Association mapping of ectomycorrhizal traits in loblolly pine (Pinus taeda L.).

To understand how diverse mutualisms coevolve and how species adapt to complex environments, a description of the underlying genetic basis of the traits involved must be provided. For example, in diverse coevolving mutualisms, such as the interaction of host plants with a suite of symbiotic mycorrhizal fungi, a key question is whether host plants can coevolve independently with multiple species of symbionts, which depends on whether those interactions are governed independently by separate genes or pleiotropically by shared genes. To provide insight into this question, we employed an association mapping approach in a clonally replicated field experiment of loblolly pine (Pinus taeda L.) to identify genetic components of host traits governing ectomycorrhizal (EM) symbioses (mycorrhizal traits). The relative abundances of different EM fungi as well as the total number of root tips per cm root colonized by EM fungi were analyzed as separate mycorrhizal traits of loblolly pine. Single-nucleotide polymorphisms (SNPs) within candidate genes of loblolly pine were associated with loblolly pine mycorrhizal traits, mapped to the loblolly pine genome, and their putative protein function obtained when available. The results support the hypothesis that ectomycorrhiza formation is governed by host genes of large effect that apparently have independent influences on host interactions with different symbiont species.

Distance decay relationships in foliar fungal endophytes are driven by rare taxa.

Foliar fungal endophytes represent a diverse and species-rich plant microbiome. Their biogeography provides essential clues to their cryptic relationship with hosts and the environment in which they disperse. We present species composition, diversity, and dispersal patterns of endophytic fungi associated with needles of Pinus taeda trees across regional scales in the absence of strong environmental gradients as well as within individual trees. An empirical designation of rare and abundant taxa enlightens us on the structure of endophyte communities. We report multiple distance-decay patterns consistent with effects of dispersal limitation, largely driven by community changes in rare taxa, those taxonomic units that made up less than 0.31% of reads per sample on average. Distance-decay rates and community structure also depended on specific classes of fungi and were predominantly influenced by rare members of Dothideomycetes. Communities separated by urban areas also revealed stronger effects of distance on community similarity, confirming that host density and diversity plays an important role in symbiont biogeography, which may ultimately lead to a mosaic of functional diversity as well as rare species diversity across landscapes.

Laboratory Evaluations of Durability of Southern Pine Pressure Treated With Extractives From Durable Wood Species.

Extracts from sawdust of four naturally durable wood species [Alaskan yellow cedar, AYC, Cupressus nootkanansis D. Don 1824; eastern red cedar, ERC, Juniperus virginiana L.; honey mesquite, HM, Prosopis glandulosa Torr.; and black locust, BL, Robinia pseudoacacia L.] were used to treat southern pine, Pt, Pinus taeda L. sapwood blocks. Extractive treated blocks were evaluated for decay resistance in standard soil bottle fungal assays challenged with brown and white rot decay fungi. Results showed that extractives did impart some improvement to decay resistance of Pt blocks. BL- and HM-treated Pt blocks were also used in choice and no-choice assays to determine feeding preference and damage by eastern subterranean termites (Reticulitermes flavipes) Kollar. Minimal feeding on treated blocks was seen in both choice and no-choice assays. In choice assays, there was similar mortality between HM and BL arenas; however, in no-choice assays, complete mortality was recorded for HM-treated Pt and high mortality was seen with BL-treated Pt. Subsequent dose mortality termite assays showed HM to be effective in killing R. flavipes at low concentrations. Both HM and BL show promise as deterrents or termiticidal protectants and will be further evaluated in field studies.

Fungal functioning in a pine forest: evidence from a ¹5N-labeled global change experiment.

• We used natural and tracer nitrogen (N) isotopes in a Pinus taeda free air CO2 enrichment (FACE) experiment to investigate functioning of ectomycorrhizal and saprotrophic fungi in N cycling. • Fungal sporocarps were sampled in 2004 (natural abundance and (15) N tracer) and 2010 (tracer) and δ(15)N patterns were compared against litter and soil pools. • Ectomycorrhizal fungi with hydrophobic ectomycorrhizas (e.g. Cortinarius and Tricholoma) acquired N from the Oea horizon or deeper. Taxa with hydrophilic ectomycorrhizas acquired N from the Oi horizon (Russula and Lactarius) or deeper (Laccaria, Inocybe, and Amanita). (15)N enrichment patterns for Cortinarius and Amanita in 2010 did not correspond to any measured bulk pool, suggesting that a persistent pool of active organic N supplied these two taxa. Saprotrophic fungi could be separated into those colonizing pine cones (Baeospora), wood, litter (Oi), and soil (Ramariopsis), with δ(15)N of taxa reflecting substrate differences. (15)N enrichment between sources and sporocarps varied across taxa and contributed to δ(15)N patterns. • Natural abundance and (15)N tracers proved useful for tracking N from different depths into fungal taxa, generally corresponded to literature estimates of fungal activity within soil profiles, and provided new insights into interpreting natural abundance δ(15)N patterns.

Fungal and bacterial community succession differs for three wood types during decay in a forest soil.

Wood decomposition by soil microorganisms is vital to carbon and nutrient cycles of forested ecosystems. Different wood types decompose at different rates; however, it is not known if there are differences in microbial community succession associated with the decay of different wood types. In this study, the microbial community associated with the decay of pine (decay-susceptible wood), western red cedar (decay resistant) and ACQ-treated pine (Ammoniacal Copper Quaternary, preservative-treated pine for decay resistance) in forest soil was characterized using DNA sequencing, phospholipid fatty acid (PLFA) analysis, and microbial activity over a 26-month period. Bray-Curtis ordination using an internal transcribed spacer (ITS) sequence and PLFA data indicated that fungal communities changed during succession and that wood type altered the pattern of succession. Nondecay fungi decreased over the 26 months of succession; however, by 18 months of decay, there was a major shift in the fungal communities. By this time, Trametes elegans dominated cedar and Phlebia radiata dominated pine and ACQ-treated pine. The description of PLFA associated with ACQ-treated pine resembled cedar more than pine; however, both PLFA and ITS descriptions indicated that fungal communities associated with ACQ-treated pine were less dynamic, perhaps a result of the inhibition by the ACQ preservative, compared with pine and cedar. Overall, fungal community composition and succession were associated with wood type. Further research into the differences in community composition will help to discern their functional importance to wood decay.

Preference of Formosan subterranean termites for blue-stained southern yellow pine sapwood.

Little research has been conducted to investigate interactions between the invasive Formosan subterranean termite, Coptotermes formosanus Shiraki, and pine bark beetles native to the southeastern United States. Facilitative interactions between these organisms could alter stand dynamics and impact wood utilization strategies. American Wood Protection Association Standard E1-09 choice tests were carried out to determine the feeding preference of Formosan subterranean termites for blue-stained versus unstained southern yellow pine sapwood. Three separate colonies of Formosan subterranean termites consumed on average twice as much air-dried blue-stained southern yellow pine sapwood over unstained air-dried controls. Additionally, Formosan subterranean termites consumed over five-times more kiln-dried blue-stained sapwood than unstained kiln-dried control wafers. The implications of these results are particularly relevant to pine forest ecology, nutrient cycling, and the utilization of blue-stained southern pine building products in the southeastern United States, where Formosan subterranean termites have become established.

A genomic map enriched for markers linked to Avr1 in Cronartium quercuum f.sp. fusiforme.

A novel approach is presented to map avirulence gene Avr1 in the basidiomycete Cronartium quercuum f.sp. fusiforme, the causal agent of fusiform rust disease in pines. DNA markers tightly linked to resistance gene Fr1 in loblolly pine tree 10-5 were used to classify 10-5 seedling progeny as either resistant or susceptible. A single dikaryotic isolate (P2) heterozygous at the corresponding Avr1 gene was developed by crossing Fr1 avirulent isolate SC20-21 with Fr1 virulent isolate NC2-40. Bulk basidiospore inoculum derived from isolate P2 was used to challenge the pine progeny. The ability to unambiguously marker classify 10-5 progeny as resistant (selecting for virulence) or susceptible (non-selecting) permitted the genetic mapping of the corresponding Avr1 gene by bulked segregant analysis. Using this approach, 14 genetic markers significantly linked to Avr1 were identified and placed within the context of a genome-wide linkage map produced for isolate P2 using samples from susceptible seedlings.

Molecular analysis of bacterial communities associated with the roots of Douglas fir (Pseudotsuga menziesii) colonized by different ectomycorrhizal fungi.

We studied the effect of ectomycorrhizal fungi on bacterial communities colonizing roots of Douglas fir (Pseudotsuga menziesii). Mycorrhizal tips were cleaned of soil and separated based on gross morphological characteristics. Sequencing of the internal transcribed spacers of the nuclear rRNA gene cluster indicated that the majority of the tips were colonized by fungi in the Russulaceae, with the genera Russula and Lactarius comprising 70% of the tips. Because coamplification of organellar 16S rRNA genes can interfere with bacterial community analysis of root tips, we developed and tested a new primer pair that permits amplification of bacterial 16S rRNA genes but discriminates more effectively against organellar sequences than commonly used bacterial primer sets. We then used terminal restriction fragment length polymorphism (T-RFLP) and sequence analysis of the 16S rRNA gene to examine differences in bacterial communities associated with the mycorrhizal tips. Cluster analysis of T-RFLP profiles indicated that there were different bacterial communities among the root tips; however, the communities did not seem to be affected by the taxonomic identity of the ectomycorrhizal fungi. Terminal restriction fragment profiling and sequencing of cloned partial 16S rRNA genes indicated that most bacteria on the ectomycorrhizal tips were related to the Alphaproteobacteria and the Bacteroidetes group.

Resin flow responses to fertilization, wounding and fungal inoculation in loblolly pine (Pinus taeda) in North Carolina.

Resin flow is the primary means of natural defense against southern pine beetle (Dendroctonus frontalis Zimm.), the most important insect pest of Pinus spp. in the southern United States. As a result, factors affecting resin flow are of interest to researchers and forest managers. We examined the influence of fertilization, artificial wounding and fungal inoculation on resin flow in 6- and 12-year-old stands of loblolly pine (Pinus taeda L.) and determined the extent of that influence within and above the wounded stem area and through time. Fertilization increased constitutive resin flow, but only the younger trees sustained increased resin flow after wounding and inoculation treatments. An induced resin flow response occurred between 1 and 30 days after wounding and inoculation treatments. Wounding with inoculation resulted in greater resin flow than wounding alone, but increasing amounts of inoculum did not increase resin flow. Increased resin flow (relative to controls) lasted for at least 90 days after wounding and inoculation. This increase appeared to be limited to the area of treatment, at least in younger trees. The long-lasting effects of fungal inoculation on resin flow, as well as the response to fertilization, suggest that acquired resistance through induced resin flow aids in decreasing susceptibility of loblolly pine to southern pine beetle.

Two new endophytic Atractiellomycetes, Atractidochium hillariae and Proceropycnis hameedii.

Sterile fungal isolates are often recovered in leaf and root endophytic studies, although these seldom play a significant role in downstream analyses. The authors sought to identify and characterize two such endophytes-one representing the most commonly recovered fungal isolate in recent studies of needle endophytes of Pinus taeda and the other representing a rarely isolated root endophyte of Populus trichocarpa. Both are shown by DNA sequencing to be undescribed species of Atractiellomycetes (Pucciniomycotina, Basidiomycota), a poorly characterized class of mostly plant-associated and presumably saprobic microfungi. The authors describe the new genus and species Atractidochium hillariae (Phleogenaceae) and the new species Proceropycnis hameedii (Hoehnelomycetaceae), both in the Atractiellales, to accommodate these unusual isolates. Following incubations of 1-2 mo, A. hillariae produces minute white sporodochia, similar to those produced by several other members of Atractiellales, whereas Pr. hameedii forms conidia singly or in chains in a manner similar to its sister species Pr. pinicola. Additionally, we provide a taxonomic revision of Atractiellomycetes based on multilocus analyses and propose the new genera Neogloea (Helicogloeaceae) and Bourdotigloea (Phleogenaceae) to accommodate ex-Helicogloea species that are not congeneric with the type H. lagerheimii. Atractiellomycetes consists of a single order, Atractiellales, and three families, Hoehnelomycetaceae, Phleogenaceae, and Helicogloeaceae. Accumulated evidence suggests that Atractiellomycetes species are common but infrequently isolated members of plant foliar and root endobiomes.

Soil DIC uptake and fixation in Pinus taeda seedlings and its C contribution to plant tissues and ectomycorrhizal fungi.

Plants can acquire carbon from sources other than atmospheric carbon dioxide (CO(2)), including soil-dissolved inorganic carbon (DIC). Although the net flux of CO(2) is out of the root, soil DIC can be taken up by the root, transported within the plant, and fixed either photosynthetically or anaplerotically by plant tissues. We tested the ability of Pinus taeda L. seedlings exposed to (13)C-labeled soil DIC and two NH(4)(+) availability regimes to take up and fix soil DIC. We also measured the concentration and distribution of the fixed soil DIC within the plant and mycorrhizal tissues, and quantified the contribution of soil DIC to whole-plant carbon (C) gain. Seedlings exposed to labeled DIC were significantly enriched in (13)C compared with seedlings exposed to unlabeled DIC (6.7 versus -31.7 per thousand). Fixed soil DIC was almost evenly distributed between above- and belowground biomass (55 and 45%, respectively), but was unevenly distributed among tissues. Aboveground, stem tissue contained 65% of the fixed soil DIC but represented only 27% of the aboveground biomass, suggesting either corticular photosynthesis or preferential stem allocation. Belowground, soil DIC had the greatest effect (measured as (13)C enrichment) on the C pool of rapidly growing nonmycorrhizal roots. Soil DIC contributed approximately 0.8% to whole-plant C gain, and approximately 1.6% to belowground C gain. We observed a slight but nonsignificant increase in both relative C gain and the contribution of soil DIC to C gain in NH(4)(+)-fertilized seedlings. Increased NH(4)(+) availability significantly altered the distribution of fixed soil DIC among tissue types and increased the amount of fixed soil DIC in ectomycorrhizal roots by 130% compared with unfertilized seedlings. Increased NH(4)(+) availability did not increase fixation of soil DIC in nonmycorrhizal roots, suggesting that NH(4)(+) assimilation may be concentrated in ectomycorrhizal fungal tissues, reflecting greater anaplerotic demands. Soil DIC is likely to contribute only a small amount of C to forest trees, but it may be important in C fixation processes of specific tissues, such as newly formed stems and fine roots, and ectomycorrhizal roots assimilating NH(4)(+).

Diversity and phylogenetic affinities of foliar fungal endophytes in loblolly pine inferred by culturing and environmental PCR.

We examined endophytic fungi in asymptomatic foliage of loblolly pine (Pinus taeda) in North Carolina, U.S.A., with four goals: (i) to evaluate morphotaxa, BLAST matches and groups based on sequence similarity as functional taxonomic units; (ii) to explore methods to maximize phylogenetic signal for environmental datasets, which typically contain many taxa but few characters; (iii) to compare culturing vs. culture-free methods (environmental PCR of surface sterilized foliage) for estimating endophyte diversity and species composition; and (iv) to investigate the relationships between traditional ecological indices (e.g. Shannon index) and phylogenetic diversity (PD) in estimating endophyte diversity and spatial heterogeneity. Endophytes were recovered in culture from 87 of 90 P. taeda leaves sampled, yielding 439 isolates that represented 24 morphotaxa. Sequence data from the nuclear ribosomal internal transcribed spacer (ITS) for 150 isolates revealed 59 distinct ITS genotypes that represented 24 and 37 unique groups based on 90% and 95% sequence similarity, respectively. By recoding ambiguously aligned regions to extract phylogenetic signal and implementing a conservative phylogenetic backbone constraint, we recovered well supported phylogenies based on ca. 600 bp of the nuclear ribosomal large subunit (LSUrDNA) for 72 Ascomycota and Basidiomycota, 145 cultured endophytes and 33 environmental PCR samples. Comparisons with LSUrDNA-delimited species showed that morphotaxa adequately estimated total species richness but rarely corresponded to biologically meaningful groups. ITS BLAST results were variable in their utility, but ITS genotype groups based on 90% sequence similarity were concordant with LSUrDNA-delimited species. Environmental PCR yielded more genotypes per sampling effort and recovered several distinct clades relative to culturing, but some commonly cultured clades were never found (Sordariomycetes) or were rare relative to their high frequency among cultures (Leotiomycetes). In contrast to traditional indices, PD demonstrated spatial heterogeneity in endophyte assemblages among P. taeda trees and study plots. Our results highlight the need for caution in designating taxonomic units based on gross cultural morphology or ITS BLAST matches, the utility of phylogenetic tools for extracting robust phylogenies from environmental samples, the complementarity of culturing and environmental PCR, the utility of PD relative to traditional ecological indices, and the remarkably high diversity of foliar fungal endophytes in this simplified temperate ecosystem.

Biotransformation of limonene by an endophytic fungus using synthetic and orange residue-based media.

Aroma and fragrances have high commercial value for use in food, cosmetics and perfumes. The biotransformation of terpenes by microorganisms represents an attractive alternative method for production of flavourings. Endophytic fungi offer a great potential for the production of several groups of compounds; however, few studies have evaluated the biotransformation of limonene. Following preliminary studies on the biotransformation of limonene, submerged fermentation was carried out using an endophytic fungus isolated from Pinus taeda and identified as Phomopsis sp. The presence of several biotransformation products was detected and identified by mass spectrometry (GC-MS). The studied strain showed a divergent metabolic behaviour, as compounds of interest such as α-terpineol, carvone, and limoneno-1,2-diol were produced under different conditions. In addition to the minor metabolites terpinen-4-ol, menthol and carveol, this strain also produced major metabolites, including 0.536 g L-1 carvone and 2.08 g L-1 limonene-1,2-diol in synthetic medium and 2.10 g L-1 limonene-1,2-diol in a natural orange extract medium with single fed-batch, while the cyclic fed-batch resulted in concentrations less than 1 g L-1. Therefore, our study produced a wide variety of limonene derivatives at a high concentration using a natural medium and a newly isolated endophytic fungal strain.

Soil bacterial diversity in a loblolly pine plantation: influence of ectomycorrhizas and fertilization.

We studied the effect of ectomycorrhizas and fertilization on soil microbial communities associated with roots of 10-year-old loblolly pine. Ectomycorrhizas were identified using a combination of community terminal restriction fragment profiling and matching of individual terminal restriction fragments to those produced from ectomycorrhizal clones and sequences recovered from roots and sporocarps. Differences between bacterial communities were initially determined using cluster analysis on community terminal restriction fragment profiles and through subsequent recovery of 16S rDNA clones. Analysis of bacterial clones revealed that terminal restriction fragment length was often shared between taxonomically dissimilar bacterial types. Consequently, we could not reliably infer the identity of peaks in the bacterial community profile with some exceptions, notably chloroplast rDNA that generated an approximate peak size of 80.2 bp. Fertilization increased the frequency of a Piloderma-like ectomycorrhiza. However, we did not detect clear effects of fertilization or the presence of viable ectomycorrhizas on bacterial communities. Bacterial communities seemed to be determined largely by the carbon and nitrogen content of soil. These results suggest that important soil microbial groups respond differently to soil conditions and management practices, with ectomycorrhizal communities reflecting past nutrient conditions and bacterial communities reflecting current environmental conditions of soil microsites.

Purification and properties of a xylanase from Ceriporiopsis subvermispora cultivated on Pinus taeda.

The production of hemicellulose and cellulose degrading enzymes by the white-rot fungus Ceriporiopsis subvermispora was determined while growing in Pinus taeda wood chips. Enzymes produced by the fungus were extracted after 30 days of cultivation and at least two different xylanases were secreted. An endo-(1,4)-beta-xylanase was purified by means of ultrafiltration, anion exchange chromatography and gel filtration. Its molecular mass was 29 kDa and the pH and temperature optima were 5.0 and 60 degrees C, respectively. The endo-xylanase was able to hydrolyze xylan to principally xylotriose and xylotetraose and it has different activities against different xylans. With birchwood xylan as substrate, the enzyme showed a K(m) of 1.93 mg/ml and specific activity of 538 units/mg protein at 50 degrees C.

Effects of mass inoculation on induced oleoresin response in intensively managed loblolly pine.

Oleoresin flow is an important factor in the resistance of pines to attack by southern pine beetle, Dendroctonus frontalis Zimm., and its associated fungi. Abiotic factors, such as nutrient supply and water relations, have the potential to modify this plant-insect-fungus interaction; however, little is known of the effects of inoculation with beetle-associated fungi on oleoresin flow. We observed that constitutive and induced resin yield in loblolly pine, Pinus taeda L., were affected by either fungal inoculation (with the southern pine beetle-associated fungus Ophiostoma minus (Hedgcock) H. & P. Sydow) or silvicultural treatment. The effects of mass wounding (400 wounds m(-2)) and mass wounding and inoculation with O. minus were assessed by comparison with untreated (control) trees. The treatments were applied to trees in a 2 x 2 factorial combination of fertilizer and irrigation treatments. Fertilization did not significantly affect constitutive resin yield. Even as long as 105 days post-treatment, however, mass-inoculated trees produced higher induced resin yields than control or wounded-only trees, indicating a localized induced response to fungal inoculation. We noted no systemic induction of host defenses against fungal colonization. Although beetles attacking previously attacked trees face a greater resinous response from their host than beetles attacking trees that had not been previously attacked, the effect of an earlier attack may not last more than one flight season. Despite mass inoculations, O. minus did not kill the host trees, suggesting that this fungus is not a virulent plant pathogen.

A comparison of the community diversity of foliar fungal endophytes between seedling and adult loblolly pines (Pinus taeda).

Fungal endophytes represent one of the most ubiquitous plant symbionts on Earth and are phylogenetically diverse. The structure and diversity of endophyte communities have been shown to depend on host taxa and climate, but there have been relatively few studies exploring endophyte communities throughout host maturity. We compared foliar fungal endophyte communities between seedlings and adult trees of loblolly pines (Pinus taeda) at the same seasons and locations by culturing and culture-independent methods. We sequenced the internal transcribed spacer region and adjacent partial large subunit nuclear ribosomal RNA gene (ITS-LSU amplicon) to delimit operational taxonomic units and phylogenetically characterize the communities. Despite the lower infection frequency in seedlings compared to adult trees, seedling needles were receptive to a more diverse community of fungal endophytes. Culture-free method confirmed the presence of commonly cultured OTUs from adult needles but revealed several new OTUs from seedling needles that were not found with culturing methods. The two most commonly cultured OTUs in adults were rarely cultured from seedlings, suggesting that host age is correlated with a selective enrichment for specific endophytes. This shift in endophyte species dominance may be indicative of a functional change between these fungi and their loblolly pine hosts.

Effects of tropospheric ozone on loblolly pine seedlings inoculated with root infecting ophiostomatoid fungi.

Seedlings from four loblolly pine (Pinus taeda L.) families were exposed in open-top chambers to charcoal-filtered air (CF), non-filtered air (NF) or air amended with ozone to 2 times ambient (2×). Two of the families used were selected for their tolerance to fungi associated with Southern Pine Decline while two were selected for their susceptibility. Seedlings were treated with five inoculation treatments: no wound (NW), wound only (W), wound + media (WM), Grosmannia huntii (GH) and Leptographium terebrantis (LT). After 118 days of exposure (AOT40 = 31 ppm-hr(-1) for 2× ozone) seedling volume, dry matter, chlorophyll content, water potential and lesions were measured and analyzed using ANOVA procedures. Our results indicate that seedlings selected for their susceptibility to root infecting ophiostomatoid fungi were also more sensitive to ozone. Overall lesion length was greater on seedlings exposed to elevated ozone concentrations but was not specific to either root infecting ophiostomatoid fungi.

Interactions of Hylastes species (Coleoptera: Scolytidae) with Leptographium species associated with loblolly pine decline.

Hylastes spp. (Coleoptera: Scolytidae) were evaluated as potential vectors of Leptographium spp. fungi. Bark beetles were trapped from stands ofloblolly pine, Pinus taeda L., exhibiting a range of decline symptoms in central Alabama. Under controlled conditions, field-collected adult Hylastes salebrosus Eichoff (Coleoptera: Scolytidae) and Hylastes tenuis Eichoff (Coleoptera: Scolytidae), which had been surface-sterilized and inoculated with Leptographium terebrantis Barras & Perry and Leptographium serpens (Goid.) Wingfield, transmitted the fungi into 100% of wounded and unwounded loblolly root sections with which they were confined. None of the sterilized and uninoculated beetles transmitted any Leptographium spp. to roots. Significantly more H. salebrosus and H. tenuis brood emerged from roots infected with Leptographium species than from sterile roots, indicating an enhancement of Hylastes reproduction.

Metabolite secretion, Fe(3+)-reducing activity and wood degradation by the white-rot fungus Trametes versicolor ATCC 20869.

Trametes versicolor is a promising white-rot fungus for the biological pretreatment of lignocellulosic biomass. In the present work, T. versicolor ATCC 20869 was grown on Pinus taeda wood chips under solid-state fermentation conditions to examine the wood-degrading mechanisms employed by this fungus. Samples that were subjected to fungal pretreatment for one-, two- and four-week periods were investigated. The average mass loss ranged from 5 % to 8 % (m m(-)(1)). The polysaccharides were preferentially degraded: hemicellulose and glucan losses reached 13.4 % and 6.9 % (m m(-)(1)) after four weeks of cultivation, respectively. Crude enzyme extracts were obtained and assayed using specific substrates and their enzymatic activities were measured. Xylanases were the predominant enzymes, while cellobiohydrolase activities were marginally detected. Endoglucanase activity, ß-glucosidase activity, and wood glucan losses increased up to the second week of biodegradation and remained constant after that time. Although no lignin-degrading enzyme activity was detected, the lignin loss reached 7.5 % (m m(-)(1)). Soluble oxalic acid was detected in trace quantities. After the first week of biodegradation, the Fe(3+)-reducing activity steadily increased with time, but the activity levels were always lower than those observed in the undecayed wood. The progressive wood polymer degradation appeared related to the secretion of hydrolytic enzymes, as well as to Fe(3+)-reducing activity, which was restored in the cultures after the first week of biodegradation.