| Ordos is a serious desertification area,its green area and forest cover rate of rapid increase have been controlled and treated nearly 40 years,one of the most important afforestation trees is Salix matsudana Koidz,which can be resistant the cold,heat and drought.The local willow wilt disease outbreak suddenly since 2012,it was a huge threat to local projects in windbreak and sand fixation and afforestation.Based on previous studies on pathogens,we have studied on the prevention and control technology from various aspects in order to obtain efficient,convenient,safe and reliable methods to control this disease.The pathogens are Pantoea agglomerans and Erwinia salicis,the latter pathogenic ability is weak,has been recorded in the territory of the willow watermark disease and domestic Jin Jiuchen studied the pathogen of willow wilt disease,the study of prevention and control of the E.salicis has been documented in abroad,so this study is mainly control the Pantoea agglomerans1.Effect of different germicide on disease prevention and treatmentObtained 4 kinds of highly effective agent,such as streptomycin,tetracycline,allicin and thiamethoxazole,we were screened out from the 14 kinds of fungicides tested by the plate punching confinement method.Diluted the 4 agents to 1/100 and confronted to pathogen,the inhibition rate respectively is 71%,61%,55%and 6%,the efficacy index r is bacteriostatic diameter:active ingredient content,the inhibition rate of benziothiazolinone is 6%,but r=100.00 for the largest test agent,it is also included in the efficient pharmaceutical.Used the 4 kinds of germicide for the forest for irrigation and drilling injection control test.The irrigation can control the disease during the early period,the streptomycin-50-II control efficiency is 47%,tetracycline-100-IV is 48%,after 3 trials?60 days?,the test group was almost equal to that of the CK,it showed the 4 kinds of germicide can not control disease commendably.In pesticide injection,the best control is streptomycin-5-III and tetracycline-5-III the control efficiency are 81%and 79%,the control efficiency is compared with CK.Combined with the incidence of disease reduction and control effect analysis,the best inhibition is streptomycin agent,the incidence of disease reduction rate is 15.85%,control effect rate is72%;the second is 1/5 liquid of the tetracycline,the incidence of reduction rate is 8.69%,control effect rate is 79%,and the tetracycline agent 6.86.8%of disease reduction rate,50%of control effect were less than 1/5 liquid.2.Isolation and screening of the antagonist and the determination of bacteriostatic spectrumIn April 2015,collected 96 soil samples from the four counties of Ordos,isolated bacteria,fungi and actinomycetes in the laboratory,and obtained more than 1,000 strains of bacteria,21strains of actinomycetes and 2489 strains of fungi.The most common fungi such as Penicillium sp.,Trichoderma sp.and Aspergillus sp.,the difficult to isolate fungi such as Cunninghamella Matr,Gliocladium sp.,Merimbla sp.and Zymonema sp.were also successfully isolated.The antagonistic bacterium YQT13 was screened by platelet confrontation,and further morphological and molecular identification is Rhizopus oryzae.Screening with 8 media PD,1/2PD,1/5PD,MMN,Martin,Sabouraud,Czapek-Dox and Saouraud Dextrose broth.The results showed that the inhibition zone of Saouraud Dextrose and PD culture solution is 12 mm and 11 mm,and the rate of antibacterial activity is 39%and 35%less than 1/100 of the streptomycin and the tetracycline liquid,and the rate of bacteriostatic is 71%and 61%,but the5 times the concentration of Saouraud Dextrose and PD broth and the rate of antibacterial activity 77%is slightly larger than two chemical pesticides.Determination of Bacteriostatic spectra of antagonist by 6 pathogens,1 m L of 5-fold concentrated sterile fermentation broth was prepared with 15 m L of PDA medium,the center was put a 8 mm pathogen cake.The inhibition zone is determined by cross method and calculated the inhibition rate.The results showed that all of the pathogens could be inhibited,and the inhibition rate is over the 60%Microdiplodia sp.,Fusarium sporotrichioides,Mycosphaerella?Fr.?,Cytospora chrysospcrma?Pcrs.?Fr.,accounting for 2/3 of the tested strains,and the inhibition rate is 100%to Microdiplodia sp.which completely inhibited mycelial growth.3.The stability of antimicrobial substancesThe results of light,heat and pH stability showed that the antibacterial activity was not affected when the temperature was maintained at 121?for 30min or at low temperature-80?to 0?for 20 days,but the inhibition rate decreased by about 45%at 60?for 20 days.Stored in the low temperature?-80?to 0??long-term or 0?to 121?short-term the antimicrobial substance activity is not affected;Stored at-80?to 0?20 days in dark the same antibacterial activity is also not affected,and more stable under the dark;at acid condition?pH<3.0?the antimicrobial activity can be stably preserved,neutral and alkaline condition?pH>10.0?can make its antibacterial activity decreased rapidly or even inactivation.In July 2016 injectd the 10 times of the concentration to the willow for prevention and treatment test,found that the application of 40 mL of liquid II level of the best control effect,the incidence of reduction rate is 9.97%,control effect rate is 68%,were close to streptomycin and tetracycline control effect.4.The purification of the antibacterial active substanceUsed 5 extracting agent to extract and chromatograph the 5 times sterile broth,The results showed that the extraction phase of ethyl acetate,benzene,carbon tetrachloride and S-methyl ester have good antibacterial effect.The inhibition rate of benzene,carbon tetrachloride,S-methyl ester and their extraction phase are 100%,so they can not used as the active material extractant.The inhibition rate of N-hexane and its extraction phase are 0.The extraction phase of ethyl acetate can not restrain the pathogen,but inhibition rate of the extraction phase of the ethyl acetate is equal to the 5 times concentrate of the R.oryzae fermentation broth 77%.Stored the extraction phase of the ethyl acetate at-20?to-30?,separate out the colorless crystal,the precipitation rate is 38.4?L·mL-1,the inhibition rate of crystal is almost equal to that of the 5 times concentrate fermentation broth and extraction phase of the extraction phase of ethyl acetate indicating that ethyl acetate is the best extractant of the active substance?Combine with the active substance can stay at high temperature 121?and acid not alkali condition,the substance probably is an acidic substances protein or glycoprotein. |
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