Killer Yeasts - Cause of Stuck Fermentations in a Wine Cellar

Sluggish fermentations in five fermenters in a wine cellar were investigated. Methylene blue-stains of yeast suspensions revealed that approximately 90% of the total yeast population in each of the fermenters were dead. The viable cells in each fermenter were killer yeasts. Polyacrylamide gel electrophoresis of total soluble cell proteins showed that the same killer yeast occurred in each of the five fermenters. The effect of killer yeast on viability and fermentation activity of the wine yeast was studied in an enriched grape juice medium at 20°C and 30°C. Death rate of the wine yeast was considerably higher in the presence of the killer yeast and fermentations were retarded at both temperatures. The killer yeast induced flocculation of the non-flocculent wine yeast

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

Multi-gene phylogenies and phenotypic characters distinguish two species within the Colletogloeopsis zuluensis complex associated with Eucalyptus stem cankers

Colletogloeopsis zuluensis, previously known as Coniothyrium zuluense, causes a serious stem canker disease on Eucalyptus spp. grown as non-natives in many tropical and sub-tropical countries. This stem canker disease was first reported from South Africa and it has subsequently been found on various species and hybrids of Eucalyptus in other African countries as well as in countries of South America and South-East Asia. In previous studies, phylogenetic analyses based on DNA sequence data of the ITS region suggested that all material of C. zuluensis was monophyletic. However, the occurrence of the fungus in a greater number of countries, and analyses of DNA sequences with additional isolates has challenged the notion that a single species is involved with Coniothyrium canker. The aim of this study was to consider the phylogenetic relationships amongst C. zuluensis isolates from all available locations and to support these analyses with phenotypic and morphological comparisons. Individual and combined phylogenies were constructed using DNA sequences from the ITS region, exons 3 through 6 of the β-tubulin gene, the intron of the translation elongation factor 1-α gene, and a partial sequence of the mitochondrial ATPase 6 gene. Both phylogenetic data and morphological characteristics showed clearly that isolates of C. zuluensis represent at least two taxa. One of these is C. zuluensis as it was originally described from South Africa, and we provide an epitype for it. The second species occurs in Argentina and Uruguay, and is newly described as C. gauchensis. Both fungi are serious pathogens resulting in identical symptoms. Recognising them as different species has important quarantine consequences

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

A multi-gene phylogeny for species of Mycosphaerella occurring on Eucalyptus leaves

Species of the ascomycete genus Mycosphaerella are regarded as some of the most destructive leaf pathogens of a large number of economically important crop plants. Amongst these, approximately 60 Mycosphaerella spp. have been identified from various Eucalyptus spp. where they cause leaf diseases collectively known as Mycosphaerella Leaf Disease (MLD). Species concepts for this group of fungi remain confused, and hence their species identification is notoriously difficult. Thus, the introduction of DNA sequence comparisons has become the definitive characteristic used to distinguish species of Mycosphaerella. Sequences of the Internal Transcribed Spacer (ITS) region of the ribosomal RNA operon have most commonly been used to consider species boundaries in Mycosphaerella. However, sequences for this gene region do not always provide sufficient resolution for cryptic taxa. The aim of this study was, therefore, to use DNA sequences for three loci, ITS, Elongation factor 1-alpha (EF-1α) and Actin (ACT) to reconsider species boundaries for Mycosphaerella spp. from Eucalyptus. A further aim was to study the anamorph concepts and resolve the deeper nodes of Mycosphaerella, for which part of the Large Subunit (LSU) of the nuclear rRNA operon was sequenced. The ITS and EF-1α gene regions were found to be useful, but the ACT gene region did not provide species-level resolution in Mycosphaerella. A phylogeny of the combined DNA datasets showed that species of Mycosphaerella from Eucalyptus cluster in two distinct groups, which might ultimately represent discrete genera

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

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

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

Molecular basis of cycloheximide resistance in the Ophiostomatales revealed

DATA AVAILABILTY : The genome data used in this study are available in the NCBI repository, https://www.ncbi.nlm.nih.gov. The accession numbers for all genomes are indicated in Table 1. The Microascus genome data is available on the JGI mycocosm website (https://mycocosm.jgi.doe.gov/mycocosm/home). The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.Resistance to the antibiotic Cycloheximide has been reported for a number of fungal taxa. In particular, some yeasts are known to be highly resistant to this antibiotic. Early research showed that this resulted from a transition mutation in one of the 60S ribosomal protein genes. In addition to the yeasts, most genera and species in the Ophiostomatales are highly resistant to this antibiotic, which is widely used to selectively isolate these fungi. Whole-genome sequences are now available for numerous members of the Ophiostomatales providing an opportunity to determine whether the mechanism of resistance in these fungi is the same as that reported for yeast genera such as Kluyveromyces. We examined all the available genomes for the Ophiostomatales and discovered that a transition mutation in the gene coding for ribosomal protein eL42, which results in the substitution of the amino acid Proline to Glutamine, likely confers resistance to this antibiotic. This change across all genera in the Ophiostomatales suggests that the mutation arose early in the evolution of these fungi.The South African National Research Foundation.https://link.springer.com/journal/294hj2023BiochemistryForestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant Patholog