Potential Utility of Bacillus amyloliquefaciens SFB-1 as a Biocontrol Agent for Sweetpotato Black Rot Caused by Ceratocystis fimbriata

<b>Background/Objectives</b>: Sweetpotato black rot, caused by <i>Ceratocystis fimbriata</i>, is a severe fungal disease in sweetpotato production. Biological control strategies represent a promising, environmentally sustainable approach to managing this disease. This study investigates the biocontrol potential of <i>Bacillus amyloliquefaciens</i> SFB-1 against <i>C. fimbriata</i>. <b>Methods</b>: The antagonistic activities of strain SFB-1 on <i>C. fimbriata</i> were assessed through <i>in vitro</i> assays, including evaluations of mycelial inhibition, spore germination, and mycelial morphology. Pathogenicity assays on harvested sweetpotato roots assessed lesion diameter and depth. A transcriptomic analysis of <i>C. fimbriata</i> exposed to strain SFB-1 was performed to explore the underlying antifungal mechanism of SFB-1 on <i>C. fimbriata</i>. The qRT-PCR was employed to validate the RNA-seq results. <b>Results</b>: <i>In vitro</i> assays demonstrated that strain SFB-1 inhibited <i>C. fimbriata</i> mycelial growth by up to 81.01%, caused mycelial swelling, and completely suppressed spore germination at 10⁸ CFU/mL. The cell-free supernatant of strain SFB-1 also suppressed <i>C. fimbriata</i> growth. Pathogenicity assays revealed that strain SFB-1 treatments reduced lesion diameter and depth on harvested sweetpotato roots by over 50% compared to untreated controls. Transcriptomic analysis of <i>C. fimbriata</i> treated with strain SFB-1 identified 1164 differentially expressed genes, with significant alterations in genes associated with cell wall integrity, cell membrane stability, spore germination, detoxification, and antioxidant responses. The qRT-PCR validation of 16 genes confirmed the consistency with the RNA-seq results. <b>Conclusions</b>: <i>B. amyloliquefaciens</i> SFB-1 demonstrates significant biocontrol efficacy against <i>C. fimbriata</i> through multiple mechanisms, positioning it as a promising solution for the sustainable management of sweetpotato black rot.