Population structure, inter-mycelial interactions and infection biology of Stereum gausapatum

Abstract

Isolates from wood, fruit body tissue and single basidiospores of Stereum gausapatum from several locations in South-West England showed several types of reaction when paired on 2% malt agar. ‘Compatible’ reactions resulted in the formation of a distinct secondary mycelium between monospore isolates. ‘Lytic’ reactions resulted in the development, between monospore isolates, of a crescent-shaped zone of appressed mycelium bounded by regions of liquid droplet exudation. In pairings between sibs, the distribution of these two reaction types showed a reciprocal relationship depending on which fruit body had been used for isolation. In non-sib pairings the compatible reaction predominated although, as in a few sib pairings, in many instances it appeared to follow an initial lytic reaction. A narrow pigmented zone of ‘mutual antagonism’ was usually formed between different wood or fruit body tissue isolates, or laboratory-produced secondary mycelia, and also between certain non-compatible/non-lytic combinations of monospore sibs. Some interactions between monospore sibs were ‘weak’, with little or no pigment production or other obvious effect. These observations suggest that S. gausapatum is heterothallic and that there is a link between the mechanisms underlying the lytic and compatible reactions. The implications in the infection biology of S. gausapatum and in relation to findings for other Stereum spp. are discussed.