Studies on the fungicidal activity of secondary metabolic products of actinomycetes

The fermentation extracts of NO.24 strain of actinomycete isolated from the soil of Qinling mountainous areas were assayed. The results showed that the fermentation extracts had a high fungicidal activity to mycelium growth or spore germinaltion of Botrytis cintrea , Fusarium graminearum , Alternaria longipes , Fusarium oxysporium , Exserohilum turcicum , Alternaria solani and Bipolaris sorokiniana at the concentration of 2 000 mg/L. The mycelium growth EC50 values for E. turcicum and B . cintrea were 240.13 mg/L and 350.48 mg/L, respectively. The spore germination EC50 values for E. turcicum and F. oxysporium were 155.01 mg/L and 124.15 mg/L, respectively. The results of pot tests showed that the fermentation extracts exhibited a protective efficacy of 76. 13% and a therapeutic efficacy of 70.78% a gainst Pseudoperonospora cubensis , a protective efficacy of 63.93 % and a therapeutic efficacy of 59. 66 % against Blume ria guaminis at the concentration of 6 000 mg/L. The results of preliminary isolation of the fermentation extracts from strain NO.24 indicated that the main active components was water-solubable.