Biocontrol and plant growth-promoting potential of Streptomyces strains against fungal pathogens of tomato and wheat for a sustainable agriculture.

BACKGROUND: Modern agriculture urgently requires sustainable alternatives to synthetic chemical pesticides to mitigate crop yield losses while protecting human health and the environment. This study evaluated the biocontrol potential and plant growth-promoting (PGP) traits of three newly isolated Streptomyces strains (Strep_22, Strep_23, and Strep_24) against severe soilborne fungal pathogens affecting durum wheat (Triticum durum Desf.) and tomato (Solanum lycopersicum L.), two economically crucial crops. RESULTS: In in vitro dual-culture assays, strain Strep_22, identified as Streptomyces netropsis, demonstrated the highest overall efficacy, achieving a mean fungal growth inhibition rate of 91.52% and near-complete suppression of critical pathogens such as Agroathelia rolfsii, Fusarium solani, and Sclerotinia sclerotiorum. Kinetic modelling confirmed that Strep_22 significantly reduced fungal growth rates. Based on these outstanding findings, Strep_22 was selected for in vivo glasshouse validation. Glasshouse trials demonstrated that treatments with this strain significantly reduced disease incidence and severity (such as root rot and wilt) in both wheat and tomato crops. Concurrently, Strep_22 exhibited strong PGP traits, inducing a significant increase in plant biomass, shoot height, and root development compared to untreated, infected controls. CONCLUSION: The Streptomyces strain Strep_22 represents a highly promising, dual-action biocontrol agent. It effectively protects wheat and tomato crops against devastating fungal infections while simultaneously stimulating plant vegetative growth and development. Consequently, it constitutes a valuable ecological alternative for the formulation of commercial biofertilizers and biopesticides, paving the way toward sustainable agricultural systems. © 2026 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.