We determined the occurrence of birth rust fungus (Melampsoridium betulinum) within mature mountain birch (Betula pubescens var. czerepanovii) trees and compared the airborne urediniospore concentrations with overall rust infection levels over five successive years. Fifteen groups of three trees 3–5 m high were chosen from a homogenous mountain birch stand. Each group contained a tree with ‘low’, ‘moderate’ and ‘high’ infection covering the natural range of infection levels. The difference in rust classes remained constant throughout the study; trees in class ‘high’ consistently had always highest infection levels and trees in class ‘low’ always the lowest infection levels. Infection levels remained constant between years in ‘low’ class, while the infection levels varied significantly between years in ‘moderate’ and ‘high’ classes. The incidence of disease caused by M. betulinum varied from year to year and was correlated with the total airborne urediniospore counts. The data indicate that trees differ in resistance to birch rust and that infection levels of susceptible compared to resistant trees are more dependent on environmental conditions.

Isolates of Fusarium oxysporum from different habitats were compared with respect to intra- and extracellular isozymes. Five intracellular enzymes: esterase, superoxide dehydrogenase, malate dehydrogenase, dihydrolipoamide dehydrogenase and succinate dehydrogenase were extracted from the mycelium, and four extracellular enzymes: protease, cellulase (endoglucanase), amylase and lipase were obtained from the culture medium. Proteins were separated either by discontinuous PAGE or by IEF, and isozymes were detected by specific staining. The intracellular enzyme data were analysed by an unweighted paired group method analysis (UPGMA), which separated the isolates into three main clusters. The clusters generated from the intracellular enzymes were weakly correlated with the electrophoretic types based on the extracellular enzymes. These results suggest that extracellular enzymes may be of limited value for classification within F. oxysporum.

Transmission electron microscopy was used to study the development and structure of resting spores and sporosori of Polymyxa graminis. Osmiophilic bodies generally distributed in the cytoplasm moved to the periphery as spores matured. The spore wall consisted of four or five layers, two of which extended into spines linking adjacent spores. An unstained plug in the wall, faced towards the outside of the sporosorus. Some spores germinated in situ by producing primary zoospores. Bundle-like structures in some spores may have been barley yellow mosaic virus particles.

At a high arctic, polar semi-desert site (79°N) in Svalbard, nitrogen, phosphorus and potassium fertilizers were added to the soil for 5 yr to simulate increases in decomposition and nutrient mineralization which may occur as a result of increases in soil temperature and soil moisture caused by environmental change. Abundance of decomposer fungal species, isolated from standing-dead leaves of Dryas octopetala, varied between fertilized and unfertilized plots. Fungal biodiversity, as indicated by the Brillouin index, was lower in dead Dryas leaves from the fertilized plots, although more colonies were isolated from leaves of plants which had been fertilized. The fungi were cosmopolitan and not restricted to tundra areas. The dead leaves from the fertilized plots contained more nitrogen and phosphorus than those of the unfertilized plants. Leaves in the fertilized plots appeared to have been killed by winter injury resulting from an extended growing season in an atypically mild and wet autumn, which was followed quickly by extreme subzero temperatures.

The effects of temperature and water availability on growth and interactions between fumonisin-producing isolates of Fusarium moniliforme and F. proliferatum and seven other fungi from maize grain were determined in vitro. The type of interaction and index of dominance (ID) between species were markedly influenced by temperature and aw. Generally, F. moniliforme and F. proliferatum were very competitive and dominant against the Penicillium spp. and A. flavus. They were in turn dominated by A. niger, but mutually antagonistic when paired with F. graminearum and A. ochraceus. Under slightly drier conditions (<0·98 aw) A. ochraceus became more competitive and dominant over the fumonisin-producing species. A. flavus was dominant only at 30°C and <0·96 aw. F. moniliforme and F. proliferatum demonstrated dominance against all species over a range of temperatures and 0·994 to 0·96 aw. At lower aw levels they were less competitive. The growth rate of the two fumonisin-producing species was significantly reduced by F. graminearum, regardless of aw. F. moniliforme and F. proliferatum reduced growth of Penicillium and Aspergillus spp., especially at >0·96 aw. At <0·96 aw, growth of these species was unaffected. Using Biolog plates the effect of aw and temperature on utilization patterns of carbon sources in maize were evaluated for the first time. The niche overlap indices relative to F. moniliforme and F. proliferatum were determined and compared with that of each interacting species. NOIs for F. moniliforme and F. proliferatum were >0·90 at >0·96 aw and 25 and 30°, indicative of co-existence with other species. Most of species had NOIs >0·90, except in some cases when paired with F. moniliforme, where NOIs <0·80 suggested the occupation of different niches. Although there was no significant correlation between the ID and NOI methods both suggested that the niche overlap between species was in a state of flux and significantly influenced by both temperature and water availability. This suggests that interpretation of ID, or NOIs carried out under one set of environmental conditions may be misleading when considering interactions between species and also where screening for biocontrol potential is being considered.

Orphella catalaunica and O. helicospora spp. nov. both from the hindgut of stonefly (Leuctra) nymphs from Spain, are described and illustrated. They are compared with the other species of the genus. Orphella haysii is reported for the first time in Europe. The generic description of Orphella is emended to accommodate the new characters described for the new species. A dichotomous key for separating the species is provided.

Schizochytrium limacinum sp. nov, a thraustochytrid, is described from sea water from a mangrove area of the Yap Islands in the west Pacific Ocean. It is closest to S. aggregatum, and differs from other Schizochytrium spp. in its limaciform amoeboid cells, the size of zoospores, released without an amoeboid stage, and the assimilation profile of carbon sources.

Torrubiella dimorpha sp. nov. on an infected spider from Taiwan is described and illustrated. It is characterized by producing perithecia on an orange white, pulvinate, lanose mycelial mat covering the host. The anamorph, Gibellula dimorpha sp. nov., produces gibelluloid and granulomoid synanamorphs on aspergillate, distinctly roughened or warty conidiophores, or sometimes produces both synanamorphs on the same aspergillate vesicle. The differences between T. dimorpha and the closely related T. globosa, T. globoso-stipitata, T. arachnophila, T. ratticaudata and T. clavata are briefly discussed.

Conioscypha is reviewed, with a discussion on generic concepts and conidiogenesis. A new genus, Conioscyphopsis, is described from submerged wood in Australia, and a key to species in both genera is provided. Conioscyphopsis australiensis sp. nov. is similar to species of Conioscypha in lacking conspicuous conidiophores, but its dematiaceous, unicellular conidia are produced from ampulliform conidiogenous cells borne on semi-immersed hyphae. Conioscyphopsis differs from Conioscypha mainly in its conidiogenesis. Conidiogenesis in Conioscypha is intermediate between ‘annellidic’ and ‘phialidic’, single conidia being produced endogenously within indeterminate, percurrently proliferating conidiogenous cells. In Conioscyphopsis, conidiogenesis is ‘enteroblastic-phialidic’, solitary conidia being produced exogenously from determinate, but percurrently regenerating conidiogenous cells.

A coelomycetous genus, Pseudophragmotrichum gen. nov., with the type species P. cubense sp. nov., is described from dead culms of Oncidium lucidum from Cuba. It differs from other coelomycete genera in having intercalary conidiogenous cells, thallic conidiogenesis and flattened conidia.

A taxonomic and chorologic study of Protophysarum phloiogenum, including light and SEM micrographs is presented. The authors propose the new family Protophysaraceae in the Physarales.

Hirsutella petchabunensis is described from a single specimen collected on a Lepidoptera larva in tropical forest in Thailand. This is linked, both in the field and through cultural studies, with a distinctive helicosporous synanamorph that is assigned to Helicoma.

The uredinial stage of Skierka agallocha was detected on leaves of Excoecaria agallocha, collected for the first time from mangroves of the Sundarbans during 1992. This communication deals with light microscope and scanning electron microscope characters of this mangrove rust.

Pleurotus pulmonarius is a species of the oyster mushroom which has become the second most popularly cultivated mushroom in the world. In this study, we show that renewed fruiting from excised stipes can be used as a simple and rapid in vitro bioassay system to detect fruiting modulators. We used this and conventional cultivation techniques to examine the effects of cadmium, a potential contaminant from industrial sources, calcium, which is an ingredient in mushroom compost, and manganese, which has been claimed to improve the yield of P. ostreatus. All the three metallic salts did not affect sporulation. Calcium chloride addition shortened the time taken for the mushroom to fully cover the cultivation compost and improved yield. Insoluble calcium salts at higher concentrations had a similar though less pronounced effect. The calcium and total amino acid contents of fruit bodies also increased. Compost supplementation with calcium is desirable for cultivation of the oyster mushroom but not indispensable since the straw-based cultivation substrate is itself able to provide the required minerals. By contrast, manganese chloride retarded mycelial growth and decreased yield but increased the total amino acid content in the stipe whilst manganese sulphate did not enhance accumulation of manganese into fruit bodies. Excess manganese induced browning of vegetative tissues. Cadmium ions did not kill the oyster mushroom at 4·5 mM but reduced yield by 50%. At this concentration cadmium decreased the total amino acid content and affected the amino acid profile but did not affect the form and shape of the fruit bodies. Pleurotus pulmonarius concentrated cadmium to such an extent that consumption of as little as 20 g (D.W.) of the most contaminated samples would exceed the weekly limit tolerated by humans and thus pose a health hazard. Monitoring the heavy metal contents of mushrooms marketed for food is, therefore, advised as the source of the substrate for cultivation is usually not known.

The effect of water activity (aw, 0·995–0·85) and temperature (15, 25°C) on the in vitro inter- and intra-specific interactions between thirteen fungi commonly isolated from maize grain were investigated. The fungi were paired and their interactions given a numerical score to obtain an Index of Dominance (ID) for each species. Aspergillus niger had the highest overall ID in most of the conditions tested, while the Aspergillus species tested were also quite dominant. Fusarium species appeared to be dominant only at high water availability (0·995 aw), while Eurotium species dominated at the lower aws (0·85–0·90). The relative growth rates of each fungus were also calculated under the same range of environmental conditions. In general, Aspergillus, Fusarium and Trichoderma species grew most rapidly under the combination of aw and temperature conditions in which they were able to grow, while Penicillium species had the slowest growth rates. There was a positive correlation between growth rate and ID for Trichoderma viride and three Fusarium spp. but not for Aspergillus and Penicillium and Eurotium spp. The different possible strategies in fungal competition for grain are discussed in relation to these in vitro findings.

Three British rust fungi reported to form aecia on daisy (Bellis perennis) are compared. A recently discovered species, possibly introduced from Australia, is identified as Puccinia distincta. It is a short-cycled -opsis form lacking uredinia, with aecia and telia confined to Bellis and its aeciospores capable of reinfecting the same host. This rust is compared with a macrocyclic heteroecious eu-form, P. obscura, which produces pycnia and aecia on Bellis and uredinia and telia on Luzula. Puccinia distincta is probably derived from and correlated with P. obscura because both species have the same aecial host, and because their teliospores are closely similar in morphology and dimensions. Comparison is extended to P. lagenophorae, a common rust with aecia and telia on Senecio spp., which has been reported to form aecia on Bellis following inoculation with aeciospores from Senecio. The repeated failure of our own reciprocal inoculation experiments using aeciospores from the two different hosts and differences in teliospore morphology between P. distincta and P. lagenophorae lead us to conclude that the current rust epidemic on daisies is caused by P. distincta which is distinct from P. lagenophorae.

Prosthemium betulinum and Pleomassaria siparia are found in the same sites on birch branches. Single spore cultures of P. siparia produced conidia similar to those of P. betulinum. Restriction analysis of 18S rDNA did not differentiate between P. betulinum and P. siparia. Random amplified microsatellite fingerprints showed a high amount of variation, which was not explained by the origin of cultures. We conclude that P. betulinum is the anamorphic state of P. siparia.

In some filamentous ascomycetes, karyotypic data by conventional light microscopy are not consistent with the electrophoretic karyotypes by pulsed field gel electrophoresis (PFGE). In this study, the three methods, conventional light microscopy on asci, PFGE, and the germ tube burst method (GTBM), were compared for their concordance in karyotyping by using Nectria haematococca (anamorph: Fusarium solani). GTBM was included in the study for cytological karyotyping on mitotic metaphase in germlings of conidia. Conventional light microscopy on asci was concluded to lead to the underestimation of chromosome number in this fungus. PFGE was effective for analysing chromosomes smaller than ca 6 Mb, but did not yield a complete karyotype due to the poor resolution of larger chromosomes. GTBM was useful for determining chromosome numbers as well as chromosome morphology. Analyses by these methods revealed that each of five strains used, two homothallic and the other three heterothallic, has a unique karyotype different from others in number and size of chromosomes. The present results indicate that combination of PFGE and GTBM constitutes a powerful tool to determine karyotypes of filamentous ascomycetes including N. haematococca.

From 1991 to 1996, Phellinus noxius was collected on 60 host plant species at 136 different sites in Taiwan, and two host plant species at two different sites on Kinmen Island. It was collected mostly on hosts growing in the low elevation plains and hills of western, eastern and southern Taiwan, while it was found on only a few hosts in northern Taiwan and was absent from the high mountain areas. P. noxius was observed on and isolated from 57 woody species, and three annual herbaceous plants. In the field, basidiomes of P. noxius have only been observed on Casuarina equisetifolia, Delonix regia and Ficus microcarpa. A dark brown mycelial mat on the surface of the roots and up the base of stems was used reliably for the field identification of P. noxius. Although P. noxius did not favour a particular soil pH, it was not found in extreme pH conditions. It was found in soils from pH 4 to 9 and most frequently in soil from pH 5 to 8. P. noxius occurred mostly in soils with sand, loamy sand and sandy loam textures.

The formation of oxidases and peroxidases by newly isolated ectomycorrhizal fungi was examined with agar spot tests for tyrosinase, laccase, polyphenol oxidase and peroxidase as well as with the Bavendamm test. Extracellular peroxidase was released by virtually all isolates. Tyrosinase (taken as cresolase) was presumably intracellular and occurred in the majority of isolates. The strong laccase reaction was predominantly extracellular, although in some ectomycorrhizal genera the intracellular laccase seemed to dominate. Polyphenol oxidase, as the catecholase/monophenol monooxygenase complex, was found in all isolates although its detection was complicated in the presence of laccase. Lactarius and Russula and the possibly more saprotrophic Morchella showed the most intense enzyme reactions. A comparison with wood and litter decaying fungi indicated that at least some species of several ectomycorrhizal genera possess extracellular oxidative enzymes that are normally characteristic of white rot fungi. It is concluded that mycorrhizal fungi grown asymbiotically can release extracellular enzymes capable of oxidizing a wide range of aromatic compounds.