| Tobacco bacterial wilt are serious diseases on tobacco plant and cause huge economic losses in tobacco production.Pesticides are generally used in controlling of these diseases and the disadvantage was very obvious.Biological control using the rhizobacteria as biological agents could be a new and effective method.Because there is a considerable number of rhizospheric microbial species that may have beneficial effects on plant growth and disease control.In this study,108 isolates were isolated from rhizosphere of tobacco plant and 5 strains were selected for further use because of their high antimicrobial activity.The growth promoting and biocontrol effects of different strains were analyzed in greenhouse and field respectively.The main researching results were as follow:1 ? 5 strains were named 3183,G2-7,H1-2,1441 and D2,which showed high antimicrobial effect,were selected for further use.Based on colony morphological and sequencing of 16 SrDNA,strains of 3183 and 1441 were identified as Bacillus subtilis,G2-7and D2 were Burkholderia gladioli and H1-2 were Paenibacillus polymyxa respectively.To obtained a mixed strains for synergistic use,inter-antagonism of 5 strains were tested on NA medium and the results showed that all 5 strains grow well when cocultured with each other.2 ? Auxin(IAA)producing were analyzed for five strains.The result showed that concentration of IAA in strain 3183 and 1441 were 104.71?g/mL and 86.42?g/mL respectively.No IAA were tested in G2-7,H1-2 and D2.3?Phosphate solubilizing activities of 5 strains were tested on different medium.The soluble-P concentration of G2-7 and D2 was 119.42?g/mL and 123.24?g/mL respectively.No soluble-P were tested in 3183,H1-2 and 1441.4?To understand the tolerance of 3183 strain to NaCl,growth curve of 3183 in NB medium with different concentration of NaCl was measured.The result showed that 3183 growth well in NB medium with 2.5% NaCl.However 3183 growth was inhibited as NaCl concentration was above 7.5%.Growth of other strains were inhibited at 2.5% NaCl.5? To prolonging conservation of strain 3183,different protectant were added to the medium and survival were analyzed after 60 d storage at room temperature.The result showedthe survival were the best at 0.5%MHJ and 1.0% MNA.6 ? Growth promoting and biocontrol effect of tobacco seedling to Ralstonia solanacearum were tested using each single strain and mix strain in pot respectively.Tobacco seedling showed obvious growth promoting after treated with mixture of H1-2 and 3183 with the height,chlorophyll,fresh weight of aboveground and underground increased 29.38%,15.92%,28.98% and 44.78%.Biocontrol effect of tobacco seedlings to R.solanacearum were tested in pot.As showed in the result that the control effect were varied in each treatment with the highest effect was65% after treated with strain 3183 and mix of 5 strain respectively.Effect was 60%respectively after treated with G2-7.7?Field experiments were conducted to analysis the effects of 5 strains on the growth of tobacco and the control of tobacco bacterial wilt and black shank.The results showed that the height,the chlorophyll and the fresh mass of the aboveground plants were increased by10.9%?6.1% and 20.44%.The control effect on the bacterial wilt was 33.5%,and the control of the black shank was 37.7%. |
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