Antifungal mechanism of Streptomyces ma. FS-4 on fusarium wilt of banana

Aim: Research on prevention and cure of banana wilt is important to ensure the healthy development of the banana industry. In this study, antifungal mechanism of Streptomyces ma. FS-4 on fusarium wilt of banana was investigated.

Methods and results: The physiological strain of banana fusarium pathogen F. oxysporum f. sp. cubense Race 4 (FOC.4). was used as the target fungus, and the antifungal mechanism of the crude extract of Streptomyces ma. FS-4 was investigated. Eighteen different compounds identified by gas chromatography-mass spectrometry were composed of aldehydes, methyl, hydrocarbons, amides, esters, and acids. FS-4 significantly inhibited the spore germination of the target fungi, with an EC50 of 22.78 μg/mL. After treatment with 100 μg/mL FS-4 crude extract, the N-acetylglucosamine content in the mycelium increased 1.95-fold. However, the extract had no significant effect on β-1,3-glucanase. At the FS-4 crude extract dose of 100 μg/mL, the total sugar and protein contents decreased by 28.6% and 29.1%, respectively, and the fat content was 41.3%. FS-4 significantly inhibited the activity of the mitochondrial complex III of Foc4, which was reduced by 52.45%. Moreover, FS-4 reduced the activity of succinate dehydrogenase, a key enzyme in the Krebs cycle, by 60.2%. However, FS-4 had no significant effect on malate dehydrogenase. The membrane potential on the mitochondrial inner membrane was significantly reduced at the test concentration of 100 μg/mL. ROS gradually accumulated in the Foc4 hypha, and the burst was 3.97 times higher than the control.

Conclusions: This study demonstrated that the antifungal mechanism of Streptomyces ma. FS-4 against Foc4 includes the destruction of the plasma membrane and mitochondrial dysfunction and finally induction of cell apoptosis.

Significance and impact of the study: These results may indicate the prevention and control of banana wilt, which is of great significance to the healthy development of banana industry system.

Keywords: Streptomycetes; Antimicrobials; Cell injury; Mechanism of action; Plant diseases.