Intra- and interspecific variation in patterns of organic and inorganic nitrogen utilization by three Australian Pisolithus species

The ability of three Australian Pisolithus species, discriminated on the basis of ITS sequence data, to utilize a range of inorganic and organic nitrogen sources was assessed in liquid axenic culture. Both intra-, and putative interspecific, variation in nitrogen source utilization was observed. Most isolates demonstrated a preference for NH₄⁺ over NO₃^-, although some showed no significant preference for either inorganic source. All isolates utilized a range of amino acids. Species I isolates demonstrated a preference for acidic and/or neutral amino acids over basic acids, while species II and III isolates generally utilized amino acids poorly relative to species I. Although most isolates utilized BSA poorly, two species I isolates that had been maintained in axenic culture for > 10 y grew well on this substrate, suggesting possible changes in nitrogen utilization with extended storage in axenic culture.