Edible sporocarp production by age class in a Scots pine stand in Northern Spain

With the aim of increasing knowledge of community structure, dynamics and production of ectomycorrhizal fungi, edible sporocarp yields were monitored between 1995 and 2004 in a Pinus sylvestris stand in the northeast zone of the Iberian Peninsula. A random sampling design was performed by stand age class according to the forest management plan: 0–15, 16–30, 31–50, 51–70 and over 71-years-old. Eighteen 150 m plots were established and sampled weekly every year from September to December. One hundred and nineteen taxa belonging to 51 genera were collected, 40 of which were edible and represented 74% of the total biomass. Boletus edulis, Lactarius deliciosus, Cantharellus cibarius and Tricholoma portentosum sporocarps, which are considered to be of high commercial value, represented 34% of the total production. B. edulis and L. deliciosus were the most remarkable and abundant species, and both were collected in more than 60% of the samplings. B. edulis fructified every year of the experiment; its mean production was 40 kg/ha and year and its maximum productivity was more than 94 kg/ha in 1998. The age class with the largest production of this taxa was the fourth (51–70 years), with 70 kg/ha. L. deliciosus only failed to fructify one autumn (2000); its mean production was almost 10 kg/ha and its maximum productivity close to 30 kg/ha in 1997. The maximum productivity of this species was found in the second (16–30 years) and fifth (71–90 years) stand age classes, with 18 and 16 kg/ha, respectively. Advances in this field can certainly offer new insights into factors affecting sporocarp production.     

Transfer of <Superscript>14</Superscript>C-photosynthate to the sporocarp of an ectomycorrhizal fungus <Emphasis Type="Italic">Laccaria amethystina</Emphasis>

Sporocarps of ectomycorrhizal fungi are strong carbon sinks for the source in host trees, but the details of carbon transfer from the host to the sporocarp are unknown. In this study, single seedlings of Japanese red pine (Pinus densiflora) colonised by Laccaria amethystina were grown on floral foam plates fitted in rhizoboxes, resulting in fruiting on the substrate. The seedlings were photosynthetically labelled with ¹⁴CO₂; ¹⁴C-labelled photosynthate transfer from leaves to sporocarps was then chased using a time-course autoradiography technique. ¹⁴C was transferred to healthy, fresh sporocarps in a purple colour ranging from primordial to elongate sporocarps, but hardly to senesced ones that had faded to white or grey, or browned. This suggested that C is transferred only to physiologically active sporocarps. Two seedlings associated with a growing sporocarp were labelled again 7 and 16 days after the first labelling, respectively. ¹⁴C accumulation in the sporocarps rose in a stepwise manner after the second labelling, indicating that sporocarps mainly used recently rather than previously photosynthesised C.     

Intraspecific variability of Lactarius deliciosus isolates: colonization ability and survival after cold storage

Intraspecific variability in root colonization, extraradical growth pattern, and survival after cold storage of Lactarius deliciosus isolates was determined in pure culture conditions using Pinus pinaster as a host plant. The ectomycorrhizal ability of L. deliciosus at 30, 45, and 60 days from inoculation was highly variable among isolates and was negatively correlated to the age of the culture (time elapsed from isolation). The formation of rhizomorphs was related to colonization ability, but no relationship was found between colonization and formation of extraradical mycelium. The final colonization achieved at 60 days from inoculation was not related to the tree species under which the sporocarps were collected. However, isolates from sporocarps collected under P. pinaster colonized more rapidly the seedlings than those collected under other pine species. The climatic range of the sporocarps from which the isolates were obtained (maritime vs. continental) was not related to the formation of mycorrhizas at 60 days from inoculation. However, isolates from sporocarps collected from a maritime climate area colonized more rapidly the P. pinaster seedlings than those collected from a continental zone. Tolerance to cold water storage of L. deliciosus was also isolate dependent. Growth revival in agar was obtained from most of the isolates after 28 months of cold storage at 4°C, but only 10 out of 29 isolates showed unaffected growth. The ITS rDNA alignment of all the L. deliciosus isolates showed a low variability with identities over 99%. Most of the variation was detected in the ITS1 region and consisted in single nucleotide changes and/or punctual indel mutations. The number of base differences per sequence from averaging over all sequence pairs was 1.329, which is in the low range when compared with other ectomycorrhizal species. No ITS pattern due to geographical origin of the isolates could be discerned.     

Quantification of extraradical soil mycelium and ectomycorrhizas of Boletus edulis in a Scots pine forest with variable sporocarp productivity

The availability of most edible ectomycorrhizal mushrooms depends on their natural fructification. Sporocarp formation of these fungi is linked to habitat characteristics and climate conditions, but these data alone do not explain all the trends of fungal fruiting and dynamics. It could be hypothesized that the amount of soil mycelia could also be related to the production of carpophores. Soil samples (five cylinders of 250 cm³ per plot) were taken monthly, from September to November, in five fenced permanent plots (5 × 5 m) in Pinar Grande (Soria, Spain), a Pinus sylvestris stand situated in the north of the Sistema Ibérico mountain range. Plots were chosen to establish a gradient of Boletus edulis productivity from 0 to 38.5 kg/ha year, according to the mean fresh weight of sporocarps collected during the last 10 years. B. edulis ectomycorrhizal root tips were identified in each soil sample according to its morphology and counted. DNA extractions were performed with the PowerSoil^TM DNA Isolation Kit and quantification of extraradical soil mycelium by real-time polymerase chain reaction using specific primers and a TaqMan? probe. The concentration of soil mycelium of B. edulis (mg mycelium/g soil) did not differ significantly between plots (p = 0.1397), and sampling time (p = 0.7643) within the fructification period. The number of mycorrhizal short roots per soil volume showed significant differences between the plots (p = 0.0050) and the three sampling times (p < 0.0001). No significant correlation between the number of mycorrhizas and the productivity of the plot (kg of B. edulis/ha year) was detected (p = 0.615). A statistically significant positive correlation (p = 0.0481) was detected between the concentration of mycelia of B. edulis in the soil samples and the presence of short roots mycorrhizal with B. edulis in these samples. The productivity of the plots, in terms of sporocarps produced during the last 10 years, was not correlated either with the concentration of soil mycelium or with the presence or abundance of ectomycorrhizas.     

Effects of manipulation of litter and humus layers on ectomycorrhizal colonization potential in Scots pine stands of different age

Effects of manipulation of litter and humus layers (removal, doubling and control treatments) on the colonization potential of ectomycorrhizal fungi were studied in two secondary stands of Pinus sylvestris (5 and 18 years old) in The Netherlands. Five-mont-hold, sterile-grown Scots pine seedlings, inoculated with Laccaria bicolor, Paxillus involutus or Rhizopogon luteolus and noninoculated seedlings were used as baits. The seedlings were harvested after one growing season. For comparison, sporocarps of ectomycorrhizal fungi were also investigated. Genus composition on the seedlings was independent of initial inoculum, but determined by both treatment and age of the stands. In both stands, removal of litter and humus layers increased, and addition of organic material decreased the number of ectomycorrhizal types on the seedlings. Not all indigenous genera were observed by either outplanting seedlings or sporocarp surveys.     

Seasonal dynamics of Boletus edulis and Lactarius deliciosus extraradical mycelium in pine forests of central Spain

The annual belowground dynamics of extraradical soil mycelium and sporocarp production of two ectomycorrhizal fungi, Boletus edulis and Lactarius deliciosus, have been studied in two different pine forests (Pinar Grande and Pinares Llanos, respectively) in Soria (central Spain). Soil samples (five per plot) were taken monthly (from September 2009 to August 2010 in Pinar Grande and from September 2010 to September 2011 in Pinares Llanos) in eight permanent plots (four for each site). B. edulis and L. deliciosus extraradical soil mycelium was quantified by real-time polymerase chain reaction, with DNA extracted from soil samples, using specific primers and TaqMan® probes. The quantities of B. edulis soil mycelium did not differ significantly between plots, but there was a significant difference over time with a maximum in February (0.1576 mg mycelium/g soil) and a minimum in October (0.0170 mg mycelium/g soil). For L. deliciosus, significant differences were detected between plots and over time. The highest amount of mycelium was found in December (1.84 mg mycelium/g soil) and the minimum in February (0.0332 mg mycelium/g soil). B. edulis mycelium quantities were positively correlated with precipitation of the current month and negatively correlated with the mean temperature of the previous month. Mycelium biomass of L. deliciosus was positively correlated with relative humidity and negatively correlated with mean temperature and radiation. No significant correlation between productivity of the plots with the soil mycelium biomass was observed for any of the two species. No correlations were found between B. edulis sporocarp production and weather parameters. Sporocarp production of L. deliciosus was positively correlated with precipitation and relative humidity and negatively correlated with maximum and minimum temperatures. Both species have similar distribution over time, presenting an annual dynamics characterized by a seasonal variability, with a clear increase on the amounts of biomass during the coldest months of the year. Soil mycelial dynamics of both species are strongly dependent on the weather.     

Age class influence on the yield of edible fungi in a managed Mediterranean forest

Lack of information and difficulty in predicting wild edible sporocarp yields is blocking its integration in forest management. In the Mediterranean area, this nontimber forest product has increased its market value, consumption demand, and interest over the last decade. In this work, sampling year and stand age effects are analyzed in order to advance knowledge of edible fungi community structure, dynamics, and production. Weekly autumnal sporocarp monitoring was performed from 1997 to 2011 in a Pinus pinaster managed forest in central Spain. After applying a random stand age-stratified survey, 21 plots of 150 m² have been set with three per stand age class. The forest age classes have been defined as follows: 0–10 years, mixture of parent and regenerated trees, 11–20, 21–40, 41–60, 61–90, and over 90 years. A total of 153 species belonging to 56 genera were recorded, 55 of which are edible. The production of edible sporocarps was 19.8 kg ha^?1, representing 31 % of total production. Sporocarp production presents a sharp interannual variability with autumns 62 times more productive than others. The most abundant edible species in terms of fresh weight per hectare has been Lactarius deliciosus with 7.0 kg ha^?1. Edible fungi yields registered a significant decline in 10 years following regenerative cutting. The presence of parent trees significantly increases production with regard to the first class. The highest production of edible species occurs in the middle age, 41–60 years, and in the following classes, a decrease is produced. L. deliciosus production registered differences with age, manifesting in a high yield in young stands (11–20 years) and significant recovery in woodlands near to the cutting.     

Biomass and nutrient concentrations of sporocarps produced by mycorrhizal and decomposer fungi in Abies amabilis stands

Summary Sporocarps and sclerotia were collected for a one-year period in 23- and 180-year-old Abies amabilis stands in western Washington. All sporocarps were classified and chemically analyzed for N, P, K, Ca, Mg, Na and Fe. Lactarius sp. and Cortinarius sp. contributed the largest proportion of the total annual epigeous sporocarp production in both stands. Annual epigeous production was 34 kg/ha in the young stand and 27 kg/ha in the mature stand. Hypogeous sporocarp production increased from 1 kg ha^-1 yr^-1 to 380 kg ha^-1 yr^-1 with increasing stand age. High sclerotia biomass occurred in the young (2,300 kg/ha) and mature (3,000 kg/ha) stands. Peak sclerotia and epigeous sporocarp biomass in the young stand and epigeous and hypogeous sporocarp biomass in the mature stand coincided with the fall peak of mycorrhizal root biomass.In the young stand, sporocarps produced by decomposer fungi concentrated higher levels of Ca and Mn than those produced by mycorrhizal fungi. In the mature stand, sporocarps of decomposer fungi concentrated higher levels of N, P, Mn, Ca and Fe than sporocarps of mycorrhizal fungi. Epigeous and hypogeous sporocarps concentrated higher levels of N, P, and K than sclerotia or mycelium. The highest concentration of N (4.36%), P (0.76%), K (3.22%) and Na (1,678 ppm) occurred in epigeous sporocarps. Highest Mn (740 ppm) and Ca (20,600 ppm) concentrations occurred in mycelium, while highest Mg (1,929 ppm) concentrations were in hypogeous sporocarps and highest Fe (4,153 ppm) concentrations were in sclerotia.     

Effect of forest fire prevention treatments on bacterial communities associated with productive Boletus edulis sites

Cistus ladanifer scrublands, traditionally considered as unproductive, have nonetheless been observed to produce large quantities of king bolete (Boletus edulis) fruitbodies. These pyrophytic scrublands are prone to wildfires, which severely affect fungi, hence the need for fire prevention in producing C. ladanifer scrublands. In addition, B. edulis productions have severely decreased in the last years. A deeper understanding of the B. edulis life cycle and of biotic and abiotic factors influencing sporocarp formation is needed to implement management practices that facilitate B. edulis production. For example, some bacteria likely are involved in sporocarp production, representing a key part in the triple symbiosis (plant–fungus–bacteria). In this study, we used soil DNA metabarcoding in C. ladanifer scrublands to (i) assess the effect of site history and fire prevention treatment on bacterial richness and community composition; (ii) test if there was any correlation between various taxonomic groups of bacteria and mycelial biomass and sporocarp production of B. edulis; and to (iii) identify indicator bacteria associated with the most productive B. edulis sites. Our results show that site history drives bacterial richness and community composition, while fire prevention treatments have a weaker, but still detectable effect, particularly in the senescent plots. Sporocarp production correlated positively with genera in Verrucomicrobia. Several genera, e.g. Azospirillum and Gemmatimonas, were identified as indicators of the most productive sites, suggesting a potential biological role in B. edulis fructification. This study provides a better understanding of the triple symbiosis (plant–fungus–bacteria) involved in C. ladanifer–B. edulis systems.     

Molecular approaches to ectomycorrhizal diversity studies: variation in ITS at a local scale

In most ectomycorrhizal (EM) community studies involving molecular identification methods there is a poor correspondence between fungi that appear dominant as sporocarps and those that appear dominant on EM roots and the species richness belowground is higher than that above ground. As a consequence, many fungi from root tip samples remain unidentified. In most studies, genetic data from multiple samples of an EM morphotype collected from various sampling locations are compared to genetic data from one to a few sporocarps of each species for identification purposes. The mismatch between above- and belowground species richness may be influenced by these different sampling efforts. To address this, intra-specific variation in the ITS region first investigated in Kårén et al. (1997) is revisited here, but at a spatial scale in which variation is expected to be low. Sporocarps were collected across a 7 km region of the Oregon Dunes National Recreation Area in western North America. ITS–RFLP data are presented for 3-18 sporocarps from each of 44 EM species in 18 genera. A total of 311 sporocarps were analyzed. Fifty-three ITS–RFLP types were observed. Of the 44 species, 38 (86% of total) yielded a single, species specific, RFLP type. No 2 species had the same RFLP type. Polymorphic ITS–RFLP types were observed in six species (14%). The following three species had two ITS-RFLP types with one type dominating: Inocybe lacera, Laccaria proxima, and Rhizopogon subcaerulescens. The following three species had three RFLP types with no type dominating: Laccaria laccata, Lactarius deliciosus, and Tricholoma flavovirens. A phylogenetic analysis of ITS sequences in Tricholoma revealed that two of the RFLP types in T. flavovirenswere apparently the result of intra-specific variation, while the third RFLP type was likely a cryptic species. All the other RFLP types observed in Tricholoma represented unique phylogenetic species. These results suggest that ITS–RFLP data from single samples (sporocarp or EM) are robust for characterizing most of the species at this scale. However, restriction endonucleases detect a limited amount of existing nucleotide variation and thus have limited value to detect cryptic species. Therefore, additional analyses of sequence data should be added to the RFLP matching technique to identify unknown RFLP types. These data also suggest that polymorphic RFLP types within species do not adequately explain the mismatch between above- and belowground views of EM species richness.     

TRIASSIC FUNGUS FROM ANTARCTICA WITH POSSIBLE ASCOMYCETOUS AFFINITIES

Hyphae, sporocarps, and structures which appear to represent arthroconidia are described from silicified peat deposits of Triassic age from Antarctica. Sporocarps with a single ostiole possess a multilayered wall with internally produced aseptate appendages that ornament the sporocarp surface. The primitive features exhibited by this fungus, together with previously described sporocarps, provide evidence for the existence of a group of fungi that may be ancestral to modern Ascomycotina.     

Ectomycorrhizal fungi are shared between seedlings and adults in a monodominant Gilbertiodendron dewevrei rain forest in Cameroon

Ectomycorrhizal networks may facilitate the establishment and survival of seedlings regenerating under the canopies of tropical forests and are often invoked as a potential contributor to monodominance. We identified ectomycorrhizal fungi in a monodominant Gilbertiodendron dewevrei (Fabaceae) rain forest in Cameroon, using sporocarps and ectomycorrhizae of three age categories (seedlings, intermediate trees, and large trees) and tentatively revealed nutrient transfer through ectomycorrhizal networks by measuring spontaneous isotopic (¹³C and ¹⁵N) abundances in seedlings. Sporocarp surveys revealed fewer ectomycorrhizal fungal taxa (59 species from 1030 sporocarps) than molecular barcoding of ectomycorrhizal roots (75 operational taxonomic units from 828 ectomycorrhizae). Our observations suggest that ectomycorrhizal fungal diversity is similar to that in other mixed tropical forests and provide the first report of the Tuber‐Helvella lineage in a tropical forest. Despite some differences, all age categories of G. dewevrei had overlapping ectomycorrhizal fungal communities, with families belonging to Thelephoraceae, Russulaceae, Sebacinaceae, Boletaceae, and Clavulinaceae. Of the 49 operational taxonomic units shared by the three age categories (65.3% of the ectomycorrhizal fungal community), 19 were the most abundant on root tips of all categories (38.7% of the shared taxa), supporting the likelihood of ectomycorrhizal networks. However, we obtained no evidence for nutrient transfer from trees to seedlings. We discuss the composition of the ectomycorrhizal fungal community among the G. dewevrei age categories and the possible role of common ectomycorrhizal networks in this rain forest.     

Six newly developed microsatellite markers of <Emphasis Type="Italic">Laccaria amethystina</Emphasis>, using an improved CSSR approach

Microsatellite markers were established by an improved combined simple sequence repeat (CSSR) approach for the ectomycorrhizal basidiomycete Laccaria amethystina. Six markers delivered codominant polymorphic results, with up to six different alleles. They were tested with DNA originating from sporocarps and ectomycorrhizal root tips from silver fir (Abies alba), collected in the northern Black Forest. Sporocarps and ectoymcorrhizae exhibited similar allelic profiles, without any distorting influence of the host tree species. Results were compared to allelic profiles delivered by three published Asian markers. Allelic frequencies of the new markers showed a higher resolution of individuals within the population community, but partially a lower grade of heterozygosity. Possible reasons are discussed, and further questions addressed.     

Dosage and duration effects of nitrogen additions on ectomycorrhizal sporocarp production and functioning: an example from two N‐limited boreal forests

1. Although it is well known that nitrogen (N) additions strongly affect ectomycorrhizal (EM) fungal community composition, less is known about how different N application rates and duration of N additions affect the functional role EM fungi play in the forest N cycle.
2. We measured EM sporocarp abundance and species richness as well as determined the δ¹⁵N in EM sporocarps and tree foliage in two Pinus sylvestris forests characterized by short- and long-term N addition histories and multiple N addition treatments. After 20 and 39 years of N additions, two of the long-term N addition treatments were terminated, thereby providing a unique opportunity to examine the temporal recovery of EM sporocarps after cessation of high N loading.
3. In general, increasing N availability significantly reduced EM sporocarp production, species richness, and the amount of N retained in EM sporocarps. However, these general responses were strongly dependent on the application rate and duration of N additions. The annual addition of 20 kg·N·ha⁻¹ for the past 6 years resulted in a slight increase in the production and retention of N in EM sporocarps, whereas the addition of 100 kg·N·ha⁻¹·yr⁻¹ during the same period nearly eliminated EM sporocarps. In contrast, long-term additions of N at rates of ca. 35 or 70 kg·N·ha⁻¹·yr⁻¹ for the past 40 years did not eliminate tree carbon allocation to EM sporocarps, although there was a decrease in the abundance and a shift in the dominant EM sporocarp taxa. Despite no immediate recovery, EM sporocarp abundance and species richness approached those of the control 20 years after terminating N additions in the most heavily fertilized treatment, suggesting a recovery of carbon allocation to EM sporocarps after cessation of high N loading.
4. Our results provide evidence for a tight coupling between tree carbon allocation to and N retention in EM sporocarps and moreover highlight the potential use of δ¹⁵N in EM sporocarps as a relative index of EM fungal sink strength for N. However, nitrogen additions at high dosage rates or over long time periods appear to disrupt this feedback, which could have important ramifications on carbon and nitrogen dynamics in these forested ecosystems.

     

Ecophysiology of ectomycorrhizal fungi associated with Pinus spp. in low rainfall areas of Western Australia

As a potential means of monitoring functional properties of plantations of Pinus pinaster and Pinus radiata established as part of land rehabilitation in the wheatbelt of Western Australia, we examined aspects of the ecophysiology of ectomycorrhizal fungi associated with tree roots. A single species of ectomycorrhizal fungi, Rhizopogon roseolus, dominated the mycorrhizal flora. Sporocarps of Rhizopogon roseolus appeared with the onset of winter rains in May, increased in number and total biomass to peak in September, and decreased to negligible levels at the beginning of the summer drought in December. A greater number of sporocarps, and consequently a greater biomass of sporocarp tissue, was associated with roots of P. radiata than P. pinaster. A similar seasonal pattern of mycorrhizal root infection was determined by counts of individual ectomycorrhizal root tips from bimonthly collection of soil core samples. At the low rainfall (380 mm annually) site, greater numbers of live root tips were more strongly correlated with soil moisture than organic matter content of soil. In contrast, in wetter areas closer to Perth (800 mm annually), highest numbers of active root tips and greatest amounts of organic matter were both within 0–10 cm depths. Results suggest an overriding importance of soil moisture rather than nutrient status of the soil as the key determinant of spatial and temporal distribution of the fungus. Results from a range of assays determining enzyme activity of soil (protease, phosphomonoesterase, cellulase, L-asparaginase, L-glutaminase and β-glucosidase) surrounding mycorrhizal roots indicated seasonal patterns to be similar to those described for reproductive activity of mycorrhizal fungi. Factors responsible for patterns of seasonal activity and distribution of ectomycorrhizal roots are discussed in terms of managing systems in order to maximise tree growth and form while effectively restoring soil water balance.     

Abundance and utilization of Pyrenacantha sylvestris in Budongo Forest Reserve,western Uganda

Pyrenacantha sylvestris S. Moore (Icacinaceae), locally known as Kateganende, has been extensively harvested by local people yet poorly managed. This has created a gap between its utilization and conservation. A study was therefore conducted to document its abundance and utilization in Budongo Forest Reserve. Abundance was assessed in ten systematically sampled plots of 20 × 50 m. Five of the plots were established in logged forest (compartment N2) and the other five in the nature reserve (compartment N15). Individual P. sylvestris and trellises were recorded and their respective diameter at breast height measured. Questionnaires designed to capture information on the utilization of P. sylvestris were administered to 40 systematically selected respondents adjacent to the forest reserve. Abundance was highest in logged areas of the forest (χ² = 14.8, d.f. = 4, P < 0.01). Individuals in the diameter class 0.1–0.5 cm were the most abundant. Pyrenacantha sylvestris in the forest were mostly hosted in the trellises of the diameter class 1.0–10 cm. Over‐reliance and use of P. sylvestris threaten the survival of the species. There is a need to create awareness and regulate its harvesting. In addition, research needs to be conducted on the possibility of propagating and domesticating this plant.     

Improving the Production of Ectomycorrhizal Fungus Mycelium in a Bioreactor by Measuring the Ergosterol Content

The cultivation of some ectomycorrhizal fungi growing in bioreactors under submerged aerobic conditions was modified by regulating the cultivation parameters and determining the optimum duration of the process. For this goal, the active mycelium was determined by quantifying its ergosterol content. Lactarius deliciosus (strain LDF5) and Suillus mediterraneensis (strain 35 AM) were cultivated in a BRAUN Biostat^®B bioreactor under the following fermentation conditions: 23 °C, pH 5.5, 60’% dissolved oxygen, 100 rpm stirring, and 1.2‐‐2 L/min air flow. In addition, several cultivation conditions were assayed for L. deliciosus. During the fermentation cycle, samples were taken at different times. Ergosterol was extracted and quantified using high‐performance liquid chromatography (HPLC). The quantity of ergosterol in L. deliciosus increased with the age of the culture up to 4.7 μg/mg (17‐day‐old culture). In the case of S. mediterraneensis, this quantity increased up to day 11 of the cultivation, and then it decreased. Three days after the addition of fresh medium, a maximum of 8.9 μg/mg was reached. On the other hand, the highest ergosterol content in L. deliciosus (6.3 μg/mg) was obtained using MMN medium with the addition of agar.     

Contribution to the knowledge on macrofungi in mangroves of the southwest India

Forty-six species of macrofungi (27 genera) were recorded in 25 quadrats (625 m²) in five mangroves of the southwest India (Paduhithlu, Nadikudru, Sasihithlu, Thokottu and Batapady). A maximum of 20 species occurred in Sasihithlu with a highest diversity value. Four species belong to coregroup ( ≥ 10 sporocarps/quadrat), while 29 species were confined to specific mangrove (exclusive species). Out of 1591 sporocarps, Paduhithlu supported the highest number of sporocarps (564) followed by Nadikudru (502). Rarefaction curves showed a steep increase in the expected number of species against the number of sporocarps in Sasihithlu. Pearson correlation between biotic factors (species richness, sporocarp richness and species diversity) and edaphic factors (air and soil) was not significantly correlated. Woody litter supported the highest number of macrofungi (26 species) followed by soil (22 species) and least in leaf litter (7 species). Up to one-third of macrofungi recovered in mangroves are economically valuable (edible, medicinal and ectomycorrhizal).     

Population structure of Guyanagaster necrorhizus supports termite dispersal for this enigmatic fungus

Understanding how species accomplish dispersal of their propagules can shed light on how they are adapted for their ecosystem. Guyanagaster necrorhizus is a sequestrate fungus, meaning its dispersal propagules, or spores, are entirely enclosed within a fruiting body, termed a sporocarp. This fungus is most closely related to Armillaria and its allies. While Armillaria species form mushrooms and have forcibly discharged spores, G. necrorhizus spores have lost this ability, and by necessity, must be passively dispersed. However, G. necrorhizus does not possess characteristics of other sequestrate fungi with known dispersal mechanisms. Repeated observations of termites feeding on G. necrorhizus sporocarps, and spores subsequently adhering to their exoskeletons, led to the hypothesis that termites disperse G. necrorhizus spores. To test this hypothesis, we used microsatellite markers and population genetics analyses to understand patterns of clonality and population structure of G. necrorhizus. While Armillaria individuals can spread vegetatively over large areas, high genotypic diversity in G. necrorhizus populations suggests spores are the primary mode of dispersal. Spatial genetic structure analyses show that G. necrorhizus sporocarps within 238 m of each other are more closely related than would be expected by chance and conservative estimates from population assignment tests suggest gene flow no longer occurs between sporocarps separated by 2 km. These distances are consistent with previous studies analysing foraging distances of the termites found associated with G. necrorhizus sporocarps. Termites have rarely been recorded to specifically target fungal sporocarps, making this a potentially novel fungal–insect interaction.     

Effects of bacterial strains isolated from the ectomycorrhizal roots of Laccaria parva on sporocarp production by the fungus in vitro

The effects of bacteria isolated from ectomycorrhizas on sporocarp production of Laccaria parva were examined in vitro. Three bacterial strains of Bradyrhizobium were selected on the basis of their affinity for L. parva LL02 in previous confrontation tests: a positive or a negative strain that significantly increased or decreased hyphal extension areas, and a neutral strain that did not have significant effects on them. Mycelia of LL02 and a suspension of each bacterial strain were inoculated onto a surface-sterilized pine seedling in a glass bottle and then incubated for 3 mo in an illuminated incubator. Plant biomass did not differ significantly among the treatments, but the level of ectomycorrhizal colonization was low in the treatment inoculated with a negative strain (Neg treatment). The frequency with which mature sporocarps occurred was higher in treatments inoculated with positive (Pos treatment) or neutral strains (Neu treatment) compared with control and Neg treatments. The ratio of biomass accounted for by mature sporocarps was low in control and Neg treatments, and high in Pos and Neu treatments. These results indicate that bacteria colonizing ectomycorrhizas affect the production of sporocarps and that the affinity between fungi and bacteria is likely to underlie this interaction.