Streptomyces taiwanensis sp. nov., a novel actinobacteria mediated management of banana Fusarium wilt

• A Streptomyces (KHY26 T ) suppresses banana Fusarium wilt. • KHY26 T inhibits Foc TR4 growth and reduces microconidia germination in vitro. • Greenhouse assays show lower disease index and higher biomass vs infected control. • Genome-based analyses support a novel species, Streptomyces taiwanensis sp. nov. • Metabolites, enzymes and siderophore production suggest multi-mode antagonism. A newly identified Streptomyces strain, designated KHY26 T , was isolated from organic soil in Qishan District, Kaohsiung city, Taiwan, and displayed a broad range of antagonistic activity against plant fungal pathogens. KHY26 T inhibited Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4) mycelial growth by up to 75.14% in dual-culture assays which suppressed microconidia germination, reduced spore germination to 3.4% in the presence of viable cells. KHY26 T also displayed broad-spectrum antifungal activity against 8 phytopathogenic fungi. In a greenhouse pot assay, we tested three application concentrations (1.25, 2.5, and 5 × 10⁶ CFU/mL). Higher concentrations (≥ 2.5 × 10⁶ CFU/mL) of KHY26 T significantly reduced Fusarium wilt incidence in banana plantlets (cv. ‘Pei-Chiao’, Cavendish AAA group). The highest concentration (5 × 10⁶ CFU/mL) lowered the disease severity index to ∼ 13% and reduced disease incidence to 44%, compared with ∼ 50% and 100%, respectively, in the infected control. Phenotypic and chemotaxonomic analyses, together with 16S rRNA gene phylogeny and whole-genome comparisons, supported classification of KHY26 T as a novel species, Streptomyces taiwanensis sp. nov. During exploratory observations of metabolites and secreted factors produced by KHY26 T , we found that it can produce multiple cell wall–degrading enzymes (chitinase, β-glucanase, protease, and cellulase) as well as siderophores. GC–MS and LC–MS analyses further predicted several putative antibiotic-related compounds, including antimicrobial sesquiterpenes (e.g., germacrene D and nootkatone), a phenolic derivative (2,4-di- tert -butylphenol), and specialized metabolites annotated as antibiotics (e.g., tetracenoquinocin and streptopyrazinone B). Collectively, these results indicate that S. taiwanensis KHY26 T is a promising biocontrol candidate for managing banana Fusarium wilt and warrants field evaluation, although the potential mechanisms remain uncertain.