Screening And Optimization Of Root Rot Control Bacteria Of Atractylodes Chinensis And Their Disease Control And Growth Promotion Effects

Atractylodes chinensis is an important local medicinal herb in Jilin Province.In recent years,due to excessive resource exploitation and severe damage to the local ecological environment,the wild resources of this area are in danger of extinction.To solve the problem of A.chinensis’s resource shortage,a large amount of artificial cultivation has appeared.However,long-term continuous cultivation often leads to a series of soil diseases,including root rot disease,which seriously threatens the A.chinensis industry.Compared with traditional physical and chemical methods,using beneficial microorganisms as a biocontrol strategy is considered an environmentally friendly choice for managing fungal diseases.Therefore,this article focuses on the biological control of A.chinensis,a Chinese medicinal herb with significant economic value in Jilin Province,screening microbial strains suitable for biocontrol of A.chinensis,using microbiological techniques to screen for multi-functional microbial strains that are disease-resistant and promote growth,optimizing nutrient composition and fermentation conditions to prepare efficient biocontrol agents,and returning them to the rhizosphere of A.chinensis to improve its disease resistance.In this study,A.chinensis,one of the genuine medicinal materials in Jilin Province,was selected as the main object of study.Two strains of pathogenic bacteria were screened from the rhizosphere of sick A.chinensis,and a variety of beneficial microbial resources were selected from the rhizosphere of healthy A.chinensis,and a composite biocontrol agent was prepared.Finally,a tieback experiment was carried out.The main conclusions are as follows:（1）Two strains of pathogenic bacteria,Fusarium solani and Fusarium oxysporum,were screened from the inter-root soil and leaves of diseased A.chinensis,and 43 strains of bacteria with different morphologies were screened from the inter-root soil of healthy A.chinensis.and one fungal strain.In the standoff test,13 bacterial strains and one fungal strain were found to inhibit both F.oxysporum and F.solani.The five strains that were more than 80%antagonistic to F.oxysporum were selected and assayed for proliferation and disease resistance.Four strains of Bacillus spp.were found to have the ability of phosphorus solubilization,potassium solubilization,nitrogen fixation and IAA production,while Trichoderma harzianum and four strains of Bacillus spp.also contained a variety of biocontrol factors.（2）The four strains of Bacillus spp.were constructed as composite inoculants.The inoculation sequence of composite inoculants was determined by the growth curves of the four strains of Bacillus spp..The range of carbon source,nitrogen source and carbon nitrogen ratio was determined by single factor experiment.Sucrose 10 g,peptone 15 g,KH₂PO₄5 g,distilled water 1000 m L.The selection levels of fermentation temperature,initial pH value of medium,inoculum ratio and loading volume were determined by single-factor test,and on this basis,the Box-Benhnken central combination test was used to optimize the test,and the optimal fermentation conditions were determined by response surface analysis and combined with actual operation:temperature 33℃,starting pH value 8,inoculum volume 3%,and loading volume 50m L/250 m L.（3）The different treatments obtained by screening and compounding with T.harzianum and Bacillus complex were found to be resistant not only to F.oxysporum but also to A.chinensis.It increased the content of total nitrogen,phosphorus,potassium,IAA and chlorophyll in the leaves and promoted the growth of the plants.In addition,the application of F.oxysporum combined with Bacillus subtilis complex preparation significantly reduced MDA content and increased the activities of plant antioxidant enzymes such as PPO,PAL,and POD through the verification test of F.oxysporum infestation,thus improving the antagonistic ability of northern celandine to root rot.In addition,analysis of inter-root soil after inoculation with biocontrol fungicides showed that Bacillus complex and T.harzianum could increase the abundance and diversity ratio of soil fungal populations,improve soil microbial community structure,reduce the abundance of pathogenic bacteria such as Fusarium and Volutella,increase the content of beneficial bacteria such as Holtermanniella and Metarhizium,and improve the potential of root rot prevention of A.chinensis.The potential of A.chinensis for root rot prevention was improved by increasing the content of beneficial bacteria.