Ectomycorrhizae of sessile oak (Quercus petraea (Matt.) Liebl.)

Investigations were performed during the years 1999 to 2001 on a limed and unlimed plot within a high-elevated sessile oak forest. The oak forest (with 90 years old European beech at the understorey) was 170 to 197 years old. It is located at forest district Merzalben, location 04/0705, which is situated in the Palatinate Forest in south-west Germany. Liming was performed in December 1988 when 6 tons/ha of powdered Dolomite were brought up by the forestry department. Liming was performed to counteract the effects of soil acidification (pH(H2O) at Horizon A (0-10 cm): 3.9), which is induced by long-term (anthropogenic) acidic cloud cover and precipitation. Potentially toxic Al3+ ions, which become solubilized below pH 5, were suspected to be responsible for forest dieback and sudden death of the mature oaks. The most logical entry point for these toxic ions was suspected to occur in the highly absorptive region of the ectomycorrhizae (fungal covered root tips). However, the diversity and abundance of oak-ectomycorrhizal species and their actual roles in aluminum translocation (or blockage) were unknown. It was hypothesized that the ectomycorrhizae of sessile oaks in a limed forest would exhibit greater seasonal diversity and abundance with less evidence of incorporated aluminum than similar oak ectomycorrhizae from unlimed soils. To test this hypothesis, 12 oaks in the limed plot and 12 in an adjacent unlimed plot were selected. Each spring and fall for 2 years (1999 & 2000), 2 sets of soil cylinders (9.9 cm dia.) were extracted from Horizon A (0-10 cm), Horizon B (30-40 cm) and Horizon C (50-60 cm depth) at a distance of 1 meter from each tree base. Roots were extracted from each probe by gentle sieving and rinsing. Soil samples were retained for pH (H2O, CaCl2, and KCl) and moisture analysis. One set of roots was sorted by size and air-dried for biomass analysis. The finest mycorrhizal roots of this set were used for bound and unbound (cytosolic) mineral [Al, Ca, Mg, K, Na, Mn, S, Zn, Fe, Cd and Pb] analysis (by Landwirtschaftliche Untersuchungs- und Forschungsanstalt Rheinland Palatinate (LUFA)). Within 7 days of collection, the mycorrhizal tips from the second set of probes were excised, sorted, identified (using Agerer’s Color Atlas), counted and weighed. Seasonal diversity and abundance was characterized for 50 of the 93 isolates. The location and relative abundance of Al within the fungal and root cell walls was characterized for 68 species using 0.01% Morin dye and fluorescence microscopy. Morin complexes with Al to produce an intense yellow fluorescence. The 4 most common species (Cenococcum geophilum, Quercirhiza fibulocsytidiata, Lactarius subdulcis, Piceirhiza chordata) were prepared for bound Al, Ca, Fe and K mineral analysis by LUFA. The unlimed and limed plots were then compared. Only 46 of the 93 isolated ectomycorrhizal species had been previously associated with oaks in the literature. Mycorrhizal biomass was most abundant in Horizon A, declining with depth, drought and progressive soil acidification. Mycorrhizae were most diverse (32 species) in the limed plot, but individual species abundance was low (R Selection) in comparison to the unlimed plot, where there were fewer species (24) but each species present was abundant (K Selection). Liming increased diversity and altered dominance hierarchy, seasonal distributions and succession trends of ectomycorrhizae at all depths. Despite an expected reduction in Al content, the limed ectomycorrhizae both qualitatively (fluorescence analysis) and quantitatively (mineral analysis) contained more bound Al, especially so in Horizon A. The Al content qualitatively and quantitatively increased with depth in the unlimed and limed plots. The bound Al content fluctuated between 4000-and 20000 ppm while the unbound component was consistently lower (4 -14 ppm). The relative amount of unbound Al declined upon liming implying less availability for translocation to the crown area of the trees. This correspouds with the findings of good crown appearance and lower tree mortality in the limed zone. Each ectomycorrhizal species was unique in its ability to block, sequester (hold) or translocate Aluminum. In several species, Al uptake varied with changes in moisture, pH, depth and liming. According to the fluorescence study, about 48% of the isolated ectomycorrhizal species blocked and/or sequestered (held) Al in their mantle and/or Hartig net walls, qualitatively lowering bound Al in the adjacent root cell walls. Generally, if Al was more concentrated in the fungal walls, it was less evident in the cortex and xylem and conversely, if Al was low or absent from the fungal walls it was frequently more evident in the cortex and xylem.

Eucalypt NADP-Dependent Isocitrate Dehydrogenase1 : cDNA Cloning and Expression in Ectomycorrhizae

NADP-dependent isocitrate dehydrogenase (NADP-ICDH) activity is increased in roots of Eucalyptus globulus subsp. bicostata ex Maiden Kirkp. during colonization by the ectomycorrhizal fungus Pisolithus tinctorius Coker and Couch. To investigate the regulation of the enzyme expression, a cDNA (EgIcdh) encoding the NADP-ICDH was isolated from a cDNA library of E. globulus-P. tinctorius ectomycorrhizae. The putative polypeptide sequence of EgIcdh showed a high amino acid similarity with plant NADP-ICDHs. Because the deduced EgICDH protein lacks an amino-terminal targeting sequence and shows highest similarity to plant cytosolic ICDHs, it probably represents a cytoplasmic isoform. RNA analysis showed that the steady-state level of EgIcdh transcripts was enhanced nearly 2-fold in ectomycorrhizal roots compared with nonmycorrhizal roots. Increased accumulation of NADP-ICDH transcripts occurred as early as 2 d after contact and likely led to the observed increased enzyme activity. Indirect immunofluorescence microscopy indicated that NADP-ICDH was preferentially accumulated in the epidermis and stele parenchyma of nonmycorrhizal and ectomycorrhizal lateral roots. The putative role of cytosolic NADP-ICDH in ectomycorrhizae is discussed.

Cortinarius subgenus Telamonia p.p. in North Europe

Cortinarius is the largest genus of Agaricales with a worldwide distribution. So far, over 4000 Cortinarius names and combinations have been published. Cortinarius spp. form ectomycorrhizae with different trees and shrubs. A majority of the Cortinarius species have narrow ecological preferences and many form ectomycorrhiza with only one or few host species. The subgenus Telamonia sensu lato (s. lat.), comprising the greatest number of species, is the most poorly known of the subgenera of Cortinarius. The centre of diversity is in the northern hemisphere, although some species of the group are also recognized in the southern hemisphere. The aim of this thesis was to study the taxonomy of Cortinarius subgenus Telamonia p.p. species based on morphological and molecular data, as well as to study the ecology and distribution of the species in North Europe. The taxonomical problems encountered and the difficulty in finding and studying all the relevant names and types slowed down the study. The diversity of the subgenus Telamonia s. lat. in North Europe (excluding sect. Hydrocybe, Icrustati and Anomali) was found to be far greater than previously thought. Even many of the common species have not yet been described. So far, ca. 200 species have been recognised from the Nordic countries, but the sampling in most groups does not cover the whole diversity and especially the southern deciduous forest species are underrepresented in our study. In most cases phylogenetic (only based on ITS data) and morphological species recognition were in concordance, but in a few cases morphologically delimited species had almost identical ITS sequences, raising the question as to whether ITS is always variable enough for species recognition. The opposite situation, in which a morphologically uniform species included two phylogenetically distinct lineages, however, was also encountered, suggesting the possibility of cryptic species in Cortinarius. In our studies no taxa below species level were recognised and the aforementioned results indicate that presumably they can only be recognised genetically. Based on our preliminary results a revision of the infrageneric classification in Cortinarius subgenus Telamonia s. lat. is needed, and more sections should be established for a meaningful and functional classification. Many groups have turned out to be artificial, and it seems evident that many characteristics have been over- or underemphasised. Many morphological characteristics, however, are useful in the identification of telamonioid species and e.g. some spore characteristics have often been overlooked. Our studies have concentrated on North Europe, but we have found some similarities with North European and North American taxa.

Do ectomycorrhizal fungi exhibit adaptive tolerance to potentially toxic metals in the environment?

The effects of potentially toxic metals on ectomycorrhizal (ECM) fungi and their higher plant hosts are examined in this review. Investigations at a species and community level have revealed wide inter- and intraspecific variation in sensitivity to metals. Adaptive and constitutive mechanisms of ECM tolerance are proposed and discussed in relation to proven tolerance mechanisms in bacteria, yeasts and plants. Problems with methodology and research priorities are highlighted. These include the need for a detailed understanding of the genetic basis of tolerance in the ECM symbiosis, and for studies of ECM community dynamics in polluted sites.

Fungos ectomicorrízicos em áreas de Mata Atlântica do Nordeste do Brasil

Ectomycorrhizal associations are poorly known from tropical lowlands of South America. Recent field trips to the reserve Parque Estadual das Dunas in Natal, in Rio Grande do Norte state, Brazil, revealed a undocumented community of ectomycorrhizal fungi. This type of Mycorrhizal association is frequently in the north hemisphere in temperate and boreal forests. The aim of this work is to analyze the occurrence of ectotrophic areas in atlantic rainforest. Collections along and around the trails in the reserve revealed six genera of putatively ECM fungi which belong to the basidiomycete, Amanitaceae, Boletaceae, Russulaceae, Entolomataceae, and Sclerodermataceae family which are poorly documented in Brazil. Plants belonging to Myrtaceae, Polygonaceae, Leguminosae/Caesalpinioideae, Erythroxylaceae, Malphigiaceae, Bromeliaceae, Loganiaceae, Sapotaceae e Celastraceae were found living next to the species of fungi analized. Our results suggest that the area studied is an ectotrophic environment which shows high diversity of putatively ECM fungi and some plants probably host ECM. The tropical lands are a potential focus to study reinforced by the new records of Scleroderma in Brazil and Northwest of Brazil

ARBUSCULAR MYCORRHIZAE AND RHIZOBIUM IN ROOTING AND NUTRITION OF ANGICO-VERMELHO SEEDLINGS

The objective of this study was to evaluate the effect of inoculation of arbuscular mycorrhizae fungi (AMF) and rhizobium on rooting, growth and nutrition of seedlings of angico-red (Anadenanthera macrocarpa (Benth) Brenan) propagated by minicutting. Six progenies were used, of which were prepared cuttings with a pair of complete leaves. It was used a 55 cm(3)container filled with commercial substrate Bioplant (R). Four treatments were tested: 8 kg m-3 of superphosphate (SS) added to substrate; 4 kg m-3 SS added to substrate; 4 kg m-3 SS added to substrate and adition of a suspension solution containing rhizobium; 4 kg m-3 SS and suspension solution containing rhizobium plus 5 g of soil contaminated by AMF spores. There was no interaction among treatments for survival rate of cuttings and roots observed at bottom of the container, evaluated in the greenhouse exit (30 days) and the shade house exit (40 days), probably because the root system was still in formation. There were differences among the progeny for survival rate of the shoots, the percentage of cuttings with roots observed at bottom of the container, height, stem diameter and shoot dry weight. The evaluations of the growth characteristics of the cuttings in, particularly with respect to survival at full sun (140 days), demonstrate the efficiency of rhizobium and AMF on seedling production of this species. We conclude that the symbiotic association with rhizobium and / or FMA favors the production of seedlings of A. macrocarpa by minicutting.

New evidence for the symbiosis between Tuber aestivum and Picea abies

The Burgundy truffle (Tuber aestivum Vittad.), an ectomycorrhizal fungus living in association with host plants, is one of the most exclusive delicacies. The symbiosis with deciduous oak, beech, and hazel dominates our concept of truffle ecophysiology, whereas potential conifer hosts have rarely been reported. Here, we present morphological and molecular evidence of a wildlife T. aestivum symbiosis with Norway spruce (Picea abies Karst.) and an independent greenhouse inoculation experiment, to confirm our field observation in southwest Germany. A total of 27 out of 50 P. abies seedlings developed T. aestivum ectomycorrhizae with a mean mycorrhization rate of 19.6 %. These findings not only suggest P. abies to be a productive host species under suitable biogeographic conditions but also emphasize the broad ecological amplitude and great symbiotic range of T. aestivum. While challenging common knowledge, this study demonstrates a significant expansion of the species' cultivation potential to the central European regions, where P. abies forests occur on calcareous soils.

Evidence of species-specific neighborhood effects in the dipterocarpaceae of a Bornean rain forest

Although accumulating evidence indicates that local intraspecific density-dependent effects are not as rare in species-rich communities as previously suspected, there are still very few detailed and systematic neighborhood analyses of species-rich communities. Here, we provide such an analysis with the overall goal of quantifying the relative importance of inter- and intraspecific interaction strength in a primary, lowland dipterocarp forest located at Danum, Sabah, Malaysia. Using data on 10 abundant overstory dipterocarp species from two 4-ha permanent plots, we evaluated the effects of neighbors on the absolute growth rate of focal trees (from 1986 to 1996) over increasing neighborhood radii (from 1 to 20 m) with multiple regressions. Only trees 10 cm to < 100 cm girth at breast height in 1986 were considered as focal trees. Among neighborhood models with one neighbor term, models including only conspecific larger trees performed best in five out of 10 species. Negative effects of conspecific larger neighbors were most apparent in large overstory species such as those of the genus Shorea. However, neighborhood models with separate terms and radii for heterospecific and conspecific neighbors accounted for more variability in absolute growth rates than did neighborhood models with one neighbor term. The conspecific term was significant for nine out of 10 species. Moreover, in five out of 10 species, trees without conspecific neighbors had significantly higher absolute growth rates than trees with conspecific neighbors. Averaged over the 10 species, trees without conspecific neighbors grew 32.4 cm(2) in basal area from 1986 to 1996, whereas trees with conspecific neighbors only grew 14.7 cm(2) in basal area, although there was no difference in initial basal area between trees in the two groups. Averaged across the six species of the genus Shorea, negative effects of conspecific larger trees were significantly stronger than for heterospecific larger neighbors. Thus, high local densities within neighborhoods of 20 m may lead to strong intraspecific negative and, hence, density-dependent, effects even in species rich communities with low overall densities at larger spatial scales. We conjecture that the strength of conspecific effects may be correlated with the degree of host specificity of ectomycorrhizae.

Carbohydrate and Amino Acid Metabolism in the Eucalyptus globulus-Pisolithus tinctorius Ectomycorrhiza during Glucose Utilization1

The metabolism of [1-13C]glucose in Pisolithus tinctorius cv Coker & Couch, in uninoculated seedlings of Eucalyptus globulus bicostata ex Maiden cv Kirkp., and in the E. globulus-P. tinctorius ectomycorrhiza was studied using nuclear magnetic resonance spectroscopy. In roots of uninoculated seedlings, the 13C label was mainly incorporated into sucrose and glutamine. The ratio (13C3 + 13C2)/13C4 of glutamine was approximately 1.0 during the time-course experiment, indicating equivalent contributions of phosphoenolpyruvate carboxylase and pyruvate dehydrogenase to the production of α-ketoglutarate used for synthesis of this amino acid. In free-living P. tinctorius, most of the 13C label was incorporated into mannitol, trehalose, glutamine, and alanine, whereas arabitol, erythritol, and glutamate were weakly labeled. Amino acid biosynthesis was an important sink of assimilated 13C (43%), and anaplerotic CO2 fixation contributed 42% of the C flux entering the Krebs cycle. In ectomycorrhizae, sucrose accumulation was decreased in the colonized roots compared with uninoculated control plants, whereas 13C incorporation into arabitol and erythritol was nearly 4-fold higher in the symbiotic mycelium than in the free-living fungus. It appears that fungal utilization of glucose in the symbiotic state is altered and oriented toward the synthesis of short-chain polyols.

Nitrogen transfer within and between plants through common mycorrhizal networks (CMNs)

Mycorthizae play a critical role in nutrient capture from soils. Arbuscular mycorrhizae (AM) and ectomycorrhizae (EM) are the most important mycorrhizae in agricultural and natural ecosystems. AM and EM fungi use inorganic NH4+ and NO3-, and most EM fungi are capable of using organic nitrogen. The heavier stable isotope N-15 is discriminated against during biogeochemical and biochemical processes. Differences in N-15 (atom%) or delta(15)N (parts per thousand) provide nitrogen movement information in an experimental system. A range of 20 to 50% of one-way N-transfer has been observed from legumes to nonlegumes. Mycorrhizal fungal mycelia can extend from one plant's roots to another plant's roots to form common mycorrhizal networks (CMNs). Individual species, genera, even families of plants can be interconnected by CMNs. They are capable of facilitating nutrient uptake and flux. Nutrients such as carbon, nitrogen and phosphorus and other elements may then move via either AM or EM networks from plant to plant. Both N-15 labeling and N-15 natural abundance techniques have been employed to trace N movement between plants interconnected by AM or EM networks. Fine mesh (25similar to45 mum) has been used to separate root systems and allow only hyphal penetration and linkages but no root contact between plants. In many studies, nitrogen from N-2-fixing mycorrhizal plants transferred to non-N-2-fixing mycorrhizal plants (one-way N-transfer). In a few studies, N is also transferred from non-N-2-fixing mycorrhizal plants to N-2-fixing mycorrhizal plants (two-way N-transfer). There is controversy about whether N-transfer is direct through CMNs, or indirect through the soil. The lack of convincing data underlines the need for creative, careful experimental manipulations. Nitrogen is crucial to productivity in most terrestrial ecosystems, and there are potential benefits of management in soil-plant systems to enhance N-transfer. Thus, two-way N-transfer warrants further investigation with many species and under field conditions.

Fungos ectomicorrízicos em áreas de Mata Atlântica do Nordeste do Brasil

Ectomycorrhizal associations are poorly known from tropical lowlands of South America. Recent field trips to the reserve Parque Estadual das Dunas in Natal, in Rio Grande do Norte state, Brazil, revealed a undocumented community of ectomycorrhizal fungi. This type of Mycorrhizal association is frequently in the north hemisphere in temperate and boreal forests. The aim of this work is to analyze the occurrence of ectotrophic areas in atlantic rainforest. Collections along and around the trails in the reserve revealed six genera of putatively ECM fungi which belong to the basidiomycete, Amanitaceae, Boletaceae, Russulaceae, Entolomataceae, and Sclerodermataceae family which are poorly documented in Brazil. Plants belonging to Myrtaceae, Polygonaceae, Leguminosae/Caesalpinioideae, Erythroxylaceae, Malphigiaceae, Bromeliaceae, Loganiaceae, Sapotaceae e Celastraceae were found living next to the species of fungi analized. Our results suggest that the area studied is an ectotrophic environment which shows high diversity of putatively ECM fungi and some plants probably host ECM. The tropical lands are a potential focus to study reinforced by the new records of Scleroderma in Brazil and Northwest of Brazil