6 Wood Discoloration

2.4 Identification 39
in view of a data collection to be used for identification by fragment length
comparison, the limited ITS size of only 600–700 bases prevents a separation of
all relevant fungi in a certain biotope by specific digest pattern. Third, the great
number of possible fungi in a biotope is much greater than the few fragment
patterns that would be present in data collections, that is, a not yet analyzed
species may feign another fungus by exhibiting identical fragments.
RFLP analysis of a 5.8S rDNA/ITS II/28S rDNA fragment was used to characterize
five species of the Phellinus igniarius group (Fischer 1995) and 13 species
of the Phellinus pini group (Fischer 1996). Corresponding DNA digestion of
52 lignicolous European species with HpaII resulted in 44 distinct phenotypes
and additional application of Hin6 IandHinf I in 48 species-specific and
two genera-specific phenotypes (Fischer and Wagner 1999). RFLP patterns
obtained from seven restriction enzymes assigned 34 Pleurotus strains to 11
RFLP types, of which ten corresponded to biological species (Bao et al. 2004b).
The intergenic spacer, either the IGS I alone or both IGS parts, has often
been used for RFLP studies of Armillaria species (e.g., Harrington and Wingfield
1995; Frontz et al. 1998; White et al. 1998; Terashima et al. 1998a; Kim
et al. 2001). IGS I-RFLPs were also used to assign isolates of Heterobasidion
annosum to intersterility groups (Kasuga and Mitchelson 2000) and to investigate
the population structure of five Fennoscandian geographic populations
of Phellinus nigrolimitatus (Kauserud and Schumacher 2002).
rDNA Sequencing
PCR-amplification and subsequent sequencing of parts of the ribosomal DNA
avoid the main limitations of RFLPs because the whole information of hundreds
of nucleotides of the target DNA is used. rDNA sequences may be used for diagnosis
and for phylogenetic analyses (dendrograms) on relationships among
fungi. Sequencing is nowadays the most important tool for molecular systematics
and led to taxonomic rearrangements and changes in nomenclature.
TheITSsequencesofagreatnumberofwoodfungiareknown,e.g.,from
mycorrhizal fungi like Hebeloma velutipes (Aanen et al. 2001), from parasites
like Armillaria species (Chillali et al. 1998) and Laetiporus sulphureus
(Rogers et al. 1999), and from the red streaks producing Trichaptum abietinum
(Kauserud and Schumacher 2003). Regarding wood decay fungi, a data set of
rDNA-ITS sequences of 18 house-rot fungi is shown in Table 2.8 (Schmidt and
Moreth 2002/2003) complemented by the 18S and 28S rDNA sequences of some
important species (Moreth and Schmidt 2005). The ITS of some brown-rot and
white-rot fungi was sequenced by Jellison et al. (2003).
It is normal to deposit sequences in the international electronic databases
for everyone’s use (European Molecular Biology Laboratory EMBL: www.ebi.
ac.uk/embl; American GenBank: www.ncbi.nlm.nih.gov/genbank; DNA Data
Bank of Japan DDBJ: www.ddbj.nig.ac.jp).
www.taq.ir