Isolation And Idenification Of Chitosan Degrading Bacteria And Inhibition Of Bacteria Cultures To The Cucumber Blight Disease

1. Studies the biological activity controls the plant disease of chitosanMake the different contents solution of chitosan, and choose 6 kinds of pathogenic fungi for trial: Fusarium.sp,Fusarium.acuminatum,Fusarium.oxysporum,Fusarium.semitectum,Alternaria.solani,Alternaria.cucumerina. The results showed that 0.2% of the solutions was the best to the inhibition the pathogenic fungi. We found with different contents solution of chitosan, soaked the seeds, within 1h, 5% solution (10×) better than other treatment and control. Soaked seeds with 5% solution (10×) and dipped the roots, inoculate the cucumber seedling with blight pathogens, compared with control group, the enzyme activity of chitin will be reduced which were treated by chitosan and meanwhile the incidence of a disease lower than control. The incidence of a disease is 50% by dipped the roots, 82% by soaked seeds, 94% by control, respectively.2. Separating and screening of the bacteria with chitosanCollected 166 soil samples from Gansu and screened the microorganism in the soil with chitosan culture medium. We selected 2 bacteria which can grow in the chitosan culture medium: SQ-2-H and H-5-B. The results show that on NA culture medium the logarithm growth period within 20-32h (SQ-2-H and H-5-B); on chitosan culture medium the optimum pH within 6.1—6.6 (SQ-2-H and H-5-B); the SQ-2-H logarithm growth period within 40-70h in optimum pH and H-5-B logarithm growth period within 60-72h in optimum pH. We used Schales to examine the changes of activities of enzyme: enzyme activity of SQ-2-H to be greatest under optimum pH needed 50h and H-5-B needed 70h under optimum pH.3. Preliminary identify the SQ-2-H and H-5-B16S rDNA array analysis results show the SQ-2-H is Chryseobacterium sp. RHA2-18 and H-5-B is Bacillus cereus 1Re107 in gene bank, they have 98% similar and 96% similar, respectively. We could see the relation far between SQ-2-H and H-5-B by the systematic tree. It shows that SQ-2-H is G^-, H-5-B is G⁺.4. Preliminary research to prevent the cucumber blight disease of solution of chitosanScreened fungus (SQ-2-H and H-5-B) in quick-acting N ((NH)₂SO₄) and have no quick-acting N of chifosan culture medium fostered continuously 192h, respectively. Every 24h checked the results of restrain impression. From the results we could know: in quick-acting N ((NH)₂SO₄) culture medium the restrain impression higher than the no quick-acting N culture medium, both SQ-2-H and H-5-B. The experiment to prevent the cucumber blight disease, we found:using SQ-2-H dipped roots by quick-acting N of chitosan, the effect of prevention the cucumber blight disease is the best.