MYCELIAL INTERACTIONS AND OUTCROSSING IN THE CONIOPHORA-PUTEANA COMPLEX

Outcrossing populations of the Coniophora puteana complex had a multiallelic unifactorial (bipolar) homogenic incompatibility (mating) system regulating the emergence of a secondary mycelium (stable mating-type heterokaryon) between paired single basidiospore-derived strains (homokaryons). Emergence of the secondary mycelium involved a switch to fast-effuse development at the interaction interface, probably dependent on resources redistributed from progenitor hyphae whose extension was arrested. This switch was preceded by a short phase of nuclear migration associated with eccentric erosion of dolipore septa, accompanied by formation of lateral bulges superficially resembling clamp connexions. The secondary mycelium was sometimes delimited from progenitor mycelium by a brown zone. Pairings between genetically different secondary mycelia invariably resulted in such zones, due to somatic incompatibility. Pairings between homokaryons from Europe and the U.S.A. revealed four breeding units. There was no clear correlation between breeding ability and geographic origin, angiospermous or gymnospermous hosts, but one breeding unit was solely from Britain and another was from a single domestic collection. © 1990, British Mycological Society. All rights reserved.