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This issue of Mycological Research News features a new Phytophthora linked to sudden deaths of oaks, a re-examination of the
phylogeny of Agaricales, and permanent microscopic preparations. Editorial News covers fast-track (3–4 month) publication in the
journal, the inclusion of sequence alignments in papers, and temporary contact details for the Executive Editor.
This month's Mycological Research includes fifteen papers. Molecular studies concern the detection and relationship of glomalean
mycorrhizal fungi, the recognition of an additional order of ascomycetes (Agyriales), the identification of dark septate endophytic
fungi (by inter-sequence-repeat-anchored PCR), the systematics of Paraphaeosphaeria, and variability in Cryphonectria cubensis on
Eucalyptus, Pythium irregulare from selected crops, Rhizoctonia solani AG-1 1A isolates from rice, and Uromyces pisi s. lat. on Euphorbia.
The biocontrol potential of fungi against Colletotrichum musae on banana, and of Epicoccum purpurascens and its metabolites against
Sclerotinia head rot of sunflowers have been assessed. The polygalacturonase activity of different Fusarium species from Pinus is
studied, and the ability of ericoid mycorrhizal fungi from Woollsia pungens and of Hymenoscyphus spp. to grow on different amino
acids compared. A mathematical model for predicting intraspecific competition outcomes is evaluated experimentally using two
The ultrastructure of Tubakia dryina is documented, and notes on Cresporhaphis are presented with a key to the known species.
One new species is described: Cresporhaphis ulmi sp. nov.
Arbuscular mycorrhizal (AM) fungi, classified in the order Glomales, cannot easily be identified by hyphal morphology. PCR can be
used successfully to identify the fungi within the host or soil. Some of the primers that have been used are based on a few
sequences of a variable region in the SSU rRNA gene. To verify the specificity of primers of this type which have been used in
earlier publications, and to provide data for future primer design, we analysed 51 partial Glomales SSU rRNA gene sequences from
33 glomalean isolates.
To distinguish contaminants from the AM fungi (AMF) all sequences were verified by phylogenetic analyses. Together with
sequences from the EMBL database a set of 88 sequences from 58 isolates was analysed, comprising 39 species. The phylogenetic
trees reveal at least three distinct well supported Glomus clades and other interesting relationships within the Glomales. Sequence
data show that most of the primers published in earlier studies are not useful at the proposed taxonomic level. For example, the
VANS1 primer site is not specific for the Glomales, and is homologous to fewer than half of the AMF sequences investigated.
Primer regions that have been considered to be family-specific within the Glomales do not show strict specificity. Because clades in
the phylogenetic trees fit well to several sequence patterns, priming sites for AMF are discussed and sequence data for future
SSU rRNA gene sequences of Anamylopsora pulcherrima (Anamylopsoraceae), Placopsis gelida, Trapelia involuta and T. placodioides
(Agyriaceae) were determined and aligned with the corresponding sequences of 39 other ascomycetes. Phylogenetic analysis
(maximum parsimony, spectral analysis) of these sequences placed the Agyriineae outside the Lecanorales and suggested a sister group
relationship to Ostropales/Pertusariales. The resurrection of the order Agyriales is proposed based on molecular and morphological
data, such as faintly amyloid asci opening by dehiscence. The sequence data support the two families Agyriaceae and
Anamylopsoraceae to be accommodated within the order Agyriales. The Agyriales, Ostropales and Pertusariales can be placed in the class
Suitability and reproducibility of ISSR–PCR to find strain-specific and taxon specific markers for strains of the tree-root endophytes
Phialocephala fortinii and ‘Type 1’, a non-sporulating dematiaceous mycelium, were examined. The results were compared with data
previously generated by isozyme analyses. P. fortinii and ‘Type 1’ are two DSE taxa and are abundant colonisers of coniferous
forest-tree roots in the North Temperate zone. ‘Type 1’ was never observed to sporulate in pure culture but is well defined by its
cultural characteristics. DNA of 14 strains per taxon was amplified with three short, 17–18-nucleotide-long, tandemly-repeated
primers (CCA, CGA, ACA) with two (CCA) or three degenerated bases at their 5′-ends. The resulting DNA products were
separated by agarose gel electrophoresis. The bands were scored for absence/presence, respectively, and the binary matrix subjected
to multiple correspondence analysis (MCA). ISSR–PCR was found to be highly reproducible since amplification of DNA from several
single-hyphal-tip cultures of the same strain resulted in identical banding patterns. Eighty-five (92.4%) of the 92 DNA fragments
were polymorphic. The fragments ranged from 320 to 4100 bp. ISSR–PCR was found to be a powerful tool to find strain-specific
and taxon-specific markers. Each strain showed a unique banding pattern and diagnostic bands for the two taxa could be identified.
ISSR–PCR data correlated neither with the geographical nor the host origin of the strains. The strains grouped into similar clusters
independently of whether MCA was performed with ISSR–PCR or isozyme data. However, ISSR–PCR allowed the differentiation of
strains with the same allozyme phenotype.
Reference strains of Rhizoctonia solani from AG-1 1A, -1–1B, 1–1C, 2–1, 2–2, and 3 to 9, isolates of AG-1 1A from various rice
growing countries and field isolates from a paddy rice field experiment in Côte d'Ivoire were analysed by pectin enzyme analysis. A
subset of these isolates was also analysed by A+T-rich DNA (AT-DNA) RFLPs, both with the objectives to study the diversity at
various taxonomic levels and to obtain a clearer picture of the relationships between these isolates. Field isolates were submitted to
simple sequence repeat PCR (SSR-PCR). Pectin enzyme analysis as well as AT-DNA RFLP showed that isolates of different
anastomosis groups generated very distinct patterns. Isolates of AG-1 1A from various countries had a lower degree of variability in
zymogram patterns and AT-DNA RFLPS, while zymograms and AT-DNA RFLPs of field isolates obtained from one field experiment
consisted of one identical pattern. However, these isolates showed variation in RFLPs obtained through SSR-PCR, indicating that
they were not clones sensu stricto.
The genus Paraphaeosphaeria (Loculoascomycetes) was described as a segregate of Leptosphaeria for species producing brown, usually
punctate ascospores with rounded ends, a submedian primary septum, an inflated cell above the primary septum, and a Coniothyrium
sensu lato anamorph. This study evaluated the taxonomic value of the morphological characters, host range, ecology, and anamorphs
in relation to DNA sequence data in order to determine the relationship between species described in Paraphaeosphaeria. Nine species
were characterized morphologically and the ITS and 18S regions of the rDNA were sequenced and a phylogeny was inferred.
Morphological studies and results of the sequence analyses provide strong support for polyphyly of this genus. Based on these
analyses, the concept of Paraphaeosphaeria should be narrowed to reflect a monophyletic generic concept. Characters such as spore
septation and method of conidiogenesis were found to predict relatedness.
To attract insects for sexual reproduction, some fungi can induce the formation of pseudoflowers on their hosts. Pseudoflowers are
rosettes of yellow host leaves upon which the fungus presents gametes in sweet nectar. Eleven species of the fungus complex
Uromyces pisi can induce pseudoflowers on the host Euphorbia cyparissias. The taxonomy of these species is based on the choice of
the alternate host, a species of Fabaceae, as well as on teliospore morphology on the Fabaceae hosts. Morphological identification of
the fungi on E. cyparissias is impossible. To identify the fungal species on infected E. cyparissias, we compared sequences from the
ITS region of the rDNA to the DNA from five identified fungal species on Fabaceae. From 43 specimens on E. cyparissias, collected
in 1997–99 in Switzerland, 24 specimens could be identified as U. pisi s. str. and 16 specimens as U. striatus. Two specimens were
identified as U. laburni and U. loti, respectively, and one specimen could not be identified. We therefore conclude that fungal
pseudoflowers are typically induced by U. pisi s. str. on U. striatus in Switzerland, although other species do sometimes occur. The
ITS sequences were then used to reconstruct the phylogenetic relationship among species in the U. pisi complex and two closely
related microcyclic rust species of the complex Uromyces scutellatus. Phylogenetic analyses indicated that the microcyclic species may
be descendants from macrocyclic U. pisi s.l. ancestors. The ITS region sequenced in this study was found to be appropriate for
answering phylogenetic, as well as ecological questions, and provided valuable markers for future studies.
Single-strain biocontrol agents often look promising when tested against single-strain pathogens. When confronted with a biodiverse
field population, however, biocontrol is inconsistent. This study implies that biodiversity of the crown rot pathogen Colletotrichum
musae leads to strain discrimination by antagonists which results in variable biocontrol of the disease. Broad host-range
mycoparasites of fungi of the crown rot disease complex of banana (C. musae, Fusarium moniliforme and Botryodiplodia theobromae)
which attacked at least two of the pathogen genera, exhibited significant differences in aggression against different strains of C.
musae, the main pathogen. Antagonists acted via several different mechanisms, i.e. parasitism, antibiosis or competition,
simultaneously. The relative importance of each mechanism differed with the individual mycoparasites. Strain discrimination was
correlated to differential susceptibility to one or more minor mechanism(s). When as many as four antagonists were combined into
one inoculum, they complemented rather than antagonised each other. Biocontrol efficiency increased with the number of antagonist
strains combined. Therefore, strain mixtures should be sought to control the crown rot disease complex of banana.
Epicoccum purpurascens was evaluated as a biocontrol agent of Sclerotinia head rot of sunflower. The potential of antifungal
compounds produced by E. purpurascens as fungicides was also assayed. Treatments consisted of application of E. purpurascens conidia
and of partially-purified antifungal compounds produced in broth culture before inoculation with ascospores of S. sclerotiorum.
Application of conidia resulted in reduced head rot incidence on greenhouse grown plants, but the application of antifungal
compounds had no effect on head rot development. Capitula colonization by E. purpurascens had no negative effects on capitula
development. After application of E. purpurascens to field grown plants, capitula were much less colonized than under greenhouse
conditions. As a consequence, this treatment had no effect on head rot development in the field when plants were artificially
inoculated with S. sclerotiorum. The search for new isolates of E. purpurascens well adapted to the fluctuating conditions typical of
natural environments could contribute to achieving an acceptable level of efficacy of this organism as a biological control agent of
Genetic variation within 34 Pythium irregulare isolates was analyzed using restriction fragment length polymorphisms (RFLPs) as
genetic markers. Most isolates had two alleles at several codominant RFLP loci and were scored as heterozygous. Heterozygotes
were detected in F1 progeny from an in vitro cross and segregation ratios of the F2 progeny were not significantly different from
those expected for allelic variation in a diploid. This confirmed that outcrossing occurs and contributes to genetic variation within
the species. Phenetic analysis showed that isolates formed genetically related groups due to their host species and not due to
similarities in their geographical origins. All isolates originating from medic formed a discrete group and were highly differentiated
from the cereal and sub-clover isolates. The allelic distributions between isolates from these host-groups were significantly different.
Most isolates also showed significant differences in their pathogenicity between hosts, indicating that they varied in pathogenic
fitness and were better adapted to parasitising some hosts relative to others. These isolates were however, not necessarily more
pathogenic on their host of origin. This research provided estimates of the extent of genetic and pathogenic diversity within P.
irregulare and qualitative evidence for the occurrence of host-mediated selection and sexual outcrossing in the field.
Cryphonectria canker caused by Cryphonectria cubensis is one of the most destructive diseases of Eucalyptus plantations in South
Africa. To implement a meaningful management of plantation diseases, it is important to have an understanding of the population
diversity of the pathogen. In this study, trees were surveyed to determine whether C. cubensis reproduces sexually in South Africa.
The diversity of the South African C. cubensis population was assessed based on vegetative compatibility tests. Field inoculations
were used to determine whether VC groups correlated with virulence. Only pycnidia were found on cankered trees, indicating that
sexual reproduction does not occur. Only 23 VC groups were found amongst 100 isolates each collected from single diseased trees.
A low degree of genetic diversity also indicated that sexual reproduction is absent or rare in the South African C. cubensis
population. Inoculation studies revealed that isolates belonging to different VC groups differ significantly in their ability to cause
lesions. The low level of genetic diversity enhances opportunities to capitalise on hypovirulence to reduce the impact of the
pathogen in the future. It also supports the view that the fungus was recently introduced into South Africa.
Polygalacturonases (PGs) are important pectolytic enzymes produced by phytopathogenic fungi during the process of infection and
colonisation of the host plants. In this work, PGs produced by isolates of seven Fusarium species associated to Pinus pinea have been
analysed for: activity, isoform pattern observed by isoelectric focusing, endo- or exo-mode of action and their production in cultures
growing on pectin and galacturonic acid. Of the seven isolates, those of F. oxysporum and F. moniliforme exhibited high PG activity
and the most complex isoform patterns including acidic ones. These isolates were also more efficient in degrading the PG substrate,
during which both endo and exo type polygalacturonase activities were detected. It is suggested that these features could be useful
to the fungus during infection and colonisation of its host, specially during seed germination and early development.
The abilities of 12 ericoid mycorrhizal endophytes isolated from Woollsia pungens (Epacridaceae) and three Hymenoscyphus spp.
isolates to grow on a range of amino acids as sole nitrogen sources were investigated in axenic liquid culture. The majority of
endophytes grew to some extent on all amino acids tested, with most isolates from W. pungens showing a significant preference for
histidine and/or alanine. Poorest growth of the endophytes from W. pungens was observed on lysine. In contrast, the Hymenoscyphus
spp. isolates showed either no preference or a preference for lysine over histidine. Although some isolates produced some growth on
the sulphur-containing amino acid cysteine, biomass production on this substrate by all isolates was significantly enhanced in the
absence of inorganic sulphur.
This paper presents an experimental test of a model that predicts the outcome of intraspecific competition between unit-restricted
decomposer fungi. The model was tested using two isolates each of two species of the mushroom genus Coprinus (Basidiomycota).
The fungi were grown on yeast extract agar at several resource densities. The effect of intraspecific competition was measured as the
reduction of stipe dry weight (an indicator of spore production) when an individual grows in competition with a second individual
of the same species as compared to the stipe dry weight when it grows alone. Additionally, competition often caused a significant
change in the growth rate of the isolates. In general, the model accurately predicted the stipe dry weight of the isolates growing in
competition, but it incorrectly predicted the outcome of competition for at least one resource density for each isolate.
Pycnothryria of Tubakia dryina on naturally infected sweet gum (Liquidamber styraciflua) leaves were examined using transmission
electron microscopy. The conidioma was attached to mycelium within the leaf tissue by a multicellular columella. Columellar cells
were multinucleate. The surface layer of the pycnothyrium, the scutellum, was composed of thick walled prosenchymatous hyphae.
Numerous conidiogenous cells were associated with the ventral surface of the scutellum and the columella. Conidia were produced
enteroblastically from conidiogenous cells exhibiting a prominent collarette at their apex.
A taxonomic and ecological reassessment of the genus Cresporhaphis is presented, with a key to all 7 species currently known,
including C. ulmi sp. nov. from Spain, on twigs of Ulmus minor. Species are facultatively lichenized with chlorococcoid algae,
Trentepohlia and other algae, or saprobic.