Newly Isolated Streptomyces sp. JBS5-6 as a Potential Biocontrol Agent to Control Banana Fusarium Wilt: Genome Sequencing and Secondary Metabolite Cluster Profiles

Abstract

Banana is a key staple food and fruit in countries all over the world. However, the development of the global banana industry is seriously threatened by Fusarium wilt disease, which is caused by Fusarium oxysporum f. sp. cubense (Foc). In particular, Foc tropical race 4 (Foc TR4) could infect more than 80% of global banana and plantain crops. Until now, there were no commercial chemicals or resistant cultivars available to control the disease. Biological control using actinomycetes is considered a promising strategy. In this study, 88 actinomycetes were isolated from a banana orchard without symptoms of Fusarium wilt disease for more than 10 years. An actinobacterial strain labeled as JBS5-6 has exhibited strong antifungal activities against Foc TR4 and other selected 10 phytopathogenic fungi. Based on phenotypic and biochemical traits as well as complete genome analysis, strain JBS5-6 was assigned to Streptomyces violaceusniger. Extracts of the strain inhibited the mycelial growth and spore germination of Foc TR4 by destroying membrane integrity and the ultrastructure of cells. The complete genome of strain JBS5-6 was sequenced and revealed a number of key function gene clusters that contribute to the biosynthesis of active secondary metabolites. Sixteen chemical compounds were further identified by gas chromatography-mass spectrometry (GC-MS). 5-hydroxymethyl-2-furancarboxaldehyde was one of the dominant components in strain JBS5-6 extracts. Moreover, fermentation broth of strain JBS5-6 significantly reduced the disease index of banana seedlings by inhibiting the infection of Foc TR4 in a pot experiment. Hence, strain JBS5-6 is a potential biocontrol agent for the management of disease and the exploitation of biofertilizer.

A Novel Antifungal Actinomycete Streptomyces sp. Strain H3-2 Effectively Controls Banana Fusarium Wilt

“…H4, and Streptomyces sp. YYS-7 against Foc TR4 were 136.9, 32.6, and 21.1 μg/ml, respectively ( Jing et al, 2020 ; Wei et al, 2020 ; Li et al, 2021b ). Notably, no inhibition activity was observed against endophytic bacteria isolated from banana roots ( Supplementary Figure 2 ), suggesting that Streptomyces sp.…”

“…Accumulated evidence indicated Streptomyces sp. as a biological agent against plant pathogenic fungi mainly because it produced a large number of secondary metabolites with antimicrobial activity ( Chen et al, 2018 ; Yun et al, 2018 ; Jing et al, 2020 ; Wei et al, 2020 ; Li et al, 2021b ). Streptomyces is also widely used in the medicine industry.…”

“…The five evaporated solutions were dissolved into 10% of dimethyl sulfoxide (DMSO) with a final concentration of 20.0 mg/ml, respectively. Then, inhibitory efficiency against Foc TR4 was carried out by a plate diffusion method according to previous reports ( Jing et al, 2020 ; Li et al, 2021b ): 20 mg/ml of five crude extract solutions were transferred to 60 ml of the autoclaved PDA medium at 50–55°C; 10% of DMSO was used as a control. A 5-mm-diameter fungal disc of Foc TR4 was inoculated in the center of plate.…”

“…Streptomyces sp. JBS5-6 also exhibits strong antifungal activity against Foc TR4 ( Jing et al, 2020 ). However, these functional microbes for controlling plant diseases are limited by their different growth conditions or poor activity in a complex environment ( Saravanan et al, 2003 ).…”

Biofertilizers and Biocontrol Agents for Agriculture: How to Identify and Develop New Potent Microbial Strains and Traits

“…Most recently, reports on the genomes of potential biocontrol strains Streptomyces sp. JBS5-6 and B. toyonensis BAC3151 listed similarly gene clusters responsible of secondary metabolite biosynthesis [ 88 , 89 ]. Common traits found in sequenced B. polymyxa strains with plant-growth-promoting ability are phytohormone production and increased nutrient availability [ 90 ].…”