Isolation,Identification And Growth Promoting Effect Of Endophytic Bacteria From Atractylodes Macrocephala Koidz

Endophytic bacteria are a group of microorganisms that reside within the healthy tissues and organs of plants at various stages of growth without causing any noticeable negative effects on plant development.Some of these bacteria play a crucial role in promoting plant growth and influencing their development.The medicinal plant Atractylodes macrocephala Koidz has been adversely affected by the excessive use of pesticides and chemical fertilizers during cultivation.Therefore,the development and utilization of A.macrocephala endophytic promoting bacteria can significantly reduce the use of these chemicals during cultivation.In this study,we aimed to isolate,purify,and identify endophytic bacteria from A.macrocephala,determine their growth-promoting properties,optimize their culture conditions,and evaluate their effects on the growth of other plants,including A.macrocephala.We also analyzed the fermentation broth of the strain to provide a foundation for the development of microbial fertilizers.The study yielded the following results:1.Four endophytic bacteria of A.macrocephala were isolated,and their growthpromoting properties were tested.Strain BZ-8 produced IAA,phosphorus,and iron carriers,and showed antagonistic effects against Fusarium graminearum and Rhizoctonia solani Kuhn.Strain BZ-29 produced IAA,phosphorus,and iron carriers,and showed antagonistic effects against Sclerotium rolfsii Sacc,Rhizoctonia solani Kuhn,Gaeumannomyces graminis var.graminis(Sacc.)Walker,Rhizoctonia solani Kuhn and Fusarium oxysporum Schltdl.Strain BZ-12 produced IAA,phosphorus,and iron carriers,while strain BZ-13 produced IAA,phosphorus,and iron carriers.2.The four endophytes of A.macrocephala were identified using morphological and molecular biological methods.Strain BZ-8 was identified as Serratia marcescens,strain BZ-12 as Enterobacter asburiae,strain BZ-13 as Bacillus toyonensis,and strain BZ-29 as Bacillus amyloliquefaciens.3.The media formulation and culture conditions of A.macrocephala endophytic bacteria were determined through single-factor experiments and response surface optimization,respectively.Compared to the formulation before optimization,the optimized formulation significantly increased the growth of A.macrocephala endophytes.The growth of strains BZ-8,BZ-12,BZ-13,and BZ-29 were enhanced by 208%,155%,160%,and 200%,respectively.4.The fermentation solution of A.macrocephala endophytic bacteria significantly promoted the growth of A.macrocephala,Nicotiana tabacum L.,and Zea mays L.Strain BZ-13 had the most significant growth-promoting effect on the agronomic traits of A.macrocephala,N.tabacum,and Z.mays,while strains BZ-8,BZ-12,and BZ-13 had very significant growth-promoting effects on the agronomic traits of N.tabacum.Strain BZ-29 had the most significant growth-promoting effect on the agronomic traits of Z.mays.5.All four endophytic bacteria fermentation solution of A.macrocephala significantly affected the expression of key genes for the synthesis of sesquiterpene lactones in A.macrocephala after three days of addition to A.macrocephala roots.Analysis of GC-MS data from the fermentation broth of A.macrocephala endophytic bacteria revealed that it was rich in secondary metabolites such as Digitoxin,1,2-Benzenedicarboxylic acid,butyl octyl ester,Retinal,and Undecanal.In conclusion,the study provides valuable insights into the isolation,identification,and growth-promoting properties of A.macrocephala endophytic bacteria.The optimized culture conditions and significant growth-promoting effects of these bacteria on A.macrocephala,N.tabacum,and Z.mays highlight their potential as microbial fertilizers.The analysis of secondary metabolites in the fermentation broth of A.macrocephala endophytic bacteria is an important step towards developing microbial fertilizers that can promote the growth of various crops.