| EBS05, an endophytic bacteria strain from Cinamonum camphora periderm organization, had strongly antagonist activity to many kinds of the plant pathogenic fungus and the tobacco mosaic virus, and had many excellent properties as biological controls factor, such as tolerance of acid and alkali, salt, heat, etc.In order to further research the bio-control potential of EBS05, colonization trends, fermentation conditions and control effect of EBS05 were investigated in this paper. Results were as follows:1. Mutation strains derivative of original endophytic bacteria strain EBS05 were obtained by the method of continuous screening on series concentration of antibiotic in media and ultraviolet rays induction, which had resistance to 120μg/mL streptomycin and 5μg/mL rifampicin and showed genetic stability and steady antifungal activity against Rhizoctonia cerealis. Colonization trends of endophytic bacteria EBS05 in wheat was assayed using the mutation strains as screening marker by means of spread-plate technique,.The results showed that the endophytic bacteria EBS05 exhibited strong colonization capacity in wheat, and could move from root to stem and/or leaf. The colonization amount was in direct proportion to inoculation concentration, only which was more than 10~8 cfu/mL, the colonization and further transfer could effectively occurred. After treatment by soaking seed and drench with fermentation broth at 10~8 cfu/mL cell density, colonization amount of strains EBS05 in wheat root was more than that in stem and leaf at the same treatment time. The colonization amounts in root, stem and leaf increased gradually in the early stage of treatment, reached peaks at the tenth or twelfth day after treatment, then start to decrease.2. In order to improve the control effect of EBS05 endophytic bacteria ,The optimum fermentation conditions were determined by means of one-factor design and orthogonal array design methods used Rhizoctonia cerealis as target pathogen. Results indicated that the optimum fermentation medium was constituted of soluble starch3%, peptone 2% and sodium chloride 0.25%. The optimum fermentation conditions were as following: initial pH 5~9, temperature 34°C, medium volume 25 mL/250 mL flask, inoculation volume 3%, incubated for 72 h..3. The fermentation broth of EBS05 had significant inhibitory effect to Rhizoctonia cerealis, With fermentation processing Rhizoctonia cerealis, cell inclusion increased, intercellular diaphragm became thicker, some cells got deformitied, hyphac bifurcate significantly increased.4. The control efficiency of endophytic bacteria EBS05 for wheat sharp eye-spot by pot experiment and the field experiment Application of the culture broth of endophytic bacteria EBS05 was proved to be more effective in controlling wheat sharp eyespot, compared with fungicide fludioxonil. The suppressive effects of fermentation broth and bacteria-free filter on the wheat sharp eyespot were up to 91.2% and 88.2% in the greenhouse, and 66.3% and 56.2% in the field, respectively.5. The association toxicity of EBS05 and Celest was studied ,by method of .through determiningthe hypha growth rate . Results show that there is certain inhibition when EBS05 and Celest role in Rhizoctonia Cerealis.EC50 is 109.365μg/mL、80.318μg/mL respectively, After both according to certain proportion mixtured, EC50 is 81.845μg/mL, Efficiency ratio is SR=1.23, In 0.5-2.6 area, Control effect that using the mixture for Rhizoctonia Cerealis equales to that summing EBS05 and Celest,and Control effect stability. |
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