit the growth of mold, the inhibitory rate was92%, and also found that most of the pathogen mycelium distortion and fracture occurs.Biological control application of experimental subjects potted tomato plants, The fermentation broth of the antagonistic strains of tomato early blight prevention and play the most significant role in the prevention of early blight.