Screening, Fermentation And Metabolite Of Antagonistic Actinomycetes Against Alternaria Alternata

In this study, a total of 251 strains were isolated from 20 different soil samples in Qinling. Among these strains, we obtained 51 strains actinomycetes to have the different degree resistance to Alternaria alternata through panel confrontation measurement.Inhibitation zone of 12 strains exceed 13mm. we measured the antibiogram of 12 strain, a genetically stable actinomycetes strain LJ198-7 was selected after comparison on inhibition activity of pathogenic fungi by means of selected in solied culture and fermental filtrate.Through fermentation medium screen experiments, we obtained the optimum medium composition: D-Glucose 1%,starch 1.5%,soybean 2%,CaCO2 0.25%,K2HPO4 0.05%. The optimum fermentation condition of strain LJ198-7 was also determined, which indicated that antibiotics of strain LJ198-7 had strong inhibition activity with the initiative pH of 8.0, 100m1/250ml medium volume, 30-34℃temperature, 150r/min rotatory velocity and fermentation 72 hours. The result of orthogonal experiment of fermentation condition shows that the effect of pH is significant. Thee ffect degree of three factors is pH >poured solution volume >culture time.By means of mycelium growth rate we measured the antibiogram of LJ198-7 strain, it's fermentation products were tested against Pyricularia grisea, Bipolaris sorokiniana, Fusarium oxysporium, Exserohilum turcicum and so on. The results of bioassay indicated the crude active-product of LJ198-7 strain has a wide-range of inhibition. The inhibiting rate of 1mg/L fermentation products exceed 45%. The results showed that the fermentation products of LJ198-7 can resist many plant pathogenic fungus and bacterium, which expanded the application field of antibiocits.The avtive product was isolated and purified,it was a mono-component,named An-2.The physico-chemical property was studied: it was soluble in water ,methyl alcohol ,ethyl alcohol and insoluble in acetone,ether,ethyl acetate,benzene,chloroform,petroleum etc. UVmax is 316nm; melt-point is 241-244℃; According to the physical and chemical properties as well as the UV , IR, 1H-NMR, and Mass spectrums, the structure of An-2 was confirmed as 1-(3-furanyl-4-carbamoyl)-2-N-glucoside, a new inhibitory substances of glucoside- containing component, which will be a base for developing some new glucoside-containing family agricultural antibiotics.The inhibiting range and mechanism of the active product of LJ198-7 was studied. The result showed that the active product of LJ198-7 has a strongly inhibition of the mycelia growth and spore germination which lead to the mycelia twisted and inflated, the abnormal branching increased, the mycelia wall broke and the material of the cell let out, the spores was reduced and deformation. The rate of germination and length of the tube was decreased. The active product of LJ198-7 not only can prevent the invasion of Alternaria alternata mycelia,and has a good control efficacy, showed a good curing efficacy.