Study On Characterization And Antagonistic Effects Of An Antifungal Substance Produced By Biocontrol Bacteria For Pathogens Of Pine Seedlings Damping-off

Slash pine(Pinus elliottii) is an important tree species for foresting in the south China.On the base that the slash pine disease is caused by Rhizoctonia sp.,Fusarium oxysporum and Alternaria sp..We measuring the inhibiting disease efficacy of C23 and the bacteria,including Q2-87,Ps2-79,Pf-5,1M1-96,Q37-87, HT5-1,MVP1-4 and FFL1R8 afforded by the lab of roots diseases biocontrol department of agriculture USA in the greenhouse and the field.Screening the new bacteria which have antagonistic effects on the pathogens of slash pine damping-off.Studying the characterization of an antifungal substance produced by C23.The research demonstrate that:1.21 isolates of the bioncontrol bacteria are gained by new screening,we decide the number W1-13,L1-8,Q1-8,B1-4,J1-4 as the names.there are 12 strong isolates of the biocontrol ones.We have base biology assay,maybe having 3 isolates (L-2,L-5,L-8) as Bacillus subtilis.2.The inhibiting disease efficacy of nine biocontrol bacteria demonstrate that:for Rhizoctonia sp.,MVP1-4 and C231M1-96 show very good antagonistic ability on the plate against the pathogens;for Fusarium oxysporum,FFL1R8 and Q2-87 show good antagonistic ability;for Alternaria sp.Pf-5 shows good antagonistic ability.3.1M1-96,HT5-1,Q37-87,FFL1R8,C23 show very good antagonistic ability in the greenhouse test by the method of dipping the roots with bacteria liquid.1M1-96 and C23 show good antagonistic ability beyond CK by the method of watering the roots with bacteria liquid.All of the strains show very good antagonistic ability in the field test.4.Media screening experiment disclosed that the optimum media for C23 producing the antifungal substance is 1/2PDA⁺.Treated at 20-40℃for 30 min,the crude extract maintained more than 80%of its antifungal activity.Treated at about pH6,the crude extract have the best antifungal activity.Treatment with proteinase K,there has no antifungal activity of the crude extract.The antifungal substance can precipitate full with 80%(NH₄)SO₄.The substance can not be extracted by the nonpolarity solvent(methenyl trichloride,ethyl acetate,ethyl oxide).These demonstrate that the antifungal substance must be protein or peptide.The research show diseases biocontrol in the greenhouse and the field,screens new bioncontrol strains,Studying the characterization of an antifungal substance of C23.This will provide the theoretical reference for further utilizing the bioncontrol bacteria to control the slash pine damping-off.