Effect of phosphate solubilizing microorganism to Aspergillus flavus development on peanut germination. Phosphate solubilizing microorganisms (PSM) are microorganisms which could increase the available P in plant media. The aim of this research is to determine the effect of PSM on A. flavus growth, and to identify it's effects on the growth dynamics of A. flavus as long as the peanut germination. The research were conducted in the Laboratory of Plant Diseases Department, Faculty of Agriculture, University of Jember, from August 2005 to May 2006 and divided in 2 stages: in vitro and germination stage. Base on in-vitro stage we concluded that Bacillus subtilis strain SK had better inhibition toward the growth of A. flavus than Pseudomonas fluorescent strain GM. B. subtilis strain SK could inhibit A. flavus as much as 74%, whereas P. fluorescent strain GM was only reached 60% compared to control. Base on the germination stage, B. subtilis in the desiccator supernatant (BsDS) could increase the dry weight of root up to 24.1 g better than P. fluorescens strain GM and control. We also found that B. subtilis strain SK was more effective to change the availability of P on plant media.