Isolation, Identification And Biocontrol Effect Of Antagonistic Bacteria Against Pathogen

Panax notoginseng is not only a unique precious Chinese herbal medicine, but also one of the most important chinese medicines which have experienced rapid development. It has special requirements on the growing environments like climate,soil and plants. From sowing to harvest, a period of 3-5 years’ continuous cultivation is needed, which consequently lead to the happening of many barriers like root rot,etc. and root rot has already become a major barrier restricting the development of P.notoginseng industry. With the development of the plant biological control technology,the bacteria have played a quite important role in the biological prevention and control of plants. Whereas, few researches on the biological control of root rot in P.notoginseng had been reported. Focused on the biological control and application technical problems of root rot in P. notoginseng, in this study the different categories of soil samples of the P. notoginseng produced according to healthy plant soil,diseased plant soil and uncultivated soil in Wenshan were collected, the antagonistic bacteria against root rot pathogens of P. notoginseng were obtained by separating, and16S r RNA gene sequence similarity analysis the compose and diversity of active bacteria. The biological control capability of antagonistic bacteria for root rot was assessed by conducting the experiments of isolated root and living plants biological prevention, screening the stronger antagonistic activities bacteria resources and providing a new biological control method for the root rot of P. notoginseng finally.The results showed that a total of 344 bacterial isolates were obtained from the main plant areas of P. notoginseng. All the soil bacterial isolates were evaluated for their antagonistic activity to Fusarium solani, F. oxysporum, Alternaria tenuissima,Phoma herbarum by cylinder-plate and plate-confrontation methods, 146 isolates displayed antagonistic activity against pathogens in different degrees.Based on the 16S rRNA gene sequence similarity analysis, the antagonistic strains belonged to 53 species, 23 genera, 4 phyla, among which, the Firmicutes and Proteobacteria were richer than others. At the genus level, Bacillus spp. is thedominant rhizosphere antagonistic bacteria for root rot of P.notoginseng. At the species level, B. siamensis, B. tequilensis and B.thuringiensis showed much stronger antagonistic activities, and maybe were potential broad-spectrum antagonistic strains.Judged from the sources of separation, the antagonistic strains of healthy plant soil and diseased plant soil were richer, the strains of uncultivated soil was relatively single.The research showed that the B. siamensis Hs02 exhibited the stronger antagonistic activities for many pathogens of root rot in P. notoginseng, especially for the A. tenuissima. The presented sound antagonistic efficiency was as high as 85.3%.The biocontrol experiment of isolated root demonstrates that the biocontrol efficiency of B. siamensis Hs02 was ideal, the rot symptom was not obvious than the control group(only with A. tenuissima), with different bacterial cell concentrations, the root rot symptom was different and the biocontrol efficiency could reach 82.6% with the bacterial suspension concentration of 1 × 1010 cfu/mL. Therefore, the study found that B. siamensis Hs02 strains had broad-spectrum antibacterial activity for root rot of P.notoginseng, It showed the good effect to suppress the occurrence of root rot in P.notoginseng.