Abstract
Decayed-wood samples were collected from a naturally-infected bridge made of Quercus robur. Fruiting bodies of the white-rot basidiomycetes Hymenochaete rubiginosa and Stereum hirsutum were sampled. The white-rot fungus Fuscoporia ferrea and the secondary saprobiont Mycena galericulata were identified from the rotten wood by means of rDNA-ITS sequencing. The topochemistry of lignin degradation within individual cell-wall layers was determined by cellular UV-microspectrophotometry (UMSP) at 278 nm wavelength. Increased delignification occurred in compound middle lamella regions (CML), secondary wall layers of fibres (S2), longitudinal and ray parenchyma cells as well in vessels. The highest lignin content at initial and medium decay was recorded in the CML, whereas in advanced decay secondary wall layers of the vessels exhibited the highest content of residual lignin. In all stages of degradation, the S2 layers of fibres had the lowest lignin amount.
Highlights
Wood degradation occurs through brown, white- and soft-rot fungi (Eaton and Hale 1993, Schmidt 2006)
To identify fungi growing inside the rotten wood, a molecular technique was used (Schmidt et al 2012): Small wood chips were taken from the interior of the wood with a flamed forceps
Investigated bridge and fungi The bridge made of Quercus robur wood showed severe degradation after only 13 years in service, in the deck and railings (Figure 1)
Summary
Wood degradation occurs through brown-, white- and soft-rot fungi (Eaton and Hale 1993, Schmidt 2006). White-rot predominates in hardwoods (Gilbertson 1980). It is divided into simultaneous white rot and selective delignification (Liese 1970, Nilsson 1988). Carbohydrates and lignin are almost uniformly degraded at the same time and similar rate (Rayner and Boddy 1988, Eriksson et al 1990). Fungi are identified by their fruiting bodies or other characteristics, such as rhizomorphs (Schmidt 2006). The ITS sequences of many wood- and tree-rot fungi have been deposited in public DNA databases. The BLAST (Basic Local Alignment Search Tool) program compares the sequence of an unknown fungus with those of deposited sequences
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