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

ABSTRACT

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 Fusarium 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-1 . After treatment with 100 µg ml-1 FS-4 crude extract, the N-acetylglucosamine content in the mycelium increased 1·95-fold. However, the extract had no significant effect on ß-1,3-glucanase. At the FS-4 crude extract dose of 100 µg ml-1 , 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-1 . 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.