| Peach crown gall is a kind of harmful bacteria diseases. It’s very difficult to be prevented. Biological control is an important approach and the future direction for preventing and controlling plant diseases at home and abroad at present. Biological control of plant diseases based on the isolation of beneficial organisms. How isolated effective strains from a huge number of microbial population in nature would be very important. In this experiment, the pathogen of peach crown gall were isolated and identified at first, and then isolating a series of bacteria, fungi and actinomycetes from soil. Through the corresponding plates confrontation test against pathogens to filter out the antagonistic strain, and preliminary control tests were performed on the indicator plants by the use of antagonistic strains. The main results are summarized as follows:In the test, twenty isolates with configuration character of Agrobacterium tumefaciens were obtained from peach root. Strain A-4 was initially identified as Agrobacterium tumefaciens through the cultivation of character, staining observation and molecular identification of 16 S r DNA. The identifications of Physiological and biochemical and BIOLOG further determined the biotype of Agrobacterium tumefaciens A-4 strain was biotype II type. Through the molecular biology, sunflower seedling and peach seedling inoculation tests determined that it contained Ti plasmid and had strong pathogenicity, which could cause sunflower and peach occur crown gall.Twenty one strains of bacteria, nine strains of fungi, thirty three strains of actinomycetes were isolated from diseased soil samples and healthy soil samples, which were tested for antagonizing pathogenetic strain A-4 of peach crown gall respectively by using agar diffusion method. Through the determination of antibacterial ability of fermentation liquid to pathogenic strain A-4, further verifing the inhibitory effect of screened biocontrol agents.The result showed that 6 strains of bacterial strains with obviously antagonistic activity were screened out. The strain H-B-1 showed the highest bacteriostatic effect, the strain S-B-10 showed a relatively higher bacteriostatic effect. Antibiotic experiments with fermentation filtrate of bacteria, results showed that fermentation filtrate of all the 6 strains bacteria had strong antibacterial activities against pathogenic strain A-4 of peach crown gall. All the nine strains of fungi showed no antagonistic effect. Four strains of 33 actinomycetes exhibit a certain ability of antagonizing the Agrobacterium tumefaciens relatively. The bacteriostatic effect of strain H-A-6 is the best, the strain H-A-4 is the second. Antibiotic experiments with fermentation filtrate of actinomycetes, results showed that fermentation filtrate of strain H-A-6、strain H-A-4 and strain S-A-12 exhibited the strong antibacterial activities against pathogens. Compared with the antibacterial activities of 6 strains soil bacteria, actinomycetes showed weaker antibacterial abilities. The results of the experiment of plate confrontations showed that 6 strains of soil bacteria as biocontrol agents showed obvious advantage, and preliminary identification of 6 soil bacteria strains were Bacillus spp.. Therefore, this study chose 6 soil bacteria strains as antagonistic strain for the initial prevention on the indictor plant, in order to provide for further selection.Using the tomato seedlings as indicator plants to evaluate the effect of disease resistance and growth-promoting of antagonistic microorganisms on indicator plants. The result turned out that strain H-B-7 not only can prevent the occurrence of crown gall, but also can promote the growth of plant; strains S-B-6 and S-B-7 also had stronger resistance to pathogenic bacteria; strains S-B-10 and H-B-1 had poor abilities to against the pathogen, but they had stronger abilities to promote host plant growth. |
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