Shuichi Doi

Asian origin and rapid global spread of the destructive dry rot fungus Serpula lacrymans

The dry rot fungus Serpula lacrymans (Basidiomycota) is the most damaging destroyer of wood construction materials in temperate regions. While being a widespread aggressive indoor biodeterioration agent, it is only found in a few natural environments. The geographical source of spread and colonization by this fungus in human environments is thus somewhat of an enigma. Employing genetic markers (amplified fragment length polymorphisms, DNA sequences and microsatellites) on a worldwide sample of specimens, we show that the dry rot fungus is divided into two main lineages; one nonaggressive residing naturally in North America and Asia (var. shastensis), and another aggressive lineage including specimens from all continents, both from natural environments and buildings (var. lacrymans). Our genetic analyses indicate that the two lineages represent well‐differentiated cryptic species. Genetic analyses pinpoint mainland Asia as the origin of the aggressive form var. lacrymans. A few aggressive genotypes have migrated worldwide from Asia to Europe, North and South America and Oceania followed by local population expansions. The very low genetic variation in the founder populations indicate that they have established through recent founder events, for example by infected wood materials transported over land or sea. A separate colonization has happened from mainland Asia to Japan. Our data also indicate that independent immigration events have happened to Oceania from different continents followed by admixture.

Removal of Hexavalent Chromium from Dilute Aqueous Solution by Coniferous Leaves

Summary The ability of coniferous leaves to remove Cr(VI) from dilute aqueous solutions by physico-chemical adsorption and chemical reduction was investigated. Of 30 coniferous tree species tested, relatively high removal ability was found in Ginkgo, Larix, Pinus, Cryptomeria, Metasequoia, Taxodium, Thuja and Thujopsis spp. To search for optimum operation condition for treatment of wastewater containing Cr(VI), factors affecting Cr(VI) removal were studied using P. densiflora leaves. The extent of the removal was dependent upon the initial solution pH, contact time, temperature and initial concentration of Cr(VI) in solution. The Cr(VI) removal was mainly governed by the physico-chemical adsorption onto the substrate. The adsorption data were well fitted to the Freundlich isotherm.

Effects of Heat Treatments of Wood on the Feeding Behaviour of Two Subterranean Termites

Summary This paper deals with the results of choice feeding tests of two termite species, Coptotermes formosanus Shiraki and Reticulitermes speratus (Kolbe), with steam-treated and dry-heated samples of Japanese commercial woods. Some steam-treated species were heavily attacked by C. formosanus and R. speratus while all dry-heated samples were attacked not more than unheated controls except for the combination Japanese larch-R. speratus. The steam treatment in some wood species produced feeding attractants which were removed by hot water extraction. Termite species showed some differences in the susceptibility to these substances. Attraction of the termites to steam-treated Japanese beech was different from that to the steam-treated softwoods. These phenomena were discussed with references to heat treatment of wood as well as to termite attractive factors.

Attraction of steamed Japanese larch (Larix leptolepis (Sieb. et Zucc.) Gord.) heartwood to the subterranean termite Coptotermes formosanus Shiraki (Isoptera : Rhinotermitidae)

The attraction of steamed Japanese larch (Larix leptolepis (Sieb. et Zucc.) Gord.) heartwood to the subterranean termite Coptotermes formosanus Shiraki was investigated with choice tests and no-choice tests. Wood samples were prepared from green larch boards steamed at 170°C for 30-240 min. In a choice test and a no-choice test, weight losses due to the termite attack were very small in non-steamed samples while they were large in steamed ones. Steamed samples extracted with hot water were not attacked by termite in a choice test. Japanese cedar (Cryptomeria japonica D. Don.) wood specimens treated with water soluble fractions from the hot water extractives of larch were preferably attacked in a choice test. These phenomena suggest that steaming produces attractants and degrades, removes and/or modifies some larch wood constituents which suppress the termite attack.

Qualitative and quantitative PCR methods using species-specific primer for detection and identification of wood rot fungi

Species-specific oligonucleotide primers for detecting wood rot fungi, Gloeophyllum trabeum, Trametes versicolor, Coniophora puteana, and Serpula lacrymans, and the primer detecting a group of related fungi to G. sepiarium were developed. These primer sequences were picked up from the internal transcribed spacer region between small-subunit rDNA and large-subunit rDNA. The species selectivities of the developed primers were checked. Real-time polymerase chain reaction (PCR) was carried out using these highly specific primers to quantitatively detect at least of 0.01 ng genome DNA of the target species. This quantitative PCR was also used to differentiate the target species DNA from mixed species DNA. A PCR-based technique using the species-specific primers would be applicable to multiple-sample assay in diagnosis of wood decay and to investigation of environmental fungal populations.

Antifungal constituents in the bark ofMagnolia obovata Thunb

The acetone extract of the bark ofMagnolia obovata Thunb. had potent antifungal activity against plant pathogenic and wood destroying fungi. The active principles were isolated and identified to be eudesmols (I), magnolol (II) and honokiol (III). Eudesmols, which are main components of the volatile bark oil, showed strong antifungal activity against all of the fungi tested, especially basidiomycetes. It completely inhibited the growths ofCoriolus versicolor, Lepista sordida, Pycnoporus coccineus, Rhizoctonia solani, Serpula lacrymans andTyphula ishikariensis at a concentration of 500 μg mL−1. Two biphenyl type neolignans, magnolol and honokiol, also exhibited potent antifungal activity against these fungi except againstC. versicolor andL. sordida. They completely depressed the growths ofS. lacrymans andT. ishikariensis at the same concentration.ZusammenfassungDer Acetonextrakt der Rinde vonMagnolia obovata Thunb. zeigte pilzhemmende Wirkungen gegen pflanzliche Krankheitserreger und abbauende Pilze auf. Die aktiven Stoffe wurden isoliert und identifiziert als Eudesmol (I), Magnolol (II) und Honokiol (III). Die Endesmole, die die Hauptkomponenten der ätherischen Öle in der Rinde ausmachen, wiesen starke Hemmwirkung gegen alle getesteten Pilze auf, besonders gegen Basidomyceten. Mit einer Konzentration von 500 μg mL−1 ergab sich ein völlige Hemmung des Wachstums vonCoriolus versicolor, Lepista sordida, Pycnoporus coccineus, Rhizoctonia solani, Serpula lacrymans andTyphula ishikariensis. Zwei Neolignane vom Biphenyltyp, Magnolol und Honokiol, zeigten ebenfalls pilzhemmende Wirkung außer gegenC. versicolor undL. sordida. Das Wachstum vonS. lacrymans undT. ishikariensis wurde bei der gleichen Konzentration völlig gehemmt.

Effects of high temperature kiln drying on the practical performances of Japanese cedar wood (Cryptomeria japonica) I: changes in hygroscopicity due to heating

The effect of heating on the hygroscopicity of Japanese cedar wood was investigated as a simple evaluation of thermal degradation in large-dimension timber being kiln-dried at high temperatures (>100°C). Small wood pieces were heated at 120°C in the absence of moisture (dry heating) and steamed at 60°, 90°, and 120°C with saturated water vapor over 2 weeks, and their equilibrium moisture contents (M) at 20°C and 60% relative humidity (RH) were compared with those of unheated samples. No significant change was induced by steaming at 60°C, while heating above 90°C caused loss in weight (WL) and reduction in M of wood. The effects of steaming were greater than those of dry heating at the same heating temperature. After extraction in water, the steamed wood showed additional WL and slight increase in M because of the loss of water-soluble decomposition residue. The M of heated wood decreased with increasing WL, and such a correlation became clearer after the extraction in water. On the basis of experimental correlation, the WL of local parts in large-dimension kiln-dried timber was evaluated from their M values. The results indicated that the thermal degradation of inner parts was greater than that of outer parts.

Two invasive populations of the dry rot fungus Serpula lacrymans show divergent population genetic structures.

The dry rot fungus Serpula lacrymans is a devastating basidiomycete occurring in wooden constructions in temperate regions worldwide. In this study, we compare the genetic structures of two invasive populations from Europe and Japan. Microsatellite data from 14 loci and DNA sequences from four loci demonstrated that the two populations were highly differentiated. Significant isolation by distance effect was observed in Europe and Japan. Higher genetic variation was observed within the Japanese population than within the European population, corresponding with the observed higher richness of vegetative compatibility types in Japan, indicating that there has been a higher level of gene flow from the Asian source populations to Japan than to Europe. The European population is genetically more homogenous with only six detected vegetative compatibility types. Various tests indicate that both the European and the Japanese populations have gone through population bottlenecks prior to population expansion. No identical multi‐locus genotypes were observed within Japan and very few within Europe, indicating limited clonal dispersal. Deviations from Hardy Weinberg expectations were observed both in Europe and Japan and heterozygote excess were observed at several loci, especially in Europe. Possible explanations for this pattern are discussed.

Spectrochemical characterization by FT-Raman spectroscopy of wood heat-treated at low temperatures: Japanese larch and beech

Test samples of Japanese larch (Larix leptolepis) heartwood and Japanese beech (Fagus crenata) sapwood were heated for 22u2009h at constant temperatures (50°–180°C) under three water content conditions. Raman spectra of the samples were recorded before and after the heat treatments, and spectral changes in the range from 1000u2009cm−1 to 1800u2009cm−1 were evaluated using the difference spectrum method. For both wood species, the Raman band intensity at 1655–1660u2009cm−1 due mainly to the C=C and C=O groups in lignin clearly decreased with increasing heat-treatment temperature (HTT). The spectral change was thought to reflect the progress of condensation reactions of lignin molecules during the heat treatment. Moreover, the decrease in band intensity was considerably facilitated by the presence of water in the cell wall, suggesting that the condensation is closely related to the softening of lignin. From the spectral changes in the wavenumber region of 1200–1500u2009cm−1, it was considered that wood constituents are partially decomposed at the higher HTT.

Composition of intake sugars and emission of gases from paper sludges by Coptotermes formosanus Shiraki.

Paper sludge is a by-product of the pulping process and is landfilled or incinerated for disposal. In this study, we evaluated ingestion and digestibility of carbohydrates, by the termite Coptotermes formosanus, in two kinds of sludges: sludge C from the chemical pulp mill and sludge M from the mechanical pulp mill. The no-choice tests using the termite for three weeks showed that the mass loss of sludge C was significantly higher than that of the control samples: a bleached pulp and red pine wood. It is considered that the higher inorganic content of sludge C resulted in the higher mass loss when the same amount of carbohydrates was taken by the pulp- or wood-fed termite. Although the inorganic content of sludge M was almost the same as that of sludge C, the higher lignin content in sludge M is thought to have resulted in the lower mass loss. Analysis of sugar composition in the faecal materials of the termite showed that about 73% of glucose and 81% of xylose in sludge C were digested. It was concluded that the digestibility of these sugars in sludge C was the same as that of the control samples despite containing high amounts of inorganic compounds. However, the hydrogen conversion rate by the termites that were fed sludge was lower than that of the termites that were fed pulp in the no-choice test for three days: one mole of glucose from the sludge and pulp was converted to 0.51 and 0.80 moles of hydrogen, respectively.