830 research outputs found
Celoporthe dispersa gen. et sp. nov. from native Myrtales in South Africa
In a survey for Cryphonectria and Chrysoporthe species on
Myrtales in South Africa, a fungus resembling the stem canker
pathogen Chrysoporthe austroafricana was collected from native
Syzygium cordatum near Tzaneen (Limpopo Province), Heteropyxis
canescens near Lydenburg (Mpumalanga Province) and exotic Tibouchina
granulosa in Durban (KwaZulu-Natal Province). The fungus was associated
with dying branches and stems on S. cordatum, H.
canescens and T. granulosa. However, morphological
differences were detected between the unknown fungus from these three hosts
and known species of Chrysoporthe. The aim of this study was to
characterise the fungus using DNA sequence comparisons and morphological
features. Pathogenicity tests were also conducted to assess its virulence on
Eucalyptus (ZG 14 clones), H. natalensis and T.
granulosa. Plants of H. canescens were not available for
inoculation. Results showed distinct morphological differences between the
unknown fungus and Chrysoporthe spp. Phylogenetic analysis showed
that isolates reside in a clade separate from Chrysoporthe and other
related genera. Celoporthe dispersa gen. et sp. nov. is, therefore,
described to accommodate this fungus. Pathogenicity tests showed that
C. dispersa is not pathogenic to H.
natalensis, but that it is a potential pathogen of
Eucalyptus and Tibouchina spp
A disease epidemic on Zizyphus mucronata in the Kruger National Park caused by Coniodictyum chevalieri
This study records a severe outbreak of a disease on Zizyphus
mucronata (Rhamnaceae) in Greater Kruger National Park, South
Africa. The causal agent of the disease was found to be Coniodictyum
chevalieri, a fungus previously believed to be very rare. Detailed
illustrations of the symptoms and fungus are presented in order to facilitate
future studies. The known geographical distribution of Coniodictyum
is presented in relation to the distribution of its host, and a short review
of its systematic history is also given. This also treats an invalidly
published species name in South Africa, which has confused the literature. A
DNA-based phylogeny is presented for the pathogen and this reflects the unique
nature of its geographical distribution and biology
Microthia, Holocryphia and Ursicollum, three new genera on Eucalyptus and Coccoloba for fungi previously known as Cryphonectria
Cryphonectria havanensis is a fungus associated with
Eucalyptus species in Cuba and Florida (U.S.A.). Until recently,
there have been no living cultures of C. havanensis and it has thus
not been possible to assess its taxonomic status. Isolates thought to
represent this fungus have, however, emerged from surveys of
Eucalyptus in Mexico and Hawaii (U.S.A.). Results of this study
showed that these isolates represent C. havanensis but reside in a
genus distinct from Cryphonectria sensu stricto, which is described
here as Microthia. Isolates of an unidentified fungus occurring on
Myrica faya in the Azores and Madeira also grouped in
Microthia and were identical to other M. havanensis
isolates. Cryphonectria coccolobae, a fungus occurring on sea grape
(Coccoloba uvifera) in Bermuda and Florida, was found to be
morphologically identical to Microthia and is transferred to this
genus, but as a distinct species. Surveys for M. coccolobae on sea
grape in Florida, yielded a second diaporthalean fungus from this host. This
fungus is morphologically and phylogenetically distinct from M.
coccolobae and other closely related taxa and is described as
Ursicollum fallax gen. et sp. nov. Phylogenetic analyses in this
study have also shown that isolates of C. eucalypti, a pathogen of
Eucalyptus in South Africa and Australia, group in a clade separate
from all other groups including that representing Cryphonectria sensu
stricto. This difference is supported by the fact that Cryphonectria
eucalypti has ascospore septation different to that of all other
Cryphonectria species. A new genus, Holocryphia, is thus
erected for C. eucalypti
Pestalotioid fungi from Restionaceae in the Cape Floral Kingdom
Eight pestalotioid fungi were isolated from the Restionaceae
growing in the Cape Floral Kingdom of South Africa. Sarcostroma
restionis, Truncatella megaspora, T.
restionacearum and T. spadicea are newly described.
New records include Pestalotiopsis matildae, Sarcostroma
lomatiae, Truncatella betulae and T. hartigii.
To resolve generic affiliations, phylogenetic analyses were performed on ITS
(ITS1, 5.8S, ITS2) and part of 28S rDNA. DNA data support the original generic
concept of Truncatella, which encompasses Pestalotiopsis
species having 3-septate conidia. The genus Sarcostroma is retained
as separate from Seimatosporium
Fungal phoenix rising from the ashes?
During May 2010, sporocarps of what appeared to be an Armillaria sp. were found in large clumps in historic Kirstenbosch Botanical Gardens on the foot of Table Mountain, Cape Town, South Africa. These sporocarps could be physically linked to the roots of unidentified dead trees and Protea spp. The aim of this study was to identify the Armillaria sp. found fruiting in Kirstenbosch. To achieve this goal isolates were made from the mycelium under the bark of dead roots linked to sporocarps. The ITS and IGS-1 regions were sequenced and compared to sequences of Armillaria spp. available on GenBank. Cladograms were generated using ITS sequences to determine the phylogenetic relationship of the isolates with other Armillaria spp. Sequence comparisons and phylogenetic analyses showed that the isolates represented A. mellea. They were also identical to isolates of this species previously discovered in the Company Gardens in South Africa and introduced from Europe apparently by the early Dutch Settlers. Armillaria mellea is alien and apparently invasive in Cape Town, fruits profusely and has the potential to spread to sensitive native forests on the foothills of the City
Multi-gene phylogenies define Ceratocystiopsis and Grosmannia distinct from Ophiostoma
Ophiostoma species have diverse morphological features and are
found in a large variety of ecological niches. Many different classification
schemes have been applied to these fungi in the past based on teleomorph and
anamorph features. More recently, studies based on DNA sequence comparisions
have shown that Ophiostoma consists of different phylogenetic groups,
but the data have not been sufficient to define clear monophyletic lineages
represented by practical taxonomic units. We used DNA sequence data from
combined partial nuclear LSU and β-tubulin genes to consider the
phylogenetic relationships of 50 Ophiostoma species, representing all
the major morphological groups in the genus. Our data showed three
well-supported, monophyletic lineages in Ophiostoma. Species with
Leptographium anamorphs grouped together and to accommodate these
species the teleomorph-genus Grosmannia (type species G.
penicillata), including 27 species and 24 new combinations, is
re-instated. Another well-defined lineage includes species that are
cycloheximide-sensitive with short perithecial necks, falcate ascospores and
Hyalorhinocladiella anamorphs. For these species, the
teleomorph-genus Ceratocystiopsis (type species O. minuta),
including 11 species and three new combinations, is re-instated. A third group
of species with either Sporothrix or Pesotum anamorphs
includes species from various ecological niches such as Protea
infructescences in South Africa. This group also includes O.
piliferum, the type species of Ophiostoma, and these species are
retained in that genus. Ophiostoma is redefined to reflect the
changes resulting from new combinations in Grosmannia and
Ceratocystiopsis. Our data have revealed additional lineages in
Ophiostoma linked to morphological characters. However, these species
are retained in Ophiostoma until further data for a larger number of
species can be obtained to confirm monophyly of the apparent lineages
Truncation of MAT1-2-7 deregulates developmental pathways associated with sexual reproduction in Huntiella omanensis
The MAT1-1-1 and MAT1-2-1 genes are thought to be the master regulators
of sexual development in most ascomycete fungi, and they are often essential for
this process. In contrast, it has been suggested that the secondary mating-type genes
act to calibrate the sexual cycle and can be dispensable. Recent functional characterization
of genes such as Aspergillus fumigatus MAT1-2-4, Huntiella omanensis MAT1-2-7,
and Botrytis cinerea MAT1-1-5 has, however, shown that these secondary genes may
play more central roles in the sexual pathway and are essential for the production of
mature fruiting structures. We used a comparative transcriptome sequencing (RNAseq)
experiment to show that the truncation of MAT1-2-7 in the wood inhabiting H.
omanensis residing in the Ceratocystidaceae is associated with the differential expression
of approximately 25% of all the genes present in the genome, including the
transcriptional regulators ste12, wc-2, sub1, VeA, HMG8, and pro1. This suggests that
MAT1-2-7 may act as a transcription factor and that DMAT1-2-7 mutant sterility is the
result of layered deregulation of a variety of signaling and developmental pathways.
This study is one of only a few that details the functional characterization of a secondary
MAT gene in a nonmodel species. Given that this gene is present in other
Ceratocystidaceae species and that there are diverse secondary MAT genes present
throughout the Pezizomycotina, further investigation into this gene and others like it
will provide a clearer understanding of sexual development in these eukaryotes.
IMPORTANCE Secondary mating-type genes are being described almost as quickly as
new fungal genomes are being sequenced. Understanding the functions of these genes
has lagged behind their description, in part due to limited taxonomic distribution, lack of conserved functional domains, and difficulties with regard to genetic manipulation protocols.
This study aimed to address this by investigating a novel mating-type gene, MAT1-
2-7, for which two independent mutant strains were generated in a previous study. We
characterized the molecular response to the truncation of this gene in a nonmodel,
wood-infecting fungus and showed that it resulted in widespread differential expression
throughout the transcriptome of this fungus. This suggests that secondary MAT genes
may play a more important role than previously thought. This study also emphasizes the
need for further research into the life cycles of nonmodel fungi, which often exhibit
unique features that are very different from the systems understood from model species.The University of Pretoria, the Department of Science and Technology (DST)/National Research Foundation (NRF) Centre of Excellence in Tree Health Biotechnology (CTHB) as well as B.D. Wingfield’s DST/NRF SARChI chair in Fungal Genomics and A. M. Wilson’s DST/NRF Scarce Skills Postdoctoral Fellowship.https://journals.asm.org/journal/spectrumam2023BiochemistryForestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant Patholog
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