Antifungal Activity of the Fermentation Broth fromEndophytic Streptomyces sp. YDG17 of Euonymus japonicus

A strain of endophytic Streptomyces sp. YDG17 was isolated from the root of Euonymus japonicus. The result of bioassay indicated that the mycelial growth of 11 species of plant-pathogenic fungus could be inhibited in vitro by the broth of YDG17,and the value of EC50 against Fusarium graminearum,Botrytis cinerea and Alternaria solani were 259.98,336.13 and 100.72 mg/L,respectively. The spore germination of 3 species of plant-pathogenic fungus could also be inhibited by the broth of YDG17,and the value of EC50 in the spore germination tests against B.cinerea was 87.84 mg/L.The results also showed that the protective efficacy and curative efficacy of the undiluted fermentation products against B.cinerea were 97.62% and 79.23% on detached cucumber leaves,and were 71.34% and 64.23% on potted cucumber plants,respectively.By comparing with the curves of classical antibiotics in Doskochilova system,the active ingredients in the fermentation were identified as alkaline and water soluble compounds.The broth of YDG17 was isolated by weak acid cation resin and the active fraction was identified as some streptothricins by ESI-MS/MS.