Agaricus subgenus Pseudochitonia in Malakand, Pakistan: An updated phylogeny and description of three new species.

Agaricus is a genus with more than 500 species. Most of the new species reported since 2000 are tropical or subtropical. The study area, the Malakand region, located in the north of Pakistan, has a subtropical climate. In this study, nine species, including three new species, of Agaricus subgenus Pseudochitonia, are reported from this region. Description of the new species are based on morphological characteristics and phylogenetic analyses using three DNA regions: nuc ribosomal DNA internal transcribed spacers (ITS), fragments of the large subunit of nuc ribosomal DNA (28S), and the translation elongation factor 1-alpha gene (TEF1). One new species, Agaricus lanosus, with wooly squamules on its cap, forms a lineage within Agaricus sect. Bivelares and cannot be classified with certainty in one of the two subsections (Cupressorum and Hortenses) of this section. Agaricus rhizoideus with rhizoid-like structure at the base of the stipe forms a basal clade in Agaricus sect. Hondenses. Specimens of the third new species, Agaricus malakandensis, form a species-level clade within Agaricus sect. Catenulati and exhibits the morphological characteristics of this section. Due to their similar ITS sequences, two previously unnamed specimens from Thailand (A. sp. LD2012162 and CA799) are considered conspecific with A. malakandensis.

Insight into the evolutionary and domesticated history of the most widely cultivated mushroom Agaricus bisporus via mitogenome sequences of 361 global strains.

Agaricus bisporus is the most widely cultivated edible mushroom in the world with a only around three hundred years known history of cultivation. Therefore, it represents an ideal organism not only to investigate the natural evolutionary history but also the understanding on the evolution going back to the early era of domestication. In this study, we generated the mitochondrial genome sequences of 352 A. bisporus strains and 9 strains from 4 closely related species around the world. The population mitogenomic study revealed all A. bisporus strains can be divided into seven clades, and all domesticated cultivars present only in two of those clades. The molecular dating analysis showed this species origin in Europe on 4.6 Ma and we proposed the main dispersal routes. The detailed mitogenome structure studies showed that the insertion of the plasmid-derived dpo gene caused a long fragment (MIR) inversion, and the distributions of the fragments of dpo gene were strictly in correspondence with these seven clades. Our studies also showed A. bisporus population contains 30 intron distribution patterns (IDPs), while all cultivars contain only two IDPs, which clearly exhibit intron loss compared to the others. Either the loss occurred before or after domestication, that could suggest that the change facilitates their adaptation to the cultivated environment.

Experimental Outcrossing in Agaricus bisporus Revealed a Major and Unexpected Involvement of Airborne Mycelium Fragments.

Agaricus bisporus var. bisporus, the button mushroom, has a predominantly pseudohomothallic life cycle. Most of its spores are heterokaryotic and give rise to fertile heterokaryons. However, previous studies have suggested that outcrossing should not be rare in wild populations. In order to discover how outcrossing occurs, we experimentally favored it between aerial propagules of a fruiting donor mycelium and a delayed receiver mycelium that only invaded culture trays. Two donor/receiver pairs were studied, and potentially hybrid basidiomata collected on the receiver trays were analyzed with a mitochondrial marker, two unlinked nuclear CAPS markers, then haplotype markers based on DNA sequences obtained after PCR cloning of the rDNA ITS region and the fruk gene. For one of the two pairs, most basidiomata were hybrids between the donor and the receiver. Genotyping of the hybrids revealed only two genotypes consistent with outcrossing involving airborne mycelium fragments rather than basidiospores. The resident receiver heterokaryon that provided its mitochondria to the hybrid basidiomata is suspected to have had a trophic contribution to their growth and successful fruiting. The high level of heterozygosity and the cultivar introgression previously revealed in wild populations of this pseudohomothallic species may result from outcrossing involving airborne pieces of mycelium.

Large-scale phenotyping of 1,000 fungal strains for the degradation of non-natural, industrial compounds.

Fungal biotechnology is set to play a keystone role in the emerging bioeconomy, notably to address pollution issues arising from human activities. Because they preserve biological diversity, Biological Resource Centres are considered as critical infrastructures to support the development of biotechnological solutions. Here, we report the first large-scale phenotyping of more than 1,000 fungal strains with evaluation of their growth and degradation potential towards five industrial, human-designed and recalcitrant compounds, including two synthetic dyes, two lignocellulose-derived compounds and a synthetic plastic polymer. We draw a functional map over the phylogenetic diversity of Basidiomycota and Ascomycota, to guide the selection of fungal taxa to be tested for dedicated biotechnological applications. We evidence a functional diversity at all taxonomic ranks, including between strains of a same species. Beyond demonstrating the tremendous potential of filamentous fungi, our results pave the avenue for further functional exploration to solve the ever-growing issue of ecosystems pollution.

An overview of Agaricus section Hondenses and Agaricus section Xanthodermatei with description of eight new species from Pakistan.

In a recent revision of the genus Agaricus, A. section Xanthodermatei was split into two sections A. sect. Hondenses and A. sect. Xanthodermatei. Our objectives were to investigate the species diversity of both sections in Pakistan and to give an overview of the major clades. Phylogenetic analyses based on the combined nucLSU, ITS and TEF1 dataset from 35 specimens of both sections revealed three major clades. Analyses based on ITS dataset and 106 specimens, including 33 from Pakistan, reveal eight new species and one new record species. These nine species are described in detail. It is noteworthy that intraspecific variability as well as interspecific variability between closely related species were very low in ITS sequences in many cases. In the case of the two new species A. xanthochromaticus and A. griseovariegatus, TEF1 sequence data were much more efficient than ITS to distinguish these species from each other. The other new species are A. atroumbonatus, A. fumidicolor, A. macropeplus, A. parviniveus, A. swaticus and A. bambusetorum. The latter is the only new species of A. sect. Hondenses in which it is morphologically atypical and also the unique (sub)tropical species. Agaricus gregariomyces is recorded for the first time in Pakistan. In addition, brief descriptions are provided not only for A. bisporiticus, A. endoxanthus and A. punjabensis, which are reported again in Pakistan, but also for A. californicus, which is reported for the first time in Spain and outside North America. In total 12 species of both sections were reported in Pakistan and half of them were from subtropical climatic areas, underlining the contribution of the climatic diversity to the high species richness in this country.

Four new species of Agaricus subgenus Spissicaules from China.

Agaricus subgenus Spissicaules is widely distributed in the world. In this study, 114 specimens were included in multigene phylogenetic analyses that allowed a better circumscription of the four sections in A. subg. Spissicaules. Three new species from China, A. brunneovariabilis, A. beijingensis, and A. planiceps, are described and placed in different sections. The invalidly described A. catenariocystidiosus is validated here as an additional new species. Comparisons between the sequences of the three closely related species A. thiersii, A. parasubrutilescens, and A. linzhiensis support the distinction between these three species despite the paraphyly of A. linzhiensis, which results from its high intraspecific variability with numerous heteromorphisms.

Patterns of PCR Amplification Artifacts of the Fungal Barcode Marker in a Hybrid Mushroom.

The polymerase chain reaction (PCR) is widely used in modern biology and medicine. However, PCR artifacts can complicate the interpretation of PCR-based results. The internal transcribed spacer (ITS) region of the ribosomal RNA gene cluster is the consensus fungal barcode marker and suspected PCR artifacts have been reported in many studies, especially for the analyses of environmental fungal samples. At present, the patterns of PCR artifacts in the whole fungal ITS region (ITS1+5.8S+ITS2) are not known. In this study, we analyzed the error rates of PCR at three template complexity levels using the divergent copies of ITS from the mushroom Agaricus subrufescens. Our results showed that PCR using the Phusion® High-Fidelity DNA Polymerase has a per nucleotide error rate of about 4 × 10-6 per replication. Among the detected mutations, transitions were much more frequent than transversions, insertions, and deletions. When divergent alleles were mixed as templates in the same reaction, a significant proportion (∼30%) of recombinant molecules were detected. The in vitro mixed-template results were comparable to those obtained from using the genomic DNA of the original mushroom specimen as template. Our results indicate that caution should be in place when interpreting ITS sequences from individual fungal specimens, especially those containing divergent ITS copies. Similar results could also happen to PCR-based analyses of other multicopy DNA fragments as well as single-copy DNA sequences with divergent alleles in diploid organisms.

Offspring analysis using two cleaved amplified polymorphic sequence (CAPS) markers reveals amphithallism in the edible mushroom Agaricus sinodeliciosus.

Agaricus sinodeliciosus is an edible wild mushroom known in northwest China. It belongs to Agaricus section Bivelares that includes several popular cultivated species, such as A. bisporus, the button mushroom. The life cycle of the latter species has been described as amphithallic because both homokaryotic (n) and heterokaryotic (n+n) spores are produced that lead to heterothallic and pseudohomothallic life cycles, respectively. The type of life cycle can impact population structures and breeding strategies. The main objective of this study was to identify the different categories of spores produced by A. sinodeliciosus. Using either a morphological approach based on the number of sterigmata per basidium or a genetic approach based on the genotypes of the progeny at two loci, the proportion of heterokaryotic spores was estimated at 6% and 15%, respectively. Two codominant markers were chosen from the mitochondrial intermediate peptidase gene (MIP) and the nuc rDNA internal transcribed spacer (ITS1-5.8S-ITS2 = ITS) region. Genotypic analysis and mating tests confirmed that in A. sinodeliciosus, MIP is centromere-linked and tightly linked to the mating type locus as in A. bisporus and A. subrufescens. We conclude that A. sinodeliciosus has a unifactorial system of sexual incompatibility and an amphithallic life cycle that is predominantly heterothallic, and that its pseudohomothallism follows a nonrandom model with nonsister postmeiotic nuclei paired in the same spore, which give rise to a potentially fertile heterokaryon. This method of using two informative markers is reliable not only in selecting the homokaryotic offspring but also in classifying the homokaryons in two breeding stocks according to their mating type alleles.

A phylogenetic and morphological overview of sections Bohusia, Sanguinolenti, and allied sections within Agaricus subg. Pseudochitonia with three new species from France, Iran, and Portugal.

The genus Agaricus was recently rearranged to accommodate numerous tropical taxa. Accordingly, the genus was split into six subgenera and 22 sections of which 12 are included in A. subg. Pseudochitonia. Preliminary data indicated that three putative new species belong to this subgenus. Our objectives were to describe these species, to determine to which sections they belong, and to experience the interest of some traditional traits in this new context. We morphologically described Agaricus coniferarum from France and Portugal, Agaricus iranicus from Iran, and Agaricus lusitanicus from Portugal. Multi-gene phylogenetic analyses based on ITS, LSU, and tef1 sequence data of representatives of the 12 sections clearly indicated that A. coniferarum and A. lusitanicus are placed in Agaricus sect. Bohusia, while A. iranicus is in A. sect. Sanguinolenti. Incidentally, we replaced the illegitimate name Agaricus magnivelaris by Agaricus fiardianus. In a phylogenetic tree, based on all available ITS sequence data and focussing on six related sections, we examined the phylogenetic distribution of various characters. The intensity of red discolouration when the sporocarp is rubbed or cut appeared as a phylogenetically weak informative trait. We propose a determination key leading to a group of three hardly distinguishable sections (Bohusia, Nigrobrunnescentes, and Sanguinolenti).

Correction: Genetic Analyses of the Internal Transcribed Spacer Sequences Suggest Introgression and Duplication in the Medicinal Mushroom Agaricus subrufescens.

[This corrects the article DOI: 10.1371/journal.pone.0156250.].

Genetic Analyses of the Internal Transcribed Spacer Sequences Suggest Introgression and Duplication in the Medicinal Mushroom Agaricus subrufescens.

The internal transcribed spacer (ITS) region of the nuclear ribosomal RNA gene cluster is widely used in fungal taxonomy and phylogeographic studies. The medicinal and edible mushroom Agaricus subrufescens has a worldwide distribution with a high level of polymorphism in the ITS region. A previous analysis suggested notable ITS sequence heterogeneity within the wild French isolate CA487. The objective of this study was to investigate the pattern and potential mechanism of ITS sequence heterogeneity within this strain. Using PCR, cloning, and sequencing, we identified three types of ITS sequences, A, B, and C with a balanced distribution, which differed from each other at 13 polymorphic positions. The phylogenetic comparisons with samples from different continents revealed that the type C sequence was similar to those found in Oceanian and Asian specimens of A. subrufescens while types A and B sequences were close to those found in the Americas or in Europe. We further investigated the inheritance of these three ITS sequence types by analyzing their distribution among single-spore isolates from CA487. In this analysis, three co-dominant markers were used firstly to distinguish the homokaryotic offspring from the heterokaryotic offspring. The homokaryotic offspring were then analyzed for their ITS types. Our genetic analyses revealed that types A and B were two alleles segregating at one locus ITSI, while type C was not allelic with types A and B but was located at another unlinked locus ITSII. Furthermore, type C was present in only one of the two constitutive haploid nuclei (n) of the heterokaryotic (n+n) parent CA487. These data suggest that there was a relatively recent introduction of the type C sequence and a duplication of the ITS locus in this strain. Whether other genes were also transferred and duplicated and their impacts on genome structure and stability remain to be investigated.

The Genetic Linkage Map of the Medicinal Mushroom Agaricus subrufescens Reveals Highly Conserved Macrosynteny with the Congeneric Species Agaricus bisporus.

Comparative linkage mapping can rapidly facilitate the transfer of genetic information from model species to orphan species. This macrosynteny analysis approach has been extensively used in plant species, but few example are available in fungi, and even fewer in mushroom crop species. Among the latter, the Agaricus genus comprises the most cultivable or potentially cultivable species. Agaricus bisporus, the button mushroom, is the model for edible and cultivable mushrooms. We have developed the first genetic linkage map for the basidiomycete A. subrufescens, an emerging mushroom crop known for its therapeutic properties and potential medicinal applications. The map includes 202 markers distributed over 16 linkage groups (LG), and covers a total length of 1701 cM, with an average marker spacing of 8.2 cM. Using 96 homologous loci, we also demonstrated the high level of macrosynteny with the genome of A. bisporus The 13 main LG of A. subrufescens were syntenic to the 13 A. bisporus chromosomes. A disrupted synteny was observed for the three remaining A. subrufescens LG. Electronic mapping of a collection of A. subrufescens expressed sequence tags on A. bisporus genome showed that the homologous loci were evenly spread, with the exception of a few local hot or cold spots of homology. Our results were discussed in the light of Agaricus species evolution process. The map provides a framework for future genetic or genomic studies of the medicinal mushroom A. subrufescens.

Spore behaviors reveal a category of mating-competent infertile heterokaryons in the offspring of the medicinal fungus Agaricus subrufescens.

Strain breeding is much less advanced in the edible and medicinal species Agaricus subrufescens than in Agaricus bisporus, the button mushroom. Both species have a unifactorial system of sexual incompatibility, a mating type locus tightly linked to a centromere, and basidia producing both homokaryotic (n) and heterokaryotic (n + n) spores. In A. bisporus, breeding is mainly based on direct selection among the heterokaryotic offspring and on hybridization between homokaryotic offspring. The parental heterozygosity is highly maintained in the heterokaryotic offspring due to suppression of recombination and preferential pairing in the spores of nuclei, each one per second meiotic divisions; such "non-sister nuclei" heterokaryons are fertile. In A. subrufescens, recent studies revealed that recombination is not suppressed and that nuclei from the same second meiotic division can also be paired in a spore that give rise to a "sister nuclei" heterokaryon in which the nuclei bear the same mating type allele. The objective of the present work was to investigate the potential function of the different categories of spores in A. subrufescens and their possible use in a genetic breeding program. Using eight co-dominant molecular markers, we found that half of the offspring of the A. subrufescens strain WC837 were heterokaryotic, one quarter of them being sister nuclei heterokaryons. These heterokaryons were infertile and behaved like homokaryons, being even able to cross between each other. In contrast, non-sister nuclei heterokaryons could fruit but inconsistently due to inbreeding depression. Potential roles of these two categories of heterokaryons in nature and consequences for strain breeding are discussed.

Agaricus section Arvenses: three new species in highland subtropical Southwest China.

Agaricus is a genus of saprobic basidiomycetes with more than 400 species recognized worldwide, with about 50 species known in China. Our objective was to investigate three new species of section Arvenses in highland subtropical Southwest China. Agaricus guizhouensis is a new species characterized by a white pileus with yellowish squamules, small ellipsoid spores and cheilocystidia with yellowish-brown pigments; another new species, Agaricus longistipes is recognized by its slender stipe, and its elongate-ellipsoid basidiospores; the third new one, Agaricus megalocarpus is remarkable by its large size and its pileus surface covered with fine brown squamules. It is firstly reported for Guizhou Province that Agaricus abruptibulbus, Agaricus flocculosipes, and Agaricus subrufescens are illustrated. Two probable new species require further studying. A phylogenetic analyses of rDNA-ITS sequence data belonging to section Arvenses showed that the section Arvenses is monophyletic and can be subdivided in five branches, the branch of A. subrufescens and four clades (A-D). The eight species from highland subtropical Southwest China were distributed in all five branches, indicating that this highland is at the climatic crossroads. The white pileus trait and the potential interest are discussed. These data suggest a potential species richness that remains to be discovered.

The intraspecific variability of mitochondrial genes of Agaricus bisporus reveals an extensive group I intron mobility combined with low nucleotide substitution rates.

Intraspecific mitochondrial variability was studied in ten strains of A. bisporus var. bisporus, in a strain representative of A. bisporus var. eurotetrasporus and in a strain of the closely related species Agaricus devoniensis. In A. bisporus, the cox1 gene is the richest in group I introns harboring homing endonuclease genes (heg). This study led to identify group I introns as the main source of cox1 gene polymorphism. Among the studied introns, two groups were distinguished according to the heg they contained. One group harbored heg maintained putatively functional. The other group was composed of eroded heg sequences that appeared to evolve toward their elimination. Low nucleotide substitution rates were found in both types of intronic sequences. This feature was also shared by all types of studied mitochondrial sequences, not only intronic but also genic and intergenic ones, when compared with nuclear sequences. Hence, the intraspecific evolution of A. bisporus mitochondrial genome appears characterized by both an important mobility (presence/absence) of large group I introns and by low nt substitution rates. This stringent conservation of mitochondrial sequences, when compared with their nuclear counterparts, appears irrespective of their apparent functionality and contrasts to what is widely accepted in fungal sequence evolution. This strengthens the usefulness of mtDNA sequences to get clues on intraspecific evolution.

Evidence for amphithallism and broad geographical hybridization potential among Agaricus subrufescens isolates from Brazil, France, and Thailand.

Agaricus subrufescens is a cultivated edible and medicinal mushroom. Its known geographical distribution encompasses the Americas, Europe, Oceania, and Asia. The objective of this study was to assess mating compatibility and interfertility of strains originating from Brazil, France, and Thailand. Progeny of each strain were analyed with codominant molecular markers. Multilocus genotype tests revealed that the three strains were amphithallic with percentages of heterokaryotic single spore progenies of 75% for the Thai strain and around 40% for the Brazilian and French strains. In mating tests A. subrufescens had a multiallelic unifactorial system of sexual incompatibility. The three parent strains were interfertile based on experimental pairings of single-spore isolates, the recovery of hybrid heterokaryons from compatible matings, and the ability of hybrids to produce mushrooms and fertile spores. This biological approach supports the inclusion of the European strains within the species and the extension of the geographical distribution range to Asia. Our data should help to develop breeding strategies and to better manage and exploit the diversity existing in A. subrufescens.

Morphological and molecular characterization of three Agaricus species from tropical Asia (Pakistan, Thailand) reveals a new group in section Xanthodermatei.

The genus Agaricus is known for its medicinal and edible species but also includes toxic species that belong to section Xanthodermatei. Previous phylogenetic reconstruction for temperate species, based on sequence data of nuc rRNA gene (rDNA) internal transcribed spacers (ITS), has revealed two major groups in this section and a possible third lineage for A. pseudopratensis. Recent research in Agaricus has shown that classifications need improving with the addition of tropical taxa. In this study we add new tropical collections to section Xanthodermatei. We describe three species from collections made in Pakistan and Thailand and include them in a larger analysis using all available ITS data for section Xanthodermatei. Agaricus bisporiticus sp. nov. and A. fuscopunctatus sp. nov. are introduced based on molecular and morphological studies, whereas A. microvolvatulus is recorded for the first time in Asia. Specimens from Thailand however have a much larger pileus than the type specimens from Congo. In maximum likelihood (ML) and maximum parsimony (MP) phylogenetic analyses these three species cluster with A. pseudopratensis from the Mediterranean area and A. murinocephalus recently described from Thailand. In Agaricus section Xanthodermatei this new group is monophyletic and receives low bootstrap support whereas the two previously known groups receive strong support. Within the new group, the most closely related species share some traits, but we did not find any unifying morphological character; however the five species of the group share a unique short nucleotide sequence. Two putatively toxic species of section Xanthodermatei are now recognized in Pakistan and six in Thailand.

A molecular contribution to the assessment of the Tricholoma equestre species complex.

In recent years, interest in the Tricholoma equestre species complex has increased because of several cases of severe and sometimes fatal rhabdomyolysis reported in France and Poland. These occurred after repeated consumption of large portions of T. equestre sporophores during consecutive meals, despite the fact that this species is renowned as a tasty edible wild mushroom. The T. equestre species complex includes three ectomycorrhizal species Tricholoma flavovirens (Pers.) S. Lundell, Tricholoma auratum (Paulet) Gillet, and T. equestre (L.) P. Kummer. All these species produce sporophores with intense yellow gills but are difficult to distinguish by morphological analyses at both the macroscopic and microscopic levels. In T. equestre, two additional varieties are recognized: T. equestre var. populinum (Christensen & Noordeloos) associated with Populus sp. and/or Betula sp. trees and sometimes recognized as Tricholoma frondosae (Kalamees & Shchukin) and T. equestre var. pallidifolia characterized by pale to white gills, frequently recognized as Tricholoma joachimii (Bon & Riva). To explore the taxonomic (species delimitation), ecological, and geographical extent and limits of the T. equestre species complex, we have carried out a molecular comparison of worldwide strains belonging to this complex by using sequences of two molecular markers: the internal transcript spacer (ITS)1/5.8S/ITS2 region of the nuclear ribosomal unit and the 5' part of the mitochondrial cox1 gene. Phylogenetic analyses support the placement of European T. equestre, T. flavovirens, and T. auratum strains as representatives of a single species. This species appears associated with various conifers trees, depending on the geographic origin (Pinus pinaster for T. auratum, Pinus sylvestris or Abies alba for T. equestre and T. flavovirens). However, in the context of a single T. equestre species, the geographical location could lead to the characterization of sub-species or varieties, as suggested by the gathering of the four Asian (Japanese) T. auratum strains in a strongly supported distinct phylogenetic clade. Moreover, our analysis strongly argues for considering T. joachimii and the synonymised T. equestre var. pallidifolia as two representatives of a different species not belonging to the T. equestre group. This species would be phylogenetically related to the Tricholoma columbetta species with which they share white gills. Similarly, the phylogenetic analysis of the molecular data and the lack of gene flow between the strains associated with broad-leaved trees and those of the T. equestre complex, rather argues for two distinct species depending on the ecological niche: T. frondosae under broad-leaved trees and T. equestre under conifers.

Development of polymorphic microsatellite markers issued from pyrosequencing technology for the medicinal mushroom Agaricus subrufescens.

The recently described procedure of microsatellite-enriched library pyrosequencing was used to isolate microsatellite loci in the gourmet and medicinal mushroom Agaricus subrufescens. Three hundred and five candidate loci containing at least one simple sequence repeats (SSR) locus and for which primers design was successful, were obtained. From a subset of 95 loci, 35 operational and polymorphic SSR markers were developed and characterized on a sample of 14 A. subrufescens genotypes from diverse origins. These SubSSR markers each displayed from two to 10 alleles with an average of 4.66 alleles per locus. The observed heterozygosity ranged from 0 to 0.71. Several multiplex combinations can be set up, making it possible to genotype up to six markers easily and simultaneously. Cross-amplification in some closely congeneric species was successful for a subset of loci. The 35 microsatellite markers developed here provide a highly valuable molecular tool to study genetic diversity and reproductive biology of A. subrufescens.

Agaricus subrufescens: A review.

Medicinal mushrooms have currently become a hot issue due to their various therapeutic properties. Of these, Agaricus subrufescens, also known as the "almond mushroom", has long been valued by many societies (i.e., Brazil, China, France, and USA). Since its discovery in 1893, this mushroom has been cultivated throughout the world, especially in Brazil where several strains of A. subrufescens have been developed and used as health food and alternative medicine. This article presents up-to-date information on this mushroom including its taxonomy and health promoting benefits. Medicinal properties of A. subrufescens are emphasized in several studies which are reviewed here. In addition, safety issues concerning the use of this fungus will be discussed.