<i>Streptomyces</i>-Induced 6-Nitrocoumarin Coordinates Rhizosphere Microbiome Recruitment for Pepper Blight Suppression

<i>Phytophthora capsici</i> causes devastating losses in global pepper production. This study deciphers a sophisticated plant-microbe-metabolite collaboration initiated by rhizosphere-colonizing <i>Streptomyces</i>. We demonstrate that <i>Streptomyces</i> specifically primes pepper root biosynthesis of 6-nitrocoumarin, a nitrated coumarin derivative exhibiting potent broad-spectrum antioomycete activity (EC₅₀: <i>P. capsici</i> 44.39 mg/L, <i>Phytophthora palmivora</i> 47.06 mg/L, <i>Peronophythora litchii</i> 34.92 mg/L). Crucially, this <i>Streptomyces</i>-recruited metabolite functions as a keystone rhizosphere signal, selectively enriching beneficial bacterial consortia while directly disrupting the ABC transporters of pathogens. The restructured microbiome synergistically amplifies plant systemic resistance through upregulating defense genes and enhancing root immunity. Our work establishes 6-nitrocoumarin as a dual-functional inoculant, a direct actinomycete compound and microbiome modulator, revealing a novel plant-microbe codefense paradigm driven by <i>Streptomyces</i>-induced metabolic rewiring for sustainable crop protection.