Diversity of Streptomyces and Their Plant Growth-Promoting Potential for Sustainable Crop Production

AIMS: To isolate and characterize rhizospheric Streptomyces with plant growth-promoting and biocontrol properties, and to evaluate their potential as microbial bioinoculants for sustainable crop production. METHODS AND RESULTS: Actinomycete isolates obtained from rhizosphere soils were screened for plant growth-promoting attributes, hydrolytic enzyme production, and antagonistic activity against important phytopathogens. Taxonomic identification was performed by 16S rRNA gene sequencing, confirming that the selected isolates belonged to diverse Streptomyces lineages. Several isolates exhibited multiple beneficial traits, including phosphate, potassium and zinc solubilization, siderophore and ammonia production, together with amylase, protease and lipase activities. The isolates also inhibited the growth of Rhizoctonia solani under in vitro conditions. Five multifunctional isolates (Xen-NIP-ACT-33, Xen-NIP-ACT-39, Xen-NIP-ACT-10, Xen-NIP-ACT-38 and Xen-NIP-ACT-35) were subsequently evaluated under greenhouse conditions using maize, wheat and rice. All five strains improved plant growth compared with untreated and diammonium phosphate-treated controls, with Xen-NIP-ACT-35 consistently producing the greatest increase in plant biomass. CONCLUSIONS: Indigenous rhizospheric Streptomyces possess complementary plant growth-promoting and biocontrol characteristics that support their use as multifunctional bioinoculants. The superior performance of selected isolates under greenhouse conditions highlights their potential to improve crop growth while reducing reliance on chemical inputs.