Streptomyces nobilis C51 Suppresses Gray Mold Caused by Botrytis cinerea in Tomato

This study sought to develop a biological control agent against gray mold disease caused by Botrytis cinerea in tomato using a strain of Streptomyces, which showed significant antagonistic activity against B. cinerea. Such strain (C51) was screened by dual culture method from a total of 78 actinomycetes and was identified as Streptomyces nobilis by morphological, biochemical and molecular analysis. The influence of different environmental conditions, such as temperature degree, pH range and medium type on the expression of the antifungal activity was thoroughly examined. The metabolites involved in the antagonistic action of C51 strain showed to be produced independently by the presence of B. cinerea. We also found that the culture filtrate of C51 potently inhibited the mycelial growth of B. cinerea, and morphological changes such as hyphal swelling and abnormal shapes were observed using culture filtrates. The antifungal activity of the culture broth was stable across a broad range of temperatures (28-121℃) and pH (pH 2-12), suggesting a wide range of applications of Streptomyces nobilis C51. The results of greenhouse test showed that Streptomyces nobilis C51 had the same disease inhibition effect as well as azoxystrobin against B. cinerea. The current observations could support the application of Streptomyces nobilis C51 as a promise biocontrol agent.