IAA-producing and phosphate solubilizer of rhizosphere actinobacteria consortium to promote plant growth in soybean (Glycine max L.)

Abstract

Plant Growth-Promoting Rhizobacteria (PGPR) are microbes that inhabit the rhizosphere and rhizoplanes environment and can enhance plant growth. The application of PGPR in agriculture can reduce the use of chemical fertilizers on soil. The purpose of this study was to determine the ability of the actinobacteria consortium to produce Indole-3-Acetic Acid (IAA), solubilize phosphate, and improve soybean growth in the greenhouse. The results of this study showed that the actinobacteria (Streptomyces sp. ASR58, Streptomyces sp. ASR67) and Rhizobium sp. which are used in this study are mutually compatible and tolerant to several types of fungicides and bactericides. Meanwhile, the consortium of Streptomyces sp. ASR58 and Streptomyces sp. ASR67 produces the highest concentration of IAA i.e. 25.11 ppm compared to each isolate and other bacterial consortia. Accordance to the quantitative phosphate solubilization assay, Streptomyces sp. ASR67 resulted in the highest dissolved inorganic phosphate i.e. 179.7 + 13.3 mg / L. Inoculation of Streptomyces sp. ASR58 and Streptomyces sp. ASR67 consortium into soybean seeds can significantly increase 54.6% in stem length, 29% root growth, and 20.4% in plant dry weight. This research indicated that Streptomyces sp. ASR58 and Streptomyces sp. ASR67 consortium resulted in the best growth toward soybean plants compared to other bacterial  consortia.