| Snf009 was a fungus obtained from which its product of metabolism could kill root-knot nematode(Meloidogyne sp.)and sweet potato stem nematode(Ditylenchus destructor).The experiments were studied systematically on Snf009 such as the taxonomy,fermentation conditions,qualitative and quantitative analysis of bioactive compounds of metabolites, biocontrol effect in greenhouse and field and evaluation of safety.1.Snf009 was identificated as Aspergillus niger by traditional classification,belongs to Mitosporic fungi,Hyphomycetes,Moniliales,Moniliaceae,Aspergillus,A.nigerThe 5L fermentation liquor was fermented by GUGS-50 fermentation cylinder.The fermentation liquor possessed nematicidal activities against the nematode M.incognita and D.destructor with ED50values 7.07μL·mL-1and 142.71μL·mL-1.2.The fermentation mediums of Snf009 were tested by single factor at first.The optimum carbon and nitrogen resource were maltose(3～4),amylum(2～3%), carbamide(0.2～0.4),respectively.The nematicidal activites of fermentation liquid was influenced by concentrations of KCl and MgSO4·7H2O.Components of the liquid medium were quantitative analysed by the quadratic regression orthogonal rotationa combinational design,and calculated regressive equation.According to taking maximum motality of juvenile of M.incognita,the optimum liquid medium of fermentation constituted by maltose:4.04%,amylum 2.45%,carbamide 0.29%,KCl 0.04%,K2HPO40.1%,MgSO4 7H2O 0.06%),Fe SO4 0.001%).Motality of juvenile of M.incognita was 76.74%)in theory on condition that strain Snf009 ferment by these components.Acording to taking maximum motality of D.destructor,the optimum liquid medium of fermentation constituted by maltose:4.71%,amylum 2.12%,carbamide 0.05%,KCl 0.07%,K2HPO40.1%,MgSO4 7H2O 0.05%),Fe SO4 0.001%.Motality of D.destructor was 38.21%in theory on condition that Snf009 ferment by these components.The optimum fermentation conditions were tested by the uniform combinational design, and calculated regressive equation between motality of nematode and fermentation conditions. Acording to taking maximum motality of juvenile of M.incognita,the optimum fermentation conditions:times:10d,pH:5.13,rotate speed:150rpm,temperature:40℃and ventilatory capacity:50L·min-1.Motality of juvenile of M.incognita was 83.1%in theory on condition that Snf009 ferment under this fermentation condition.Acording to taking maximum motality of D.destructor,the optimum fermentation conditions was as follows:times:10d,pH:5.13, rotate speed:150rpm,temperature:40℃and ventilatory capacity:50L·min-1.Motality of D.destructor was 83.1%in theory on condition that Snf009 ferment under this fermentation condition.Finally,optimization of culture medium and fermentation conditions to verify test results showed that the observed mortality were in line with the theoretical value,except that the fermentation conditions of D.destructor was biased.This regression equation could accurate forecast the relation between fermentation broth of strain Snf009 and motality of nematode in a certain range.3.The major parts nematicidal product of metabolism fungi Snf009 was acidity according to the experiment of paper chromatography,pH paper chromatography and paper electrophoresis.The experiment results showed that the total organic acid was equivalent to 20.79 g·L-1 oxalic acid.The most content was oxalic acid which was 18.8 g·L-1.At the concentration of 142.71 mL·L-1and 7.06 mL·L-1,the fermented liquid causes 86%and 69%mortality against D.detructor and M.incognita respectively,and at the same pH,the mortality was 45%and 62%by oxalic acid solution.There were significant differences both them.The concentrations of citric acid were 4.56 g·L-1,respectively.The pH value of fermentation liquor,oxalic acid+citric acid,oxalic acid and citric acid were adjusted in the range 3-7 then test nematicidal effects by the mortality of juvenile and the hatching rate of egg masses.The results showed that the mortality of juvenile significant rise in the range 3-7.Hatching rate of egg masses were significantly different between the treatments of pH≥5 and pH＜5, Fermentation liquor,oxalic acid+citric acid,oxalic acid and citric acid against juvenile of M.incognita to evaluate nematicidal activity:fermentation liquor＞oxalic acid＞oxalic acid+citric acid＞citric acid.Hatching rate of egg masses were significantly inhibited by treatment of fermentation liquor than others,contents of oxalic acid and citric acid combined were benefit to hatching of egg masses.There were no significant differences among other treatments.The nematicidal activities compound A from the metabolites of Snf009 was isolated and the structure was determined by UV/Vis,IR,MS and NMR.Molecular formula of the compound A was C9O6N2H12,Molecular weight:244.The nematicidal activities of compounds A was assayed against juvenile of M.incognita in vitro.4.The control effect of fermentation liquor of fungi strain Snf009 on tomato root-knod nematode diseases showed treatment with Snf009 of fermentation liquor to nearly 50% control of galling.There were significant differences between the treatments by fermentation liquor and sterilized water.At the control effect of sweet potato stem nematode,the control effect of fermentation liquor treatment attained at 63.89%,and Temik treatment at 99%. There were significant differences between these treatments and CK.5.The test of evaluation safety to dermal toxicity of mouse showed that fermentation liquor of fungi strain Snf009 belong to"lower toxicity"by LD50:male mouse:＞2150 mg·kg-1;female mouse:＞2150 mg·kg-1.The test of evaluation safety to oral toxicity of mouse showed that fermentation liquor of Snf009 belong to"micro-toxicity"by LD50:male mouse:＞5000 mg·kg-1;female mouse:＞5000 mg·kg-1...
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