Biocontrol Potential of Borrelidin Metabolites Derived from Streptomyces rochei A144 as a Fungicide

Abstract Aims This study aimed to isolate and identify antifungal metabolites and evaluate potential applications for biocontrol. Methods and Results Using a bioactivity-guided fractionation approach, we obtained the macrolide metabolite borrelidin from Streptomyces rochei A144, which exhibited significant inhibitory effects on V. mali mycelial growth (EC50 = 22.23 μg mL−1). Scanning and transmission electron microscopy analyses revealed that borrelidin caused damage to V. mali hyphae, such as breakage, increased swelling and branching at the hyphal tips, irregular cell wall thickness, plasmolysis, and degeneration of cellular organelles. After borrelidin treatment, the lesion length on detached twigs and lesion area on leaves were reduced by 49.38% and 89.16%, respectively. The mycelial growth rate method was used to evaluate the antifungal activity of borrelidin against various plant pathogenic fungi. The study findings indicate that borrelidin possesses broad-spectrum antifungal activity, with inhibition rates in the range of 21.32%–100%. Conclusions The macrolide metabolite borrelidin, derived from S. rochei A144, exhibited significant antifungal activity against V. mali and broad-spectrum inhibition of phytopathogenic fungi.