Screening, Identiifcation And Liquid Fermentation Of Antagonistic Actinomyceies To Setosphaeira Turcica

The northern corn leaf blight （NCLB） is a serious foliar wilt disease of maize inmany corn belts. It is incited by the ascomycete fungus Setosphaeria turcica （Luttrell）Leonard and Suggs, with its Asexual phase Exserohilum turcicum （Passerini） Leonardand Suggs. NCLB is mainly controlled by resistant cultivars, while cultivationmanagement and chemicals are the complement. But Chemicals control effect is notstable, and easy to pollute the environment. So use of safety and efficient antagonisticmicrobe is one of the most important.In this study, actinomycetes were isolated by Pour Plate method from soil collectedfrom Taonan, Panax ginseng C. A. Mey. planting area and Changbai Mountain NaturalReserve in Jilin, and gain527strains.108antagonistic actinomycetes againstRhizoctonia solani, Setosphaeria turcica, Cercospora zeaemaydis, Pyricularia oryzae,Sclerotinia sclerotiorum, Fusarium oxysporum, Cylindrocarpon destructans,Colletotrichum gloeosporioides were selected by using confrontation culture method.From them strain BZ45possessed prominent bioactivity and were further studied. Thefermentation filtrates of BZ45were determined by suppression of mycelial growthmethod, cylinder plate method and inhibition on the spore germination in vitro. It wasdemonstrated to be antagonistic against Rhizoctonia solani, Setosphaeria turcica,Cercospora zeaemaydis, Pyricularia oryzae,Sclerotinia sclerotiorum, Fusariumoxysporum, Cylindrocarpon destructans, Colletotrichum gloeosporioides withdiameters of inhibition zones of31.00⁴6.60mm. The fermentation filtrates of strainsBZ45had antagonistic activity to the mycelial growth of8plant pathogens,too.Inhibition rate of fermentation filtrates was10.48%⁷5.51%. The fermentationfiltrates have higher inhibition on the mycelial growth of Setosphaeria turcica withzones of inhibition of23.80mm. The fermentation filtrates have higher inhibition onthe spore germination of Setosphaeria turcica. Strain BZ45were identified as Streptomyces spectabilis by morphological andcultural traits, physio-biochemical characteristics and16S rDNA sequence andphylogenetic analysis.By using single-factor test and orthogonal test,the optimum fermentation mediumcomponent and condition of strain BZ45were cultured in1.5%fructose,3%peptone,0.1%KH₂PO₄,0.04%NaCl,0.1%CaCO₃, the initial pH of7.2, liquidvolume50ml in250ml,at28℃,200r/min, inoculation volume10%and shaked for4d.Strain BZ45have genes of type I polyketide synthases （PKSI）, nonribosomalpeptide synthase （NRPS） by PCR, don’t have type II polyketide synthases （PKSII）.Itproduce volatile and diffusible metabolite. It produces protease, also producessiderophore, does not produce the IAA and cellulose enzyme.