This issue of Mycological Research News features instability in ectomycorrhizal associations, and the use of scanning electron microscopy (SEM) to examine the internal structures of fungi.

This month's Mycological Research includes 17 papers. The first reports catastrophic rupture of germinating conidia in a Glomerella graminicola mutant. The discovery of effective primers for the separation of ectomycorrhizal basidiomycete species is reported, genetic transformation of a Cercospora with a particle gun has been achieved, ploidy and aneuploidy levels in Armillaria have been analyzed by fluorescence flow cytometry and molecular methods, the molecular phylogeny of Collybia s. str. investigated, and the identity of a fungus cultivated by a leaf-cutter ant confirmed molecularly.

Protein production in different states of Flammulina velutipes is compared, and a remarkable heterogeneity of incompatible genets of Heterobasidion annosum found in a single stump. The intracellular thermotolerant lipoxygenase of Thermomyces lanuginosus has been characterized, and cell-wall degrading enzymes of Colletotrichum acutatum examined.

The identification of Fusarium species by the computer imaging of macroconidia is assessed. Other systematic papers provide a revision of Hygrocybe subgen. Pseudohygrocybe sect. Firmae in the Greater Antilles, and describe: a new aflatoxin-producing Aspergillus, a new Ophiostoma on Protea, a new genus of smuts on Arthropodium, and five new ascomycetes from native plants in Mauritius.

The following new scientific names are introduced: Dendrocollybia, Pellucida, and Yelsemia gens. nov.; Aspergillus pseudotamarii, Englerodothis oleae, Hygrocybe brunneosquamosa, H. cinereofirma, H. flavocampanulata, H. laboyi, H. miniatofirma, H. neofirma, H. olivaceofirma, Lepteutypa tropicalis, Ophiostoma africanum, P. pendulina, Pseudorhynchia mauritiana, and Y. arthropodii spp. nov.; and D. racemosa (syn. Agaricus racemosus) comb. nov.

Video microscopy was used to examine a genetically tagged mutant (T30) of Glomerella graminicola whose conidia have a propensity to burst during the germination process. Before the germ tube is produced, the cell wall ruptures and the cytoplasm is extruded. The bursting takes place in less than 0.1 second. Bursting can be prevented by adding osmotica to the germination medium. By phase-contrast microscopy of alkali-washed conidia, we found that each ruptured conidium had a single gaping hole that was oriented parallel to the long axis of the spore. The holes were more frequent in the middle region of the conidia than at the apices. A mathematical model for stress based on conidial shape indicated that conidia ruptured where the stress on the wall was greatest. The microscopic observations on the orientation and distribution of the rupture sites are consistent with the hypothesis that T30 conidia have weaker walls than the wild-type. Comparative tests of resistance to mechanical breakage support this hypothesis.

Techniques to rapidly identify the basidiomycete fungal partner of ectomycorrhizal associations would be a major advantage for ecological, fungal population dynamics and life history studies of epigeous and hypogeous forms in plantations, forests, wild lands and other native or natural vegetation. PCR–RFLP (Polymerase Chain Reaction–Restriction Fragment Length Polymorphism) identification of DNA regions is an available technique; however, primers which have a high probability of amplifying only the basidiomycete DNA are needed. Here we have assessed the specificity, sensitivity and discrimination of six different primer pairs, three targeting nuclear and three mitochondrial regions, for use in identification of Australian basidiomycete fungi from Eucalyptus forests by matching PCR–RFLP patterns to morphologically defined species. Two sets of primers, one newly designed and targeting the nuclear ribosomal DNA internal transcribed spacers (ITS) and the other amplifying a fragment of mitochondrial large subunit ribosomal DNA met the requirements of high specificity and sensitivity, amplifying DNA from a broad range of larger basidiomycetes, with no amplification of plant, bacterial or ascomycete DNA. The specificity of the ITS primer pair was compared with that of ITS1-F/ITS4-B. PCR–RFLP of the two regions discriminated fungi to species level for 91 fungal species from 28 families. Hence these two DNA regions and the specific primers are a potential practical PCR–RFLP tool for identifying basidiomycetes associated with plants from field samples.

Cercospora caricis is being considered as a bioherbicide agent for use against purple nutsedge (Cyperus rotundus), one of the world's worst weeds. However, first its efficiency must be improved, for example by genetic transformation. By optimizing physical and biological parameters, the particle gun acceleration method (biolistics) has been adapted to transform mycelial cells of C. caricis. Two genes were expressed in C. caricis by biolistic transformation. The β-glucuronidase gene (GUS) fused to the GDP1 promoter of Cochliobolus hetrostrophus and the hygromycin B resistance gene under control of the PtrpC promoter of Aspergillus nidulans. Although the transformation frequency was not high, all transformants were stable when they were propagated on a selective medium after eight subsequent transfers.

For assessments of intraspecific mating using flow cytometry and fluorescence microscopy, two compatible basidiospore-derived isolates were selected from each of four parental basidiomata of North American Biological Species (NABS) X. The nuclear status in NABS X varied with basidiospore-derived isolates. Nuclei within basidiospore-derived isolates existed as haploids, diploids (doubled haploids), or a mixture of haploids and diploids (doubled haploids). Depending on the nuclear status of the basidiospore-derived lines of NABS X, intraspecifically mated cultures can exist as diploids or tetraploids, and possibly triploids or aneuploids under in vitro conditions. Based on previous in vitro mating studies, seven basidiospore isolates were specifically selected to assess rare, interspecific mating among Armillaria cepistipes, A. sinapina, NABS X, and NABS XI. Cultures from basidiospore-derived isolates were paired to produce four interspecifically paired cultures, and matings were assessed using flow cytometry and restriction fragment length polymorphism (RFLP) analyses. Based on flow cytometric analysis, the A. cepistipes isolate exhibited compatibility with a NABS X isolate, and the A. sinapina isolate exhibited compatibility with a NABS X isolate, and the A. sinapina isolates were individually compatible with isolates of NABS X and NABS XI. Mean fluorescence intensities of A. cepistipes × NABS X, A. sinapina × NABS X, and A. sinapina × NABS XI mated cultures revealed a triploid or tetraploid nuclear status compared to the haploid or diploid (doubled haploid) nuclear status of initial basidiospore-derived isolates. Polymerase chain reaction (PCR) and RFLP of the intergenic spacer (IGS) region generated banding patterns for basidiospore-derived isolates and mated cultures. Four species-specific RFLP banding patterns were observed in basidiospore-derived isolates of A. cepistipes, A. sinapina, NABS X, and NABS XI. PCR-RFLP analysis showed combined banding patterns from mated cultures. Flow cytometry and PCR-RFLP analysis are effective tools to assess matings of Armillaria species.

Collybia, as understood by Antonin & Noordeloos, comprises four species: C. racemosa, C. tuberosa, C. cirrhata and C. cookei. Collybia tuberosa, C. cirrhata and C. cookei are morphologically similar and are primarily distinguished from each other by the presence or absence and the colour of sclerotia. All four share a common and unique habitat. Phylogenetic reconstructions using DNA sequences of the ribosomal ITS1–5.8S–ITS2 support four distinct clades, each corresponding to a morphological species, with the C. tuberosa, C. cirrhata and C. cookei clades forming a larger group. Analyses of ribosomal Large Subunit DNA sequences confirmed that Collybia tuberosa, C. cirrhata and C. cookei formed a monophyletic group. In both analyses, the C. racemosa sequence was highly divergent from those of the other three species of the complex and we propose a separate genus name, Dendrocollybia, for this species. Simple diagnostic RFLP patterns were identified for the four species and were used to validate morphological designations and distributions.

That the symbiotic fungus of leaf-cutting ants only occasionally produces the sexual phase makes their identification confusing. This has occurred so rarely, either in laboratory nests, or in unbalanced field nests, that the possibility of contamination of the fungal garden by other fungi cannot be disregarded. In this paper we describe the formation of several basidiomata in a healthy and free-living nest of the leaf-cutting ant Acromyrmex hispidus fallax, the cultivation in vitro of the sterile mycelia (isolated from the fungal garden) with their typical inflated tips, and the similarity of both forms confirmed by RAPD analysis of their genomic DNA. The fungus was identified as Leucoagaricus gongylophorus.

Patterns of protein expression in the monokaryons and the derived dikaryon of the basidiomycete Flammulina velutipes were investigated using two-dimensional polyacrylamide gel electrophoresis and silver staining. Over 300 spots were detected on each gel, and 19 proteins were expressed in the dikaryon before fruiting treatment but not expressed in the monokaryon before fruiting treatment. On the other hand, 9 proteins were expressed in the monokaryon specifically. Newly expressed proteins increased after fruiting treatment (at 7 d and 14 d), but decreased after fruit bodies were formed (at 21 d). The number of newly expressed proteins after the fruiting treatment was similar in the monokaryon. Proteins expressed characteristically were classified into 7 types. The highest number of proteins (13 proteins) were specifically expressed in the dikaryon at 14 d when the fruit-bodies were formed. Twenty-seven proteins were expressed specifically in the fruit body. Fruit body specific proteins Pf1 and Pf3 were sequenced. This revealed Pf1 and Pf3 had amino acid sequences that were similar to each other, as well as a high similarity to the deduced amino acid sequence of the FDS gene isolated from F. velutipes.

The wood of one Picea abies stump, including its roots (1·3 m in length), was sliced into 2 cm thick discs. The stump originated from a thinning conducted 7 yr prior to the investigation in a 30 yr old spruce stand planted on previous farmland that became heavily infected by Heterobasidion annosum. After incubation of the wood discs, interaction zones were observed on the surfaces and H. annosum was isolated from the areas between the zones and from the zone lines, resulting in 296 isolates. The isolates were tested with somatic incompatibility to detect 35 different genets. Of the 27 genets colonising the upper part of the stump (excluding the roots), 12 had proceeded into the roots. Seven genets found in the roots were not found in the upper part of the stump and one genet isolated from an interaction zone on the top of the stump was not found elsewhere in the stump or in the roots. Two of the genets had grown into root contact with other trees.

A thermostable intracellular lipoxygenase from Thermomyces lanuginosus was purified to sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) homogeneity by ion-exchange chromatography on diethylaminoethyl (DEAE)-Sepharose, ion-exchange chromatography on carboxymethyl (CM)-Sepharose and Phenyl-Sepharose hydrophobic interaction chromatography. The molecular weight of the enzyme was estimated to be 100 kDa by SDS-PAGE. The lipoxygenase exhibited maximal activities at pH 6.0. The optimum temperature for the activity was 55 °C. The enzyme was thermostable at 50 ° with half-lives at 60 ° of 20 min and 70 ° of about 7 min. The lipoxygenase activity was completely lost by heating at 80 ° for 5 min. The lipoxygenase catalyzed the oxidation of linoleic acid into 13-L-hydroperoxy-9,11(Z,E)-octadecadienoic acid(13-HPOD) as the major product. The enzyme had an apparent Km of 8.5 μM and Vmax of 10.8 μmol mg−1 min−1 with linoleic acid as substrate.

Colletotrichum acutatum is the major causative agent of secondary leaf fall disease of rubber. All isolates of the fungus examined secreted polygalacturonase (PG), pectin lyase (PL) and the cellulolytic enzymes, β-glucosidase, and cellobiase in culture. Molecular weight determinations suggest that PG as well as the PL produced by all isolates are similar. PG activity was absent in infected rubber leaves. However, PL activity was detected in infected tissues associated with the enlargement of lesions. β-glucosidase was present in both healthy and infected leaves while cellobiase was detected only in infected leaf tissue.

Vesicular–arbuscular (VA) mycorrhizas are described from anatomically preserved roots of the Middle Eocene taxodiaceous conifer Metasequoia milleri, and compared to those of the living species M. glyptostroboides. Virtually identical VA mycorrhizal structures occur in the root cortex of both species, where they conform to the Paris-type. Coiled hyphae are most common within cells of the inner cortical region, and these produce numerous, highly branched arbuscules. Close similarity of fungal position and structure within roots of the living and fossil Metasequoia species demonstrates that modern Paris-type VA mycorrhizal associations characterized taxodiaceous conifers by the early Tertiary.

This paper describes digital image recording and measurement procedures of Fusarium species macroconidia with reference strains of F. avenaceum, F. culmorum, F. graminearum, F. oxysporum, F. sambucinum and Microdochium nivale. Computerized taxonomic recognition of the most important Fusarium species occuring on cereals was achieved by statistical tests based on morphometric parameters from macroconidia (numerical taxonomy). A first grouping resulted from Brandt-Snedecor contingency tests (χ2) indicating different frequency distributions of macroconidia with various numbers of septa. For discrimination and ranking within these groups by clustering procedures, analysis of variance and multiple comparison of means, deviation from circular (circular form factor) was most suitable out of 12 morphometric parameters tested on macroconidia of the most frequent septation classes.

A key to 13 species in the genus Hygrocybe subgenus Pseudohygrocybe section Firmae is provided for the Greater Antilles. Seven new species and one species that is a new report for the Greater Antilles are described. The new species are H. brunneosquamosa, H. cinereofirma, H. flavocampanulata, H. laboyi, H. miniatofirma, H. neofirma and H. olivaceofirma. The new report is H. trinitensis.

Yelsemia arthropodii, causing smut galls of Arthropodium in Australia, is described as a new genus and species of Tilletiales. It has been found twice in the field as a capsule smut, in dry inland areas of Western Australia and New South Wales. Seed inoculated with ustilospores produced infected plants with systemic mycelium and galls in capsules, pedicels, peduncles and leaf axils. Dark brown, unicellular ustilospores have two prominent opposite hyaline polar caps through which they geminate to produce holobasidia bearing 2–5 apical septate fusiform sporidia. Sporidial cells germinate by hyphae which often anastomose with one another or with cells of other sporidia. Yelsemia is compared with Ustilago speculariae, a capsule smut of Triodanis in the USA with similar ustilospores, whose germination is unknown.

A recent report of an aflatoxin producing isolate of Aspergillus tamarii prompted a taxonomic re-examination of aflatoxigenic and non-aflatoxigenic isolates identified as A. tamarii as well as the closely related A. caelatus. Representatives of each species, including atypical isolates, were compared morphologically, for mycotoxin production, and for divergence in ITS, 28S, β-tubulin and calmodulin gene sequences. Because of genetic, morphological, and mycotoxin differences, the aflatoxin producing isolates of A. tamarii are given species rank as Aspergillus pseudotamarii sp. nov.

Two distinct and unrelated groups of ophiostomatoid fungi are associated with Protea infructescences. Two species, Gondwanamyces proteae and G. capensis, have unique anamorphs that reside in Knoxdaviesia. This anamorph genus is infrequently found amongst species of Ceratocystis sensu lato. The second group includes Ophiostoma splendens and O. protearum that have Sporothrix anamorphs typical of Ophiostoma. During recent collections of Protea gaguedi infructescences from the Northern Province in South Africa, an apparently new species of Ophiostoma with a Sporothrix anamorph was discovered. It can be distinguished from O. splendens and O. protearum based on its short ostiolar hyphae and its associated plant host. This teleomorph is described as O. africanum and the anamorph as S. africanum. Five species of ophiostomatoid fungi are now known from Protea infructescences and a key is presented for them.

Englerodothis oleae and Lepteutypa tropicalis spp. nov., Pellucida pendulina gen. et sp. nov., and Pseudorhynchia mauritiana sp. nov., collected from the Mauritian native plants Cordemoya integrifolia, Olea lancea and species of Pandanus, are described, illustrated and compared with related taxa. A key is provided to the currently accepted species of Lepteutypa.