Streptomyces biostimulants: an effective sustainable approach to reduce inorganic N input and maintain high yield of wheat crop in different soil types.

This article focuses on the isolation and characterization of endophytic plant growth-promoting (PGP) actinomycetes from the wild medicinal plant Zygophyllum album and their application as biostimulants to reduce inorganic nitrogen (N) fertilizer input while maintaining high wheat crop yields across different soil types. Eight diverse actinobacterial strains were isolated, with two Streptomyces strains (NGB-Act4 and NGB-Act6) demonstrating significant in vitro PGP traits—including indole-3-acetic acid production, phosphate solubilization, siderophore production, and antagonism against Fusarium graminearum—and enhancing wheat growth under reduced N inputs in greenhouse and two-year field trials on both low-fertility sandy and high-fertility clay soils. Notably, inoculation with Streptomyces sp. NGB-Act4 combined with 50% of the recommended synthetic N dose resulted in grain yield and grain nitrogen content comparable to or exceeding those of full N fertilization, indicating its potential as an effective sustainable alternative to reduce chemical N fertilizer use in wheat cultivation. This study represents the first field-scale evidence supporting the use of endophytic streptomycetes from wild medicinal plants as bioinoculants to improve wheat productivity under low inorganic nitrogen conditions.