Showing papers on "Bark published in 2007"

Fungal Associates of European Bark Beetles With Special Emphasis on the Ophiostomatoid Fungi

Abstract: Fungi are common and well-known associates of bark beetles (Coleoptera: Scolytidae). The relationship between fungi and scolytids was recognized relatively long ago. Schmidberger (1836) described an “ambrosia” in the galleries of the wood-inhabiting bark beetle Xyleborus dispar, and Hartig (1844) discovered the fungal nature of this “ambrosia” lining the tunnels of the insects. Likewise, Hartig (1878) first recognized the interrelationships between insect damage, discoloration of wood and fungi, and during his studies on blue-stain in the sapwood of conifers, Munch (1907, 1908) observed that blue-stain in living trees and lumber is associated with attack by bark beetles. Since these early discoveries a large number of investigations on various aspects of the association of fungi with bark beetles have been carried out. Scolytids are among the most economically important pests of the world s forests, especially conifer forests in the boreal and temperate regions of the Northern hemisphere (Postner 1974; Schwerdtfeger 1981; Wood 1982; Wood and Bright 1992). A considerable number of fungal associates of bark beetles are known as forest pathogens in their own right, causing vascular wilt or vascular stain diseases (Webber and Gibbs 1989; Harrington 1993a, 1993b; Wingfield et al. 1993). Many other species give rise to discoloration in the sapwood of conifers and cause enormous losses to forestry and wood industry worldwide (Whitney 1982; Seifert 1993; Butin 1996). Although the association between scolytids and fungi has been recognised for more than one century, many fundamental aspects of this relationship are still poorly

The endophytic mycoflora of bark, leaf, and stem tissues of Azadirachta indica A. Juss (neem) from Varanasi (India).

Abstract: A systematic study was made of the endophytes of Azadirachta indica A. Juss (the neem tree) growing in several of its natural habitats in India. A total of 233 isolates of endophytic fungi representing 18 fungal taxa were obtained from segments of bark, stem, and leaves of this tree. Hyphomycetes (62.2%) were the most prevalent followed by the Coelomycetes (27.4%) and Mycelia Sterilia (7.7%). As mathematically determined, the maximum species richness and frequency of colonization of endophytes appeared in leaf segments rather than stem and bark tissues from each location. Endophytic colonization frequency was also greater in leaves (45.5%) than bark (31.5%). The leaf samples from all locations were nearly constant in their endophytic composition, whereas bark samples showed maximum diversity at different locations. Inter-site comparisons for endophytic diversity, however, were not significantly different with Loc1 and Loc2 having a maximum of 66.67% Jc. The smallest similarity was between Loc2 and Loc3 of 54.17% Jc. The dominant endophytic fungi isolated were Phomopsis oblonga, Cladosporium cladosporioides, Pestalotiopsis sp., Trichoderma sp, and Aspergillus sp. Genera such as Periconia, Stenella, and Drechslera are reported here for the first time as endophytes from this host plant. This report illustrates the value of sampling different tissues of a given plant in several locations to obtain the greatest species diversity of endophytes. The rich and sizeable collection of endophytic fungi from this specific plant may represent a unique source of one or more of the interesting and useful bioactive compounds normally associated with A. indica such as the azadirachtins and related tetranortriterpenoids.

Isolation of stigmasterol and beta-sitosterol from methanolic extract of root bark of Calotropis gigantea (Linn).

Abstract: Aim of this study is to identify and characterize the bioactive principles from the root bark of Calotropis gigantea. It has wide folk medicinal use. For isolation of the compounds, the dried root bark's powder of Calotropis gigantea were subjected to hot extraction and then the crude methanol (MeOH) extract was fractionated with petroleum ether, chloroform and ethyl acetate. Two compounds were isolated and purified from petroleum ether fraction of crude methanol extract and the structures were determined as stigmasterol and beta-sitosterol by analysis of physical, chemical and spectral characteristics (1D NMR and mass spectrometry).

Study of endophytic fungal community from different parts of Aegle marmelos Correae (Rutaceae) from Varanasi (India)

Abstract: Endophytic fungi were isolated from healthy, living, and symptomless tissues of inner bark, leaf, and roots of Aegle marmelos, a well-known medicinal plant, growing in different parts of India including Varanasi. A total of 79 isolates of endophytic fungi were isolated, representing 21 genera, adopting a standard isolation protocol. Members of the deuteromycotina were more prevalent than ascomycotina and others. The result was quite encouraging in terms of maximum isolates recovery from hyphomycetes (78.5%) followed by ascomycetes (8.9%) and coelomycetes (7.6%) respectively, which corroborates previous studies in same area. However, 5.1% isolates remained unidentified and were classified under Mycelia Sterilia. No isolate was obtained from either basidiomycotina or from zygomycotina. Fusarium spp. had maximum colonization frequency (8.00%) in this plant. The other dominant endophytic genera were Aspergillus spp., Alternaria sp., Drechslera sp., Rhizoctonia sp., Curvularia sp., Nigrospora sp., and Stenella sp. Only two ascomycetous members Chaetomium globosum and Emericella sp. (perfect state of Aspergillus sp.) were obtained from the bark sample. These results indicated that distribution of endophytic fungi within the A. marmelos is not even. Bark harbors more endophytic fungi than leaf and root.

Short Communication Antioxidant activities of natural phenolic compounds from Acacia confusa bark

Abstract: The present study showed that the ethanolic extracts from the bark of Acacia confusa exhibited a strong antioxidant activity. Among all the fractions from ethanolic extracts of bark, the EtOAc soluble fraction exhibited the best antioxidant performance. Furthermore, following by CC and HPLC, 11 pure phenolic compounds were isolated and identiWed from the ethanolic extracts.

A genomic approach to suberin biosynthesis and cork differentiation

Abstract: Cork (phellem) is a multilayered dead tissue protecting plant mature stems and roots and plant healing tissues from water loss and injuries. Cork cells are made impervious by the deposition of suberin onto cell walls. Although suberin deposition and cork formation are essential for survival of land plants, molecular studies have rarely been conducted on this tissue. Here, we address this question by combining suppression subtractive hybridization together with cDNA microarrays, using as a model the external bark of the cork tree (Quercus suber), from which bottle cork is obtained. A suppression subtractive hybridization library from cork tree bark was prepared containing 236 independent sequences; 69% showed significant homology to database sequences and they corresponded to 135 unique genes. Out of these genes, 43.5% were classified as the main pathways needed for cork biosynthesis. Furthermore, 19% could be related to regulatory functions. To identify genes more specifically required for suberin biosynthesis, cork expressed sequence tags were printed on a microarray and subsequently used to compare cork (phellem) to a non-suberin-producing tissue such as wood (xylem). Based on the results, a list of candidate genes relevant for cork was obtained. This list includes genes for the synthesis, transport, and polymerization of suberin monomers such as components of the fatty acid elongase complexes, ATP-binding cassette transporters, and acyltransferases, among others. Moreover, a number of regulatory genes induced in cork have been identified, including MYB, No-Apical-Meristem, and WRKY transcription factors with putative functions in meristem identity and cork differentiation.

Chemical Ecology of Bark Beetles in a Complex Olfactory Landscape

Abstract: The Scolytidae (bark and ambrosia beetles) comprise a taxonomic group of at least 6000 species that, although appearing similar, may differ widely in their ecology and biochemical adaptations to host trees. Bark beetle species that feed on phloem (a relatively thin layer just under the corky bark) are usually restricted to one or a few host species, whereas ambrosia beetle species that are xylomycetophagous (woodfeeding) and introduce symbiotic fungi for "cultivation" in their galleries generally colonize a larger range of hosts (S.L. Wood 1982). Most biological knowledge on bark and ambrosia beetles derives from studies on relatively few pest species in the genera Dendroctonus, Ips, Scolytus, Xyleborus, Trypodendron, Tomicus=Blastophagus (Fig. 1), Pityogenes, Hypothenemus, Pityophthorus, Hylastes, and Gnathotrichus. Many of these species are obligate and facultative tree-killing bark beetles that comprise only about 10% of scolytid species in the United States and Canada (Raffa et al. 1993). However, these pests that kill trees are the most likely to significantly influence the evolution of the host tree and its chemistry. The diversity of bark beetle biology, in which each species is adapted to only one or a few host tree species, probably has resulted due to natural selection from the great variety of plant biochemicals. It is also theorized that each species of tree has coevolved various chemicals to defend against the herbivorous selection pressures of the tree-killing bark beetles (Erlich and Raven 1965; Feeny 1975; Cates 1981; Berryman et al. 1985; Byers 1995). Semiochemicals (behavior modifying chemicals) from both the tree and the beetle have many functions during the life cycle of a bark beetle (for reviews see D.L. Wood 1982; Borden 1982, 1997; Lanier 1983; Birch 1984; Borden et al. 1986; Byers 1989a, b, 1995; Raffa et al. 1993; Schlyter and

A Genomic Approach to Suberin Biosynthesis and Cork Differentiation 1(C)(W)(OA)

Abstract: Cork (phellem) is a multilayered dead tissue protecting plant mature stems and roots and plant healing tissues from water loss and injuries. Cork cells are made impervious by the deposition of suberin onto cell walls. Although suberin deposition and cork formation are essential for survival of land plants, molecular studies have rarely been conducted on this tissue. Here, we address this question by combining suppression subtractive hybridization together with cDNA microarrays, using as a model the external bark of the cork tree (Quercus suber), from which bottle cork is obtained. A suppression subtractive hybridization library from cork tree bark was prepared containing 236 independent sequences; 69% showed significant homology to database sequences and they corresponded to 135 unique genes. Out of these genes, 43.5% were classified as the main pathways needed for cork biosynthesis. Furthermore, 19% could be related to regulatory functions. To identify genes more specifically required for suberin biosynthesis, cork expressed sequence tags were printed on a microarray and subsequently used to compare cork (phellem) to a non-suberin-producing tissue such as wood (xylem). Based on the results, a list of candidate genes relevant for cork was obtained. This list includes genes for the synthesis, transport, and polymerization of suberin monomers such as components of the fatty acid elongase complexes, ATP-binding cassette transporters, and acyltransferases, among others. Moreover, a number of regulatory genes induced in cork have been identified, including MYB, No-Apical-Meristem, and WRKY transcription factors with putative functions in meristem identity and cork differentiation. Land plants have evolved lipophilic barriers that protect the internal living tissues from dehydration, injuries, and pathogens, and have evolved regulatory networks to adjust the barriers to the changing physiological and environmental conditions of the plant. Plant primary organs, such as young stems and leaves, are protected by the cuticle, a lipophilic extracellular polymer membrane composed of cutin and waxes. Secondary (mature) stems and roots, tubers, and healing tissues are protected by cork, a tissue with multiple

Phorophyte specificity and environmental parameters versus stochasticity as determinants for species composition of corticolous crustose lichen communities in the Atlantic rain forest of northeastern Brazil

Abstract: A transect of 47 mature trees was studied within an Atlantic rain-forest plot in northeastern Brazil to determinate effects of phorophyte specificity and environmental parameters vs. stochasticity on the structure of corticolous, crustose microlichen communities. A total of 150 lichen species was found, most being rare to extremely rare. Multivariate analysis of sample plots indicated subtle phorophyte preferences among certain lichen species, corresponding to differences in bark pH, degree of bark shedding, density and size of bark lenticels, and presence of milk sap. Individual and multiple regressions revealed correlations between lichen species richness; respectively, area cover and bark pH (negative); density and size of bark lenticels (negative); degree of bark shedding (negative); presence of milk sap (positive); and diffuse site factor (positive). No strongly delimited lichen communities were detected, but cluster analysis revealed three main groups and six subgroups with slightly different lichen species composition, each one with characteristic indicator species but with highly variable overall species composition. Beta diversity was high among samples and lacked spatial structure. However, beta diversity was significantly lower among samples belonging to the same tree species, independent of their spatial arrangement. It was concluded that community formation in tropical rain-forest understory lichens subtly correlates with two main environmental factor complexes—phorophyte bark characteristics and microclimate—but is to a large extent determined by the stochastic effects of species dispersal, especially of rare species.

Host specificity of ambrosia and bark beetles (Col., Curculionidae: Scolytinae and Platypodinae) in a New Guinea rainforest

Abstract: 1. Bark and ambrosia beetles are crucial for woody biomass decomposition in tropical forests worldwide. Despite that, quantitative data on their host specificity are scarce. 2. Bark and ambrosia beetles (Scolytinae and Platypodinae) were reared from 13 species of tropical trees representing 11 families from all major lineages of dicotyledonous plants. Standardised samples of beetle-infested twigs, branches, trunks, and roots were taken from three individuals of each tree species growing in a lowland tropical rainforest in Papua New Guinea. 3. A total of 81 742 beetles from 74 species were reared, 67 of them identified. Local species richness of bark and ambrosia beetles was estimated at 80–92 species. 4. Ambrosia beetles were broad generalists as 95% of species did not show any preference for a particular host species or clade. Similarity of ambrosia beetle communities from different tree species was not correlated with phylogenetic distances between tree species. Similarity of ambrosia beetle communities from individual conspecific trees was not higher than that from heterospecific trees and different parts of the trees hosted similar ambrosia beetle communities, as only a few species preferred particular tree parts. 5. In contrast, phloeophagous bark beetles showed strict specificity to host plant genus or family. However, this guild was poor in species (12 species) and restricted to only three plant families (Moraceae, Myristicaceae, Sapindaceae). 6. Local diversity of both bark and ambrosia beetles is not driven by the local diversity of trees in tropical forests, since ambrosia beetles display no host specificity and bark beetles are species poor and restricted to a few plant families.

The trophic structure of bark-living oribatid mite communities analysed with stable isotopes ( 15 N, 13 C) indicates strong niche differentiation

Abstract: The aim of the present study was to identify food sources of bark-living oribatid mites to investigate if trophic niche differentiation contributes to the diversity of bark living Oribatida. We measured the natural variation in stable isotope ratios (15N/14N, 13C/12C) in oribatid mites from the bark of oak (Quercus robur), beech (Fagus sylvatica), spruce (Picea abies) and pine (Pinus sylvestris) trees and their potential food sources, i.e., the covering vegetation of the bark (bryophytes, lichens, algae, fungi). As a baseline for calibration the stable isotope signatures of the bark of the four tree species were measured and set to zero. Oribatid mite stable isotope ratios spanned over a range of about 13 δ units for 15N and about 7 δ units for 13C suggesting that they span over about three trophic levels. Different stable isotope signatures indicate that bark living oribatid mites feed on different food sources, i.e., occupy distinct trophic niches. After calibration stable isotope signatures of respective oribatid mite species of the four tree species were similar indicating close association of oribatid mites with the corticolous cover as food source. Overall, the results support the hypothesis that trophic niche differentiation of bark living oribatid mites contributes to the high diversity of the group.

Alelopatia de extratos aquosos de canela-sassafrás (Ocotea odorifera (Vell.) Rohwer)

Abstract: Allelopathic studies investigate the positive and negative effects of secondary metabolites of plants, microorganisms and fungi on the development of neighboring individuals. In this work, the allelopathic effects of aqueous extracts of leaves, bark and root bark of Brazilian sassafras (Ocotea odorifera (Vell.) Rowher) on seed germination, root and shoot growth, chlorophyll content and respiratory activity of the root cells of sorghum seedlings (Sorghum bicolor (L) Moench cv. Embrapa BR 303) were analyzed. The extracts were prepared by adding dried, powdered plant material to distilled non-ionized water at 1:10 (w/v). After continuous agitation for 24 h, these solutions were decanted and vacuum-filtered through filter paper, thus constituting the tested extracts. Bark and root bark aqueous extracts caused root growth inhibition in sorghum seedlings while shoot growth was stimulated by the root bark extract. Leaf and bark extracts induced an increase in wet root biomass and a decrease in chlorophyll content. All extracts caused negative effects on sorghum seedling root cell respiration. We concluded that secondary metabolites from Brazilian sassafras caused metabolic and morphological alterations in the sorghum seedlings and the presence of these plants in the environment can cause similar effects on other neighboring plant species.

Exploitation of polyphenol-rich pine barks for potent antioxidant activity

Abstract: The phenolic composition of pine bark from a variety of Pinus species was estimated by measuring Klason lignin, acid-soluble lignin, and a 1% NaOH extract. Polyphenol contents of hot water extracts from pine bark were determined by the Folin-Ciocalteu assay and the vanillin-H2SO4 assay. Among the pine bark varieties investigated, Pinus radiata bark showed the highest polyphenol content and potent antioxidant activity. Pinus rigida bark was also a usable polyphenol-rich source, whereas Pinus densiflora bark had a low yield (5.1%) of hot water extract, although it showed potent antioxidant activity. Correlations between proanthocyanidin content in pine bark and antioxidant activity were observed. The results suggested that proanthocyanidin was the crucial contributor to potent antioxidant activity in pine bark.