Study On The Antimicrobial Mechanism And The Control Effect Of Endophytic Bacteria

Ginseng (Panax ginseng C. A. Meyer) is known as the king of herb medicines, which grew mainly at Changbai Mountain in the northeast of China. At present, ginseng productions in the market were mainly produced by cultivation. Change from wild to artificial cultivation, soil-born diseases of P. ginseng becoming more and more severily, and which results in the significant lose of yield and decrease of quality. Though traditional chemical controlling method can control most of disease in the field, however, pesticide residues problem made ginseng industry suffered huge economic losses. Endobacteria lived in the interior of plants, relatively stable living environment made biocontrol agents from them helpful for us to resolve problems, such as pesticide residue, resistance to pesticide and instability control effect, etc. In the present study, we focused on isolation and identification endobacteria by molecular biology and morphological methods, screening and characterization strains that having antagonistic activity to ginseng pathogens. Moreover, antagonistic mechanism and their controlling effect on ginseng diseases in the field were studied, also. All of them provided us theoretical foundation for further development of biocontrol agents.In total, forty types of endophytic bacteria were isolated from two-year ginseng, and ge15in them having antagonistic activity to can prevention and control pathogens. By16S rDNA homology analysis and microscopic observation, ge15was belonging to Stenotrophomonas sp., and with the highest similarity with Stenotrophomonas rhizophila. When cultured ge15with ginseng pathogens, wide inhibition zone indicated that ge15has significant antagonistic activity.Through microscopic observation we found that, pathogen mycelia in treatment cultured with ge15grows abnormally, sporulation decreased significantly and the spores can not germinate.The supernatant of fermentation broth and crude lipopeptid could inhibit the growth of ginseng pathogens significantly. And also, the crude lipopeptid was insensitive to high-temperature, high-pressure, enzymatic hydrolysis.When cultivated with PDA medium containing antibiotic, we found that ge15with antibiotic marker could keeping a certain population in ginseng root, stem, and leaves. And the recovered ge15strain still has strong antagonistic activity to ginseng phytopathogens. The controlling effect of ge15was similar to pesticide carbendazol, and the emergence rate and seedling survive rate was significantly higher than control, and showed no harmful effect on the growth of ginseng seeds and seedlings.