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

Aims: This study aimed to isolate and characterize endophytic plant growth-promoting (PGP) actinomycetes from the wild medicinal plant Zygophyllum album.

Methods And Results: Eight actinomycetes were isolated, identified, and screened for their PGP activities to improve the growth and production of wheat plants under low N-inputs. Based on 16S rRNA analysis, the isolated actinobacteria showed high diversity and had multiple in vitro PGP attributes. In pot experiments, Streptomyces sp. NGB-Act4 and NGB-Act6 demonstrated the highest significant PGP activities to enhance the growth of wheat plants under reduced N-inputs. Under various field conditions (high-fertility clay soils and low-fertility sandy soils), in combination with 50% N-dose, the two streptomycetes showed significant increases in grain N% and grain yield of the wheat crop compared with the 50% N-fertilized treatment. Irrespective of soil type, wheat plants inoculated with strain NGB-Act4 produced grain yield and grain N% significantly greater than or comparable to the full N-dose treatment.

Conclusions: This is the first field report on the successful use of endophytic streptomycetes as an effective strategy to improve wheat yield and reduce the use of synthetic N fertilizers.