Abstract
Some plant growth promoting rhizobacteria (PGPR) have the ability to solubilize the insoluble inorganic forms of phosphorus (P) through the production of specific metabolites such as organic acids. These phosphate solubilizing bacteria (PSB) are routinely screened by qualitative method (NBRIP medium agar plate assay) by observing the size of a halo/ clear zone on plate around the bacterial colony due to production of organic acids into surrounding medium. In this study, this qualitative method was compared with quantitative (colorimetery) method of measuring the P solubilization by PSB to evaluate the validity/accuracy of the former method. Results of quantitative and qualitative methods indicated that qualitative method did not reflect the real potential of PSB to solubilize insoluble P as no relationship was observed when values regarding P solubilization by PSB determined by qualitative method were regressed against respective values recorded for quantitative method. Interestingly, same strains which showed very poor performance in qualitative method were proven good P solubilizers in quantitative method and vice versa. It could be concluded that only quantitative method should be considered reliable when studying P solubilization by phosphate solubilizing microbe (PSM).
K.S. Baig1, M. Arshad*1, , Z.A. Zahir1, M.A. Cheema2. (2010) Comparative efficacy of qualitative and quantitative methods for rock phosphate solubilization with phosphate solubilizing rhizobacteria, The Journal Soil & Environment , Volume 29, Issue 1.
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