Inhibitory effects of volatile 2-methylbutyric acid produced by Bacillus tequilensis XK29 on Ceratocystis fimbriata

Abstract:

[Objective] To investigate the inhibitory effects of 2-methylbutyric acid produced by Bacillus tequilensis XK29 on Ceratocystis fimbriata, and to evaluate its control effects on sweet potato black rot. [Methods] I-plates (2-section) and gas-phase antimicrobial system were used to study the inhibitory effects of 2-methylbutyric acid on mycelial growth and spore germination of C.fimbriata, and its effect on the micro-morphology of C.fimbriata was observed by lactophenol cotton blue staining. Fluorescent probes calcofluor white and propidium iodide were adopted to detect the influences of 2-methylbutyric acid on cell wall structure and cell membrane permeability of C.fimbriata, and the change of intracellular reactive oxygen species of C.fimbriata was explored by fluorescence probe 2ʹ,7ʹ-dichlorodihydrofluorescein diacetate. Additionally, the content of glutathione was determined to analyze the ability of the pathogenic fungus to deal with oxidative damage, and the activity of mitochondrial dehydrogenase and the content of pyruvic acid were determined to clarify the effects of 2-methylbutyric acid on mitochondrial function and energy metabolism of C.fimbriata. In the end, we evaluated the application of 2-methylbutyric acid to the control of sweet potato black rot. [Results] 2-methylbutyric acid significantly inhibited the mycelial growth and spore germination of C.fimbriata, thus reducing the sporulation ability of C.fimbriata and resulting in folded mycelia and discontinuous cavities. The cell wall structure was changed, and the membrane permeability and the content of intracellular reactive oxygen species were increased. 2-methylbutyric acid markedly reduced the content of glutathione, thereby decreasing the ability of pathogens to deal with oxidative damages. Furthermore, the activity of mitochondrial dehydrogenase and the content of pyruvic acid dropped, which induced mitochondrial dysfunction and interfered with cell energy metabolism, thus leading to cell death. In addition, 2-methylbutyric acid controlled the sweet potato black rot.[Conclusion] 2-methylbutyric acid had remarkable inhibitory effects on C.fimbriata. It could be used as a safe and efficient gas-phase antimicrobial material for the development of new fumigants.