Exploration and Screening of Clove Plant Growth Promoting Rhizobacteria in Pucaksari Soil

PGPR are soil bacteria in the plant root zone (rhizosphere) that provide nutrients for plant growth, plant development, and plant protection against certain pathogens. The use of PGPR in Indonesia, especially in Pucaksari Village, Buleleng Regency as a biostimulant and its application to clove plants to increase agricultural production is still very rarely studied. The purpose of this study was to find the presence of PGPR rhizosphere bacteria in clove plants in the root zone of the Pucaksari Buleleng plantation that have the ability to fix nitrogen, produce IAA and dissolve phosphate. The method of data analysis of characteristics and bioactivity tests of PGPR was compiled and analyzed descriptively. Isolation was carried out by dilution using clove plant rhizosphere soil samples. Phosphate solubilization ability was carried out using Pikovskaya media and calculating the Phosphate Solubility Index. Detection of nitrogen fixation was tested using Ashby's Mannitol Agar growth media. IAA production was qualitatively tested using tryptic soy broth enriched with tryptophan and Salkowsky's reagent. Three isolates (BRC01, BRC02, and BRC03) were isolated from the rhizosphere of clove plants. All isolates could solubilize phosphate and produce IAA. However, only one isolate successfully fixed nitrogen, as seen from its growth on Ashby's medium. Isolate BRC02 had the highest phosphate solubilization with an IKF of 1.86 and produced 14.71 ppm of IAA. This bacterium was identified as Klebsiella aerogenes, which has potential as a biostimulant agent.