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Review: A Review on Streptomyces spp. as Plant-Growth Promoting Bacteria (PGPB) 
Chelsea Mae Ferrer, Jizelle Elyza Olivete, Sam Luigi Orias, Mark Romulo Rocas, Clydine San Juan, Julieta Z. Dungca, Tooba Mahboobb, Sahapat Barusrux, Veeranoot Nissapatorn

Abstract
The bacteria Streptomyces spp. are known to be the most important and well-acknowledged microorganisms that produce secondary metabolites. Increasing population density has greatly influenced the demand for agricultural intensification, which is economically relevant to tackle. This review was conducted to evaluate the properties of microorganisms, specifically genus Streptomyces and its effect on the plant as growth promoting bacteria. It was found that a vast number of Streptomyces strains are capable of producing a wide variety of biologically active compounds, which helps plant growth. Various studies and research had shown that inoculation of Streptomyces on plants has resulted in increased in plant heights, leaf volume, roots volume, and stem weights. Streptomyces corchorusii strain UCR3-16 exhibited significant biocontrol potential against important rice fungal pathogens showing highest inhibition against Rhizoctonia solani. About 130 strains of Streptomyces were also evaluated against destructive soil-borne pathogens. Plant growth-promoting activities of Streptomyces sp.in sorghum and rice were also conducted. Some Streptomyces species are now being used agriculturally. In conclusion, these promising studies are suggested for more future research not just on Streptomyces but in different soil-dwelling microorganisms that could contribute to plant growth promotion.

Keywords: Plant-Growth Promoting Bacteria; Streptomyces spp.