One of the causal agents of human sporotrichosis, Sporothrix schenckii, is the type species of the genus Sporothrix. During the course of the last century the asexual morphs of many Ophiostoma spp. ...have also been treated in Sporothrix. More recently several DNA-based studies have suggested that species of Sporothrix and Ophiostoma converge in what has become known as Ophiostoma s. lat. Were the one fungus one name principles adopted in the Melbourne Code to be applied to Ophiostoma s. lat., Sporothrix would have priority over Ophiostoma, resulting in more than 100 new combinations. The consequence would be name changes for several economically important tree pathogens including O. novo-ulmi. Alternatively, Ophiostoma could be conserved against Sporothrix, but this would necessitate changing the names of the important human pathogens in the group. In this study, we sought to resolve the phylogenetic relationship between Ophiostoma and Sporothrix. DNA sequences were determined for the ribosomal large subunit and internal transcribed spacer regions, as well as the beta-tubulin and calmodulin genes in 65 isolates. The results revealed Sporothrix as a well-supported monophyletic lineage including 51 taxa, distinct from Ophiostoma s. str. To facilitate future studies exploring species level resolution within Sporothrix, we defined six species complexes in the genus. These include the Pathogenic Clade containing the four human pathogens, together with the S. pallida-, S. candida-, S. inflata-, S. gossypina- and S. stenoceras complexes, which include environmental species mostly from soil, hardwoods and Protea infructescences. The description of Sporothrix is emended to include sexual morphs, and 26 new combinations. Two new names are also provided for species previously treated as Ophiostoma.
The polyphagous shot hole borer (PSHB), an ambrosia beetle (Coleoptera: Curculeonidae: Scolytinae) native to Asia, together with its fungal symbiont
Fusarium euwallaceae,
has emerged as an important ...invasive pest killing avocado and other trees in Israel and the United States. The PSHB is one of three cryptic species in the
Euwallacea fornicatus
species complex, the taxonomy of which remains to be resolved. The surge in the global spread of invasive forest pests such as the PSHB has led to the development of programmes utilising sentinel tree plantings to record new host-pest interactions. During routine surveys of tree health in botanical gardens of South Africa undertaken as part of a sentinel project, an ambrosia beetle/fungal associate was detected damaging
Platanus
x
acerifolia
(London Plane) in the KwaZulu-Natal National Botanical Gardens, Pietermaritzburg. Identification of the beetle by sequencing part of the mitochondrial cytochrome oxidase
c
subunit 1 (COI) gene confirmed its identity as PSHB, and specifically one of the invasive haplotypes of the beetle. The associated fungus
F. euwallaceae
was identified based on phylogenetic analysis of elongation factor (
EF 1-α
) sequences. Koch’s postulates have confirmed the pathogenicity of fungal isolates to
P.
x
acerifolia
. This is the first report of PSHB and its fungal symbiont causing Fusarium dieback in South Africa. This report also represents the first verified case of a damaging invasive forest pest detected in a sentinel planting project, highlighting the importance of such studies. Given the potential impact these species present to urban trees, native biodiversity and agriculture, both the PSHB and its fungal symbiont should be included in invasive species regulations in South Africa.
The plant pathogenic asexual fungus Thielaviopsis basicola (Ascomycota) causes black root rot on many important agricultural and ornamental plant species. Since its first description in 1850, this ...species has had a tumultuous taxonomic history, being classified in many different genera. Thus far, DNA‐based techniques have not played a significant role in identification of T. basicola and have been used only to confirm its placement in the Microascales. This investigation reconsidered the phylogenetic placement of T. basicola, using DNA sequence data for six different gene regions. It included 41 isolates identified as T. basicola from 13 geographical locations worldwide. Phylogenetic analyses showed that these isolates grouped in a well‐supported lineage distinct from other genera in the Ceratocystidaceae, here described as Berkeleyomyces gen. nov. The data also provided robust evidence that isolates of T. basicola include a cryptic sister species. As a result, this report provides a new combination as B. basicola comb. nov. and introduces a new species as B. rouxiae sp. nov.
The Ophiostomatales was erected in 1980. Since that time, several of the genera have been redefined and others have been described. There are currently 14 accepted genera in the Order. They include ...species that are the causal agents of plant and human diseases and common associates of insects such as bark beetles. Well known examples include the Dutch elm disease fungi and the causal agents of sporotrichosis in humans and animals. The taxonomy of the Ophiostomatales was confused for many years, mainly due to the convergent evolution of morphological characters used to delimit unrelated fungal taxa. The emergence of DNA-based methods has resolved much of this confusion. However, the delineation of some genera and the placement of various species and smaller lineages remains inconclusive. In this study we reconsidered the generic boundaries within the Ophiostomatales . A phylogenomic framework constructed from genome-wide sequence data for 31 species representing the major genera in the Order was used as a guide to delineate genera. This framework also informed our choice of the best markers from the currently most commonly used gene regions for taxonomic studies of these fungi. DNA was amplified and sequenced for more than 200 species, representing all lineages in the Order. We constructed phylogenetic trees based on the different gene regions and assembled a concatenated data set utilising a suite of phylogenetic analyses. The results supported and confirmed the delineation of nine of the 14 currently accepted genera, i.e. Aureovirgo , Ceratocystiopsis , Esteya , Fragosphaeria , Graphilbum , Hawksworthiomyces , Ophiostoma , Raffaelea and Sporothrix . The two most recently described genera, Chrysosphaeria and Intubia , were not included in the multi-locus analyses. This was due to their high sequence divergence, which was shown to result in ambiguous taxonomic placement, even though the results of phylogenomic analysis supported their inclusion in the Ophiostomatales . In addition to the currently accepted genera in the Ophiostomatales , well-supported lineages emerged that were distinct from those genera. These are described as novel genera. Two lineages included the type species of Grosmannia and Dryadomyces and these genera are thus reinstated and their circumscriptions redefined. The descriptions of all genera in the Ophiostomatales were standardised and refined where this was required and 39 new combinations have been provided for species in the newly emerging genera and one new combination has been provided for Sporothrix . The placement of Afroraffaelea could not be confirmed using the available data and the genus has been treated as incertae sedis in the Ophiostomatales . Paleoambrosia was not included in this study, due to the absence of living material available for this monotypic fossil genus. Overall, this study has provided the most comprehensive and robust phylogenies currently possible for the Ophiostomatales . It has also clarified several unresolved One Fungus-One Name nomenclatural issues relevant to the Order.
The genus Ceratocystis was established in 1890 and accommodates many important fungi. These include serious plant pathogens, significant insect symbionts and agents of timber degradation that result ...in substantial economic losses. Virtually since its type was described from sweet potatoes, the taxonomy of Ceratocystis has been confused and vigorously debated. In recent years, particulary during the last two decades, it has become very obvious that this genus includes a wide diversity of very different fungi. These have been roughly lumped together due to their similar morphological structures that have clearly evolved through convergent evolution linked to an insect-associated ecology. As has been true for many other groups of fungi, the emergence of DNA-based sequence data and associated phylogenetic inferences, have made it possible to robustly support very distinct boundaries defined by morphological characters and ecological differences. In this study, DNA-sequence data for three carefully selected gene regions (60S, LSU, MCM7) were generated for 79 species residing in the aggregate genus Ceratocystis sensu lato and these data were subjected to rigorous phylogenetic analyses. The results made it possible to distinguish seven major groups for which generic names have been chosen and descriptions either provided or emended. The emended genera included Ceratocystis sensu stricto, Chalaropsis, Endoconidiophora, Thielaviopsis, and Ambrosiella, while two new genera, Davidsoniella and Huntiella, were described. In total, 30 new combinations have been made. This major revision of the generic boundaries in the Ceratocystidaceae will simplify future treatments and work with an important group of fungi including distantly related species illogically aggregated under a single name.
Studies addressing the economic impacts of invasive alien species are biased towards ex-post assessments of the costs and benefits of control options, but ex-ante assessments are also required to ...deal with potentially damaging invaders. The polyphagous shot hole borer Euwallacea fornicatus (Coleoptera: Curculionidae) is a recent and potentially damaging introduction to South Africa. We assessed the potential impact of this beetle by working across economic and biological disciplines and developing a simulation model that included dynamic mutualistic relations between the beetle and its symbiotic fungus. We modeled the potential growth in beetle populations and their effect on the net present cost of damage to natural forests, urban trees, commercial forestry, and the avocado industry over 10 yr. We modeled high, baseline, and low scenarios using discount rates of 8, 6, and 4%, and a plausible range of costs and mortality rates. Models predicted steady growth in the beetle and fungus populations, leading to average declines in tree populations of between 3.5 and 15.5% over 10 yr. The predicted net present cost was 18.45 billion international dollars (Int. $), or about 0.66% of the country's GDP for our baseline scenario ($2.7 billion to $164 billion for low and high scenarios). Most of the costs are for the removal of urban trees that die as a result of the beetle and its fungal symbiont, as has been found in other regions. We conclude that an ex-ante economic assessment system dynamics model can be useful for informing national strategies on invasive alien species management.
The polyphagous shothole borer (
, PSHB), an ambrosia beetle, with its fungal symbiont,
, is responsible for Fusarium dieback (FD) in a wide range of woody hosts. In 2019, the first suspected case of
...was reported in macadamia in South Africa. The aims of this study were to confirm the
report and thereafter to assess the susceptibility of commercially planted macadamia cultivars to FD caused by
The identities of the beetle and associated fungal symbionts were confirmed by means of DNA sequence analysis of the 28S ribosomal large subunit gene for beetles and the internal transcribed spacer region for fungi. Isolates identified as
species were further characterized by phylogenetic analysis of the translation elongation factor 1α and the β-tubulin gene regions. Thereafter, Koch's postulates regarding
were fulfilled on a mature
tree planted at the experimental farm of the University of Pretoria. In order to determine susceptibility against FD, additional cultivar screening was conducted on nine commercially planted cultivars by means of pathogenicity trials using sterilized or inoculated toothpicks inserted into detached branches. Detached branch inoculations showed no significant lesion development six weeks post inoculation, except for cultivar 816. The restricted growth of
observed in macadamia tissues therefore suggests that macadamia may not be a suitable host for
and that the threat of FD in macadamia in the event of
infestation is less than for other
hosts. Future work on beetle attraction to macadamia is recommended for a more comprehensive understanding of the interaction between
and its fungal symbionts and macadamia.
Black root rot caused by the pathogen Thielaviopsis basicola has been known since the mid 1800s. The disease is important on many agricultural and ornamental plant species and has been found in at ...least 31 countries. Since its description, the pathogen has had a complex taxonomic history that has resulted in a confused literature. A recent revision of the Ceratocystidaceae following the advent of DNA sequencing technology has made it possible to resolve this confusion. Importantly, it has also shown that there are two pathogens in the Ceratocystidaceae that cause black root rot. They reside in the newly established genus Berkeleyomyces and are now known as B. basicola and B. rouxiae. This review considers the taxonomic history of the black root rot pathogens, and their global distribution. Prospects relating to the serious diseases that they cause and the likely impact that the era of genomics will have on our understanding of the pathogens are also highlighted.
DNA phylogenetic comparisons have shown that morphology-based species recognition often underestimates fungal diversity. Therefore, the need for accurate DNA sequence data, tied to both correct ...taxonomic names and clearly annotated specimen data has never been greater. Furthermore, the growing number of molecular ecology projects employing high-throughput sequencing require fast and effective methods for en masse species assignments. In this paper we focus on selecting and re-annotating a set of marker reference sequences that represent each currently accepted order of Fungi. The particular focus is on sequences from the internal transcribed spacer (ITS) region in the nuclear ribosomal cistron, derived from type specimens and/or ex-type cultures. Re-annotated and verified sequences were deposited in a curated, public database at the National Center for Biotechnology Information (NCBI), RefSeq Targeted Loci (RTL), and will be visible during routine BLAST searches with NR prefixed accession numbers. A set of standards and protocols is proposed in order to improve the data quality of new sequences and we suggest how type and other reference sequences can be used to improve identification of Fungi.
The Ophiostomatales (Ascomycota) include mainly insect and mite-associated fungi, the majority of which are found on trees. Very little is known regarding the occurrence or diversity of these fungi ...in South America. The aim of this study was to consider their occurrence on native Nothofagus trees in the Patagonian Andes of Argentina. Isolates were collected in national parks and provincial reserves in Patagonia between 2009 and 2011. These were grouped based on morphology, and 22 representative isolates were included in phylogenetic analyses based on sequence data of multiple loci (LSU, ITS, beta-tubulin and translation elongation factor-1 alpha genes). The isolates could be assigned to ten different taxa, and included eight species of Ophiostoma s. l., one species of Leptographium, and one species in the Sporothrix lignivora complex. Three of the species are described as new, including Ophiostoma patagonicum, Leptographium gestamen, and Sporothrix cabralii. Ophiostoma quercus and O. noveae-zelandiae are reported for the first time from Argentina, and we show that the latter species is distinct from O. pluriannulatum, in contrast to a previous suggestion that they represent the same taxon.
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