Spatial distribution of sporocarps of stipitate hydnoid fungi and their belowground mycelium

Interest in stipitate hydnoid fungi of the genera Bankera, Hydnellum, Phellodon and Sarcodon has increased due to the decline in numbers of sporocarps in Europe. Conservation of these fungi is hindered by a lack of understanding of their basic ecology. In particular, a better understanding of their belowground ecology is required. Real-time PCR in conjunction with spatially explicit sampling was used to quantify the relationship between sporocarps and mycelium of Hydnellum peckii and Phellodon tomentosus . Species-specific DNA of the target species was quantified in 100 soil samples collected on a 360 × 360 cm grid at five locations where sporocarps were present. All sporocarps within the grid and up to 2 m around the grid were mapped. Sporocarp production did not occur over the whole extent of the belowground mycelium of these two species, and mycelium extended up to 330 cm away from the immediate site of sporocarp production. Spatial analyses using Kernel-smoothing and Moran's I correlograms showed that, with a single exception, there was no quantitative relationship between sporocarp distribution and the belowground abundance of mycelium. These findings have important implications for the conservation of this rare group of fungi.     

Progress towards implementing the Biodiversity Action Plan for stipitate hydnoid fungi in Scotland

Summary

Stipitate hydnoid (‘tooth’) fungi are considered to be threatened throughout much of central and northern Europe. In response to concern about the status of these fungi in the UK, a Biodiversity Action Plan has been developed for 14 species in this group. As a first step towards implementation of this plan, a number of surveys have been initiated, to determine the current status and distribution of hydnoid fungi. An overview of the results of these surveys is described. A series of distribution maps are presented, based on a compilation of early records and the results of a recent field survey in Scottish coniferous forests. The difficulties of interpreting early records are discussed, with particular reference to the taxonomie confusion that has surrounded this group of fungi. Although available data provide little evidence for decline of hydnoid fungi, a number of species display very restricted distributions within Scotland. The recent discovery of several species new to Britain emphasises the need for further field surveys to define the current status of these fungi with greater accuracy.     

Molecular monitoring of protected fungi: mycelium persistence in soil after timber harvest

The largely subterranean nature of the mycorrhizal fungal life form impedes efforts to monitor protected fungi and evaluate the effectiveness of mitigations in timber harvest areas. In this study we developed and tested a multiplex PCR system capable of detecting 14 listed Phaeocollybia species in soil. We then investigated the persistence of Phaeocollybia species at three sites in northwestern Oregon where Phaeocollybia attenuata and other Phaeocollybia sporocarps had been observed prior to timber harvest. The three sites had three different levels of protection for the fungi. One site was in a buffer zone next to a thinned area, one was within a thinned area, and one was in a clearcut area. The method was effective at detecting the target species in soil. We detected Phaeocollybia species in the soil at all sites, even in the clearcut after 12 yr, during which no sporocarps were observed.     

树木外生菌根菌与环境因子关系研究进展

土壤、气候和立地因子等环境因子影响树木外生菌根菌的种类及数量。本文通过查阅大量国内外文献 ,综述了外生菌根菌与土壤、季节气候及立地因子等环境因子的相互关系 ,探讨了环境因子对外生菌根菌的影响 ,揭示了外生菌根菌研究中所关注的环境因子问题。同时 ,提出了外生菌根菌与环境因子关系今后研究的主要内容与方向 ,旨在为森林生态系统的可持续经营和退化森林生态系统的恢复、改造等提供科学依据。     

The annual invasive plant Impatiens glandulifera reduces hyphal biomass of soil fungi in deciduous forests

Soil fungi play a crucial role in ecosystem functioning and there is increasing evidence that exotic plants invading forests can affect soil fungal communities. We examined potential effects of the invasive plant Impatiens glandulifera on hyphal biomass of ectomycorrhizal fungi, their genetic diversity and the diversity of other soil fungi in deciduous forests in Switzerland. We compared invaded patches with patches where I. glandulifera had been removed, by establishing pairs of 3-m long transect lines at the edge of seven areas of either type. Along the transects we assessed the length of ectomycorrhizal fungal hyphae using the ‘ingrowth mesh bag method’, and used terminal restriction fragment length polymorphism (T-RFLP) analysis to examine fungal genetic diversity. The invasive plant reduced fungal hyphal biomass by 30–80%: the reduction was largest in the centre of the patch. I. glandulifera did not alter fungal richness, but affected the composition of fungal communities. This is probably the result of a decrease of mycorrhizal fungi, coupled with an increase of saprotrophic fungi. Our findings demonstrate the adverse impacts of an annual invasive plant species on both fungal hyphal biomass and the composition of soil fungal communities. This may negatively affect forest nutrient and carbon cycling, soil stability and the functionality of the fungal community, with major consequences for forest ecosystem functioning.     

Influence of autoclaved saprotrophic fungal mycelia on proteolytic activity in ectomycorrhizal fungi

The production of proteolytic enzymes by several strains of ectomycorrhizal fungi i.e., Amanita muscaria (16-3), Laccaria laccata (9-12), L. laccata (9-1), Suillus bovinus (15-4), Suillus bovinus (15-3), Suillus luteus (14-7) on mycelia of Trichoderma harzianum, Trichoderma virens and Mucor hiemalis and sodium caseinate, yeast extract was evaluated. The strains of A. muscaria (16-3) and L. laccata (9-12) were characterized by the highest activity of the acidic and neutral proteases. Taking the mycelia of saprotrophic fungi into consideration, the mycelium of M. hiemalis was the best inductor for proteolytic activity. The examined ectomycorrhizal fungi exhibited higher activity of acidic proteases than neutral ones on the mycelia of saprotrophic fungi, which may imply the participation of acidic proteases in nutrition.     

Effect of Temperature,pH, and Media on the Mycelial Growth of Tuber koreanum

Members of the genus Tuber are ectomycorrhizal fungi; this genus includes more than 180 species worldwide. In the present study, the optimal pH, temperature, and medium suitable for the mycelial growth of the Korean truffle, Tuber koreanum, were determined. Mycelium of T. koreanum, isolated from fruiting bodies collected in Korea, was used to investigate the effects of these environmental factors. The results showed that malt extract agar and potato dextrose agar were the most suitable for the mycelial growth of T. koreanum when cultured at a pH of 6.0 at 25 °C for 30 days.     

Increasing abundance of soil fungi is a driver for 15N enrichment in soil profiles along a chronosequence undergoing isostatic rebound in northern Sweden

Soil organic material (SOM) is usually enriched in ¹⁵N in deeper soil layers. This has been explained by discrimination against the heavier isotope during decomposition or by the accumulation of ¹⁵N-enriched microbial biomass versus plant biomass in older SOM. In particular, ectomycorrhizal (EM) fungi have been suggested to accumulate in old SOM since this group is among the most ¹⁵N-enriched components of the microbial community. In the present study we investigated the microbial community in soil samples along a chronosequence (7,800 years) of sites undergoing isostatic rebound in northern Sweden. The composition of the microbial community was analyzed and related to the δ¹⁵N and δ¹³C isotope values of the SOM in soil profiles. A significant change in the composition of the microbial community was found during the first 2,000 years, and this was positively related to an increase in the δ¹⁵N values of the E and B horizons in the mineral soil. The proportion of fungal phospholipid fatty acids increased with time in the chronosequence and was positively related to the ¹⁵N enrichment of the SOM. The increase in δ¹³C in the SOM was much less than the increase in δ¹⁵N, and δ¹³C values in the mineral soil were only weakly related to soil age. The C:N ratio and the pH of the soil were important factors determining the composition of the microbial community. We suggest that the N being transported from the soil to aboveground tissue by EM fungi is a driver for ¹⁵N enrichment of soil profiles.     

Fertilization alters nitrogen isotopes and concentrations in ectomycorrhizal fungi and soil in pine forests

To assess how nitrogen (N) availability affected ectomycorrhizal functioning and to test a theoretical model of ectomycorrhizal ¹⁵N partitioning, we measured C/N and δ¹⁵N in soils and nine fungal taxa in two Swedish N addition experiments. Sporocarp C/N and soil C/N decreased with fertilization, implying that N uptake per unit fungal growth increased. The S horizon was more responsive than the F and H horizons to changes in N addition, with N turnover for these horizons of 24, 57, and 57 y, respectively. Fungal and soil δ¹⁵N patterns identified fungal N sources, with N acquisition primarily from the S, F, or H horizon for two, five, and two taxa, respectively. With increasing N availability, sporocarp ¹⁵N enrichment increased in five taxa, in agreement with our model of fungal-plant N partitioning. However, it decreased in Lactarius rufus and Russula aeruginea, perhaps indicating shifts towards greater inorganic N uptake in these two taxa. This may relate to the generally lower sensitivity of these taxa to N deposition compared to the Cortinarius and Suillus taxa that fit our model of ¹⁵N partitioning.     

Measuring external mycelia production of ectomycorrhizal fungi in the field: the soil matrix matters

Assessing mycorrhizal fungi production in field settings has been hindered by the inability to measure external mycelia. Recently, external mycelia production was measured in the field using a novel in-growth core technique with acid-washed sand as the in-growth matrix. Here, we tested the assumption that external mycelia production in acid-washed sand is representative of that in native soil. External mycelia production was estimated as the difference in fungal growth between closed (allowing only saprotrophic fungal production) and open (allowing mycorrhizal and saprotrophic fungal production) cores using a factorial design of soil matrices (acid-washed sand vs native) and fertilization treatments (control vs nitrogen (N)) in a longleaf pine (Pinus palustris) plantation. In native soils, the ectomycorrhizal to saprotrophic fungal biomass signal was strong and consistent facilitating the assessment of external mycelia production, which was 300% higher than corresponding rates in acid-washed sand and inversely correlated with soil N. These results demonstrate the efficacy and importance of using native soil as the in-growth matrix to measure ectomycorrhizal fungi external mycelia production in field settings.     

Interactions between extraradical ectomycorrhizal mycelia, microbes associated with the mycelia and growth rate of Norway spruce (Picea abies) clones

Despite their ecological relevance, field studies of the extraradical mycelia of ectomycorrhizal (ECM) fungi are rare. Here we examined in situ interactions between ECM mycelia and host vigour. Ectomycorrhizal mycelia were harvested with in-growth mesh bags buried under Norway spruce (Picea abies) clones planted in 1994 in a randomized block design. Mycelial biomass was determined and fungal species were identified by denaturing gradient gel electrophoresis (DGGE) and sequencing of the internal transcribed spacer 1 (ITS1) region. Microbial community structure in the mycelium was investigated by phospholipid fatty acid (PLFA) profiling. Compared to slow-growing spruce clones, fast-growing clones tended to support denser mycelia where the relative proportions of Atheliaceae fungi and PLFAs indicative of Gram-positive bacteria were higher. Ascomycetes and PLFAs representative of Gram-negative bacteria were more common with slow-growing clones. In general, the ECM mycelial community was similar to the ECM root-tip community. Growth rate of the hosts, the ECM mycelial community and the microbes associated with the mycelium were related, suggesting multitrophic interactions between trees, fungi and bacteria.     

Ultrastructural and cytochemical aspects of the interaction between the ectomycorrhizal fungus Laccaria laccata and the saprotrophic fungi, Trichoderma harzianum and T. virens

Different interactions between soil fungi competing in the rhizosphere with each other are necessary to understand their influence on plant growth and health. The interactions between the ectomycorrhizal (ECM) fungus Laccaria laccata and soil saprotrophic fungi (T. harzianum, T. virens) were studied by transmission electron microscopy, and by gold cytochemistry to assess the potential role of cell wall lytic enzymes in mycoparasitism. Anti-β-1,3-glucan antibody, WGA/ovomucoid-gold complex and PATAg test were used to localize β-1,3-glucan, chitin and polysaccharides. Cytoplasm disorganisation of the saprotrophic fungi occurred concurrently with dissolution of β-1,3-glucan in walls of hyphae and conidia of the saprotrophic fungi. Then digestion of polysaccharides and chitin of colonised fungal structures occurred. The studies suggest sequential contribution of cell wall lytic enzymes and importance of disturbing the host's cell integrity during mycoparasitism. We conclude that the ECM fungus can parasitise on the saprotrophic fungi not only in dual culture on artificial medium but also in the rhizosphere of Scots pine.     

Climate-induced long-term changes in the phenology of Mediterranean fungi

Long-term responses in the phenology of Mediterranean macrofungi to climatic changes are poorly documented. Here, we address this issue by comparing the fruiting patterns of 159 fungal species in Southern France between the first half of the 19th century and the first decade of the 21st century. We used a trait-based approach to assess the influence of phenology and morphology of fungal fruit bodies and their site ecology and biogeography on the response to climate change. We show that early autumnal fruiters, epigeous species and species with affinities for cold climates now start to fruit on average 16.4, 17.3 and 17.3 d later compared to their emergence dates in the 19th century, while late fruiters, hypogeous species and Mediterranean-restricted species did not change their fruiting date. Among ecological guilds, saproxylic species and pine-associated mutualists delayed their autumnal emergence by 32.5 and 19.2 d, likely in response to a delayed rewetting of litter and woody debris after extended summer drought. Our results suggest that long-term climate warming in the Mediterranean was accompanied by contrasting changes in the emergence of fungal fruit bodies according to ecological guilds, sporocarp life-forms and forest types.     

Localisation of phosphomonoesterase activity in ectomycorrhizal fungi grown on different phosphorus sources

Phosphorus (P) is a major limiting nutrient for plants in boreal forest ecosystems where a substantial part of the total P is sequestered in organic compounds. Some ectomycorrhizal (ECM) fungi are known to produce phosphomonoesterases, enzymes that degrade organic P sources. Here, we test 16 ECM species for this enzymatic activity by growing them on media containing orthophosphate, phytic acid or apatite. A method with an overlay gel that determined both phosphomonoesterase activity and its spatial distribution was developed. The phosphomonoesterase activity was not significantly higher when growing on organic P; conversely some isolates only produced measurable enzyme activity when grown on apatite. Species-specific variations with respect to phosphomonoesterase activity as well as growth responses to different substrates were found. The production of phosphomonoesterases was found to be widespread in ECM fungi and the enzyme activity did not need induction by organic P. The enzyme activity was highest in the central parts of the mycelia, potentially reflecting breakdown and recycling of phospholipids from old hyphae or potentially higher mycelial density.