Abstract: Potato common scab, a soil- and seed-borne disease caused by various Streptomyces species, currently lacks effective chemical control agents. In this study, a biocontrol strain designated Apcs-1, with significant inhibitory activity against the pathogen, was screened and isolated, and the inhibition rate reached 57.92%. Based on morphological, physiological and biochemical characterization, as well as phylogenetic analysis of 16S rRNA and gyrB gene sequences, the strain was identified as Bacillus velezensis. Apcs-1 demonstrated a broad antibacterial spectrum and was capable of secreting protease and cellulase. It induced hyphal fragmentation of the pathogen and possessed genes involved in antimicrobial lipopeptide synthesis. Stability tests of its fermentation broth revealed that the inhibitory activity remained relatively stable under varying temperatures and pH conditions, with enhanced efficacy in acidic environment. Pot experiments demonstrated that the Apcs-1 fermentation broth promoted the growth of potato plants. Compared with the control group, treated plants showed significant increases in plant height, fresh weight and dry weight. In field trials, the fermentation broth provided a control efficacy of 62.73% against potato common scab. In conclusion, the Apcs-1 strain exhibits strong potential for controlling potato common scab and holds promise for future development and application.

Key words: potato common scab, Bacillus velezensis, screening and identification, biological control, growth promotion