RESUMO
BACKGROUND AND OBJECTIVE: Phosphate-solubilising bacteria (PSB) are useful for plant growth. They inhabit different soil ecosystems such as colonizing the root environment. The aims of this study was to isolate PSB from oil palm rhizosphere and to conduct a comparative analysis of the solubility of inorganic phosphates. MATERIALS AND METHODS: Rhizospheric soil samples at 0-20 cm depth collected from the distance of 2 m away from the palm were isolated and their chemical and physical properties were analyzed. Qualitative estimation of the suspected PSB was screened by inoculating and growing them at 27°C for 10 days on NBRIP agar medium with bromophenol blue. Their abilities to solubilize AlPO4, FePO4 and Ca3(PO4)2 were examined. Phosphate solubilizing activities were tested on the NBRIP growth medium by analyzing solubilisation efficiency and soluble-P content. Genomic DNA was isolated using QIAamp® genomic DNA kit. RESULTS: A total of 15 PSB were successfully isolated from oil palm rhizosphere. During 5 days of incubation, isolate K3.1, A4 and K3.3 solubilized 53.5, 63.5 and 58.6 mg L-1 phosphate inoculated in Al3PO4, Fe3PO4 and Ca3(PO4)2, respectively. Based on the 16S rRNA gene sequence analysis, those isolates were closely related to Burkholderia arboris, Burkholderia gladioli and Burkholderia seminalis, respectively. In soil analysis, P2O5, C-organic and CEC had positive correlation with the total PSB. CONCLUSION: The existence of P promoting bacteria in oil palm rhizosphere may offer effective solution on biofertilizer agent for sustainable agriculture.