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Isolation of an Strain Against Peanut Bacterial Wilt and Study of Its Fermemtation and Antagonistic Compounds

Author: SunZuo
Tutor: ShenBiao
School: Nanjing Agricultural College
Course: Microbiology
Keywords: Ralstonia solanacearum Antagonistic bacteria screening Fermentation conditions Streptomyces.spp Stability
CLC: S435.652
Type: Master's thesis
Year: 2012
Downloads: 47
Quote: 0
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Abstract


Peanut bacterial wilt, one of the main soil-borned diseases of peanut, caused by Ralstonia solanacearum, threatens production of peanut in the world. In China, it widely occurrs in the producing areas of peanut, especially in Yangtze and southern areas. It is difficult to effectively control the disease by routine control methods, such as chemical germicides. Compared with the routine control, rhizobacteria-mediated biocontrol is a more effective alternative. In order to provide the theoretical basis of biological control of peanut bacterial wilt, this dissertation focused particularly on the isolation and identification of antagonistic strains and studies on optimization of fermentation condition, stability of antimicrobial substance and their characteristics, the main results are as following:(1) Strain Rsl, a bacteria strain of peanut bacterial wilt pathogen, was obtained. Eighty strains were isolated from the soil samples using dilution method, among which eight strains were screened to show antagonistic activity against Ralstonia solanacearum. Strain A31showed the best inhibition to Ralstonia solanacearum and genetic stability. Results in pot trial showed that the control efficiency of strain A31against bacterial wilt of eggplant reached58.3%.(2) It’s morphological, cultural physiological, biochemical characteristics, chemotaxonomy and16S rRNA sequences analysis were studied. The substrate mycelium have no partition, the aerial mycelium are ramose, the spores are oval. The cell wall type I and sugar type C showed the strain with Streptomyces character.16S rRNA gene showed98%identity between strain A31and S. purpureus and S. chrysomallus.(3) The fermentation conditions of strain A31were studied. The single factor and orthogonal experiment results indicated that the optimum fermentation condition for strain A31to produce the best activity were as following:3.0%soluble starch as carbon source,0.8%soya peptone as nitrogen source,0.05%K2HPO4,0.025%MgSO4, the initial pH of6.0-8.0, inoculation level of6%,60mL medium in250mL flask, incubation at28℃and200r/minfor108h. (4) Strain A31’s crude antibiotic compounds could inhibit not only R.solanacearum, but also some fungi pathogens, such as Sclerotinia sclerotiorum (Lib.) de Bary and Rhizoctonia solani Kuhn. The antibacterial substances crude extract from strain A31showed stability to high temperature, and does not lose its antagonistic activity if treated at121℃for30min; The crude extract was very stable after treatment at pH from2to12. It was also very stable to UV and stored for a long time at4℃.(5) Thin layer chromatography of the crude extract by Jack’s eight solvents system paper chromatography indicated that the the main active antibacterial ingredient was one of aureothricin antibiotic. It’s molecular weight examined with primary MS was330.6D.

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CLC: > Agricultural Sciences > Plant Protection > Pest and Disease Control > Crop pests and diseases and their prevention > Economic crop pests and diseases > Oil Crop pests and diseases > Peanut pests and diseases
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