Chaoqun Zang, Ying Lin, Chunhao Liang, Yuanjun Bai
Abstract Peanut early leaf spot, a major disease caused by Passalora arachidicola , is responsible for considerable yield reductions in peanut production. In this study, a highly antagonistic strain, Bacillus amyloliquefaciens TL6, was isolated and characterized from healthy peanut leaves. In vitro confrontation assays showed that strain TL6 produced an inhibition zone of 69.8 mm against the pathogen. Pot experiments indicated that the undiluted fermentation broth of TL6 exhibited a biocontrol efficacy of 87.58% against peanut early leaf spot, with no statistical difference compared with 1000-fold diluted carbendazim (84.98%). Physiological and microscopic analyses revealed that the active metabolites from TL6 fermentation filtrate severely damaged P. arachidicola mycelia, causing mycelial wrinkling and fragmentation. Furthermore, the bioactive components of TL6 broth disrupted pathogen cell membrane homeostasis by inducing electrolyte leakage and suppressing ergosterol biosynthesis. Additionally, these active metabolites significantly increased the malondialdehyde content in P. arachidicola , but exhibited no significant effect on intracellular protein synthesis. Taken together, these results indicate that B. amyloliquefaciens TL6 has excellent potential as an effective biocontrol agent for the control of peanut early leaf spot disease.