Introduction to Fungi, Third Edition

RELATIONSHIPS
511
colonized by this fungus show a number of decay
columns which can be traced through a series of
transverse slices of wood extending the length
of the trunk. In stumps of birch (Betula) these
columns can be matched genetically with different
clusters of fruit bodies emerging at the
surface of the stump.
By making pairings of isolates from basidiocarps,
decaying wood, and mycelial cords or
rhizomorphs of Megacollybia platyphylla or Armillaria
bulbosa, it has been shown that a single
individual can extend over many hectares
(Anderson et al., 1979; Thompson & Rayner,
1982). Isolations from basidiocarps of the fairy
ring fungus Marasmius oreades show that the
same individual mycelium has spread in an
annular fashion and estimates of the incremental
growth rate indicate that the same individual
may be several centuries old (Mallett & Harrison,
1988; Dix & Webster, 1995).
Vegetative incompatibility enables a fungus to
distinguish between ‘self’ and ‘non-self’ and
prevents the spread of genetic information in the
form of nuclei and mitochondria and possibly also
of fungal viruses from one mycelium to another
of the same species. It thus helps to preserve the
genetic integrity of an individual mycelium.
18.11 Relationships
Basidiomycota are related to Ascomycota.
Evidence for this view is based on similarities
in composition and construction of the hyphal
wall (e.g. presence of chitin; see Section 1.2.2),
the molecular basis of mating type control
(see p. 266), the production of similar conidial
states, and molecular sequence data (see Bruns
et al., 1992; Tehler et al., 2003). It has been
Fig18.20 Vegetative incompatibility inTrametes versicolor. (a) Section of a tree stump containing several different dikaryotic
colonies. At the interfaces between adjacent colonies double black lines indicate the incompatibility reaction. (b,c). Interactions
between dikaryotic colonies in culture. (b) Reaction when two genetically identical colonies are inoculated near each other.
The two mycelia intermingle. (c) Incompatible reaction when two genetically distinct dikaryons are paired.