Isolation of endophytic actinomycetes from Rehmannia glutinosa and identification of a new species Streptomyces folium leaf-16 resistant to Phoma herbarum

Abstract:

Endophytic actinomycetes of medicinal plants have the potential to synthesize natural active compounds, and new species of actinomycetes are an important source for discovering new compounds. [Objective] To explore the resources of endophytic actinomycetes of the medicinal plant Rehmannia glutinosa, and identify a new strain leaf-16 with the activity against the pathogenic fungus causing the ring rot of R. glutinosa. [Methods] In this study, we used five-step sterilization method to isolate the endophytic actinomycetes of R. glutinosa in Henan Province. Phoma herbarum, the pathogenic fungus causing the ring rot of R. glutinosa, was used as the indicator fungus to screen the antagonistic strains via the plate confrontation assay. For the antagonistic strains, 16S rRNA gene sequencing revealed a new actinomycete strain leaf-16, which was then identified based on the morphological, physiological, biochemical, and molecular characteristics, as well as cell wall components and DNA-DNA hybridization. [Results] We obtained eight actinomycete strains resistant to P. herbarum by plate confrontation assay. Among them, strain leaf-16 was identified as a new species of Streptomyces and named Streptomyces folium. [Conclusion] Strain leaf-16 is a new species of Streptomyces and has the activity of inhibiting the pathogenic fungus caused ring rot disease of R. glutinosa. This new species lays a material foundation for further isolation of new bioactive substances against the ring rot of R. glutinosa.