6 Wood Discoloration

2.4 Identification 41
Sequences of the ITS region (and the 18S and 28S rDNA) may be used to
identify unknown fungal samples through sequence comparison by Basic local
alignment search tool (BLAST) (e.g., www.ncbi.nlm.nih.gov/blast/bast.cgi).
BLAST revealed ITS-sequence identity of a “wild” S. lacrymans isolate from
the Himalayas with indoor isolates (White et al. 2001), identified misnamed
isolates of S. lacrymans (Horisawa et al. 2004), identified Antrodia spp. and
Serpula spp. isolations from fruit bodies and wood samples (Högberg and
Land 2004), and confirmed Coniophora puteana isolates (Råberg et al. 2004).
Kim et al. (2005) used a part of the 28S rDNA for identification of a number
of basidiomycete fungi from playground wood products by BLAST. Partial 18S
rDNA sequence of Sirococcus conigenus isolated from Norway spruce cankers
was used by Lilja et al. (2005) to confirm the identification of the fungus. The
whole IGS was sequenced to investigate intraspecific variation of mycorrhizal
fungi like Laccaria bicolor (Martin et al. 1999). IGS I sequence analysis was
used for Hebeloma cylindrosporum (Guidot et al. 1999) and Xerocomus pruinatus
(Haese and Rothe 2003). IGS I analysis suggested that three different
morphotypes/genotypes of an ectomycorrhizal fungus present in Kenya represent
separate biological species (Martin et al. 1998). The IGS I region grouped
isolates of Armillaria mellea s.s. in Asian, western North American, eastern
North American and European populations (Coetzee et al. 2000).
Sequences are used to construct phylogenetic trees (dendrograms) for phylogenetic
analyses (molecular systematics). It is not unusual for those intentions
to complement own data with sequences downloaded from the databases.
For closely related fungi, like Armillaria species, IGS sequences were used for
phylogenetic analysis (e.g., Terashima et al. 1998b). Also, ITS sequences may be
applied to phylogenetic trees. An example of S. lacrymans and S. himantioides
isshowninFig.2.22.ThetreeshowsthatisolatesofS. lacrymans collected in
nature in Czechoslovakia, India, Pakistan and Russia group in the branch of
indoor isolates (“Domesticus group”) but differ from wild Californian isolates
(“Shastensis group”) (Kauserud et al. 2004b; also White et al. 2001; Palfreyman
et al. 2003), suggesting a North American link between the anthropogenic
isolates and the wild relative S. himantioides. Yao et al. (1999) applied ITS
sequences to a phylogenetic study of Tyromyces s.l.
For phylogenetic analyses of higher groups, genera, families and orders,
often the conserved 18S and 28S rDNA are used. Bresinsky et al. (1999) and
Jarosch and Besl (2001) sequenced 900 bases of the 28S rDNA of S. lacrymans, S.
himantioides, Meruliporia incrassata and of Coniophora and Leucogyrophana
species. Although it is not necessary to sequence the whole rRNA genes to construct
trees, complete 18S and 28S rDNA sequences of a number of important
wood-decay fungi are already known (Table 2.8).
Nuclear and mitochondrial genes have different inheritance. Selosse et al.
(1998) showed intraspecific polymorphism of the large subunit of mitochondrial
rDNA in Laccaria bicolor. A sequence database of several ectomycorrhizal
www.taq.ir