Diversity, activity, and effectiveness of Rhizobium bacteria as plant growth promoting rhizobacteria (PGPR) isolated from Dieng, central Java

Background and Objectives: This study was aimed to isolate Rhizobium spp., from the plant rhizosphere and to investigate their effects on the growth of peanut (Arachis hypogaea L.) as plant growth-promoting rhizobacteria (PGPR). Materials and Methods: The isolates were characterized using YEMA, YEMA + Congo Red, and YEMA + Bromothymol blue (BTB) media. The Rhizobium was tested qualitatively for their ability to produce indole acetic acid (IAA), siderophores, proteases, nitrogenases as well as phosphate solubilizing activity. A greenhouse experiment was carried out to elucidate the effect of Rhizobium inoculation on Arachis hypogaea L. growth. Results: Eleven isolates were obtained in YEMA media and they were red-pink in the YEMA + Congo Red media. The YEMA + BTB test showed that 2 isolates were slow-growing and the rest were fast-growing isolates. Seven isolates pro duced siderophores, 5 were capable of phosphate solubilizing, 9 isolates produced protease enzyme, 4 isolates could produce IAA, and 7 isolates could fix nitrogen. The B1 and the combination of some high trait-isolate treatments in Y gave the best results on Arachis hypogaea L. growth. Conclusion: These isolates can be developed as biological fertilizer agents for the peanut plant