title: Diversity, distribution, and antagonistic activities of rhizobacteria of Panax notoginseng.
abstract: BACKGROUND
  Rhizobacteria play an important role in plant defense and could be promising sources of biocontrol agents. This study aimed to screen antagonistic bacteria and develop a biocontrol system for root rot complex of Panax notoginseng.
  
  
  METHODS
  Pure-culture methods were used to isolate bacteria from the rhizosphere soil of notoginseng plants. The identification of isolates was based on the analysis of 16S ribosomal RNA (rRNA) sequences.
  
  
  RESULTS
  A total of 279 bacteria were obtained from rhizosphere soils of healthy and root-rot notoginseng plants, and uncultivated soil. Among all the isolates, 88 showed antagonistic activity to at least one of three phytopathogenic fungi, Fusarium oxysporum, Fusarium solani, and Phoma herbarum mainly causing root rot disease of P. notoginseng. Based on the 16S rRNA sequencing, the antagonistic bacteria were characterized into four clusters, Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetesi. The genus Bacillus was the most frequently isolated, and Bacillus siamensis (Hs02), Bacillus atrophaeus (Hs09) showed strong antagonistic activity to the three pathogens. The distribution pattern differed in soil types, genera Achromobacter, Acidovorax, Brevibacterium, Brevundimonas, Flavimonas, and Streptomyces were only found in rhizosphere of healthy plants, while Delftia, Leclercia, Brevibacillus, Microbacterium, Pantoea, Rhizobium, and Stenotrophomonas only exist in soil of diseased plant, and Acinetobacter only exist in uncultivated soil.
  
  
  CONCLUSIONS
  The results suggest that diverse bacteria exist in the P. notoginseng rhizosphere soil, with differences in community in the same field, and antagonistic isolates may be good potential biological control agent for the notoginseng root-rot diseases caused by F. oxysporum, Fusarium solani, and Panax herbarum.
authors.affiliation: School of Energy and Environment Science, Yunnan Normal University, Kunming, PR China; Key Laboratory of Microbial Diversity in Southwest China of Ministry of Education and Laboratory for Conservation and Utilization of Bio-Resources, Yunnan Institute of Microbiology, Yunnan University, Kunming, PR China.
authors.forename: Ze-Yan
authors.initials: ZY
authors.lastname: Fan
authors.affiliation: Key Laboratory of Microbial Diversity in Southwest China of Ministry of Education and Laboratory for Conservation and Utilization of Bio-Resources, Yunnan Institute of Microbiology, Yunnan University, Kunming, PR China.
authors.forename: Cui-Ping
authors.initials: CP
authors.lastname: Miao
authors.affiliation: Key Laboratory of Microbial Diversity in Southwest China of Ministry of Education and Laboratory for Conservation and Utilization of Bio-Resources, Yunnan Institute of Microbiology, Yunnan University, Kunming, PR China.
authors.forename: Xin-Guo
authors.initials: XG
authors.lastname: Qiao
authors.affiliation: Key Laboratory of Microbial Diversity in Southwest China of Ministry of Education and Laboratory for Conservation and Utilization of Bio-Resources, Yunnan Institute of Microbiology, Yunnan University, Kunming, PR China.
authors.forename: You-Kun
authors.initials: YK
authors.lastname: Zheng
authors.affiliation: Department of Chemistry and Life Science, Chuxiong Normal University, Chuxiong, PR China.
authors.forename: Hua-Hong
authors.initials: HH
authors.lastname: Chen
authors.affiliation: Key Laboratory of Microbial Diversity in Southwest China of Ministry of Education and Laboratory for Conservation and Utilization of Bio-Resources, Yunnan Institute of Microbiology, Yunnan University, Kunming, PR China.
authors.forename: You-Wei
authors.initials: YW
authors.lastname: Chen
authors.affiliation: Key Laboratory of Microbial Diversity in Southwest China of Ministry of Education and Laboratory for Conservation and Utilization of Bio-Resources, Yunnan Institute of Microbiology, Yunnan University, Kunming, PR China.
authors.forename: Li-Hua
authors.initials: LH
authors.lastname: Xu
authors.affiliation: Key Laboratory of Microbial Diversity in Southwest China of Ministry of Education and Laboratory for Conservation and Utilization of Bio-Resources, Yunnan Institute of Microbiology, Yunnan University, Kunming, PR China.
authors.forename: Li-Xing
authors.initials: LX
authors.lastname: Zhao
authors.affiliation: School of Energy and Environment Science, Yunnan Normal University, Kunming, PR China.
authors.forename: Hui-Lin
authors.initials: HL
authors.lastname: Guan
keywords: Panax notoginseng; antagonistic activities; diversity; rhizobacteria