6 Wood Discoloration

2.2 Growth and Spreading 21
shapedperithecium, e.g., inseveral blue-stainfungi, orthe disk-shapedapothecium
(Fig. 2.14).
2.2.3.2
Basidiomycetes
ThelifecycleofatypicalbasidiomyceteisschematicallyrepresentedinFig.2.15.
The haploid basidiospore or conidium (A) germinates to the n-mycelium
(B, monokaryon, primary mycelium). There are also asexual anamorphs in
Basidiomycetes. According to Müller and Loeffler (1992), asexual anamorphs
are supposed to occur almost just as frequently as in Ascomycetes: “they are
named however only rarely with an own name, therefore hardly considered in
the system of the Deuteromycetes and would be more frequent in the dikaryotic
phase”. A known example among the wood-decay Basidiomycetes is Heterobasidion
annosum with its anamorph Spiniger meineckellus.
In the laboratory, monokaryons are capable of indefinite growth if they
are regularly subcultured on fresh medium. In nature, characteristically the
dikaryon or secondary mycelium develops. Basidiomycetes do not form sexual
organs for plasmogamy, but monokaryotic hyphae come into contact one with
another and fuse by somatogamy (C). If the nuclei are compatible, the dikaryon
develops (D). This long-lived mycelium (Schwantes 1996) represents the essential
basidiomycete that penetrates the substratum and absorbs nourishment,
inthecaseofwoodfungiwithwood-decayfunction(D–G).Inabouthalfofthe
Basidiomycetes, the dikaryon grows by clamp connections (clamp mycelium):
Fig.2.15. Generalized life cycle of a homobasidiomycete. A basidiospores or conidia, B
monokaryons after germination, C somatogamy, D dikaryon, E–G clamp formation, H–K
basidium development, I karyogamy, J meiosis, K basidium with four basidiospores located
in sterigmata
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