| Recently,the biological control of plant diseases with environmental-friendly beneficial microorganisms has became a research hotspot and drawn increasing attention.Actinomycetes are widely existed and play a decisive role in the biological control of soil-borne diseases.At present,actinomycetes were used to control plant soil-borne diseases,including Streptomyces,Actinoplanes,and Micromonspora.It is the trend of biological control of plant diseases that the direct application of microbial agents.In this study,the antimicrobial activity of the metabolites of Streptomyces GA-5 was evluated in vitro and in vivo,and the culture conditions were optimized by single factor experiment.The wettable powder formula was also explored to determine its feasiblility on biopesticides.This study was to lay a foundation for the development and application of microbial agents.The main results are as follows:1.The activities of fermentation broth of Streptomyces GA-5 were evaluated by mycelium growth rate,agar diffusion and the dural culture method.The results showed that the metabolites of Streptomyces GA-5 have bioactivity against five tested plant pathogenic bacteria.It has significant effect against Bacillus subtilis and Xanthomonas campestris,the diameters of inhibition zone was 16.58 mm and 14.25 mm,respectively.Streptomyces GA-5 has antagonistic effects on twelve plant pathogenic fungi,ten of them were over ten mm,such as Phytophthora capsici,Gaeumannomyces tritici fungus,etc.The metabolites of Streptomyces GA-5 have significant effects against G.tritici,Sclerotinia sclerotiorum,Cytospora mandshurica and Exserohilum turcicum,the inhibitory rates were 68.56%,62.98%,59.25%,and 85.92%,respectively.The culture conditions of Streptomyces GA-5 were optimized by Single factor experiment.The result showed that the culture conditions were:millet culture medium,cultured four days,medium volume 50 mL/250 mL,rotary speed 100 r/min,inoculation volume 10%,and initial pH9.0.2.The control effects of Streptomyces GA-5 aganist Botrytis cinerea and S.sclerotiorum was evaluated in vivo,and the control effects on G.tritici and Fusarium oxysporum f.sp.cucumerinum was determined in greenhouse trail.The results showed that the protective effect of Streptomyces GA-5 on B.cinerea was 59.63%,and has a good therapeutic effect on S.sclerotiorum,was 66.34%.The results showed that spore suspension exhibited a protective efficacy(50.65%)againist F.oxysporum cucumerinum.Streptomyces GA-5 had a good control effect on take-all of wheat disease.The protective effect of its spored liquid on take-all of wheat(80.96%)was higher than the chemical treatment(70.65%),and therapeutic effect was 73.64%.The protective and therapeutic effects of fermentation broth on take-all of wheat were 65.06%and 55.46%,respectively.3.According to the formulation of the wettable powder of Streptomyces GA-5,the optimal formulation was confirmed as follows:diatomite 10%,CMC-Na 4%,DBS 6%,methyl cellulose2%,ascorbic acid 0.2%.Based on the national standard of People’s Republic of China pesticide,the results showed that the wetting time of the Streptomyces GA-5 wettable powder was 55.37s,the suspension rate was 74.86%,the pH was 7.8,the moisture content was 1.4%,the fineness rate was 98%,and the living bacteria content was 5.38×10~8cfu/g at the room temperature(25℃).The results of pot experiments showed that Streptomyces GA-5 wettable powder could significantly reduce the disease index of wheat take-all.The control efficacy of 50,200 and 800times dilutions of Streptomyces GA-5 were 63.12%,69.63%and 64.78%,respectively,which were significantly different from those of chemical treament(76.83%). |
PDF Full Text Request