Fusarium: more than a node or a foot-shaped basal cell

Recent publications have argued that there are potentially serious consequences for researchers in recognising distinct genera in the terminal fusarioid clade of the family Nectriaceae. Thus, an alternate hypothesis, namely a very broad concept of the genus Fusarium was proposed. In doing so, however, a significant body of data that supports distinct genera in Nectriaceae based on morphology, biology, and phylogeny is disregarded. A DNA phylogeny based on 19 orthologous protein-coding genes was presented to support a very broad concept of Fusarium at the F1 node in Nectriaceae. Here, we demonstrate that re-analyses of this dataset show that all 19 genes support the F3 node that represents Fusarium sensu stricto as defined by F. sambucinum (sexual morph synonym Gibberella pulicaris). The backbone of the phylogeny is resolved by the concatenated alignment, but only six of the 19 genes fully support the F1 node, representing the broad circumscription of Fusarium. Furthermore, a re-analysis of the concatenated dataset revealed alternate topologies in different phylogenetic algorithms, highlighting the deep divergence and unresolved placement of various Nectriaceae lineages proposed as members of Fusarium. Species of Fusarium s. str. are characterised by Gibberella sexual morphs, asexual morphs with thin- or thick-walled macroconidia that have variously shaped apical and basal cells, and trichothecene mycotoxin production, which separates them from other fusarioid genera. Here we show that the Wollenweber concept of Fusarium presently accounts for 20 segregate genera with clear-cut synapomorphic traits, and that fusarioid macroconidia represent a character that has been gained or lost multiple times throughout Nectriaceae. Thus, the very broad circumscription of Fusarium is blurry and without apparent synapomorphies, and does not include all genera with fusarium-like macroconidia, which are spread throughout Nectriaceae (e.g., Cosmosporella, Macroconia, Microcera). In this study four new genera are introduced, along with 18 new species and 16 new combinations. These names convey information about relationships, morphology, and ecological preference that would otherwise be lost in a broader definition of Fusarium. To assist users to correctly identify fusarioid genera and species, we introduce a new online identification database, Fusarioid-ID, accessible at www.fusarium.org. The database comprises partial sequences from multiple genes commonly used to identify fusarioid taxa (act1, CaM, his3, rpb1, rpb2, tef1, tub2, ITS, and LSU). In this paper, we also present a nomenclator of names that have been introduced in Fusarium up to January 2021 as well as their current status, types, and diagnostic DNA barcode data. In this study, researchers from 46 countries, representing taxonomists, plant pathologists, medical mycologists, quarantine officials, regulatory agencies, and students, strongly support the application and use of a more precisely delimited Fusarium (= Gibberella) concept to accommodate taxa from the robust monophyletic node F3 on the basis of a well-defined and unique combination of morphological and biochemical features. This F3 node includes, among others, species of the F. fujikuroi, F. incarnatum-equiseti, F. oxysporum, and F. sambucinum species complexes, but not species of Bisifusarium [F. dimerum species complex (SC)], Cyanonectria (F. buxicola SC), Geejayessia (F. staphyleae SC), Neocosmospora (F. solani SC) or Rectifusarium (F. ventricosum SC). The present study represents the first step to generating a new online monograph of Fusarium and allied fusarioid genera (www.fusarium.org).

Taxonomy and phylogeny of cercosporoid ascomycetes on Diospyros spp. with special emphasis on Pseudocercospora spp

A worldwide survey of cercosporoid ascomycete species on hosts of the genus Diospyros (persimmon) with key to the species based on characters in vivo is provided. Special emphasis is placed on species of the genus Pseudocercospora, which are in part also phylogenetically analysed, using a multilocus approach. Species of the latter genus proved to be very diverse, with a remarkable degree of cryptic speciation. Seven new species are described (Pseudocercospora diospyri-japonicae, P. diospyriphila, P. ershadii, P. kakiicola, P. kobayashiana, and P. tesselata), and two new names are introduced [P. kakiigena (≡ Cylindrosporium kaki, non Pseudocercospora kaki), and Zasmidium diospyri-hispidae (≡ Passalora diospyri, non Zasmidium diospyri)]. Six taxa are lectotypified (Cercospora atra, C. diospyri, C. diospyri var. ferruginea, C. flexuosa, C. fuliginosa, C. kaki), and Pseudocercospora kaki is epitypified.

Japanese species of Alternaria and their species boundaries based on host range

To clarify the diversity of plant-parasitic Alternaria species in Japan, diseased samples were collected, and fungal isolates established in culture. We examined 85 isolates representing 23 species distributed in 14 known sections based on conidial morphology and DNA phylogeny. Three species were found to be new, A. cylindrica, A. paragomphrenae and A. triangularis. Furthermore, a lectotype was designated for A. gomphrenae, and epitypes for A. cinerariae, A. gomphrenae, A. iridicola, and A. japonica. Species boundaries of isolates were also clarified by studying phenotypes and determining host ranges. Alternaria gomphrenae and related species in sect. Alternantherae were recognized as distinct species owing to their host specificity. Among the species infecting Apiaceae, the pathogenicity of A. cumini and a novel species, A. triangularis ex Bupleurum, were confirmed as host specific. Another novel species, A. cylindrica, proved to be host specific to Petunia. Alternaria iridicola was recognized as a large-spored species in sect. Alternaria, being host specific to Iris spp. On the other hand, the experimental host ranges of three morphologically and phylogenetically distinct species infecting Brassicaceae (A. brassicae, A. brassicicola, and A. japonica) showed almost no differences. Alternaria brassicicola and A. porri were even found on non-host plants. In general, host ranges of Alternaria species correlated with morphology and molecular phylogeny, and combining these datasets resulted in clearer species boundaries.

P1546 Reproducibility of right atrial myocardial deformation by two-dimensional speckle tracking

Background

Right atrial (RA) deformation by two-dimensional speckle tracking echocardiography has a relatively new technique to evaluate right heart function with pulmonary hypertension and cardiomyopathy. Reproducibility between observers of this technique is important to develop into a robust and reliable tool. Experience may pose significant challenges.

Purpose

The aim of this study is to evaluate reproducibility of RA strain (global and regional) between novice and expert.

Methods

One hundred thirty-three patients (n = 133) underwent 2D-Speckle tracking derived RA strain analysis by 3 independent blinded readers (expert and 2 novices). The novice observers were medical interns with no prior experience in performing strain analysis. Echocardiographic images were acquired from iE33 (Philips Medical System) but were analysed offline using single vendor dependent software (QLAB version 11.0; Philips Medical System). The result of novice observer was calculated by the average of novice observers. RA strain parameters were assessed: global RA strain and segmental (Basal, Mid, Roof). Intraobserver and interobserver analyses were performed using intra class correlation coefficients (ICC) between expert and novice.

Results

Expert and novice observer demonstrated good interobserver reproducibility of global RA strain (ICC 0.88) and segmental parameters (Basal: ICC 0.89, Mid: ICC 0.87, Roof: ICC 0.84). Of all parameters, the basal segment of RA strain showed the greatest interobserver agreement. Intraobserver agreement for novice observer was excellent for global RA strain and segmental parameters (ICC > 0.88).

Conclusions

Global RA strain and segmental parameters were highly reproducible by novice and expert strain observer.

Phylogeny and taxonomy of the genus Tubakia s. lat

The genus Tubakia is revised on the basis of morphological and phylogenetic data. The phylogenetic affinity of Tubakia to the family Melanconiellaceae (Diaporthales) was recently postulated, but new analyses based on sequences retrieved from material of the type species of Tubakia, T. dryina, support a family of its own, viz. Tubakiaceae fam. nov. Our phylogenetic analyses revealed the heterogeneity of Tubakia s. lat. which is divided into several genera, viz., Tubakia s. str., Apiognomonioides gen. nov. (type species: Apiognomonioides supraseptata), Involutiscutellula gen. nov. (type species: Involutiscutellula rubra), Oblongisporothyrium gen. nov. (type species: Oblongisporothyrium castanopsidis), Paratubakia gen. nov. (type species: Paratubakia subglobosa), Racheliella gen. nov. (type species: Racheliella wingfieldiana sp. nov.), Saprothyrium gen. nov. (type species: Saprothyrium thailandense) and Sphaerosporithyrium gen. nov. (type species: Sphaerosporithyrium mexicanum sp. nov.). Greeneria saprophytica is phylogenetically closely allied to Racheliella wingfieldiana and is therefore reallocated to Racheliella. Particular emphasis is laid on a revision and phylogenetic analyses of Tubakia species described from Japan and North America. Almost all North American collections of this genus were previously referred to as T. dryina s. lat., which is, however, a heterogeneous complex. Several new North American species have recently been described. The new species Sphaerosporithyrium mexicanum, Tubakia melnikiana and T. sierrafriensis, causing leaf spots on several oak species found in the North-Central Mexican state Aguascalientes and the North-Eastern Mexican state Nuevo León, are described, illustrated, and compared with similar species. Several additional new species are introduced, including Tubakia californica based on Californian collections on various species of the genera Chrysolepis, Notholithocarpus and Quercus, and T. dryinoides, T. oblongispora, T. paradryinoides, and Paratubakia subglobosoides described on the basis of Japanese collections. Tubakia suttoniana nom. nov., based on Dicarpella dryina, is a species closely allied to T. californica and currently only known from Europe. Tubakia dryina, type species of Tubakia, is epitypified, and the phylogenetic position and circumscription of Tubakia are clarified. A revised, supplemented key to the species of Tubakia and allied genera on the basis of conidiomata is provided.

Mycosphaerellaceae - Chaos or clarity?

The Mycosphaerellaceae represent thousands of fungal species that are associated with diseases on a wide range of plant hosts. Understanding and stabilising the taxonomy of genera and species of Mycosphaerellaceae is therefore of the utmost importance given their impact on agriculture, horticulture and forestry. Based on previous molecular studies, several phylogenetic and morphologically distinct genera within the Mycosphaerellaceae have been delimited. In this study a multigene phylogenetic analysis (LSU, ITS and rpb2) was performed based on 415 isolates representing 297 taxa and incorporating ex-type strains where available. The main aim of this study was to resolve the phylogenetic relationships among the genera currently recognised within the family, and to clarify the position of the cercosporoid fungi among them. Based on these results many well-known genera are shown to be paraphyletic, with several synapomorphic characters that have evolved more than once within the family. As a consequence, several old generic names including Cercosporidium, Fulvia, Mycovellosiella, Phaeoramularia and Raghnildiana are resurrected, and 32 additional genera are described as new. Based on phylogenetic data 120 genera are now accepted within the family, but many currently accepted cercosporoid genera still remain unresolved pending fresh collections and DNA data. The present study provides a phylogenetic framework for future taxonomic work within the Mycosphaerellaceae.

A phylogenetic re-evaluation of Phyllosticta (Botryosphaeriales)

Phyllosticta is a geographically widespread genus of plant pathogenic fungi with a diverse host range. This study redefines Phyllosticta, and shows that it clusters sister to the Botryosphaeriaceae (Botryosphaeriales, Dothideomycetes), for which the older family name Phyllostictaceae is resurrected. In moving to a unit nomenclature for fungi, the generic name Phyllosticta was chosen over Guignardia in previous studies, an approach that we support here. We use a multigene DNA dataset of the ITS, LSU, ACT, TEF and GPDH gene regions to investigate 129 isolates of Phyllosticta, representing about 170 species names, many of which are shown to be synonyms of the ubiquitous endophyte P. capitalensis. Based on the data generated here, 12 new species are introduced, while epitype and neotype specimens are designated for a further seven species. One species of interest is P. citrimaxima associated with tan spot of Citrus maxima fruit in Thailand, which adds a fifth species to the citrus black spot complex. Previous morphological studies lumped many taxa under single names that represent complexes. In spite of this Phyllosticta is a species-rich genus, and many of these taxa need to be recollected in order to resolve their phylogeny and taxonomy.

Species concepts in Cercospora: spotting the weeds among the roses

The genus Cercospora contains numerous important plant pathogenic fungi from a diverse range of hosts. Most species of Cercospora are known only from their morphological characters in vivo. Although the genus contains more than 5 000 names, very few cultures and associated DNA sequence data are available. In this study, 360 Cercospora isolates, obtained from 161 host species, 49 host families and 39 countries, were used to compile a molecular phylogeny. Partial sequences were derived from the internal transcribed spacer regions and intervening 5.8S nrRNA, actin, calmodulin, histone H3 and translation elongation factor 1-alpha genes. The resulting phylogenetic clades were evaluated for application of existing species names and five novel species are introduced. Eleven species are epi-, lecto- or neotypified in this study. Although existing species names were available for several clades, it was not always possible to apply North American or European names to African or Asian strains and vice versa. Some species were found to be limited to a specific host genus, whereas others were isolated from a wide host range. No single locus was found to be the ideal DNA barcode gene for the genus, and species identification needs to be based on a combination of gene loci and morphological characters. Additional primers were developed to supplement those previously published for amplification of the loci used in this study.

Phylogenetic lineages in Pseudocercospora

Pseudocercospora is a large cosmopolitan genus of plant pathogenic fungi that are commonly associated with leaf and fruit spots as well as blights on a wide range of plant hosts. They occur in arid as well as wet environments and in a wide range of climates including cool temperate, sub-tropical and tropical regions. Pseudocercospora is now treated as a genus in its own right, although formerly recognised as either an anamorphic state of Mycosphaerella or having mycosphaerella-like teleomorphs. The aim of this study was to sequence the partial 28S nuclear ribosomal RNA gene of a selected set of isolates to resolve phylogenetic generic limits within the Pseudocercospora complex. From these data, 14 clades are recognised, six of which cluster in Mycosphaerellaceae. Pseudocercospora s. str. represents a distinct clade, sister to Passalora eucalypti, and a clade representing the genera Scolecostigmina, Trochophora and Pallidocercospora gen. nov., taxa formerly accommodated in the Mycosphaerella heimii complex and characterised by smooth, pale brown conidia, as well as the formation of red crystals in agar media. Other clades in Mycosphaerellaceae include Sonderhenia, Microcyclosporella, and Paracercospora. Pseudocercosporella resides in a large clade along with Phloeospora, Miuraea, Cercospora and Septoria. Additional clades represent Dissoconiaceae, Teratosphaeriaceae, Cladosporiaceae, and the genera Xenostigmina, Strelitziana, Cyphellophora and Thedgonia. The genus Phaeomycocentrospora is introduced to accommodate Mycocentrospora cantuariensis, primarily distinguished from Pseudocercospora based on its hyaline hyphae, broad conidiogenous loci and hila. Host specificity was considered for 146 species of Pseudocercospora occurring on 115 host genera from 33 countries. Partial nucleotide sequence data for three gene loci, ITS, EF-1α, and ACT suggest that the majority of these species are host specific. Species identified on the basis of host, symptomatology and general morphology, within the same geographic region, frequently differed phylogenetically, indicating that the application of European and American names to Asian taxa, and vice versa, was often not warranted.

TAXONOMIC NOVELTIES

New genera - Pallidocercospora Crous, Phaeomycocentrospora Crous, H.D. Shin & U. Braun; New species - Cercospora eucommiae Crous, U. Braun & H.D. Shin, Microcyclospora quercina Crous & Verkley, Pseudocercospora ampelopsis Crous, U. Braun & H.D. Shin, Pseudocercospora cercidicola Crous, U. Braun & C. Nakash., Pseudocercospora crispans G.C. Hunter & Crous, Pseudocercospora crocea Crous, U. Braun, G.C. Hunter & H.D. Shin, Pseudocercospora haiweiensis Crous & X. Zhou, Pseudocercospora humulicola Crous, U. Braun & H.D. Shin, Pseudocercospora marginalis G.C. Hunter, Crous, U. Braun & H.D. Shin, Pseudocercospora ocimi-basilici Crous, M.E. Palm & U. Braun, Pseudocercospora plectranthi G.C. Hunter, Crous, U. Braun & H.D. Shin, Pseudocercospora proteae Crous, Pseudocercospora pseudostigmina-platani Crous, U. Braun & H.D. Shin, Pseudocercospora pyracanthigena Crous, U. Braun & H.D. Shin, Pseudocercospora ravenalicola G.C. Hunter & Crous, Pseudocercospora rhamnellae G.C. Hunter, H.D. Shin, U. Braun & Crous, Pseudocercospora rhododendri-indici Crous, U. Braun & H.D. Shin, Pseudocercospora tibouchinigena Crous & U. Braun, Pseudocercospora xanthocercidis Crous, U. Braun & A. Wood, Pseudocercosporella koreana Crous, U. Braun & H.D. Shin; New combinations - Pallidocercospora acaciigena (Crous & M.J. Wingf.) Crous & M.J. Wingf., Pallidocercospora crystallina (Crous & M.J. Wingf.) Crous & M.J. Wingf., Pallidocercospora heimii (Crous) Crous, Pallidocercospora heimioides (Crous & M.J. Wingf.) Crous & M.J. Wingf., Pallidocercospora holualoana (Crous, Joanne E. Taylor & M.E. Palm) Crous, Pallidocercospora konae (Crous, Joanne E. Taylor & M.E. Palm) Crous, Pallidoocercospora irregulariramosa (Crous & M.J. Wingf.) Crous & M.J. Wingf., Phaeomycocentrospora cantuariensis (E.S. Salmon & Wormald) Crous, H.D. Shin & U. Braun, Pseudocercospora hakeae (U. Braun & Crous) U. Braun & Crous, Pseudocercospora leucadendri (Cooke) U. Braun & Crous, Pseudocercospora snelliana (Reichert) U. Braun, H.D. Shin, C. Nakash. & Crous, Pseudocercosporella chaenomelis (Y. Suto) C. Nakash., Crous, U. Braun & H.D. Shin; Typifications: Epitypifications - Pseudocercospora angolensis (T. Carvalho & O. Mendes) Crous & U. Braun, Pseudocercospora araliae (Henn.) Deighton, Pseudocercospora cercidis-chinensis H.D. Shin & U. Braun, Pseudocercospora corylopsidis (Togashi & Katsuki) C. Nakash. & Tak. Kobay., Pseudocercospora dovyalidis (Chupp & Doidge) Deighton, Pseudocercospora fukuokaensis (Chupp) X.J. Liu & Y.L. Guo, Pseudocercospora humuli (Hori) Y.L. Guo & X.J. Liu, Pseudocercospora kiggelariae (Syd.) Crous & U. Braun, Pseudocercospora lyoniae (Katsuki & Tak. Kobay.) Deighton, Pseudocercospora lythri H.D. Shin & U. Braun, Pseudocercospora sambucigena U. Braun, Crous & K. Schub., Pseudocercospora stephanandrae (Tak. Kobay. & H. Horie) C. Nakash. & Tak. Kobay., Pseudocercospora viburnigena U. Braun & Crous, Pseudocercosporella chaenomelis (Y. Suto) C. Nakash., Crous, U. Braun & H.D. Shin, Xenostigmina zilleri (A. Funk) Crous; Lectotypification - Pseudocercospora ocimicola (Petr. & Cif.) Deighton; Neotypifications - Pseudocercospora kiggelariae (Syd.) Crous & U. Braun, Pseudocercospora lonicericola (W. Yamam.) Deighton, Pseudocercospora zelkovae (Hori) X.J. Liu & Y.L. Guo.

First Report of Root Rot of Cocoyam Caused by Pythium myriotylum in Sri Lanka

Root rot of cocoyam (Xanthosoma sagittifolium L. Schott) caused by Pythium myriotylum Drechsler is a major disease of this crop in Africa (1,2) but is unreported from other regions of the world. During September 1999, commercially grown cocoyam (cv. Ratu-kiri-ala) in Gampaha (7°05'N, 80°00'E), Sri Lanka suffered from severe root rot. Initial symptoms were water-soaked lesions at the root tips that gradually enlarged to rot the entire root system and tuber. Wilting and yellowing of leaves were observed in advanced stages of disease. A Pythium sp. was regularly isolated from the affected roots and an isolate, SC5, was identified as P. myriotylum on the basis of morphology and the internal transcribed spacer (ITS) rDNA sequence. Characteristics of isolate SC5, grown on a grass-leaf water culture (3) were main hyphae up to 8.5 μm wide, oogonia terminal or intercalary (22.5 to 33.8 μm in diameter), antheridia diclinous occasionally monoclinous, one to eight per oogonium, stalks branched, often more or less loosely enveloping the oogonium, antheridium clavate or crook-necked, making apical contact with the oogonium, breadth of antheridium 2.5 to 7.0 μm, oospores aplerotic (17.0 to 22.5 μm in diameter), oospore wall 0.8 to 2.0 μm in thickness, sporangia terminal or intercalary, filamentous, inflated lobulate, and digitate, of variable length, breadth of sporangia 7.0 to 17.5 μm, formed in water; zoospores formed at 25°C, and diameter of encysted zoospores 10.0 to 12.5 μm. Cardinal temperatures on potato carrot agar 8°C minimum, 34°C optimum, and 37°C maximum with daily radial growth rate for 34°C at 32.8 mm. The ITS rDNA sequence of the isolate matched the sequences of P. myriotylum in GenBank (Accession Nos. AB095051 and AF452156) and isolate CBS254.70 used for the species description by van der Plaats-Niterink (3). The sequence of SC5 has been deposited in GenBank, Accession No. DQ102701. Pathogenicity tests used potted cocoyam plants (20 cm high), planted in an autoclaved potting mix. Four agar disks (8 mm in diameter) of isolate SC5 grown at 25°C for 48 h on potato dextrose agar was mashed and injected at a depth of 2 to 3 cm in the soil around the roots. Inoculated plants were placed in transparent plastic bags and kept for 7 days in a growth chamber maintained at 24 to 26°C with continuous light (52 to 98 μmol m^-2·s^-1). The experiment was carried out twice with three replications for each test. Dark brown rotting on roots and wilting of leaves were observed in 7 days after the inoculation. P. myriotylum was reisolated from diseased tissues and found to be morphologically identical to the original isolate SC5. Noninoculated control plants remained healthy. On the basis of the symptoms, morphological and molecular characteristics and confirmation of pathogenicity, P. myriotylum is the causal agent of root rot of cocoyam. To our knowledge, this is the first report of P. myriotylum causing root rot of cocoyam in Sri Lanka. References: (1) S. Nzietchueng. L'agronomie Tropicale 38:321, 1983. (2) R. P. Pacumbaba et al. J. Phytopathol. 135:265, 1992. (3) A. J. Van Der Plaats-Niterink. Stud. Mycol. 21:1, 1981.

Confinement of pure-electron plasmas in a toroidal magnetic-surface configuration

A pure-electron plasma has been confined in a toroidal magnetic-surface configuration for as long as classical diffusion time due to neutral collisions. By controlling the potential of the internal conductor, long-term stable confinement of electrons has been achieved in a toroidal geometry.

Injection of electron beam into a toroidal trap using chaotic orbits near magnetic null

Injection of charged particle beam into a toroidal magnetic trap enables a variety of interesting experiments on non-neutral plasmas. Stationary radial electric field has been produced in a toroidal geometry by injecting electrons continuously. When an electron gun is placed near an X point of magnetic separatrix, the electron beam spreads efficiently through chaotic orbits, and electrons distribute densely in the torus. The current returning back to the gun can be minimized less than 1% of the total emission.