Mycelial interactions in Daldinia concentrica

Abstract

Genetically different isolates of Daldinia concentrica always produced demarcation zones when paired against one another. The morphology of these zones varied with respect to the width and shape of regions of white aerial mycelium ( wam ). In pairings between single ascospore isolates from the same perithecium, evidence was obtained for a multigenic recognition system. The wam usually widened, either symmetrically or asymmetrically, resulting in ‘bow-tie’ and ‘hour-glass’ shaped interaction zones. Bow-tie shaped zones were associated with inhibition of the parent colony margins and emergence of a fan-shaped wam . Pairings between isolates from different stromata and from different wood samples generally resulted in a narrower wam of more constant width at the interaction interface. However, a large number of unilateral ‘pincer-like’ interactions occurred in which one isolate gained territorial dominance over the other. These interactions followed outgrowth of a wam from the interaction interface associated with inhibition of extension of the suppressed isolate. Evidence that the wam contained temporarily heterokaryotic mycelium was obtained by subculturing single hyphal tips. These observations imply the existence of mycelial recognition systems which are fundamentally similar to those governing mating in heterothallic Basidiomycotina, but which do not enable production of a stable secondary mycelium.