Isolation And Identification Of Biocontrol Bacillus For Atractylodes Chinensis Root Rot Disease And Biocontrol Mechanism Study

Atractylodes chinensis root rot disease is a common soil-borne disease that causes rotting of the roots of Atractylodes chinensis,which has a huge impact on the quality and yield of Atractylodes chinensis.Currently,chemical control is the main method for controlling root rot disease in Atractylodes chinensis,but the control effect is not ideal.At the same time,the overuse of chemical pesticides leads to the development of resistance in pathogenic bacteria,making the disease more difficult to control.Therefore,the use of biocontrol bacteria to control root rot disease in Atractylodes chinensis has become a new approach.The aim of this study is to identify the pathogenic bacteria of root rot disease in Atractylodes chinensis,screen out biocontrol Bacillus strains that can control root rot disease,and explore the biocontrol mechanism of these strains,providing rich microbial resources for the biological control of root rot disease in Atractylodes chinensis.The results of this study are as follows:1.Isolation and identification of the pathogen of Atractylodes chinensis root rot and biocontrol Bacillus:The pathogen of the root rot disease of Atractylodes chinensis was identified as through the isolation and identification of the pathogen from the infected plants collected from Longhua,Chengde,Hebei Province.Two biocontrol Bacillus,SFJ-27 and SFJ-41,were isolated from the rhizosphere soil of the medicinal plant,which showed inhibitory effects on the pathogen of the root rot disease.Bacillus subtilis was identified as the strain SFJ-27,Bacillus velezensis was identified as the strain SFJ-41.Pot experiments showed that the strain SFJ-27 had a control effect of 52.27%on the root rot disease of Atractylodes chinensis,the strain SFJ-41 had a control effect of 68.19%.Meanwhile,the strain SFJ-27 could promote the growth of Atractylodes chinensis seedlings.2.The fermentation conditions of biocontrol Bacillus SFJ-27 and biocontrol Bacillus SFJ-41 were optimized in shake flasks.According to the results of single-factor experiments,the optimal fermentation conditions for biocontrol Bacillus SFJ-27 were temperature of 30℃,pH of 7.0,and rotation speed of 125 r/min;the optimal fermentation conditions for biocontrol Bacillus SFJ-41 were temperature of 30℃,pH of 6.0,and rotation speed of 250 r/min.The results of the orthogonal experiments finally determined that the optimized fermentation conditions for biocontrol Bacillus SFJ-27 were pH of 6.0,temperature of 28℃,and rotation speed of 225 r/min,while the optimized fermentation conditions for biocontrol Bacillus SFJ-41 were pH of 7.0,temperature of 25℃,and rotation speed of 225 r/min.3.Research on the biocontrol characteristics of biocontrol Bacillus SFJ-27 and biocontrol Bacillus SFJ-41 shows that both strains can secrete siderophores and decompose organic phosphorus,as well as produce lipase.After antibacterial peptide synthesis gene detection and antibacterial peptide mass spectrometry detection,it was finally determined that both biocontrol Bacillus SFJ-27 and biocontrol Bacillus SFJ-41 can produce three classes of antibacterial peptide substances:Iturin,Surfactin,and Fengycin.4.Research on the production of antibacterial substances by biocontrol Bacillus SFJ-27 and biocontrol Bacillus SFJ-41 shows that the main components of the volatile substances produced by biocontrol Bacillus SFJ-27 and biocontrol Bacillus SFJ-41 include alkanes,organic acid esters,amines,aldehydes,acids,sulfones,and ethers,among others.The main components of the crude extract of antibacterial peptides produced by biocontrol Bacillus SFJ-27 and biocontrol Bacillus SFJ-41 include amino acids and their derivatives,organic acids and their derivatives,lipids,vitamins,nucleotides and their derivatives,polyamines,organic heterocyclic compounds,sugars and their derivatives,and amines,among others.In summary,this study focuses on theisolation and identification of the root rot disease of Atractylis chinensis,and identified two types of biocontrol Bacillus based on this pathogen.The fermentation conditions of the two biocontrol Bacillus were optimized,and the antibacterial substances of the two biocontrol Bacillus were identified,providing new biological control methods and ideas for Atractylis chinensis root rot disease.