Background: Fusarium wilt of banana is one of the most destructive diseases in banana-growing regions worldwide. Soil-borne diseases and soil microbial communities are closely related. The screening of antagonistic bacteria from soil microorganisms in areas with Fusarium wilt of banana is of great practical significance for controlling this disease. Results: A strain designated FS-4 was isolated from healthy banana rhizosphere soil in an area affected by Fusarium wilt. This strain exhibited a significant antagonistic effect on the pathogen. Pot experiments revealed that the fermentation broth of strain FS-4 not only decreased the incidence of banana Fusarium wilt, but also promoted the growth of banana seedlings. The strain was identified as Streptomyces ma. by its morphological, physiological, and biochemical characteristics and 16S rRNA gene sequence analysis. The culture and fermentation conditions for this strain were optimized by single-factor and response surface experiments. The optimum culture conditions for Streptomyces ma. FS-4 were as follows: peptone 0.5%, saccharose 2.4, 0.05% K₂HPO₄, 0.05% MgCl₂, and 0.05% NaCl at an initial pH of 7.0; 180 g at 28 °C; and inoculation size of 6% for 62 h. The diameter of bacteriostasis circle for Bacillus subtilis reached 26.7 mm. Conclusion: Streptomyces ma. FS-4 is an important microbial resource as a biological agent for the control of plant pathogenic fungi and can be used to promote banana growth.

Banana is an essential food resource in many tropical and subtropical countries.

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.

Banana is a commercially important fruit, but its flavonoid composition and characteristics has not been well studied in detail. In the present study, the metabolism of flavonoids was investigated in banana pulp during the entire developmental period of fruit. ‘Xiangfen 1’, a novel flavonoid-rich banana germplasm, was studied with ‘Brazil’ serving as a control. In both varieties, flavonoids were found to exist mainly in free soluble form and quercetin was the predominant flavonoid. The most abundant free soluble flavonoid was cyanidin-3-O-glucoside chloride, and quercetin was the major conjugated soluble and bound flavonoid. Higher content of soluble flavonoids was associated with stronger antioxidant activity compared with the bound flavonoids. Strong correlation was observed between antioxidant activity and cyanidin-3-O-glucoside chloride content, suggesting that cyanidin-3-O-glucoside chloride is one of the major antioxidants in banana. In addition, compared with ‘Brazil’ , ‘Xiangfen 1’ fruit exhibited higher antioxidant activity and had more total flavonoids. These results indicate that soluble flavonoids play a key role in the antioxidant activity of banana, and ‘Xiangfen 1’ banana can be a rich source of natural antioxidants in human diets.

Background: Banana fruits are rich in various high-value metabolites and play a key role in the human diet. Of these components, carotenoids have attracted considerable attention due to their physiological role and human health care functions. However, the accumulation patterns of carotenoids and genome-wide analysis of gene expression during banana fruit development have not been comprehensively evaluated. Results: In the present study, an integrative analysis of metabolites and transcriptome profiles in banana fruit with three different development stages was performed. A total of 11 carotenoid compounds were identified, and most of these compounds showed markedly higher abundances in mature green and/or mature fruit than in young fruit. Results were linked to the high expression of carotenoid synthesis and regulatory genes in the middle and late stages of fruit development. Co-expression network analysis revealed that 79 differentially expressed transcription factor genes may be responsible for the regulation of LCYB (lycopene β-cyclase), a key enzyme catalyzing the biosynthesis of α- and β-carotene. Conclusions: Collectively, the study provided new insights into the understanding of dynamic changes in carotenoid content and gene expression level during banana fruit development.