• Fungal interactions;
  • genetic transfer;
  • incompatibility;
  • mating systems;
  • Stereum


Pairings between strains of Stereum hirsutum (Willd. ex Fr.) S. F. Gray pp 2% malt agar were analysed using changes in mycelial morphology and non-self recognition properties as evidence of genetic transfer between the participants. In some combinations the morphological evidence suggested the- uniform emergence of a heterokaryon following mating and reciprocal nuclear migration between two compatible homokaryons. In other combinations there was evidence of strongly selective invasion by one of two nuclear types from a heterokaryon into a homokaryon, and in a third type of pairing there was evidence for acquisition by a homokaryon of a second mating type but not an entire nuclear genome.

Combinations representing each of these three apparent classes of genetic transfer were selected, and mycelia grown from single hyphal tips and/or basidiospores taken either from pure cultures of the progenitor strains or from subcultures from interacting colonies. The DNA from each of these mycelia was extracted and analysed using restriction fragment length polymorphisms to detect genomic differences between strains. The results were consistent with the interpretation of events based on morphological criteria. The combination of morphological and molecular approaches holds considerable potential for rapid, yet precise investigation of genetic exchange between fungal strains isolated from natural populations which have not been the subject of extensive genetic analysis by classical means.