Biocontrol eggplant soft rot caused by Fusarium equiseti through Bacillus amyloliquefaciens and its lipopeptides

China is the world's leading producer and consumer of eggplant, yet effective strategies are urgently needed to manage postharvest soft rot caused by Fusarium equiseti, a newly identified pathogen. This study explores the biocontrol potential and mechanism of Bacillus amyloliquefaciens SDTA 2-1 against F. equiseti-induced soft rot in eggplants. Strain SDTA 2-1 exhibited significant inhibitory activity against F. equiseti, reducing the decay rate from 66.67 % to 26.67 %. Its biofilm-forming ability promoted colonization on eggplant fruit, enhancing disease control efficacy. Furthermore, SDTA 2-1 enhanced the activities of key defensive enzymes and reduced malondialdehyde (MDA) levels, thereby inducing host resistance. Crude lipopeptide extracts from strain SDTA 2-1 showed significant antifungal activity against F. equiseti, with an EC₅₀ value of 29.25 ± 1.45 μg/mL, effectively inhibiting both mycelial growth and conidial germination. The extract disrupted fungal cell membrane integrity, leading to cytoplasmic leakage, and increasing electrical conductivity and permeability. Notably, lipopeptide treatment significantly reduced both disease incidence and lesion size in eggplant fruits. PCR and LC-MS analyses identified three iturin A homologs in the lipopeptides. Collectively, this study highlights B. amyloliquefaciens SDTA 2-1 as a promising and sustainable biocontrol agent for managing postharvest eggplant soft rot and provides valuable insights into its antifungal mechanisms.