Unleashing the biocontrol and plant growth promoting potential of native rhizosphere Streptomyces spp. against Phytophthora foot rot in black pepper (Piper nigrum L.)

The present study aimed to isolate, characterize, and evaluate native rhizosphere microorganisms for their biocontrol potential against Phytophthora capsici (LPHPC-04) and to develop an effective talc-based bioformulation for managing foot rot disease in black pepper. A total of 64 native isolates, comprising Trichoderma , Bacillus , and Streptomyces spp., were screened through dual culture assays, among which actinobacterial isolates APN 10 and APN 07 exhibited the highest mycelial inhibition of 63.92% and 54.90%, respectively. Molecular characterization identified APN 10 as Streptomyces minutiscleroticus and APN 07 as S. longisporoflavus . SEM analysis confirmed severe morphological disruption of P. capsici hyphae and sporangia upon exposure to these antagonists. GC–MS profiling revealed diverse secondary metabolites in individual isolates and distinct metabolite sets in their interaction zones with the pathogen. Molecular docking demonstrated strong binding affinities of docosahexaenoic acid and hippuric acid with key pathogenic proteins, particularly glyceraldehyde-3-phosphate dehydrogenase and cytochrome c oxidase subunit 1. Both isolates displayed multiple plant growth-promoting traits, including production of cellulase, amylase, protease, ammonia, siderophores, and phosphate solubilization, with APN 10 additionally producing IAA. Talc-based formulations showed good microbial compatibility and maintained viable populations up to 120 days. In vivo evaluations demonstrated enhanced sprouting, vegetative growth, root development, and vigour indices in treated plants. The Streptomyces consortium (T3) achieved a 76.49% reduction in disease incidence, supported by elevated defense enzyme activities. These findings highlight S. minutiscleroticus and S. longisporoflavus as promising eco-friendly biocontrol agents for sustainable management of foot rot in black pepper.