| Walnut,a perennial of deciduous fruit trees, belongs to Juglandaceae Juglans. Walnut’s fruit, seed shell, leaves and wood all have many uses. Because of its rich nutrition, good taste and multiple uses, the walnut was named one of the four nuts in the world. Walnut is planted in many places around the world. China is one of the origins of walnut, and in China, walnut is one of the most widely distributed economic trees. As the walnut disease gradually serious, people were paying more and more attention to the study of walnut diseases. Through consulting a large number of documents, we found solution starch bacillus has stronger antagonistic to the many plant diseases. So, this experiment used a Bacillus amyloliquefaciens which has strong inhibition on walnuts root rot pathogen as bio-control bacteria. Through the optimization of fermentation process, to improve the antibacterial rate of the fermentation, finally using the fermentation liquid to make an effective wettable powder. The main content of the experimental results are as follows:(1) Optimization of Bacillus amyloliquefaciens for the medium and the fermentation conditions. Combining the single factor method and the orthogonal test, this study found that, in the formula, the best carbon source is the 1% of soluble starch, and the best nitrogen source is the 1% of peptone. The best inorganic salt is 0.01% of the KH2PO4 and 0.05% of the MgSO4. The optimal of fermentation conditions selected by the inhibitory rate of changes from different inoculation and time period in a small fermenter, using the single factor method, was 42 hours of fermentation time and the 1% of inoculums. And the optimal conditions of fermentation screened by orthogonal test is 25℃, the initial pH value is 7.0, the stirring speed is 200 r/min, and the ventilation volume is 100 L/h. In such conditions, biocontrol could obtain the higher bacteriostasis activity. Based on the orthogonal test data, the nutrient elements has the greatest effect on the antibacterial activity, and the effect of minimum was KH2PO4. In such fermentation conditions, the largest influence on the antibacterial activity is ventilation, and the minimum is the temperature.(2) Selection of wettable powder carrier and additives and determination of optimal proportion. First, according to the effects of the activity from vector and auxiliary on the biocontrol, and using the single factor method, the results showed that the carrier was kaolin, the dispersant was sodium tripolyphosphate, the wetting agent was the SDBS, the protective agent was humic acid. And then through the suspension rate and biocontrol’s activity, by comparing the data obtained from the orthogonal test, the best ratio is the 35% of kaolin,5% of sodium tripolyphosphate,10% of SDBS, and 2.5% of humic acid. The largest effect on biocontrol activity is the kaolin, and the minimum is SDBS. The greatest impact on the reagent’s suspensibility is kaolin, and the minimum is humic acid.(3) The detection index of wettable powder. Wettable powder were obtained by using the fermented liquid got from the optimization of fermentation and determine the best carrier and auxiliary mixing ratio, then drying and crushing. The test results of indicators for the preparation of the wettable powder as follows:the suspended rate was 74%, the wetting time was 97 seconds, the pH value was 6.75, the water content was 2.61% and the fineness is 44μm. In pot experiment,500 times dilution degree of drug control effect as high as 71.43%. |
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