Microecological Effects Of Bacillus Subtilis B579 And The Preparation Of Microbial Agents

The plant soil-borne Fusarium wilt caused by pathogenic fungi has been a major problem in agricultural production for a long time.The traditional method for controlling soil plant diseases was to apply chemical pesticides,but this method has great harm to the human and the environment.Therefore,the biocontrol methods using beneficial microorganisms to control plant diseases have become an important way for sustainable development of agriculture.The main method of biological control was to apply biocontrol bacteria in the rhizosphere soil of plants to played a role in controlling soil-borne diseases after its colonization.Bacillus subtilis was a commonly used biocontrol strain.In this study,Bacillus subtilis B579 was treated in rhizosphere soil of cucumber,a common vegetable crop.Through the high-throughput sequencing technology of genomics and the analysis of key enzyme activities in soil,the application of biocontrol bacteria to rhizosphere microecological was clarified.Powder preparation Bacillus subtilis B579 was prepared.It laid a theoretical foundation for the field application of B579 in the future.The main contents of the study are as follows:1.Effect of B579 on microbial diversity in cucumber rhizosphere soil.Bacillus subtilis B579 was applied to the rhizosphere soil of cucumber by field experiment.Four different treatments methods were used,which were,deionized water treatment,F.oxysporum treatment,B579 treatment and B579+F.oxysporum treatment respectively.Three parallel experimental groups were set up in each treatment.Samples were taken every four weeks during the cucumber growth cycle and were sampled four times.Genomic DNA of cucumber rhizosphere soil samples was extracted using soil genomic DNA extraction kit.The microbial community diversity of bacteria and fungi in rhizosphere soil was analyzed by high-throughput sequencing technology combined with nested PCR product cloning and sequencing technology.The results showed that the microbial diversity of the soil samples treated with B579 was significantly higher than that of the deionized water treatment group,and the B579 had different effects on the diversity of fungi and bacteria in the soil samples.2.Effect of B579 on enzyme activity of rhizosphere soil of cucumber.In order to study the effect of biocontrol bacteria B579 on the key enzyme activities in the rhizosphere soil of cucumber,the obtained soil samples were tested using a soil enzyme kit.The results showed that the application of biocontrol bacteria B579 in cucumber rhizosphere soil could significantly increase the activities of soil fertility-related enzymes such as alkaline phosphatase,catalase,chitinase and urease.And the biocontrol bacteria B579 treatment had the highest enzyme activity,followed by the antagonistic treatment and the deionized water treatment,and the pathogens treated the enzyme activity was the lowest.3.Preparation of B579 powder and its parameter detection.Diatomite,which has excellent properties such as low cost,chemical stability and strong adsorption,was used as carrier.And the sucrose as thermal protective agent.Bacillus subtilis B579 as the strain,the optimum ratio of fermentation broth and diatomite was determined by physical method.A preparation with biocontrol function and nutritional function was developed.The effective viable cell count of the powder preparation was3.0×10¹¹CFU/g.According to the preparation standard of agricultural microbial powder preparation,the technical indexes of the powder preparation were tested.All the indexes met the requirements,the water content was 6.87%,the pH was 6.23,the fineness was94.6%,and the effective period was 7.2 months,etc.