| Taxus spp. is the level of protection of plant in our country, the rare tree specie of the world. It has the value of medicine, ornamental, virescence, and as special high quality material, particularly the paclitaxel extracted from its root, stem and leaf can be processed into global necessary high-tech and anti-cancer drugs.The natural Taxus chinensis resource is very limited, cannot satisfies the need of medical market far away. So the artificial planting of Taxus chinensis becomes the main source of extraction of paclitaxol.Due to high germination rate (up to 70%-80%), Taxus chinensis var.mairer is often selected as the excellent culture.But in recent years, with the expanding of artificial planting area of Taxus chinensis var.mairer, the disease had progressed, especially serious phenomenon of seedling root rot bringed a great economic loss.In this study, after collecting the rotten root sample of Taxus chinensis var. Mairer from a production base of Tianci seedling Co., LTD. in ya'an, hongya county, Studied the pathogenic identification and biological characteristics of pathogenic bacteria.From the healthy rhizosphere soil, it carried out to screen antagonism bacillus strains which had inhibition of pathogenic bacteria, and antagonism mechanism of advantagable antagonism strains was studied, the results were as follows:1?Using the method of normal tissue separation, it was studied that 7 kinds of separation were isolated from rotten root samples, the pathogenicity of 7 kinds of separation was verified according to Koch's Postulates.the experimental result showed that only a fungal isolates can lead to stocking plant pathogenic, the symptom was consisted with symptom about Taxus chinensis var.mairer root rot in the production base, CK was no root rot phenomena appeared.According to the pathogenesis of tieback rotten root separation, the strains'colony morphology and spore morphology were no diffrience from these separated from rot toot in the base. Adopting the methods of observing morphological characteristics, measuring pathogenicity and rDNA ITS sequence analysis,the result showed that the pathogen of root-rot disease of Taxus chinensis var.mairer is Imperfecti fungi. Moniliales. Tuberculariaceae. Fusarium oxysporum,2?Studying on the biological characteristics of pathogen from the culture medium, temperature, light, pH, and carbon source, nitrogen source to optimize its culture conditions, the results showed that:(1) The optimal cultured medium for pathogenic bacteria growth was PSA, and the best spored medium was PDA+vitamin mediumlin; (2) The pathogen hyphae on pH range of 5-10 could grow well and producte spores, when pH was equal to 7, The pathogen hyphae growth and spore production were the best.(3) Range from 15? to 35?, the pathogen hyphae could grow well and produce spores, and the best temperature was 30?. (4) The most carbon source suited to mycelial growth and spore production was sucrose, nitrogen source was glutamate. (5) The Illumination experiment showed that the light from the darkness alternation was advantageous to the growth of the pathogen mycelial and spore production.3?Collecting the rhizosphere soil of health Taxus chinensis var.mairer plant,By using the method of coating cultivation,37 different strains were screened, numbers for B1-B37.Make the root rot pathogen of Taxus chinensis var.mairer as target bacteria, 9 strains which agsinsted the pathogens were screened by the means of PDA plating standoff growth.They were B6, B9, B15, B18, B20, B27,B30, B36 and B37.The 9 strains were screened again, eventually selected 3 strains which antagonistic effect were good (bacteriostatic rate is over 30%),they were B6, B15 and B37. Among them, B37's antagonistic effect was the best, its bacteriostatic belt was up to 10 mm, with further research and development potential.By the identification of morphology, physiology, biochemistry and 16S rDNA homology analysis,and building 16S rDNA phylogenetic tree, the result was that the 3 strains were respectively Bacillus cereus, Bacillus amyloliquefaciens and Paenibacillus polymyxa.4?Select B37 strain whose antagonism effect best to study its mechanism of antagonism.Drilling method was adopted to determine the biological activity, the result showed that B37 bacillus strains had the stable bacteriostasis, specific performance is as follows:(1) With the increasing of incubation time, the bacteriostatic activity of sterile fermentation filtrate of B37 strain gradually was enhanced.(2) The bacteriostatic action of sterile fermentation filtrate of B37 strain with different temperature, different pH, ultraviolet ray, proteinase K, organic solvent had a good stability. Make pathogenic bacteria hyphae which had been inhibited by B37 sterile fermentation filtrate into slice,then put it under electron microscope. The observation showed that most hyphae was distorted and winding.Another hyphae was expanded and its transparency was also increased as well as conidium terrier distorted.With the increasing concentration of sterile fermentation filtrate of B37 strain, the spore germination rate of Taxus chinensis var. Mairer pathogens gradually was decreased, the number of spores was decreased too.Determine the stability of sterile fermentation filtrate of B37,... |
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