Studies On Actinomycete LDP-18 Strain

This thesis studies on fungicidal activity of one actinomycete isolated by institute of pesticide of Northwest Sci-tech University of Agriculture and Forestry. Agricultural antagonistic spectrum , strain identification ,Fermentation Conditions Optimization, metabolites stability have been studied. The main results are as follows: By means of observation on substrate mycelium, aerial mycelium, spore and sporothrix, Cultural characteristics, Biochemical and physiological characteristics, LDP-18 was primarily identified as a variety for which the name Streptomyces.calvus Var.. By means of mycelium growth rate , the results showed that the fermentaion products of LDP-18 had more than 95%inhibition rate against six kinds of pathogenic fungi at the concentration of 6863.36mg/L. at the concentration of 13726.72mg/L, the results of spores germination tests indicated that the fermentaion products had more than 80% inhibition rate against Alternaria longipes ,Exserohilum turcicum ,Bipolaris sorokinana ,Erysiphe cichoralearum. by means of agar diffusion method ,the test exhibited that the diameter of inhibition zone had more than 15mm against Bacillus subtilis,Staphylococcus aureus,Escherichia coli, Pot tests indicated that the fermentaion products of LDP-18 exhibited 57.25% protective efficacy and 62.00%therapeutic efficacy against Blumera graminis. The field trails results showed that the control efficacy of the fermentation products of LDP-18 against Erysiphe cichoralearum and Cladosporium fulvum were 32.03% and 82.69% respectively. Stability test of fermentation products of LDP-18 had been carried out to acid,alkali, temperature,sunshine illumination.,ultraviolet radiation. taking Alternaria longipes as object, heated at 60℃and 100℃for one hour,The fungicidal activity of the fermentation products of LDP-18 decrease 3.03% and 52.34%,and the fermentaion products of LDP-18 was stable to sunshine illumination and ultraviolet radiation. when subculture several generations,The fungicidal activity of secondary metabolites of LDP-18 did not alter. The single factor and orthogonal experiment indicated that the optimal carbon source was 10g/L saccharose,the optimal nitrogen source was 10 g/L millet and peptone 3g;The optimal fermentation time was 96h;The optimal cultivation temperature was 31℃and optimal pH was 6.5.The most suitable shake rate was220r/min, and the most suitable volume of cultivated liquid in 250ml conic bottle was 100mL and inoculation was 1.6×10~7 spores in 250 flask.