Obovoid Conidia Research Articles

Isolation and characterization of novel Dothideomycetes species from forest soils in Chiang Rai and Krabi (Thailand): additions to the diversity of Curvularia and Verruconis

Fungi are adapted to diverse environments, where the forest soils have complex fungal communities with a wide range of lifestyles. This study aims to explore and isolate Dothideomycetes from the forest soils in Thailand. Sampling sites were located in Chiang Rai and Krabi provinces. Cultures were obtained through soil dilution series, and the strains were subjected to morphological observations and multigene phylogenetic analyses for identification. Maximum likelihood and Bayesian inference analyses were conducted to clarify their phylogenetic affinities using partial nuclear ribosomal DNA (ITS, LSU, and SSU) and the protein-coding genes (tef1-α and GADPH). Herein, two new species (Curvularia chiangraiensis sp. nov. and Verruconis soli sp. nov.) and two new records (C. chiangmaiensis and V. thailandica) are described based on the morphological and phylogenetic evidence. Curvularia chiangraiensis sp. nov. is distinguished by its relatively smaller conidia and the presence of sympodial proliferation of conidiogenesis and Verruconis soli sp. nov. exhibits micronematous conidiophores and obovoid conidia that transform into sub-cylindrical or ellipsoidal shapes, and becoming 1-septate when mature. These unique characteristics set them apart from closely related taxa. The newly described taxa have been subjected to a thorough comparison with closely related species, enabling a comprehensive analysis. The study offers detailed descriptions and includes high-quality micrographs, with the aim of providing a comprehensive understanding of these newly identified taxa

Conioscypha tenebrosa sp. nov. (Conioscyphaceae) from China and notes on Conioscypha species

Conioscypha is an asexual morph genus placed in the family Conioscyphaceae. During our study of brown-spored hyphomycetes, a new taxon C. tenebrosa was found on decaying wood collected in Guizhou Province, China. The new species is characterized by having micronematous, hyaline conidiophores which are often reduced to conidiogenous cells, with a cup-shaped, percurrently developed, multi-collaretted phialide, and globose to subglobose, obovoid conidia with broadly rounded apex and subtruncate base. The phylogenetic analysis of combined LSU, SSU, ITS and RPB2 sequence data showed that isolates of C. tenebrosa are phylogenetically distinct from other species. Conioscypha tenebrosa sp. nov. is therefore introduced here with a description and morphological illustration. Taxonomic notes and a morphological comparison of Conioscypha species are provided.

The Protean Acremonium. A. sclerotigenum/egyptiacum: Revision, Food Contaminant, and Human Disease.

Acremonium is known to be regularly isolated from food and also to be a cause of human disease. Herein, we resolve some sources of confusion that have strongly hampered the accurate interpretation of these and other isolations. The recently designated type species of the genus Acremonium, A. alternatum, is known only from a single isolate, but it is the closest known relative of what may be one of the planet’s most successful organisms, Acremonium sclerotigenum/egyptianum, shown herein to be best called by its earliest valid name, A. egyptiacum. The sequencing of ribosomal internal transcribed spacer (ITS) regions, actin genes, or both for 72 study isolates within this group allowed the full range of morphotypes and ITS barcode types to be elucidated, along with information on temperature tolerance and habitat. The results showed that nomenclatural confusion and frequent misidentifications facilitated by morphotaxonomy, along with misidentified early sequence deposits, have obscured the reality that this species is, in many ways, the definitive match of the historical concept of Acremonium: a pale orange or dull greenish-coloured monophialidic hyphomycete, forming cylindrical, ellipsoidal, or obovoid conidia in sticky heads or obovoid conidia in dry chains, and acting ecologically as a soil organism, marine organism, plant pathogen, plant endophyte, probable insect pathogen, human opportunistic pathogen, food contaminant, probable dermatological communicable disease agent, and heat-tolerant spoilage organism. Industrially, it is already in exploratory use as a producer of the antibiotic ascofuranone, active against trypanosomes, cryptosporidia, and microsporidia, and additional applications are in development. The genus-level clarification of the phylogeny of A. egyptiacum shows other historic acremonia belong to separate genera, and two are here described, Parasarocladium for the Acremonium radiatum complex and Kiflimonium for the Acremonium curvulum complex.

Acremonium with catenate elongate conidia: phylogeny of Acremonium fusidioides and related species.

Acremonium is one of the largest and most complex genera of hyphomycetes. Its taxonomy is not yet resolved and the phylogenetic value of the most distinctive morphological features is unknown. The species of this genus produce conidia in chains or form slimy heads or both. We have studied a set of clinical and environmental Acremonium strains morphologically characterized by producing mostly catenate, elongate, more or less fusiform conidia. Based on phenotypic data and in the analysis of the sequences of the ITS region, the D1/D2 domains of the 28S rRNA gene and a fragment of the β-tubulin gene, three new species morphologically similar to Acremonium fusidioides and belonging to the family Bionectriaceae (Hypocreales) are described and illustrated; they are Acremonium pilosum, Acremonium parvum and Acremonium citrinum. The first species produces two kinds of conidia: clavate with smooth walls and globose with abundant filiform projections. Acremonium parvum is characterized by slow growth and pyriform or slightly lanceolate conidia with an elongate and truncate base. Acremonium citrinum produces a diffusible yellow pigment and obovoid conidia.

Acremonium with catenate elongate conidia: phylogeny of Acremonium fusidioides and related species

Acremonium is one of the largest and most complex genera of hyphomycetes. Its taxonomy is not yet resolved and the phylogenetic value of the most distinctive morphological features is unknown. The species of this genus produce conidia in chains or form slimy heads or both. We have studied a set of clinical and environmental Acremonium strains morphologically characterized by producing mostly catenate, elongate, more or less fusiform conidia. Based on phenotypic data and in the analysis of the sequences of the ITS region, the D1/D2 domains of the 28S rRNA gene and a fragment of the β-tubulin gene, three new species morphologically similar to Acremonium fusidioides and belonging to the family Bionectriaceae (Hypocreales) are described and illustrated; they are Acremonium pilosum, Acremonium parvum and Acremonium citrinum. The first species produces two kinds of conidia: clavate with smooth walls and globose with abundant filiform projections. Acremonium parvum is characterized by slow growth and pyriform or slightly lanceolate conidia with an elongate and truncate base. Acremonium citrinum produces a diffusible yellow pigment and obovoid conidia.

Ulocladium systematics revisited: phylogeny and taxonomic status

The genus Ulocladium represents phaeodictyosporic Hyphomycetes that produce conidia that are essentially obovoid in shape. Previous molecular studies that included Ulocladium and related taxa in Alternaria, Embellisia, and Stemphylium revealed a conflict between morphology and phylogeny, and Ulocladium was supported as polyphyletic with a paraphyletic core group. Moreover, the genus consistently resolved within a larger Alternaria/Ulocladium clade, resulting in paraphyly of Alternaria and questions as to the taxonomic status of Ulocladium. In the present study, 13 Ulocladium species and three genetic loci were included for a more comprehensive systematic analysis of the genus than had previously been conducted. Total genomic DNA was extracted from representative taxa and sequences were determined for the nuclear internal transcribed spacer region, including the 5.8S rDNA gene, and the protein-coding genes glyceraldehyde-3-phosphate dehydrogenase and Alt a1. Subsequent phylogenetic analyses based on maximum parsimony and Bayesian methods included related Alternaria, Embellisia, and Stemphylium spp. Results supported previous findings of polyphyletic and paraphyletic relationships of Ulocladium among other taxa. Ten Ulocladium species clustered into a core Ulocladium clade and all taxa possessed the key diagnostic feature of Ulocladium, namely, conidia essentially obovoid in shape. However, A. cheiranthi and E. indefessa also clustered within this group with high bootstrap support but did not posses this diagnostic feature. This paraphyletic clade resolved basal to the core Alternaria clade with high bootstrap support, unlike previous studies in which its position was imbedded within the primary Alternaria clade. Thus, the status of the genus as an independent lineage and a unique taxon is strongly supported. As previously reported, U. alternariae and U. oudemansii, which posses the key conidium characteristics of Ulocladium, clustered as a separate clade sister to the core Ulocladium clade. Further studies are necessary to determine if these taxa represent an independent lineage or share a common ancestor with other Ulocladium species. Obovoid conidia were poorly represented in the isolate of U. lanuginosum that was included in these analyses (the only U. lanuginosum isolate currently available), and the isolate resolved as A. radicina based upon all three loci sequenced. Based upon these data and the origin of the isolate, which was originally deposited as A. malvae, a reassessment of its identity is supported.

Two new species of Spadicoides from Brunei and Hong Kong

Spadicoides hodgkissa sp. nov. and Spadicoides arengae sp. nov., recorded from submerged decaying wood in Hong Kong and from decaying palm fronds in Brunei, are described and illustrated. Spadicoides hodgkissa is characterized by versicolored, obovoid conidia with up to 2 septa, including a distal distoseptum and a proximal euseptum, while Spadicoides arengae is characterized by unicellular, ellipsoidal conidia with verruculose walls that are relatively large. Eight genera, including Dendrographium, Helminthosporium, Luzfridiella, Paliphora, Polyschema, Polytretophora, Porosubramaniania, and Weufia, have the same conidiogenesis as Spadicoides. A key to these genera is provided.

Ascochyta mycoparasitica sp. nov., a novel mycoparasite of Sclerotium oryzae in California rice fields

Ascochyta mycoparasitica sp. nov., a novel mycoparasite from sclerotia of the stem rot of rice fungus, Sclerotium oryzae, is described. It was distinguished from other Ascochyta spp. by its relatively thick-walled, papillate, black pycnidium (100–250 μm diam), guttulate, slightly obovoid conidia (13.5-17.6 × 5.7-6.8 μm), and fungicolous habit. Ascochyta mycoparasitica was isolated from field-collected sclerotia of S. oryzae at higher frequency in March than just after rice harvest (in September) and from fields employing either no residue management or conventionally tilled residue management. The fungus parasitized sclerotia of S. oryzae and Rhizoctonia solani AG 1-IB in culture but not of 6 other sclerotial fungi tested. Ascochyta mycoparasitica also attacked hyphae, spores and other structures of 16 of 42 fungal species tested in co-culture on cellophane strips coated with cornmeal agar, being most virulent on S. oryzae, Harzia verrucosa, and Absidia glauca.

Ascochyta mycoparasitica sp. nov., a Novel Mycoparasite of Sclerotium oryzae in California Rice Fields

Ascochyta mycoparasitica sp. nov., a novel mycoparasite from sclerotia of the stem rot of rice fungus, Sclerotium oryzae, is described. It was distin- guished from other Ascochyta spp. by its relatively thick-walled, papillate, black pycnidium (100-250 uim diam), guttulate, slightly obovoid conidia (13.5-17.6 X 5.7-6.8 ,tm), and fungicolous habit. Ascochyta my- coparasitica was isolated from field-collected sclerotia of S. oryzae at higher frequency in March than just after rice harvest (in September) and from fields em- ploying either no residue management or conven- tionally tilled residue management. The fungus par- asitized sclerotia of S. oryzae and Rhizoctonia solani AG 1-IB in culture but not of 6 other sclerotial fungi tested. Ascochyta mycoparasitica also attacked hyphae, spores and other structures of 16 of 42 fungal species tested in co-culture on cellophane strips coated with cornmeal agar, being most virulent on S. oryzae, Har- zia verrucosa, and Absidia glauca.