| Ginseng?Panax ginseng C.A.Meyer?is China's valuable Chinese herbal medicines,renowned Chinese and foreign.Ginseng rust caused by Cylindrocarpon destructans and ginseng black spot caused by Alternaria panax Whetz.are widely distributed in ginseng cultivation with a perennial incidence of 20%-40%,becoming the most common occurrence of ginseng production,one of the most serious fungal diseases.At present,the chemical control led to excessive pesticide residues,there is no promotion and application of pesticide residues in line with the standard chemical pesticides,making China's ginseng fungal disease breeding is difficult to make a great breakthrough,for this situation,biological control is the most ideal the way.In order to obtain the raw bacteria with excellent traits to serve the production,the experiment was carried out in this laboratory.The highly effective antagonistic bacteria,the methylotrophic bacillus B16 strain and the Bacillus amyloliquefaciens B25 strain were tested for methanogens Pathogens C.destructans and A.panax Whetz.as target bacteria,from the fermentation conditions,safety,colonization characteristics,promoting growth,control effect and antibacterial mechanism,respectively,two biocontrol bacteria biocidal potential a systematic evaluation study was conducted.The main contents of this thesis are as follows:1.The optimum fermentation medium for B16 strain was determined as follows: sucrose 1.0%,yeast extract 0.5%,MgSO4·7H2O 0.05%,FeSO4·7H2O 0.06%,NaCl 1.0%;optimum fermentation conditions: pH 7.5,Temperature 35 °C,inoculation amount 5%,liquid volume 40/250 mL,shaking speed 170 r/min,fermentation cycle 48 h.The optimum fermentation conditions were as follows: pH 7.2,temperature 32 °C,inoculation amount 3%,loading volume 50/250 mL,shaking speed 180 r/min,fermentation cycle 48 h.The results showed that the concentration of viable bacteria in the fermentation broth of B16 and B25 strains reached 6.24 × 109 cfu/mL and 1.39 × 1010 cfu/mL,respectively,which reached the technical standard of microbial fertilizer in the Ministry of Agriculture?effective activity ? 2.0 billion/mL?,The antibacterial activity of ginseng bacteria was significantly enhanced.2.The colonization rules of strains B16 and B25 in ginseng plants and rhizosphere soils were studied by antibiotic labeling method.Bacteria B16 and B25 were inoculated into the ginseng by inoculation or short-term colonization.The biocontrol strain was transferred from the root to the aerial part of the ginseng,and could be stable in the ginseng plant.Rifampicin?260 ?g/mL?and kanamycin?340 ?g/mL?were obtained.3.The biocontrol potential of B16 and B25 strains was verified in field growth environment.The application of strains B16 and B25 fermentative bacteria could increase the plant height,root diameter and root / shoot ratio of ginseng,The results showed that B25 could increase the total saponin content of Ginseng,and the B16 could not increase the ginsenoside,but the effect of B16 on the growth of ginsenoside was significantly higher than that of the control group,and the average plant height was 38.92% and 55.12% higher than that of the control.The two strains were also able to increase the content of ginsenoside.Field control experiment showed that the control effect of B16 and B25 double antibacterial strains was the best in the field,and the relative control effect was 84.36%.Compared with the pesticide control,The biocontrol strain B16 fermentative bacteria and pesticide on C.destructans prevention and control effect is quite,biocontrol strain B25 fermentation bacteria liquid higher than pesticide on A.panax Whetz.prevention and control effect.4.The pot experiment showed that the control effects of B16 and B25 were significant,and the protective effects of B16 and B25 strains were better than that of the control effects.The two treatments of B16 strain reached the significant level,and the difference between the two treatments of B25 strain not significant.Comparing with B16 strains,the preventive effect and treatment of B25 strains are better than B16,B25 strains have more better comprehensive potential.The number of bacteria and fungi in the soil was gradually restored to the control level,and the number of bacteria and fungi in the soil was gradually restored to the control level.Both of the bacteria have little effects on the population of actinomycetes in soil.5.The antibacterial mechanism of biocontrol bacteria showed that the metabolites of strains B16 and B25 had some inhibitory effects on the mycelial growth of ginseng bacteria,and the inhibitory effect was enhanced with the increase of metabolite concentration.The inhibitory effect of B25 metabolites on mycelial growth and spore germination was stronger than that of B16 strain,and the inhibitory effect of low concentration of metabolites on pathogen hyphae was not obvious.The metabolites of different dilution factors inhibited the spore germination of bacteria,and the inhibitory effect was weakened with the increase of dilution factor.The activities of inducing enzymes?POD,SOD,PPO and PAL?were lower than those in the control plants.When the biocontrol bacteria were added,the enzyme activity was enhanced and the biocontrol bacteria B16 and B25 all had the activity of enhancing the enzyme activity Disease and other adversity stress ability.The bacteria and fermentative metabolites of strains B16 and B25 did not produce significant toxic effects on mice,with a half lethal LD50>5000 mg· kg-1BW,biocontrol strains B16 and B25 could be considered as non-toxic and ginseng itself is not pathogenic.Based on the above analysis,the biocontrol strains B16 and B25 all have the functions of promoting the disease and preventing the disease,the ability to stabilize the colonization in the ginseng,the safe application,the higher the fermentation activity and the higher quality of the biocontrol bacterium.Anti-potential is stronger than B16,two strains of mixed bacteria also has a prominent biocontrol function.Biocontrol bacteria B16 and B25 has a strong practical development and application value. |
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