Variation in Copper Tolerance among Homokaryotic and Dikaryotic Mycelia of Polyporus palustris Berk. et Curt.

Investigations were made of the variation in copper toleranceamong homokaryons and dikaryons originating from one dikaryoticisolate of Polyporus palustris, as shown by their growth onnutrient agar containing copper sulphate, usually at 0.32 Mconcentration (c. 8 per cent of CuSO₄.5H₂O). Homokaryons obtainedby monobasidiospore isolation were crossed and further homokaryonsobtained in the same way. Selection for copper tolerance gavean increase in the second generation, but no further increasein the third; whilst selection for copper sensitivity gave substantialincreases in both second and third generations. It is concludedthat copper tolerance in this fungus is controlled by a numberof genes. It was found that, in this fungus, the copper toleranceof a dikaryon was substantially greater than that of eitherof its constituent homokaryons. It was also found that differentisolates of P. palustris varied very widely in copper tolerance.