Anamorphic Characters Research Articles

The asexual morph and molecular phylogeny of endemic Phyllactinia verruculosa on Indigofera tinctoria.

Phyllactinia verruculosa is a powdery mildew species (Erysiphaceae, tribe Phyllactinieae) so far only known from its type material collected in China on Indigofera scabrida in 1992, which only comprised the sexual morph. Two asexual morph samples were observed, one was collected on I. tinctoria on the campus of Guizhou University, Guiyang, China, and another one, on I. scabrida, was borrowed from Kunming Institute of Botany, Chinese Academy of Sciences. The anamorphic characters were observed, described and illustrated. The phylogenetic analysis of the combination of internal transcribed spacer regions (ITS) and 28S rDNA sequences showed that Ph. verruculosa is phylogenetically distantly related from other Phyllactinia species. To our knowledge, this is the first record of the asexual morph and first ITS+28S sequences for Ph. verruculosa, and I. tinctoria is a new host record for this species.

Genetic Diversity Analysis based on the Virulence, Physiology and Regional Variability in Different Isolates of Powdery Mildew in Pea.

Powdery mildew is an omnipresent disease that reduces the yield and quality of pea crops (Pisum sativum L.). To examine the powdery mildew pathogen’s morphological, molecular, and genetic diversity, we collected samples of powdery mildew-affected pea crops from ten distinct locations in the Nilgiris district of Tamil Nadu, India. The pathogen Erysiphe pisi was identified morphologically based on anamorphic characters. Molecular identification of E. pisi isolates was befitted by targeting the internal transcribed spacer (ITS) region of rDNA and specific primers of powdery mildew fungi. The genetic variation between ten different E. pisi isolates collected from topographically distinct mountainous areas was studied using random amplified polymorphic (RAPD). Based on its morphological characteristics, the powdery mildew fungus presented high similarities to E. pisi. Molecular characterization of the ITS rDNA of E. pisi produced 650 bp nucleotides, PMITS (powdery mildew-internal transcribed region) primers produced 700 bp nucleotides, and an Erysiphe specific ITS primer pair amplified and synthesized 560 bp nucleotides. According to the findings, the collected E. pisi strains exhibited a low level of genetic diversity and only a slight differential in virulence on the host. In the study, E. pisi isolates from Anumapuram, Emerald Valley, Indira Nagar, and Thuneri showed a greater disease incidence in the natural field conditions and shared the same genetic lineage with other isolates in UPGMA hierarchical cluster analysis based on RAPD markers. There was no evidence of a link between the occurrence of the disease and these grouped populations.

Morphological characterization and epidemiological studies of summer squash (Cucurbita pepo) powdery mildew

Samples of powdery mildew of summer squash (Cucurbita pepo L.) collected from Solan, Shimla, Hamirpur and Kinnaur districts of Himachal Pradesh during 2017-18 revealed the presence of anamorphs, whereas the cool and dry temperate region of district Kinnaur showed the occurrence of both teleomorphic and anamorphic stages of powdery mildew on summer squash. Present studies constitute the first report of cleistothecial occurrence on summer squash under Indian conditions. Based on anamorphic characters like ellipsoidal conidia, presence of fibrosin bodies and germinating conidia produced both simple and forked germ tubes without appressorium and teleomorphic characters like cleistothecia with myceloid appendages, single ascus with eight ascospores the associated pathogen was identified as Sphaerotheca fuliginea (Schlecht.) Pollaci. Maximum conidial germination was observed at 25° temperature and 100% relative humidity. The development of powdery mildew disease was significantly favored at moderate temperature coupled with high relative humidity and cumulative rainfall.

Reclassification of the butternut canker fungus, Sirococcus clavigignenti-juglandacearum, into the genus Ophiognomonia

Sirococcus clavigignenti-juglandacearum (Sc-j), which causes a canker disease on butternut, is largely responsible for the decline of this tree in the United States and Canada. The original description of the species was based on anamorphic characters because the teleomorph is unknown. Recent phylogenetic investigations have found that Sc-j is not a member of the genus Sirococcus, and accurate taxonomic classification is required. The objective of this study is to use sequence data to determine the phylogenetic placement of Sc-j within the Gnomoniaceae, Diaporthales. Isolates were recovered from infected Juglans ailantifolia var. cordiformis (heartnut), Juglans cinerea (butternut), and Juglans nigra (black walnut) in Ontario and the eastern United States. The genes coding for β-tubulin, actin, calmodulin, internal transcribed spacers 1 and 2, and the translation elongation factor 1-alpha from 28 isolates of Sc-j and representatives of the major lineages within the Gnomoniaceae were evaluated. There was no difference in the sequences of the five genes among the isolates of Sc-j studied, indicating a recent introduction followed by asexual reproduction and spread via conidia. The phylogenetic analyses demonstrate this fungus does not belong to the genus Sirococcus, and provides strong support (99% MP and 100% NJ bootstrap values, and 100% Bayesian posterior probabilities) for its inclusion in the genus Ophiognomonia, thereby supporting a reclassification of the butternut canker fungus to Ophiognomonia clavigignenti-juglandacearum.

Ruwenzoria, a new genus of the Xylariaceae from Central Africa

During a foray to the mountain rainforests of the Democratic Republic of the Congo, a peculiar species of Xylariaceae was found, which could not be accommodated in any of the existing genera. It is recognised as representative of a new genus, named Ruwenzoria, owing to the presence of a new combination of teleomorphic and anamorphic characters that are regarded as significant for generic segregation within the Xylariaceae. Studies on its secondary metabolites in stromata and cultures by high performance liquid chromatography, coupled with diode array and mass spectrometric detection (HPLC-DAD/MS), and on its phylogenetic affinities based on 5.8S/ITS rDNA sequence data, respectively, revealed a close relationship of the new taxon to the genera Daldinia and Entonaema, from which it differs by having neither a hollow, gelatinous nor a conspicuously zonate stromatal interior, and an anamorph featuring enteroblastic rather than holoblastic conidiogenesis. A specimen from the same geographic region, previously identified as Daldinia bakeri by R.W.G. Dennis was found to constitute a mixture of stromata of Ruwenzoria and an additional, undescribed Daldinia species. The latter fungus is not formally described due to the scantiness of the material, but its morphological characteristics are illustrated.

Erysiphe trifolii Causing Powdery Mildew of Lentil (Lens culinaris).

The taxonomy of the powdery mildew fungus infecting lentil in the Pacific Northwest (PNW) of the United States was investigated on the basis of morphology and rDNA internal transcribed spacer (ITS) sequences. Anamorphic characters were in close agreement with descriptions of Erysiphe trifolii. However, teleomorphs formed chasmothecial appendages with highly branched apices, whereas E. trifolii has been described as producing flexuous or sometimes loosely branched appendages. Branched appendages have been described in Erysiphe diffusa, a fungus reported from species of Lens, Glycine, and Sophora, raising the possibility that the PNW fungus could be E. diffusa. Examination of morphological characters of an authentic specimen of E. trifolii from Austria determined that it included chasmothecial appendages resembling those seen in PNW specimens. Furthermore, ITS sequences from five powdery mildew samples collected from lentils in PNW greenhouses and fields from 2006 to 2008 were identical to one another, and exhibited higher similarity to sequences of E. trifolii (99%) than to those of any other Erysiphe spp. available in GenBank. Parsimony analysis grouped the lentil powdery mildew into a clade with Erysiphe baeumleri, E. trifolii, and E. trifolii-like Oidium sp., but indicated a more distant relationship to E. diffusa. In greenhouse inoculation studies, the lentil powdery mildew fungus did not infect soybean genotypes known to be susceptible to E. diffusa. The pathogenicity of E. trifolii on lentil was confirmed using modified Koch's postulates. This is the first report of E. trifolii infecting lentil. E. diffusa and E. trifolii have different host ranges, so the discovery of E. trifolii on lentil has implications both for determining species of powdery mildews on cool-season grain legumes, and in disease management.

Anamorphs of the Bolbitiaceae (Basidiomycota, Agaricales)

We describe and illustrate thallic conidiogenesis in 14 species of the Bolbitiaceae sensu Singer studied in culture. Conidiogenesis of 12 species is shown for the first time. Bolbitius vitellinus and the investigated species of Conocybe (C. albipes, C. appendiculata, C. magnicapitata, C. semiglobata, C. subovalis, C. subpubescens, C. sulcatipes and C. teneroides) possessed a similar mode of conidiogenesis. Species of both genera formed mostly coiled conidiogenous hyphae arising sympodially from differentiated conidiophores. The anamorphs of the Agrocybe species were not uniform and predominantly differed from those of Conocybe and Bolbitius. The conidia of Agrocybe dura, A. firma and A. praecox developed by the simple fragmentation of normally branched hyphae. Sympodially proliferating conidiophores occurred in Agrocybe arvalis and A. aegerita. Secretory cells of different size and shape were found in Agrocybe and in Conocybe. Our results corroborate a close phylogenetic relationship between Bolbitius and Conocybe as well as the polyphyly of the Bolbitiaceae as currently treated, which is consistent with recent molecular phylogenetic studies. Consequently we emend the family concept based on anamorphic characters.

Anamorphs of the Bolbitiaceae (Basidiomycota, Agaricales)

We describe and illustrate thallic conidiogenesis in 14 species of the Bolbitiaceae sensu Singer studied in culture. Conidiogenesis of 12 species is shown for the first time. Bolbitius vitellinus and the investigated species of Conocybe (C. albipes, C. appendiculata, C. magnicapitata, C. semiglobata, C. subovalis, C. subpubescens, C. sulcatipes and C. teneroides) possessed a similar mode of conidiogenesis. Species of both genera formed mostly coiled conidiogenous hyphae arising sympodially from differentiated conidiophores. The anamorphs of the Agrocybe species were not uniform and predominantly differed from those of Conocybe and Bolbitius. The conidia of Agrocybe dura, A. firma and A. praecox developed by the simple fragmentation of normally branched hyphae. Sympodially proliferating conidiophores occurred in Agrocybe arvalis and A. aegerita. Secretory cells of different size and shape were found in Agrocybe and in Conocybe. Our results corroborate a close phylogenetic relationship between Bolbitius and Conocybe as well as the polyphyly of the Bolbitiaceae as currently treated, which is consistent with recent molecular phylogenetic studies. Consequently we emend the family concept based on anamorphic characters.

Ribosomal and RPB2 DNA sequence analyses suggest that Sporidesmium and morphologically similar genera are polyphyletic

Sporidesmium and morphologically similar dematiaceous, hyphomycetous genera are characterised by holoblastic phragmoconidia produced on proliferating or non-proliferating conidiophores. They include a number of asexual (anamorphic) genera taxonomically segregated from Sporidesmium sensu lato and are similar in having schizolytic conidial secession. The taxonomy of these ubiquitous asexual fungi and their affinities with known Ascomycetes are, however, still obscure. This study incorporates a phylogenetic investigation, based on the LSU nu-rDNA and RNA polymerase II second largest subunit (RPB2) gene sequence, to assess the possible familial placement of Ellisembia, Linkosia, Repetophragma, Sporidesmiella, Sporidesmium and Stanjehughesia, and justify whether anamorphic characters are proper phylogenetic indicators. Phylogenies provide conclusive evidence to suggest that Sporidesmium is not monophyletic and species are phylogenetically distributed in two major ascomycete classes, Dothideomycetes and Sordariomycetes. Morphologies currently used in their classification have undergone convergent evolution and are not phylogenetically reliable. The possible teleomorphic affinities of these anamorphic genera are discussed in light of morphology and molecular data. As these anamorphs, in most cases, are the sole known morph of the holomorph, it is proposed that in the absence of or failure to detect their teleomorphic phase, the anamorph names should be used for the holomorph.

The family Pleosporaceae: intergeneric relationships and phylogenetic perspectives based on sequence analyses of partial 28S rDNA

The Pleosporaceae is an important loculoascomycete family. There has been disagreement, however, regarding the taxonomic placement of many genera within this family. This study investigates phylogenetic relationships among the genera Cochliobolus, Kirschsteiniothelia, Leptosphaerulina, Macroventuria, Pleospora, Pyrenophora, and Wettsteinina. Partial 28S rDNA sequences from taxa within these genera were analyzed with maximum parsimony, likelihood and Bayesian methods. Cochliobolus can be segregated broadly into two groups as previously proposed. Pleospora is polyphyletic in its current sense. Taxa with Stemphylium anamorphs are closely related to Cochliobolus and fit within the Pleosporaceae, whereas the affinities of Pleospora herbarum and P. ambigua are still ambiguous. Pyrenophora constitutes a monophyletic group within the Pleosporaceae, whereas Leptosphaerulina and Macroventuria appear to share phylogenetic affinities with the Leptosphaeriaceae and Phaeosphaeriaceae. Phylogenies indicate that Wettsteinina should be excluded from the Pleosporaceae. Similar findings are reported for Kirschsteiniothelia, which is probably polyphyletic. Anamorphic characters appear to be significant (especially in Cochliobolus) while ascospore morphologies, such as shape and color and substrate occurrence are poor indicators of phylogenetic relationships among these loculoascomycetes.

The family Pleosporaceae: intergeneric relationships and phylogenetic perspectives based on sequence analyses of partial 28S rDNA

The Pleosporaceae is an important loculoascomycete family. There has been disagreement, however, regarding the taxonomic placement of many genera within this family. This study investigates phylogenetic relationships among the genera Cochliobolus, Kirschsteiniothelia, Leptosphaerulina, Macroventuria, Pleospora, Pyrenophora, and Wettsteinina. Partial 28S rDNA sequences from taxa within these genera were analyzed with maximum parsimony, likelihood and Bayesian methods. Cochliobolus can be segregated broadly into two groups as previously proposed. Pleospora is polyphyletic in its current sense. Taxa with Stemphylium anamorphs are closely related to Cochliobolus and fit within the Pleosporaceae, whereas the affinities of Pleospora herbarum and P. ambigua are still ambiguous. Pyrenophora constitutes a monophyletic group within the Pleosporaceae, whereas Leptosphaerulina and Macroventuria appear to share phylogenetic affinities with the Leptosphaeriaceae and Phaeosphaeriaceae. Phylogenies indicate that Wettsteinina should be excluded from the Pleosporaceae. Similar findings are reported for Kirschsteiniothelia, which is probably polyphyletic. Anamorphic characters appear to be significant (especially in Cochliobolus) while ascospore morphologies, such as shape and color and substrate occurrence are poor indicators of phylogenetic relationships among these loculoascomycetes.

Cryptic species related to Daldinia concentrica and D. eschscholzii, with notes on D. bakeri

Daldinia macaronesica (from the Canary Islands and Madeira), D. palmensis (from the Canary Islands), D. martinii and D. raimundi (from Sicily), and D. vanderguchtiae (from Jersey, Channel Islands) spp. nov., are described, based on new combinations of teleomorphic and anamorphic characters. They all resemble the pantropical D. eschscholzii and/or the European D. concentrica with regard to teleomorphic characters and secondary metabolite profiles generated by analytical HPLC. The status of the newly described taxa was established by SEM of ascospores and microscopic studies of their anamorphs in comparison with various materials of the aforementioned known species. HPLC and SEM studies on the holotype of D. bakeri confirmed its relationships to D. fissa and D. loculata. Yellowish pigments contained in the type specimen of D. bakeri are probably artificial.

Use of holomorph characters to delimit Microascus nidicola and M. soppii sp. nov., with notes on the genus Pithoascus

Several isolates of a perithecial microascaceous ascomycete having falcate ascospores and a Scopulariopsis anamorph were obtained from rotting wood in the boreal forest of Alberta, Canada. Additional isolates appeared conspecific based on anamorphic characters, but failed to produce a teleomorph. These isolates showed similarities to Microascus nidicola (type species of the genus Pithoascus) and Scopulariopsis flava. Sexual compatibility systems were investigated to establish holomorph concepts for these taxa. The teleomorph obtained in mating trials among anamorphic isolates was identical to that of self-fertile isolates. The new heterothallic species M. soppii is described. The anamorph is S. soppii. Single ascospore isolates derived from M. nidicola demonstrated homothallism and lacked an anamorph. Scopulariopsis flava (basionym Acaulium flavum) is considered a nomen dubium. Generic concepts of Pithoascus are evaluated and the genus is treated as a synonym of Microascus. Pithoascus stoveri is transferred as M. stoveri comb. nov.