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From the sample collection, preservation of strains isolated activity screening, strain identification, biological characteristics, the choice of the basis of the fermentation medium, mechanism of action, wheat powdery mildew control effect and other aspects of conservation tillage farmland soil strains isolated from A2. The main conclusions are as follows: (1) from the conservation tillage farmland soil samples, the choice of different isolation medium, using the method of soil dilution and plate streaking single colony isolated 38; indicator bacteria and rice blast fungus Botrytis cinerea, screening confrontation growth method to obtain a strain with antagonistic action 12. After 10 generations of subculture, re-determination of active and combined plate method the rescreening, still has a strong inhibitory effect on the instructions pathogens and more stable only bacterial strain A2. ⑵-room flat-screen confrontation results show that the strain A2 antibacterial broad spectrum showed inhibition of 20 kinds of pathogenic fungi. However, the inhibitory effect of different plant pathogenic fungi, the inhibitory effect of the inhibition rate between 29.00% to 86.00%, which Botrytis cinerea, rice blast fungus best inhibition rate of 85.61%, 81.82%; bacteriostatic bandwidth average up to 17.00mm, 15.83mm. ⑶ use of morphological, physiological, biochemical, and molecular biological methods identified strains A2. According to the A2 strains morphology, physiological and biochemical characteristics and 16S rDNA sequence alignment results identified strains A2 as a strain of Bacillus subtilis (Bacillus subtilis). Its main features are: bacterial rod, endogenous Bacillus spores oval the unaccompanied spore crystal, with flagella, Gram stain positive; pale yellow colonies on LB plate medium, no rules, protruding edge irregular, rough surface of the folds, opaque, viscous; facultative anaerobic, contact the enzyme reaction, VP (Vogos-Proskuer) was determined to be positive, citrate growth. PCR amplification of 16S rDNA sequence of this strain A2 1437b (pGenBank sequence accession number EU567068). BLAST sequence alignment analysis software will be measured gene sequences in GenBank database using software DNAMAN homology and phylogenetic tree drawn. The results show that the strain A2 sequence and B.subtilis (AY881643), the highest similarity, the smallest genetic distance, respectively, 99.7% and 0.003, and the phylogenetic tree which is a branch of Bacillus subtilis. ⑷ strains A2 beef extract peptone medium rapid growth, 14h achieve stabilization period (28 ° C, 180rpm). The optimum pH of 7, 26-35 ℃ conditions, growing well, the optimum growth temperature of 28 ° C, more appropriate for the shake flask culture solution ratio of 1:10 (250mL flask 25mL). 50mL of liquid volume, 28 ℃, 180rpm shake flask cultures optimal formulation of the basis of the fermentation medium: sucrose 30g, peptone 10g, yeast extract 5g, KH2PO4 4.5g, CaCO3 2g, (NH4) 2SO4 2.5g, distilled water 1000mL. ⑸ under in vitro conditions, paddy rice blast rotting apple tree, wheat root rot, Fusarium oxysporum mycelial growth, teratogenic effects. The results found that the strain A2 fermentation supernatant of the four kinds of bacteria showed a strong inhibition, the average inhibition zone diameter were 30.50mm, 30.00mm, 29.76mm, 21.20mm. Which apple trees rot pathogen inhibition rate up to 83.60%, with the increase of the fermentation supernatant dilution factor, inhibition decreased. But until the 7d still has more than 20.00% of the inhibition rate. Prove its metabolites also has strong antibacterial effect. The bacteria can result in abnormal morphology of mycelial growth, hypha branch exacerbate appears, swollen generate the bead shaped cystidia and cytoplasm overflow so that the mycelium collapse phenomena such as deeply stained. ⑹ greenhouse wheat vivo bioassays, the fermentation broth and fermentation supernatant of strain A2 showed better control effect (29.00%); broth mixed with supernatant (fermentation broth) plus the control effect and role. This paper is to study the preventive effect of bacteria on wheat powdery mildew, fermentation the dope control effect of up to 72.22%, fermentation supernatant dope control effect of 29.24%.
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