Effect of inorganic ions on bud cell formation by Fusarium oxysporum in potato dextrose broth

Potato dextrose broth (PDB), a well-known medium for cultivation of fungi, can be made from potato extract and glucose (handmade PDB) or bought as a commercial powder (commercial PDB). Previously, we reported that bud cell formation and fungal biomass of Fusarium oxysporum in handmade PDB are higher than in commercial PDB, and the presence of high molecular weight (>20 MDa) carbohydrates in PDB promoted bud cell formation by most strains of F. oxysporum. In this study, we report the effects of inorganic ions in PDB on bud cell formation and fungal biomass production by F. oxysporum. Concentrations of Mg, K, Fe, PO₄ ³⁻ and SO₄ ²⁻ were higher and of Na and Cl⁻ were lower in handmade PDB than in commercial PDB. Adding each inorganic ion alone to commercial PDB showed that Mg is critical for enhancement of bud cell formation by some strains of F. oxysporum. The addition of Mg²⁺ with raw potato starch to commercial PDB promoted bud cell formation by some, but not all, of the seven F. oxysporum strains tested in this study.