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.

The structure and development of galls caused by the heterobasidiomycete Biatoropsis usnearum on Usnea thalli are studied in detail using different microscopical techniques. The galls induced by this fungus are devoid of algae and composed of hyphae of both fungal symbionts. The parasite forms tremelloid haustoria primarily in the central part of the gall. Infections of the parasite start in the cortical layer of the host and induce growth of the host hyphae resembling those of the central cord. The galls include a large amount of intact Usnea hyphae, to some extent also in the uppermost parts of the gall. Mature galls are compared with those caused by other lichenicolous fungi. The investigations show that the anatomies of galls and interactions between host and parasite differ significantly in gall-forming lichenicolous fungi.

The entomopathogenic fungus Metarhizium anisopliae is generally considered to be mesophylic, although some isolates have the ability to grow at 8 °C. In two cold-active isolates (DAT-1 from Tasmania and CLB2-1vi from Ontario, Canada) and one non-cold-active isolate (Ma 2575 from South Carolina), we (1) analyzed cold-induced intracellular proteins, using two-dimensional (2D) gel electrophoresis, and (2) analyzed cold-active transcripts, using a polymerase chain reaction (PCR) based subtractive hybridization technique. Protein differences, as observed by 2D gel electrophoresis, were observed in cold active isolates grown at 8 ° when compared with 25 °, but such differences were not observed in the non-cold active isolate. Fungi were also subjected to various stresses (45 °, pH, and salinity) to determine how proteins induced under these conditions compared to proteins induced under low temperature growth. Proteins induced were either specific to cold-active growth or were general stress proteins and differences were also observed in 2D patterns between the two cold-active isolates. Transcripts upregulated during growth at 8 ° and isolated by a PCR based subtractive hybridization technique also differed between the two cold-active isolates. Analysis of the transcripts showed several novel sequences but also included transcripts with similarities to actin, NADPH quinone oxidoreductase, a thiamine biosynthesis protein and a yeast-like membrane protein. The potential role of these proteins in cold-active growth is discussed.

Proteolytic activities were detected in a cytosoluble 100000 g extract of Cryptococcus neoformans using 7-amido-4-methylcoumarin substrates. The main proteolytic activity cleaved the L-arginine-AMC substrate. This protease was purified by high performance liquid chromatography and had a molecular weight of 80 kDa as demonstrated by SDS-PAGE in the presence of reducing conditions. The enzyme was inhibited by EDTA and o-phenanthroline which are metallopeptidase inhibitors. The protease displayed high enzymatic activity between pH 5·8 and 7, and its pI was localised at pH 5·04. Furthermore, this metallopeptidase was not secreted in culture supernatants, but was able to degrade partially or totally some of the extracellular matrix components, as fibronectin or laminin, and host IgG.

Basidiomes of Amanita muscaria were collected from sites in three 30–36-yr-old Pinus radiata plantations in New South Wales, Australia. Following DNA extraction from basidiome stipes, inter-simple sequence repeat PCR using the degenerate primers 5′DHB(CGA)5 and 5′DDB(CCA)5, was used to identify the mycelial genotypes from which basidiomes arose. Each site was found to contain 8–10 A. muscaria genotypes, with six genotypes common to all three sites and one common to two sites. The presence of common genotypes at the three sites is taken to indicate that they were introduced as vegetative inocula when seedlings were planted and have persisted for < 36 yr.

In submerged carbon-limited autolysing cultures of Penicillium chrysogenum, round-ended yeast-like fragments became the dominant surviving morphological forms and a new equilibrium between cell lysis and growth was observed, termed as a phase of ‘cryptic growth’. The formation of yeast-like fragments and their cryptic growth represented the only way that enabled the fungus to cope with harsh environmental conditions and survive. The surviving morphological forms reverted to vegetative growth after carbon supplementation. The glutathione metabolism and formation of reactive oxygen species (ROS) were influenced by numerous endogenous and exogenous factors depending on the phase of growth. Consequently, no firm correlation between the redox status, ROS levels and the observed morphological and physiological characteristics of the cells was found. The Dioxygen Avoidance Theory of Cell Differentiation failed to explain the complex physiological changes observed prior to and during autolysis, and any possible intrinsic analogy between the autolysis of P. chrysogenum and the oxidative stress dependent apoptosis of higher eucaryotes was also questioned. Nevertheless, ageing yeast-like fragments accumulated ROS as a function of incubation time and seem to be promising objects for future apoptosis research in filamentous fungi.

Morphological characters and genetic markers from 35 single-ascospore isolates of a Venturia sp. collected from Populus tremula were analysed. The morphological data were compared with the literature, and genetic markers were amplified for comparison with isolates of V. populina, V. macularis and V. ditricha. According to ascospore morphology the fungus resembled V. populina, but the morphology of the conidia was closer to Pollaccia radiosa (the anamorph of V. macularis). Analysis of 49 RAMS markers, variation within the internal transcribed spacer (ITS) sequence of the ribosomal gene cluster and a single marker locus derived from RAMS fingerprint suggested that the Venturia is a previously undescribed species.

Fungi on submerged wood in streams are a diverse group, comprising taxa from various families. Fungal communities on submerged wood collected from Sungai Sitam in Brunei, Tai Po Kau Forest Stream in Hong Kong, and from a stream in Lipur Lentang Nature Reserve in Malaysia are reported. One hundred and forty-seven taxa were recorded. A higher species diversity including temperate and tropical species was recorded in Tai Po Kau Forest Stream in the subtropics. Ascomycetes and their asexual stages were dominant in tropical and subtropical freshwater habitats, while discomycetes were rare in these habitats. Distinct fungal communities are found on submerged wood in tropical, subtropical and temperate regions and these are discussed. Including the fungi identified in this study, over 1000 fungi has been recorded from freshwater habitats.

Trematosphaeria malaysiana sp. nov. is described based on light microscope and ultrastructural studies. It was found on driftwood, exposed test blocks of Avicennia marina and Rhizophora apiculata, and split twigs of R. apiculata exposed in Kuala Selangor and Morib mangroves, Malaysia. T. malaysiana is characterized by striate, pale brown ascospores and trabeculate pseudoparaphyses. Ascospore cell walls are two layered, an outer thick layer comprising fibrillar mucilaginous material, and an inner bilamellate layer (the inner layer electron-transparent; the outer electron-dense and containing melanin). Both T. malaysiana and Leptosphaeria pelagica were examined at the transmission electron microscope level and their structure compared with that of other bitunicate ascomycetes. T. malaysiana and L. pelagica were similar in that the mucilaginous sheath was the outer most layer, in the former the spore wall was two layered, while in L. pelagica it was three layered. In L. pelagica the spore wall was smooth, while in T. malaysiana it was longitudinally striate.

Fungal endophytes have been found in every plant species examined to date and appear to be important, but largely unquantified, components of fungal biodiversity. Endophytes are especially little known in tropical forest trees, where their abundance and diversity are thought to be greatest. Here, we explore the occurrence of endophytes in a broad diversity of woody, angiospermous taxa in a lowland, moist tropical forest in central Panamá. We use similarity indices to assess host preference and spatial heterogeneity of endophytes associated with two co-occurring, but distantly related, understorey tree species in two sites of that forest, and assess the utility of indices based on frequencies of morphospecies occurrence (Morisita-Horn index) and on presence-absence data (Sørensen’s index). We suggest that our understanding of fungal diversity will be enhanced by exploring ecological patterns underlying endophyte occurrence in host species, and discuss methods for assessing the proportion of fungal biodiversity represented by tropical endophytes.

The infection process of Alternaria cirsinoxia was studied on Canada thistle (Cirsium arvense) in the controlled environment and in the field. In the controlled environment, germination of conidia began at 2 h and appressoria formation at 4 h after inoculation. Approximately 75% of appressoria formed at the anticlinal wall junctions of the epidermis. Leaf penetration occurred between 6 and 24 h, most commonly in between adjoining anticlinal walls. Penetration through stomata was rare. After penetration, large, intracellular infection hyphae formed and branched within epidermal cells, ramifying throughout the leaf tissues inter- and intracellularly by 24 h. In field conditions, infection coincided with prolonged rainfall and conidia remained viable on the leaf surface for 8–9 days (d) before causing infection on leaves. A host response occurred after penetration, involving deposition of lignin and callose in the infected epidermal and mesophyll cell walls. High levels of silicon were detected in epidermal cells directly below appressoria, often appearing to form entirely silicified infected cells which were resistant to collapse after air-drying. This study shows that A. cirsinoxia has the potential for rapid invasion of the leaf tissues of Canada thistle under good moisture conditions. The implications of the host responses, in terms of defence against infection, are discussed.

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.

The temporal pattern of release and dispersal of inoculum of plant and insect pathogenic fungi play an important role in the spread of disease. Airborne concentrations of primary and secondary conidia of Erynia neoaphidis released from the rose-grain aphid Metopolophium dirhodum were monitored at the edge of two winter wheat crops on IACR-Rothamsted Experimental Farm between May and September in 1996 and 1997. Hourly average temperature and humidity were recorded at each spore trap site and daily totals of rain and sunshine hours and daily average wind speed recorded about 1.6 km from the monitoring sites. No airborne conidia were found in 1996, but large numbers were trapped at the two sites in 1997. They were present from mid-June until early August, reaching peak concentrations on 17–18 July. Concentrations were usually highest during the night and in the early morning (01:00–07:00 h GMT) and were generally low during the day. On the 3 days when significant numbers of conidia were caught in the afternoon, daytime relative humidity was high (about 89%) and day-time temperature low (about 16 °C). Night-time conditions nearly always favoured the production of conidia. This suggests day to day variation in airborne conidium concentrations may be affected more by underlying biological factors than environmental conditions.

Six new taxa of Biscogniauxia are described from Taiwan, including four new species: B. ambiens, B. cylindrispora, B. formosana, and B. latirima; and two new varieties: B. albosticta var. orientalis and B. formosana var. kentingensis. Their cultural and anamorphic data are also provided. A description is provided for B. doidgeae based on its type. Cultural and anamorphic data are given for B. philippinensis var. microspora. A key to the 57 known species of Biscogniauxia in the world is also given.

Basidiomes of a Pisolithus species were collected from a ca 2500 m2 Australian sclerophyll forest site during 1997 and 1999 and of a second Pisolithus species from a further ca 150 m2 site during 1999. Inter-simple sequence repeat (ISSR) PCR was conducted on DNA extracted from each basidiome using the primers 5′BDB(ACA)5, 5′DDB(CCA)5 and 5′DHB(CGA)5. Thirty-seven genotypes of Pisolithus species I were detected at the North Wilberforce site, with eight genotypes present during both 1997 and 1999. All other genotypes were observed during only one year. Mapping genotype distribution according to location of basidiome collection at the site suggested that most genotypes were present as small (< 2·0 m2) below-ground mycelial genets, however several larger (> 4·0 m2) genets (including one ca 120 m2 genet) were also present. All Pisolithus species II basidiomes at the North Turramurra site were of a common genotype, suggesting the presence of a single large (ca 69 m2) below-ground mycelial genet of this taxon at the site. Both Pisolithus species thus appear to produce large long-lived soil-borne mycelia, but establishment of large genets may be restricted under some circumstances.

The structure of rhizomorphs of Armillaria luteobubalina grown on agar and in liquid culture has been compared using light and scanning electron microscopy. They differed in the extent of their peripheral hyphae, amount of surface mucilage, degree of pigmentation, growth rate, and structure of their inner cortex. Otherwise their internal structure was similar. At maturity four distinct radial zones could be recognised: (1) surface layer of peripheral hyphae from which hyphae extended radially; (2) outer cortex; (3) inner cortex; and (4) central medulla. The A. luteobubalina rhizomorph can be interpreted as a relatively strong ‘tube' of hyphae with a variously developed surface, surrounding a medulla of gas space containing wefts of fluffy fine hyphae. Submerged rhizomorphs grew at much faster rates than aerial rhizomorphs. The central gas-filled cavity most likely facilitates diffusion of oxygen along the rhizomorph, allowing growth through anaerobic environments. There was no evidence for specialised translocatory hyphae such as vessel hyphae. A zone of swollen hyphae interspersed with narrow hyphae developed at the interface between the inner cortex and medulla in submerged rhizomorphs. These were alive and septate and gave the tissue a resemblance to vascular plant aerenchyma, rather than specialised translocatory tissue. Peripheral hyphae took up and hydrolysed the fluorescent probe carboxy-DFFDA (Oregon Green) and accumulated the hydrolysis product in the vacuoles, suggesting that they are permeable. In contrast penetration of the cortex by the probe was limited. These data support the view that in moist conditions these rhizomorphs can function as organs of absorption and play a role in nutrient uptake.

The heterobasidiomycete moss parasites Eocronartium and Jola have figured prominently in theories of the evolution of the rust fungi and of the basidiomycetes. Such theories made implicit assumptions about the moss parasites, although very little of their life history was known. This is the first in a series of studies to elucidate the life history of the moss parasites. Polyspore monokaryotic cultures were obtained from basidiospores, and dikaryotic cultures were obtained from hyphae inside the moss host plant. In culture, the moss parasites produced Sporothrix-like anamorphs. The uninucleate conidia germinated by a germ tube, by production of single secondary conidia, or by iterative germination. Conidial-hyphal fusion was observed. A dikaryon was produced by mating single conidial isolates of Eocronartium muscicola, completing a part of its life history. Ultrastructural characteristics of wall break at branching, condensed chromatin during interphase, and simple septal pore morphology from fruiting bodies of Jola spp. and cultured isolates of Jola javensis and E. muscicola were consistent with those of related auricularioid phytoparasitic taxa, the rust fungi, and Pachnocybe ferruginea. Jola and Eocronartium can be grown in axenic culture and are not obligate parasites. In nature, the Sporothrix-like anamorph of these fungi may function in dispersal and mating. The previously unknown anamorph of the moss parasites may be instrumental in our understanding of the origin and evolution of the rust uredinial stage.

The effects of two UV irradiances (920 and 1200 mW m−2 weighted irradiance) on the conidia and germlings of the ARSEF 2575 and ARSEF 23 strains of M. anisopliae were studied. Conidia were exposed to the two irradiance levels for 1, 2, 3, 4, 6, or 8 h. The 30% increase (from 920 to 1200 mW m−2) in UV irradiance caused a significant decrease in culturability following all periods of exposure and reduced the 50% lethal time (TL50) 36% for strain 2575 and 48% for strain 23. Exposure to UV radiation of only 1 h caused a delay of several hours in the germination of surviving conidia. Longer periods of exposure delayed germination for days, demonstrating that, depending on the dose, the fungus may require a long period of time to recover and to resume germination. The results demonstrated the inability of the fungus to germinate during direct exposure to the UV-B portion of simulated sunlight. Both strains showed a transitory increase in UV tolerance during germination. The beginning of germination increased UV tolerance. However, starting on the 6th hour of germination, a decrease in tolerance was observed, indicating that UV tolerance varies as a function of physiological state and cell-cycle phase.

Soon after coming in contact with its host, the plant pathogenic fungus Bipolaris sorokiniana produces an extracellular material that appears to be important for adhering conidia and germlings to the host surface. To further understand this step of the infection, the adhesion of B. sorokiniana to artificial solid surfaces was examined. On a hydrophobic (polystyrene) surface adhesion occurred in two stages, the first by conidia and the second by germlings. Conidial adhesion occurred shortly (0–1 h) after hydration. The conidia were easily detached by increasing the shear force and including detergents in the washing buffer. As conidia were hydrophobic, these observations indicate that conidial adhesion to polystyrene is due to weak, hydrophobic interaction. The second stage of adhesion was accompanied by conidial germination and occurred 1–2 h after hydration and contact with the surface. Concomitant with the delayed adhesion, the fungus produced an extracellular matrix (ECM). The adhesion of germlings was firm and surface-unspecific since they adhered to both hydrophobic and hydrophilic (glass) surfaces. Except for strong bases, hydrochloric acid and broad-specificity proteases (including Pronase E), none of the hydrolytic enzymes, electrolyte solutions, ionic and hydrophobic detergents and organic solvents removed germlings from the solid surfaces. The adhesion of germlings incubated in the presence of the protein glycosylation inhibitor tunicamycin or the lectins Con A (Concanavalin A) and GNA (from Galanthus nivalis) was significantly reduced, which indicates the involvement of surface glycoproteins in this process. The surface proteins of germlings were labelled with 125I, extracted and analysed by two-dimensional gel electrophoresis. This revealed about 40 surface proteins over a wide pH range (4–10) with molecular masses between 10 and 100 kDa.

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.