| Currently,prevention of plant fungal disease management is usually achieved by use of chemical pesticides which have negative impacts including:human health hazards of the chemical applications,chemical residues in plants and acquisition of microbial resistance to the used chemicals.Because of such concerns,the necessity to find a potentially effective,healthy safer and natural alternative pesticide is increased.The metabolites of actinomycetes own much bioactivitites such as antifungal,antibacterial,insecticidal,nematicidal,antivirus and anticancer in the field of medicine,public health and agriculture,which make it become a kind of novel bioresource with high potential for development and broad prospects for application.Actinomycetes are widely distributed in nature,and microbial secondary metabolites from actinomycetes are widely used in disease management in agricultural production.Therefore,actinomycetes are an important research object for the development of biological pesticides.In order to determine the antimicrobial activity of actinomycete 11-3-135 in vitro,to evaluate its preventive effects and curative effects in vivo and the status classification in the actinomycetes.We tested the antimicrobial activity of the metabolites and taxonomic status of11-3-135.The main results and conclusions of the thesis are as follows:In this study,one actinomycete isolated from the soil of the Qinghai-Tibet plateau region(No.11-3-135)was the main research object.1.The antimicrobial activity of metabolites of actinomycete 11-3-135 strain and the control of plant diseases were systematically determined using in vitro(mycelium growth rate method,plate-to-assay,spore germination method,and agar diffusion method),rape leaves in vivo and pot experiments.The results show:The metabolite of actinomycete 11-3-135strain not only has a certain inhibitory effect on 7 kinds of pathogenic bacteria,but also has strong antimicrobial activity against 18 plant pathogenic fungi and oomycetes.The results of pot experiments showed that it had high effect on Sclerotinia sclerotiorum,Gaeumannomyces tritici and Phytophthora capsici.In plate-to-assay,the results showed that 11-3-135 strain had siginificant effect against 8plant pathogenic fungi and oomycetes.The diameter of the inhibitory zone was more than 10mm.of which the antagonism to S.sclerotiorum was the strongest,with inhibitory zone 14.75mm.mycelium growth rate method results showed that the metabolites(intracellular and extracellular)of 11-3-135 strain had a certain inhibitory effect on mycelial growth of plant pathogenic fungi and oomycetes.The extracellular metabolites showed stronger antifungi activity.The mycelial growth inhibition rate of 9 plant pathogenic fungi and oomycetes was more than 70%.Broth has the strongest antifungi effectson Valsa mali,and the inhibition rate was 100%.The inhibition rate of intracellular metabolites on the mycelium growth of five plant pathogenic fungi and oomycetes was more than 60%.Intracellular metabolites also have the strongest antifungi effects on the V.mali with the inhibition rate was 79.98%.The results of spore germination showed that the inhibitory rate of spore germination of Botrytis cinerea,Fusarium oxysporum sp.cucumebrium Owen,and Fusarium graminearum was more than90%.The results of the rape leaves in vivo showed that the preventive effects of broth on S.sclerotiorum was 55.91%,and the curative effects t was 52.91%,which was equivalent to that of 80%carbendazim(65.7%).The results of pot experiments showed that the biocontrol effect of 11-3-135 broth was significant.The preventive effects and curative effects of11-3-135 against of S.sclerotiorum were 58.1%and 62.8%,respectively.While preventive effects of 80%carbendazim was 37.71%.The preventive effect of broth on G.tritici was better than curative effect;with preventive effect was 90.66%.While preventive effect of 37%difenoconazole was 70.46%.The preventive effects and curative effects of the broth of P.capsici were 79.33%and 64.67%,respectively,which was comparable to that of the control agent(25%metalaxyl).2.According to the morphological characteristics,culture characteristics,physiological and biochemical characteristics and 16S rDNA sequence results of strain 11-3-135,the strain was identified as Streptomyces.The 16S rDNA sequence has been registered in Gene Bank(MG657018).3.Using Streptomyces sp.11-3-135 broth as mother liquor,screening tests on carriers,adjuvants,stabilizers and UV protectants.The final formulation of the wettable powder was:broth 70%,diatomite 10%,sodium lauryl sulfate 10%,methyl cellulose 2%,and sodium fluorescein 0.1%.According to the relevant national standards for pesticides in the People’s Republic of China,the results showed that the viable strain of Streptomyces 11-3-135 wettable powder at room temperature at 25℃ was 2.23×10~8 cfu/g,pH 6.5,and the suspension rate was78%,wetting time 37s,fineness pass rate 98%.All physical indicators reached the national standard for wettable powder.The control effect of Streptomyces 11-3-135 wettable powder was verified by pot experiment.The results showed that the Streptomyces 11-3-135 wettable powder had better control effect on 2 soil borne diseases after root irrigation.The preventive effects of 1:50 dilutions and 1:200 dilutions on G.tritici was 73.53%and 70.77%,which was equivalent to the control agent(37%difenoconazole).The preventive effects of 1:50 dilutions and 1:200 dilutions on P.capsici was 91%and 73.33%,which was equivalent to that of the control agent(25%metalaxyl).And 1:800 dilutions have more than 50%preventive effects on the two diseases.Therefore,1:200～1:800 dilutions is the better method to use of Streptomyces 11-3-135 wettable powder. |
