Breeding And Antagonism Of Broad-spectrum Antagonistic Microorganism Against Alternaria Solani

The results of isolation by tube dilution assay from 10 samples showed that wide-spectrums antagonistic organisms to phytopathogens of fungi in ritro were obtained.All of 12 wide-spectrums were identified primary.The strain named QM3 was isolated from Qinghai yaks,and that its identification,mutation induced by He-Ne laser,fermentation,antagonistic mechanism,extraction of antagonistic substances and biocontrol diseases,promoting plant growth,colonization were studied profoundly offered academic elements for biological control of Alternaria solani.Based on the basic properties including cell shape,Gram's stain,sporulation, production of catalase and others chemic characteristic,all of the 8 antagonistic bacteria were identified as Bacillus spp.,QM3 strain was further identified as Bacillus subtilis by the sequences of 16S rRNA.QMS4 strain and 3 filamentous fungi were identified as Micropolyspora and Penicillium respectively.According to the examination of antagonistic ability of ferment liquid,QM3 strain had the strongest inhibitory activities to A.solani.The mutant QM34 obtained aider irradiation by He-Ne laser based on inhibitory activities was significantly promoted(p＜0.05)to Fusarium oxysporium and Apple Beauveria bassiana,and especially to A.solani(p＜0.01)compared with wild strain QM3.Integrating the results of OD₆₆₀and inhibition zone to A.solani,the excellent medium YPF-Ca was selected,and then orthogonal experimental of L27(3)⁷ was designed.The results of range analysis and variance analysis were suggested that the optimal fermentation conditions were given A3B2C3D3E1F2G2.The antagonisms of B.subtilis QM34 to A.solani were combined with antifungal substance,hydrolase,spatial and nutritional competition.Inhibitory activities of antifungal substance were significantly promoted(p＜0.01)by inhibiting conidia germination and germ tube growth of A.solani and arousing hyphal aberrance of A. solani.The antifungal compounds of QM34 strain obtained through 60%ammonium sulfate precipitation and extraction by methanol were primarily identified as a antifungal protein(MW＞3500Da)and a polypeptide respectively.The antifungal polypeptide presented the properties of thermostable,UV-tolerant,pH-tolerant and resistance to trypsinase and proteinase K.There was a liner relation between dilution or concentration multiple in -5～80 of sterile suspension of QM34 strain and inhibitory rate.EC₅₀of the sterile suspension for A.solani was tested by inhibitory regression equation,and the result was 3.02.Control efficacy in viro of the strain QM34 against A.solani and promoting plant growth with cell suspension of QM34 were presented.But different treatments showed different results.B.subtilis QM34 could be able to colonize in rhizosphere of tomato by strong ability of competition.In a word,B.subtilis QM34 is a potential applied valuable broad-spectrum antagonistic plant growth- promoting rhizobacteria.