DIFFERENTIAL RESPONSES OF PISOLITHUS-TINCTORIUS ISOLATES TO ALUMINUM IN-VITRO

Isolates of Pisolithus tinctorius collected from old coal mining (pH 4.3, Al 327 mg/L, mine sites), rehabilitated (pH 4.9, Al 22 mg/L), and forest sites (pH 5.3, Al 6 mg/L) were grown in axenic culture with 0-2000 mg/L Al and assessed for aluminum tolerance by comparing the mass of mycelia produced and levels of Al, Ca, and Mg in mycelia as detected by energy-dispersive X-ray microanalysis. Mine-site isolates demonstrated mycelial growth to 2000 mg/L Al, a threshold of 90 mg/L Al before accumulation of Al in mycelia, and higher levels of Ca and Mg within the mycelia than either rehabilitated- or forest-site isolates at substrate concentrations greater than 4 mg/L Al. In contrast, mycelial growth ceased at 22 and 12 mg/L Al for rehabilitated- and forest-site isolates, respectively, and was strongly correlated with a high Al and low Ca and Mg content in the mycelia. These differences indicated that an increase in Al tolerance of mine-site isolates may operate through an increase in the presence of Ca and Mg in mycelia and a physiological tolerance to the metal.