6 Wood Discoloration

50 2 Biology
or unitunicate ascus wall, the Loculoascomycetidae have ascolocular ascomata
development and mostly a bitunicate ascus wall, and the Laboulbeniomycetidae
are ascohymenial fungi with prototunicate or unitunicate ascus wall. The
separate group of the Taphrinomycetidae (Taphrinales) does not form ascomata,
but the asci develop between the epidermis cells of the host plant.
Classifications are shown in Kreisel (1969), Breitenbach and Kränzlin (1984),
Müller and Loeffler (1992), Zabel and Morrell (1992), Schwantes (1996), and
Hansen et al. (2000). However, a uniform and generally accepted classification
does not exist. Thus, the Ascomycetes treated in this book are only classified
by their orders (Tables 8.1–8.3).
The traditional differentiation of the Basidiomycetes is based on two different
principles. Practically to apply is the use of the morphology of the
basidium. Holobasidiomycetes have unicellular basidia, and Phragmobasidiomycetes
show septate basidia. To consider natural relationships better, a differentiation
that is based on the kind of spore germination seems favorable
(Müller and Loeffler 1992). The basidiospores of Homobasidiomycetes germinate
by germ hyphae. Heterobasidiomycetes show repetitive germination.
All Homobasidiomycetes possess a holobasidium. The Heterobasidiomycetes
contain orders with phragmobasidia, but initial more primitive orders have
holobasidia (Schwantes 1996). Based on the principle type of the fruit body,
the Homobasidiomycetes may be grouped in Hymenomycetes, which have
the hymenium exposed on basidiomata surface, and Gasteromycetes with the
hymenium enclosed within basidiomata.
Due to overlapping among the groups, lack of clarity, and different opinions
among systematists, some authors (Müller and Löeffler 1992) abstain from
uniting the orders into subclasses.
The former subgrouping of the Homobasidiomycetes into Aphyllophorales,
Agaricales, and Gasteromycetales did only consider the fruit body type.
Schwantes (1996) differentiates four order groups: Apphyllophoranae (six orders),
Agaricanae (three orders), Gasteromycetanae (nine orders), and Phallanae
(one order). Apphyllophoranae and Agaricanae are almost in accordance
with the term Hymenomycetes, and Gasteromycetanae and Phallanae with that
one of Gasteromycetes. Numerous order and family-schemes especially for the
polypores either use large and comprehensive groups like in Ryvarden and
Gilbertson (1993, 1994) or numerous and small groups like in Hansen et al.
(1992, 1997).
Some common wood-inhabiting Basidiomycetes treated in this book are
grouped in Table 2.12 according to Breitenbach and Kränzlin (1986, 1991,
1995), except that the Coniophoraceae were placed in the Boletales.
A great number of Deuteromycetes occur on wood, like molds (Aspergillus,
Penicillium and Trichoderma species), blue-stain fungi (e.g., Aureobasidium
pullulans, Cladosporium species, Discula pinicola), and soft-rot fungi (e.g.,
Paecilomyces variotii).
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