Abnormal genesis of basidiospores in a mutant stock ofSchizophyllum commune FR

The Kniep stock subcultured for more than 45 years in the Centraal Bureau voor Schimmelcultures at Baarn, Netherlands, contains a burden of morphological and biochemical mutations. It is said to have been originally a monokaryon; something has obviously happened to it: either it has been mislabeled, or it has become contaminated during its long period of subculturing.Our results obtained from outcrossing, indicate that the Kniep stock is a dikaryon. Even mycelia derived from single spores behave as dikaryons and heterokaryons. An explanation of the abnormal behaviour of monosporous mycelia isolated from the Kniep stock is given in terms of impaired distribution of the nuclei from the basidia to the basidiospores, resulting in mono-, di-, and heterokaryotic basidiospores.