Ascomycetes associated with ectomycorrhizas: molecular diversity and ecology with particular reference to the Helotiales

Mycorrhizosphere microbes enhance functioning of the plant–soil interface, but little is known of their ecology. This study aims to characterize the ascomycete communities associated with ectomycorrhizas in two Tasmanian wet sclerophyll forests. We hypothesize that both the phyto‐ and mycobiont, mantle type, soil microbiotope and geographical distance affect the diversity and occurrence of the associated ascomycetes. Using the culture‐independent rDNA sequence analysis, we demonstrate a high diversity of these fungi on different hosts and habitats. Plant host has the strongest effect on the occurrence of the dominant species and community composition of ectomycorrhiza‐associated fungi. Root endophytes, soil saprobes, myco‐, phyto‐ and entomopathogens contribute to the ectomycorrhiza‐associated ascomycete community. Taxonomically these Ascomycota mostly belong to the orders Helotiales, Hypocreales, Chaetothyriales and Sordariales. Members of Helotiales from both Tasmania and the Northern Hemisphere are phylogenetically closely related to root endophytes and ericoid mycorrhizal fungi, suggesting their strong ecological and evolutionary links. Ectomycorrhizal mycobionts from Australia and the Northern Hemisphere are taxonomically unrelated to each other and phylogenetically distant to other helotialean root‐associated fungi, indicating independent evolution. The ubiquity and diversity of the secondary root‐associated fungi should be considered in studies of mycorrhizal communities to avoid overestimating the richness of true symbionts.     

Forest microsite effects on community composition of ectomycorrhizal fungi on seedlings of Picea abies and Betula pendula

Niche differentiation in soil horizons, host species and natural nutrient gradients contribute to the high diversity of ectomycorrhizal fungi in boreal forests. This study aims at documenting the diversity and community composition of ectomycorrhizal fungi of Norway spruce ( Picea abies ) and silver birch ( Betula pendula ) seedlings in five most abundant microsites in three Estonian old-growth forests. Undisturbed forest floor, windthrow mounds and pits harboured more species than brown- and white-rotted wood. Several species of ectomycorrhizal fungi were differentially represented on either hosts, microsites and sites. Generally, the most frequent species in dead wood were also common in forest floor soil. Ordination analyses suggested that decay type determined the composition of EcM fungal community in dead wood. Root connections with in-growing mature tree roots from below affected the occurrence of certain fungal species on seedling roots systems in dead wood. This study demonstrates that ectomycorrhizal fungi differentially establish in certain forest microsites that is attributable to their dispersal and competitive abilities. Elevated microsites, especially decayed wood, act as seed beds for both ectomycorrhizal forest trees and fungi, thus affecting the succession of boreal forest ecosystems.     

Sustaining productivity gains in the face of climate change: A research agenda for US wheat

Wheat is a globally important crop and one of the “big three” US field crops. But unlike the other two (maize and soybean), in the United States its development is commercially unattractive, and so its breeding takes place primarily in public universities. Troublingly, the incentive structures within these universities may be hindering genetic improvement just as climate change is complicating breeding efforts. “Business as usual” in the US public wheat-breeding infrastructure may not sustain productivity increases. To address this concern, we held a multidisciplinary conference in which researchers from 12 US (public) universities and one European university shared the current state of knowledge in their disciplines, aired concerns, and proposed initiatives that could facilitate maintaining genetic improvement of wheat in the face of climate change. We discovered that climate-change-oriented breeding efforts are currently considered too risky and/or costly for most university wheat breeders to undertake, leading to a relative lack of breeding efforts that focus on abiotic stressors such as drought and heat. We hypothesize that this risk/cost burden can be reduced through the development of appropriate germplasm, relevant screening mechanisms, consistent germplasm characterization, and innovative models predicting the performance of germplasm under projected future climate conditions. However, doing so will require coordinated, longer-term, inter-regional efforts to generate phenotype data, and the modification of incentive structures to consistently reward such efforts.     

Strong host preference of ectomycorrhizal fungi in a Tasmanian wet sclerophyll forest as revealed by DNA barcoding and taxon-specific primers

Ectomycorrhizal (ECM) symbiosis is a widespread plant nutrition strategy in Australia, especially in semiarid regions. This study aims to determine the diversity, community structure and host preference of ECM fungi in a Tasmanian wet sclerophyll forest. Ectomycorrhizal fungi were identified based on anatomotyping and rDNA internal transcribed spacer (ITS)-large subunit (LSU) sequence analysis using taxon-specific primers. Host tree roots were identified based on root morphology and length differences of the chloroplast trnL region. A total of 123 species of ECM fungi were recovered from root tips of Eucalyptus regnans (Myrtaceae), Pomaderris apetala (Rhamnaceae) and Nothofagus cunninghamii (Nothofagaceae). The frequency of two thirds of the most common ECM fungi from several lineages was significantly influenced by host species. The lineages of Cortinarius, Tomentella-Thelephora, Russula-Lactarius, Clavulina, Descolea and Laccaria prevailed in the total community and their species richness and relative abundance did not differ by host species. This study demonstrates that strongly host-preferring, though not directly specific, ECM fungi may dominate the below-ground community. Apart from the richness of Descolea, Tulasnella and Helotiales and the lack of Suillus-Rhizopogon and Amphinema-Tylospora, the ECM fungal diversity and phylogenetic community structure is similar to that in the Holarctic realm.     

Invasion potential and host shifts of Australian and African ectomycorrhizal fungi in mixed eucalypt plantations

? Transportation of forestry materials results in unintended co-introduction of nonnative species that may cause enormous ecological or economic damage. While the invasion ecology of plants and animals is relatively well-known, that of microorganisms, except aboveground pathogens, remains poorly understood. ? This work addresses host shifts and invasion potential of root symbiotic ectomycorrhizal fungi that were co-introduced with Australian eucalypts and planted in clear-cut miombo woodlands in Zambia, south-central Africa. ? By use of rDNA and plastid intron sequence analysis for identification and phylogenetic techniques for inferring fungal origin, we demonstrated that host shifts were uncommon in the Australian fungi, but frequent in the African fungi, especially in mixed plantations where roots of different trees intermingle. ? There was evidence for naturalization, but not for invasion by Australian ectomycorrhizal fungi. Nevertheless, the fungi introduced may pose an invasion risk along with further adaptation to local soil environment and host trees. Inoculation of eucalypts with native edible fungi may ameliorate the potential invasion risks of introduced fungi and provide an alternative source of nutrition.     

Tidying up international nucleotide sequence databases: ecological, geographical and sequence quality annotation of its sequences of mycorrhizal fungi

Sequence analysis of the ribosomal RNA operon, particularly the internal transcribed spacer (ITS) region, provides a powerful tool for identification of mycorrhizal fungi. The sequence data deposited in the International Nucleotide Sequence Databases (INSD) are, however, unfiltered for quality and are often poorly annotated with metadata. To detect chimeric and low-quality sequences and assign the ectomycorrhizal fungi to phylogenetic lineages, fungal ITS sequences were downloaded from INSD, aligned within family-level groups, and examined through phylogenetic analyses and BLAST searches. By combining the fungal sequence database UNITE and the annotation and search tool PlutoF, we also added metadata from the literature to these accessions. Altogether 35,632 sequences belonged to mycorrhizal fungi or originated from ericoid and orchid mycorrhizal roots. Of these sequences, 677 were considered chimeric and 2,174 of low read quality. Information detailing country of collection, geographical coordinates, interacting taxon and isolation source were supplemented to cover 78.0%, 33.0%, 41.7% and 96.4% of the sequences, respectively. These annotated sequences are publicly available via UNITE (http://unite.ut.ee/) for downstream biogeographic, ecological and taxonomic analyses. In European Nucleotide Archive (ENA; http://www.ebi.ac.uk/ena/), the annotated sequences have a special link-out to UNITE. We intend to expand the data annotation to additional genes and all taxonomic groups and functional guilds of fungi.     

Longer-Term Follow-Up of Kenyan Men Circumcised Using the ShangRing Device

Objectives

To ascertain clinical sequelae, client satisfaction and sexual behavior 2+ years after male circumcision using the ShangRing device.

Methods

We enrolled 199 men from the Kenya sites (Homa Bay district) participating in a 2012 study of the ShangRing device used in routine male circumcision services (N = 552). We enrolled men who had had the ShangRing placed successfully, and over-sampled men who had had an adverse event and/or were HIV-positive during the field study. In the present study, each participant was examined and interviewed by a study clinician, and penile photographs were taken to document longer-term cosmetic results and any abnormal findings.

Results

194 men were included in the analysis. The mean and median times between circumcision and the longer-term follow-up visit in this study were 31.8 and 32 months, respectively. Four men (2.1%) had signs/symptoms of a sexually transmitted infection (STI). Virtually all (99.5%) of the men were very satisfied with the appearance of their circumcised penis, and all would recommend a ShangRing circumcision to friends or family members. The most prevalent reported advantage of the circumcision was the ease of bathing and enhanced cleanliness of the penis (75.8%). 94.3% of the men did not cite a single negative feature of their circumcision. 87.5% of men reported more sexual pleasure post-MC, the most common reason being more prolonged intercourse. The majority of men (52.6%) reported one sexual partner post-MC, but more than a quarter of the men (28.1%) reported an increased number of partners post-MC. Less than half of the men (44.3%) reported using condoms half of the time or more, but the great majority of condom users stated that condom use was much easier post-MC, and 76.9% of users said they used condoms more after circumcision than before.

Conclusions

This study supports the safety and acceptability of ShangRing male circumcision during 2–3 years of follow-up. It should allay worries that the ShangRing procedure could lead to delayed complications later than the observation period of most clinical studies.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT01567436","term_id":"NCT01567436"}}NCT01567436     

Global sampling of plant roots expands the described molecular diversity of arbuscular mycorrhizal fungi

We aimed to enhance understanding of the molecular diversity of arbuscular mycorrhizal fungi (AMF) by building a new global dataset targeting previously unstudied geographical areas. In total, we sampled 96 plant species from 25 sites that encompassed all continents except Antarctica. AMF in plant roots were detected by sequencing the nuclear SSU rRNA gene fragment using either cloning followed by Sanger sequencing or 454-sequencing. A total of 204 AMF phylogroups (virtual taxa, VT) were recorded, increasing the described number of Glomeromycota VT from 308 to 341 globally. Novel VT were detected from 21 sites; three novel but nevertheless widespread VT (Glomus spp. MO-G52, MO-G53, MO-G57) were recorded from six continents. The largest increases in regional VT number were recorded in previously little-studied Oceania and in the boreal and polar climatic zones — this study providing the first molecular data from the latter. Ordination revealed differences in AM fungal communities between different continents and climatic zones, suggesting that both biogeographic history and environmental conditions underlie the global variation of those communities. Our results show that a considerable proportion of Glomeromycota diversity has been recorded in many regions, though further large increases in richness can be expected in remaining unstudied areas.