Decay development in living sapwood of coniferous and deciduous trees inoculated with six wood decay fungi

Development of decay and/or discoloration was assessed in the functional sapwood of one coniferous and three deciduous trees after wounding and artificial inoculation with six wood decay fungi. Living stems of mature Douglas fir, beech, oak, and sycamore trees were wounded in spring 2002 and immediately inoculated with brown, white, and soft rot fungi. Extent of discoloration and decay, wood weight loss, and total phenols in the reaction zone (zone of active response at a dynamic interface between living sapwood and wood colonized by decay fungi) were assessed 16 and 28 months after inoculation.     

Ecology of wood‐inhabiting fungi in northern forests of Iran

Wood‐decay fungi are important in forest ecosystems and play an important role in nutrient and carbon recycling. The scope of this research was to identify wood‐inhabiting and wood‐decay macrofungi and determine their ecology. We sampled standing trees and dead wood of oak and hornbeam in the northern forests of Iran, specifically in Mazandaran and Golestan provinces. We assessed the influence of field slope, elevation, site direction and the height of fungal sporocarp position on the tree. The species of wood‐inhabiting and wood‐decay fungi belonged to 11 families: Polyporaceae; Stereaceae; Ganodermataceae; Physalacriaceae; Agaricaceae; Xylariaceae; Pluteaceae; Coprinaceae; Strophariaceae; Pleurotaceae; and Hydnaceae. The most common fungal species identified belonged to the Polyporaceae and Ganodermataceae and predominantly grew on trees growing on a slope of 20%, at an altitude of 700–900 m, 0–3 m from the ground a southwesterly site direction and the northern sides of both tree species. These results indicated that field slope was the most important factor in determining fungal sporocarp abundance.     

Polyporus schweinitzii Fr. und Sparassis crispa (Wulf. in Jacq.) ex Fr. als Fäuleerreger in einem Douglasienbestand (Pseudotsuga menziesii (Mirb.) Franco) mit hohem Stammfäuleanteil1

Polyporus (Phaeolus) schweinitzii and Sparassis crispa as frequent decay fungi in Douglas fir. Of fifty, 55 ears old trees in a Pseudotsuga menziesii stand. 90% showed decay of the heart- wood of the butt. The possibility of transmission of the most frequent decay fungi, P. schwei- nitzii and S. crispa, which also are frequent parasites in the roots and butts of pine, from the roots of the Pinus sylvestris trees of the previous crop into the roots of the Douglas fir is discussed. A first identification of the fungi was made possible by storing the stem discs under moist conditions. The mycelia of P. schweinitzii and S. crispa grew out of the decayed wood and possessed a characteristic form and colour.     

Wood‐rotting basidiomycetes are a minor component of fungal communities associated with Acacia hybrid trees grown for sawlogs in South Vietnam

Acacia hybrid (Acacia mangium × Acacia auriculiformis) clones are widely planted in Vietnam with a total of approximately 400,000 ha to meet the demand for pulpwood, sawn timber and wood chip exports. Silvicultural techniques such as pruning and thinning have been applied to improve productivity and sawlog quality of Acacia hybrid plantations. However, those techniques may also create opportunities for wood decay fungi to enter the Acacia hybrid stems through wounds and cause stem defects that reduce sawlog quality and the value of the plantation. The presence of fungal decay agents in Acacia hybrid trees was examined in two Vietnamese plantations. In July 2011, just prior to a second thinning, discoloured wood samples were taken from a three‐year‐old Acacia hybrid plantation at Phan Truong Hai for the isolation of fungi. In July 2012, approximately 18 months after pruning and thinning treatments, discoloured wood samples were taken from a three‐year‐old Acacia hybrid plantation at Nghia Trung for the isolation of fungi. DNA sequencing of the rDNA ITS identified the isolates. In May 2015, approximately 4 years after thinning and fertilizer treatments, discoloured and decayed wood samples were taken from the above (7‐year‐old) Acacia hybrid plantation at Phan Truong Hai for fungal identification. DNA was extracted directly from discoloured and decayed wood samples and fungal rDNA ITS amplicons sequenced on a Roche 454 sequencer. The results showed that silvicultural treatments did not affect the fungal communities associated with discoloured and decayed wood of Acacia hybrid plantation at Phan Truong Hai. A total of 135 fungal species or OTUs (operational taxonomic units) were identified, including 82 members of Ascomycota and 52 Basidiomycota.     

Fomes annosus (Fr.) Cke. und andere Stammfäulepilze in einem Douglasienbestand,Pseudotsuga menziesii (Mirb.) Franco1

Fomes annosus (Fr.) Cke. and other decay fungi in a Douglas fir stand, Pseudotsuga menziesii (Mirb.) Franco. 40% of the trees in a 40 years old Pseudotsuga menziesii stand showed butt rot. 85 trees were analysed for decay fungi. Fomes annosus, the most frequent fungus, also invaded the sap wood. Factors of the soil favourable to the rot and the possibility of transmission of the most frequent decay fungus, Fomes annosus, from (a) neighbouring spruce stands, (b) from the roots of Scots pine from the previous crop arc discussed. Caniophora puteana was isolated from about 10% of the butt rots. The importance of Calocera viscosa which grew out of the central decay of twelve trees as a decay fungus is still under investigation.     

Stamm- und Wurzelfäulen in Douglasien,Pseudotsuga menziesii (Mirb.) Franco1

Stem and root rot of Douglas fir, Pseudotsuga menziesii (Mirb.) Franco. In 20 year old Douglas fir most of the butt rot was caused by Fomes annosus. Stem decay was central as well as eccentric reaching the sap wood in either case. The side roots of 20 year old Douglas fir were compared with those of a 40 year old stand with butt rot. In individual trees with decay there were less roots with Fomes annosus decay in the younger stand. Calocera viscosa was more abundant in the older stand. Soil conditions which might have favoured root rot in the young stand are discussed.     

Fungal endophytes in woody roots of Douglas‐fir (Pseudotsuga menziesii) and ponderosa pine (Pinus ponderosa)

The fungal community inhabiting large woody roots of healthy conifers has not been well documented. To provide more information about such communities, a survey was conducted using increment cores from the woody roots of symptomless Douglas‐fir (Pseudotsuga menziesii) and ponderosa pine (Pinus ponderosa) growing in dry forests on the eastern slope of the Cascade Mountains in Washington state, USA. Fungal isolates were cultured on standard media, and then were identified using a combination of molecular and morphological methods. Fungal genera and species identified in this study will provide baseline data for future surveys of fungal endophytes. Examination of internal transcribed spacer (ITS1 and ITS2) and 5.8S rDNA sequences and morphology of cultured fungi identified 27 fungal genera. Two groups predominated: Byssochlamys nivea Westling (20.4% of isolations) and Umbelopsis species (10.4% of isolations). This is the first report of B. nivea within large woody roots of conifers. Both taxa have been previously identified as potential biological control agents. Although some trends were noted, this study found no significant evidence of host species or plant association effects on total recovery of fungal endophytes or recovery of specific fungal taxa.     

Detection of incipient decay in tree stems with sonic tomography after wounding and fungal inoculation

Picus^® acoustic tomography was used to map incipient stages of fungal decay in the sapwood of standing Douglas fir, beech, oak, and sycamore trees 2, 16, and 27 months after wounding and artificial inoculation with brown-, soft-, and white-rot decay fungi. Some wood properties were additionally measured before (velocity of sound) and after (moisture content, weight loss, and density of sound, discoloured and/or decayed wood) tree felling (28 months). With the exception of Trametes versicolor in sycamore, wood decay was not evident from the tomograms in any host-fungus combination. In comparison to measurements after two months, the device recorded a reduction in sound velocity in some host-fungus combinations after 16 and 27 months. In beech, there was a significant reduction in sound velocity after inoculation with Ganoderma applanatum, Kretzschmaria deusta, and Trametes versicolor. Similarly, a reduction in sound velocity was recorded in sycamore inoculated with Kretzschmaria deusta and Trametes versicolor. In all these combinations, losses in wood weight and wood density were also found. Results showed that the detection of incipient fungal decay at the periphery of tree stems needs to be improved such that tomograms of the Picus^® acoustic tomograph are capable of identifying decay progressing from the sapwood inwards.     

Differentiating the two closely related species,Phellinus weirii and P. sulphurascens

Phellinus weirii s.l., an aggressive root rot pathogen, causes extensive wood losses and lowers the productivity of western red cedar (WRC, Thuja plicata), Douglas fir (Pseudotsuga menziesii) and other conifers. This fungus has been recognized as a cedar form (P. weirii s.s.) and a non‐cedar form (P. sulphurascens). Differentiating the two species is difficult because their fruiting bodies and cultural morphologies are very similar. However, differences in growth rate and colony morphology were observed when they were grown on malt extract agar with WRC feeder strips. In addition, different restriction fragment length polymorphism patterns were obtained using (i) the internal transcribed spacer (ITS) region cut with the restriction enzyme RsaI, and (ii) the partial large subunit ribosomal DNA region cut with AgeI and NciI. Furthermore, a new specific primer set was designed from the ITS region of P. weirii s.s. and was used to differentiate it from P. sulphurascens and other decay fungi that are frequently found in coniferous trees. These species‐specific primers will facilitate the detection of P. weirii in standing trees well before visible signs of infection are apparent.     

Quantification of Phaeocryptopus gaeumannii colonization in Douglas‐fir needles by ergosterol analysis

Current assessments of infection levels of Phaeocryptopus gaeumannii, the incitant pathogen of Swiss needle cast disease on Pseudotsuga menziesii, typically rely on surveys of abundance of fruit bodies on diseased needles. The relationship between this measure and internal fungal colonization is unknown. In this article, a series of experiments to determine whether ergosterol can be used to quantify P. gaeumannii internal colonization within Douglas‐fir needles is reported. It was found that ergosterol content in seven commonly occurring Douglas‐fir foliar fungi is proportionally related to biomass, and in P. gaeumannii this relationship is not affected by age of the culture. Furthermore, at four sites tested, P. gaeumannii was the most common fungus species isolated from Douglas‐fir needles, accounting for approximately 50% of the isolations. Ergosterol content in these needles was best related to P. gaeumannii despite the presence of other fungi. The strong relationship between ergosterol and P. gaeumannii is attributed to its greater contribution to total fungal biomass compared with all other fungi present within Douglas‐fir needles.     

Chestnut Red Stain: Identification of the fungi associated with the costly discolouration of Castanea sativa

In Europe, fungal pathogens have reduced the overall productivity of sweet chestnut (Castanea sativa) stands and continue to threaten the economic viability of forestry operations. Chestnut Red Stain (CRS) in north‐eastern Spain, locally referred to as Roig, is capable of decreasing the market value of chestnut timber to the point of rendering chestnut coppices uneconomical. Despite its economic importance, the specific cause of this red discolouration is unknown. With the objective of verifying the presence of fungi within the symptomatic wood, and identifying the fungus or suite of fungi associated with the red stain, wood samples were collected and cultured from 37 stumps found in eight recently harvested stands in the Montseny and Montnegre‐Corredor Natural Parks. To separate the fungi associated with CRS from other species inhabiting the chestnut wood, the origin of each fungal culture was mapped in every stump. The fungi were isolated from cultures and identified by sequencing the ITS region. The results provide insight into the fungal community inhabiting chestnut wood and the potential cause of CRS; nine species were identified including two species known to cause decay in chestnut. One of them, Fistulina hepatica, appears to be a likely candidate for the causal agent of CRS. This is the first study reporting the fungi associated with CRS and opens the door to new epidemiological studies focused on F. hepatica.     

The relationship between Swiss needle cast symptom severity and level of Phaeocryptopus gaeumannii colonization in coastal Douglas‐fir (Pseudotsuga menziesii var. menziesii)*

This study examined 108 15‐year‐old Douglas‐fir (Pseudotsuga menziesii var. menziesii) trees to investigate whether trees exhibiting less severe Swiss needle cast (SNC) symptoms were more resistant (had less fungal colonization) or more tolerant (maintained healthy foliage under similar infection levels). Trees were sampled from six open pollinated families that were categorized into three disease severity groups (two families for each group; mild, moderate and severe disease symptoms). The amount of retained foliage and level of discoloration were visually assessed on trees in the field. Fungal colonization (as determined by proportion of stomata occluded with pseudothecia and by amount of Phaeocryptopus gaeumannii DNA in sampled needles) was measured on 1‐ and 2‐year‐old needles in the laboratory. Trees in the different disease severity groups were similar with respect to amount of fungus in their needles, yet the trees in the mild symptom group retained higher proportions of needles and maintained greener foliage. The relationship between amount of P. gaeumannii in needles and SNC symptom severity was statistically significant (p < 0.05) for amount of fungal DNA in 1‐year‐old needles and average needle retention (NR) over the last four growing seasons. Average NR decreased with increased amount of pathogen DNA in the mild disease symptom families. This relationship was reversed in the severe disease symptom group and there was no relationship in the moderate disease symptom group. Because the amount of P. gaeumannii DNA in foliage did not differ significantly among the groups, differences in symptom severity were attributed to tolerance, not resistance. Visual scoring of individual trees for average NR over the past four growing seasons could be used to effectively assess for SNC tolerance in Douglas‐fir.     

Effects of wounding and fungal infection with Armillaria ostoyae in three conifer species. II. Host response to the pathogen

Structural responses in the bark and wood were described following penetration by Armillaria ostoyae in the roots of 20‐ to 30‐year‐old Douglas‐fir, western hemlock and western redcedar trees. Tissue necrosis presumably caused by fungal exudates was commonly observed at inoculum contact. In Douglas‐fir and western hemlock, A. ostoyae interfered with the initiation of active defence mechanisms involving the development of a lignified zone of impervious tissue (IT), necrophylactic periderm (NP) formation and compartmentalization of infected woody tissue. Breaching of IT and NP barriers was frequent, particularly around the clusters of sclereid cells in western hemlock. In western redcedar, the IT zone was inconspicuous. Induced rhytidome formation occurred in western redcedar either simultaneously with or after completion of NP development. The formation of this tissue facilitated en masse sloughing of infected tissue from the surface of roots. In western redcedar, traumatic phloem resin ducts formed in tangential bands surrounding the margin of expanded lesions. Effective compartmentalization in western redcedar was achieved by a barrier zone comprised of a higher‐than‐average number of axial parenchyma that accumulated polyphenolic deposits. A combination of host‐mediated defence mechanisms in western redcedar resulted in a significantly higher frequency of effective resistance reactions than in western hemlock or Douglas‐fir.     

Molecular identification of decay fungi in the wood of urban trees

Trees are valuable for urban areas, however, are also susceptible to wood rot fungi. For accurate and fast assessment of the severity and evolution of decay in standing trees, a molecular technique was used to identify the causal agents of wood rot. Fruit bodies of wood decay fungi were collected from infected trees in various stands in Germany. Thirty-six species were identified by traditional methods. The DNA of fruit bodies was extracted, ITS-rDNA amplified by PCR, and ITS regions sequenced. Wood samples from infected urban trees were collected, the entire DNA extracted from affected wood parts, and fungal ITS amplified and sequenced. Fungal species were identified by comparing sequence data with the fruit body data. The technique enables an accurate and rapid identification of causal rot fungi in urban trees.     

Wundfäule in Fichtenwaldungen mit alten Schälschäden

Wound decays in spruce stands following bark stripping . 2083 trees in 91 sample plots on four trial areas (24 ha) were examined for bark stripping and decay. Only 25% of trees showed no injury. Of the injured trees, 73% showed some degree of decay, 10% discoloration. and 17% neither decay nor discoloration. Of the wood destroying fungi isolated Fomes annosus was dominant and appeared to be the most important and widespread of the wound inhabiting fungi in the test area. Besides the Basidiomycetes a considerable number of other fungi was isolated. The most frequent was Cylindrocarpon cylindroides var. tenue.     

Serpula himantioides,Heterobasidion annosum and Calocera viscosa as butt rot fungi in a Danish Douglas‐fir stand

A scattered wind fall of 50 trees in a 46‐year‐old stand of Douglas‐fir (Pseudotsuga menziesii) revealed Serpula himantioides, Heterobasidion annosum and Calocera viscosa as decay causing fungi. Sixty‐four percent of the stumps had visible rot on the stump surface. Mainly, a central brown rot was seen, caused by either S. himantioides or C. viscosa combined with eccentrically placed spots of incipient H. annosum rot. Subsequently, the appearance of fruitbodies disclosed that in total 76% of the wind thrown trees were associated with one or more of the three decay fungi. S. himantioides was present in a surprisingly large number of trees (54%), and the rot column extended up to 2 m into the stem. This investigation represents the first known incidence of S. himantioides and C. viscosa causing root and butt rot in living conifers in Denmark.     

Über Auswirkungen des Tannensterbens auf die Holzeigenschaften der geschädigten Bäume

Zusammenfassung Das Holz mehrerer gesunder, kr?nkelnder, absterbender oder bereits abgestorbener Tannen aus 3 in st?rkeren Ma? vom Tannensterben betroffenen bayerischen Wuchsgebieten war teils unmittelbar nach der F?llung, teils nach 3- bis 6-monatiger Lagerung im Wald auf Pilzbefall und m?glicherweise eingetretene Wertminderungen untersucht worden. Mit Ausnahme eines schon vor l?ngerer Zeit abgestorbenen Stammes waren alle H?lzer bei Versuchsbeginn noch frei von Mikroorganismen oder lediglich von Bakterien besiedelt. Nach einer gewissen Lagerzeit hatte neben dem Bl?uepilzCeratocystis piceae und einigen anderen harmlosen holzbewohnenden Ascomyceten oderFungi imperfecti gelegentlich auch der intensiv verf?rbende, das Tannenholz aber nur langsam abbauende Wei?f?uleerregerStereum chailletii die Probeabschnitte befallen. Zwischen dem Holz gesunder und gesch?digter Tannen war weder zum Zeitpunkt der F?llung noch sp?ter ein deutlicher qualitativer Unterschied erkennbar und die Holzdichte bzw.-festigkeitseigenschaften wurden durch eine Waldlagerung von maximal 6 Monaten nicht nennenswert beeintr?chtigt. Auch für die Anf?lligkeit gegenüber holzzerst?renden Pilzen war der Gesundheitszustand der untersuchten Tannen ohne Bedeutung.

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Effects of the fir dieback on the wood properties of the affected trees

Summary Several healthy, diseased, dying, or already dead silver firs from each of three Bavarian growth areas considerably afflicted by fir dying were examined, regarding fungal attack and possible changes in their strength properties, immediately after felling as well as after 3 or 6 months of forest storage. At the onset of the investigation all wood samples were still largely free of microorganisms or merely colonized by bacteria, with the exception of one tree that had already died some time ago. After a certain storage period occasionally the white rot fungusStereum chailletii, which strongly discoloures and slowly decomposes fir wood, appeared besides the blue staining fungusCeratocystis piceae and several other harmless wood inhabiting ascomycetes orfungi imperfecti. Wood density and strength properties were not significantly affected during forest storage for several months, and neither immediately after felling nor later a clear difference between the wood of healthy and that of diseased firs was noticeable. Their state of health also had no influence on their reaction towards the attack of wood destroying fungi.

     

Growth of Phlebiopsis gigantea in wood of seven conifer species

Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered.     

Anatomical characterization of decayed wood in standing light red meranti and identification of the fungi isolated from the decayed area

To further our understanding of wood decay in living light red meranti (Shorea smithiana) trees, microscopic characteristics of the cell and cell wall degradations of S. smithiana wood in the presence of the decay fungi, the identity of the causal fungi, and the decay potential and pattern by an isolated fungus were investigated. Cell wall degradations, including cell wall thinning, bore holes formation, rounded pit erosion, and eroded channel opening were clearly observed under light and scanning electron microscopy. In transverse view, many large voids resulting from a coalition of degraded wood tissue appeared in the decayed canker zone. All these observations suggest the well-known simultaneous decay pattern caused by white-rot fungi. By phylogenetic analysis based on the sequences of internal transcribed spacer region of ribosomal DNA, a basidiomycete fungus isolated from the decayed wood was identified as Schizophyllum commune. The degradation caused by this fungus on sound S. smithiana wood in an in situ laboratory decay test was classified as the early stage of simultaneous decay, and showed a similar pattern to that observed in the wood samples naturally decayed.     

Necrophylactic periderm formation in the roots of western larch and Douglas‐fir trees infected with Armillaria ostoyae. I. The response to abiotic wounding in non‐infected roots

The sequence of events leading to necrophylactic periderm formation was studied throughout the year following the abiotic wounding of the non‐infected roots of 10‐ and 27‐year‐old western larch (Larix occidentalis) and 11‐ and 25‐year‐old Douglas‐fir (Pseudotsuga menziesii) trees that were infected with Armillaria ostoyae. The sequence was the same for both ages and species of trees. Wound repair was more rapid in the summer compared with the spring and autumn. Following cell hypertrophy, a zone of lignified impervious tissue was in the initial stages of formation within 10 days of wounding in the summer and 14 days in the spring or autumn. The new phellogen produced a layer of phellem three to four rows of cells thick after 20 days in the summer or 40 days in the spring. Modified cells abutting the inner boundary of the impervious zone frequently developed thick lignified abaxial walls and thin suberized adaxial walls. A typical exophylactic periderm in healthy root bark tissue of both western larch and Douglas‐fir consisted of stone phellem one to four rows of cells thick and a layer of thin‐walled phellem three to six rows of cells thick in western larch and two to three rows thick in Douglas‐fir, a single row of phellogen cells and one to three rows of phelloderm cells. Mature thin‐walled phellem cells had pigmented contents, red in western larch and light brown in Douglas‐fir. In response to wounding, 27‐year‐old western larch and 25‐year‐old Douglas‐fir developed necrophylactic periderms with annual bands of phellem. The bands included a layer of phellem that was six to 12 and nine to 15 rows of cells thicker than the layer of phellem observed in the respective naturally developed exophylactic periderms. Fifty days following wounding in the summer, stone phellem, one to three rows of cells thick, was observed in the necrophylactic periderm of 10‐year‐old trees. When fully developed, the necrophylactic periderm in 27‐year‐old western larch also had a layer of stone phellem three to five rows of cells thick in each band. Stone phellem development was only sporadic in 25‐year‐old Douglas‐fir. Wounds in the winter showed no signs of activity associated with repair until dormancy broke in the spring.