Laetiporus sulphureus causes heart-rot in deciduous trees and conifers. European isolates were examined using nuclear DNA markers as well as somatic and sexual compatibility. Pairing tests for somatic compatibility with isolates from 20 different host individuals revealed that each tree is normally colonized by a different genet. The hyphae are multinucleate, basidiospores are binucleate, and conidia contain 2–6 nuclei. Basidiospore germination was erratic, and no clear mating pattern was observed. In one case all single spore isolates from the same basidioma were compatible with each other. Single spore isolates from coniferous and from broadleaf trees were incompatible. The nuclear ribosomal DNA ITS regions from six isolates of different origin revealed nucleotide distances of up to 14·6%. Phylogenetic analysis resulted in a single clade for all isolates. Within this clade, a subclade including only the isolates from gymnosperm hosts was present, indicating that these isolates were derived from ancestral lines from broadleaf hosts. While there is evidence that more than one species or ecotype is represented within the current definition of L. sulphureus, circumscription of additional taxa, and separations within this taxon, remain unclear.

A mathematical model is presented which qualitatively describes the growth kinetics of the aphid-pathogenic Erynia neoaphidis in liquid culture. An essential feature of the model is that it allows for the presence of a toxic component within the growth medium which may be broken down by an extracellular enzyme released by the biomass. In this investigation, the toxin was oleic acid which had previously been shown to be essential for the growth of E. neoaphidis, but only at low concentration.

The model reproduces a number of unusual features of the kinetics of growth of E. neoaphidis in liquid culture. These include: the requirement for a high inoculum concentration to successfully initiate growth in liquid culture; failure to grow in continuous culture under conditions similar to those supporting successful batch culture; a reduced growth yield in continuous culture compared to batch culture; a depressed apparent specific growth rate in continuous culture compared to batch culture and, deviation from the usual exponential decrease of biomass concentration during washout. Through the development of the model, and the application of predictions derived from it to the laboratory situation, continuous culture of E. neoaphidis was achieved for the first time.

Investigation of Phaeocollybia in British Columbia, Washington, Oregon and California has led to a better understanding of the characters and biology of the genus as a whole. Generically significant characters – pseudorhizas, pellicular veil, tibiiform diverticula, and sarcodimitic tissues – are examined in depth with four variations of branched and unbranched pseudorhizal patterns outlined. Basidiome development is traced from subterranean initiation to fully mature emergent basidiomes. Hypotheses on the ontogeny of Phaeocollybia basidiomes and biological associations are developed based on extensive observations of primordia and numerous field excavations. Comparisons between rhizomorphs and the thread-like pseudorhizal extensions of certain species are made and the term ‘rhizomorphic pseudorhiza’ is introduced. Possible biological strategies are explored and evidence for consideration of Phaeocollybia as a mycorrhizal genus is presented.

Collybia fusipes is the cause of a root rot of oak trees. We studied the structure of C. fusipes populations in two infected oak stands by using somatic incompatibility and DNA amplification. Isolates were obtained from different oak root systems or from within the same root system and somatic incompatibility groups (SIG) were identified. Many small SIGs that seldom encompassed more than one root system were present in both stands. More than one SIG was usually present on an individual root system: there were 3·1±1·3 SIGs on the pedunculate oaks and 2·2±0·6 on the red oaks. The largest SIG contained more than 70% of the isolates obtained from the root system of 14 of the 20 trees studied. Isolates that belonged to the same SIG usually had the same ribosomal intergenic spacer. It is concluded that C. fusipes spreads poorly from tree to tree by vegetative means.

Silver scurf is an important postharvest disease affecting potato tubers worldwide, caused by Helminthosporium solani. In the present study, key steps of infection of potato tubers (cv. ‘Dark Red Norland’) by H. solani were described using transmission (TEM) and scanning electron microscopy (SEM). The fungus entered potato tubers mainly via hyphae, although germ tubes were also able to directly penetrate the tubers. An extracellular sheath was observed around hyphae growing over the surface of tubers and the host cell wall appeared lyzed at the point of penetration. Observations suggested that both mechanical and enzymatic processes are involved in periderm penetration. Hyphae of H. solani, 9 h after tuber inoculation, were present intracellularly mostly in the periderm and in some cortical cells. Two days after inoculation, host cells were invaded and both infected and neighbouring host cells showed signs of necrosis (disrupted cytoplasm, absence of typical organelles or endomembrane systems, collapsed peridermal cells) that were not observed in healthy control tubers. Four days after inoculation, completing the infection cycle, conidiophores emerged from peridermal cells directly by erupting through the host cell walls.

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.

Faecal samples collected from the Mountain brushtail possum (Trichosurus caninus) at several sites in eastern Australia showed the presence of spores from at least 21 hypogeous fungi, and several epigeous species. Most were found in faeces of animals at one site, where samples were collected in different seasons. Further collections are needed from the other sites at different times of the year to clarify how widespread the mycophagous habits of T. caninus are. Many of the hypogeous fungi identified are either known or presumed to form mycorrhizal relationships with the roots of forest trees and shrubs and T. caninus may disperse their spores in its faeces.

Over 600 basidiomycetes were isolated from indigenous forests and commercial Eucalyptus and Pinus plantations in South Africa. One hundred and twenty of the cultures were identified and biochemical tests were done to screen the cultures for characteristics that are favourable for biopulping. Most of the white-rot fungi previously associated with biopulping elsewhere in the world were also isolated in South Africa, as well as an isolate with uniquely regulated ligninolytic systems. Phanerochaete chrysosporium was found to be a natural coloniser of wood chip piles in South Africa.

Competing ectomycorrhizal fungi can cause problems during the commercial production of edible Tuber species infected plants in greenhouses and later when infected plants are transplanted to the field. We investigated the effect of selective fungicides on Tuber borchii, in the presence of Hebeloma sinapizans, both in vitro and during the production of T. borchii infected Quercus pubescens. Oxycarboxin completely suppressed the growth of H. sinapizans but had only a weak fungitoxic effect on the growth of T. borchii both in vitro and on Q. pubescens roots. In contrast, other fungicides either suppressed both fungi or T. borchii more than H. sinapizans.

The presence of some fungi on a variety of food products, like cheeses or cured meat products, is beneficial for the ripening of the product and for the development of specific flavour features. The utilization of these fungi as starters, which are inoculated normally as asexual spores on the food products at the beginning of the ripening process, is becoming a usual procedure in the food industry. The starter culture also prevents undesirable fungi or bacteria from growing on the product. Penicillium nalgiovense is the most frequently used starter for cured and fermented meat products, but the fact that this fungus can secrete penicillin to the meat product makes it important to get strains unable to synthesize this antibiotic. In this work we report that P. nalgiovense strains impaired in penicillin production can be obtained by disruption of the pcbAB gene (the first gene of the penicillin biosynthetic pathway). When applied as starter on cecina (a salted, smoke-cured beef meat product from the region of León, Spain), the pcbAB-disrupted strain showed no differences with respect to the parental penicillin-producing strain in its ability to colonize the meat pieces and to control their normal mycoflora. Both strains exerted a similar control on the presence of bacteria in cecina. A similar proportion of penicillin-sensitive and penicillin-resistant bacteria were isolated from pieces inoculated with the penicillin-producing or the non-producing P. nalgiovense strains. The decrease of the bacterial population on the surface of cecina seems to be due to the higher competition for nutrients as a consequence of the inoculation and development of the P. nalgiovense mycelium and not due to the production of penicillin by this fungus. Penicillin production was less affected than growth in a solid medium with high NaCl concentrations; this suggests that the high salt concentration present in cecina is not a limiting factor for penicillin production by P. nalgiovense.

Rust is reported for the first time in North America on tansy (Tanacetum vulgare), a widespread and invasive Eurasian plant that was introduced into North America in the 17th century. Morphologically, the rust fungus corresponds exactly to Gäumann's description of Puccinia tanaceti, and to European specimens of P. tanaceti on T. vulgare. An inoculation study confirmed the narrow host specialization of P. tanaceti that Gäumann described, in that T. vulgare was successfully inoculated whereas four other species of the tribe Anthemidae of the Asteraceae were entirely resistant, i.e. Leucanthemum maximum (Shasta daisy), L. vulgare (ox-eye daisy), Artemisia absinthium (wormwood), and A. tridentata (sagebrush). This confirmation of a specialized P. tanaceti invalidates P. tanaceti s. lat. The latter complex has resulted from synonymies, and compilation of host records of rust fungi resembling P. tanaceti on at least 105 species representing 19 genera from six tribes of the Asteraceae from both New and Old Worlds.

Secretion of a constitutive endopectinase was detected in cultures of Venturia inaequalis grown in complex and defined media. Pectinylase or pectinesterase activity was not present. The attainable level of extracellular pectinase was present after 5–10 d post inoculation, when only about 5–10% of mycelial mass had developed. Time course culture experiments with conidial and mycelial inoculum indicated that enzyme secretion did not depend on physiological effects within or shortly after conidial germination. Cellulosic substrates did not affect pectinase production. Catabolite repression or repression by glucose was not detected and there was no stimulation of enzyme production in media supplemented with pectic substrates. Inhibition of enzyme activity by galacturonic acid was not detected. Nineteen isolates of V. inaequalis were tested, all of which displayed constitutive pectinase production. All isolates were able to grow in the defined media with galacturonic acid or the pectic substrates as the sole carbon source. Mycelial pectinolytic activity was only detectable in substantial quantities when the fungus was grown in media supplemented with 1% pectin. The pectinase preparations displayed a long-term stability at temperatures up to 20°C and within a pH-range of 5–7·5. Activity was very low at 5 and 10° and there was a distinct increase at 15 and 20°. Enzyme activity was highest at pH 4 and decreased with increasing pH. Time course viscometric assays and hplc analyses of liberated galacturonic acid indicated an endo-type degradation of pectin and polygalacturonic acid. Di- and trigalacturonic acid were released from pectin with high enzyme concentration and long incubation. Pectin with a degree of esterification of 93% showed reduced degradability. Pectinase preparations had a macerating activity on solvent extracted apple leaves and caused galacturonic acid release. Isoelectric focusing followed by a zymogram technique revealed a single activity band at pI 10. The pectinase preparations from culture filtrates or mycelia of 19 isolates did not show any differences in characteristics of degradative activity or the activity band detected after isoelectric focusing.

Spongospora nasturtii is a plasmodiophorid pathogen of watercress (Rorippa nasturtium-aquaticum), causing crook root disease. In the past, some authors have considered the plasmodiophorids as protists, and others have considered them as true fungi. This study was performed with the aims of elucidating both the relationship of S. nasturtii to other plasmodiophorids, and also the placement of the plasmodiophorids as a group when compared to other organisms. Analysis of partial 18S ribosomal DNA sequences of a range of plasmodiophorids by phylogenetic techniques including parsimony, neighbour-joining, and principal co-ordinate analysis, indicated that there was a close relationship between S. nasturtii, S. subterranea and Plasmodiophora brassicae. However, analyses incorporating 1.2 kb of 18S rDNA sequence from S. subterranea cast doubt over the long-held view that S. subterranea and S. nasturtii are more closely related to each other than to other genera of plasmodiophorids. Consideration of the entire 18S rDNA of both S. nasturtii and P. brassicae showed that they are not closely related to a range of protists and true fungi examined.

Coemansia aciculifera, C. scorpioidea and C. thaxteri were found in the rhizosphere of wheat and a fungus resembling C. spiralis was found in the rhizosphere of barley from two fields in eastern England when serially washed root pieces were incubated on low nutrient agar (SNA).

Entoleuca mammata (syn. Hypoxylon mammatum) is a damaging pathogen of Populus tremuloides and P. grandidentata in North America and P. tremula in Europe, where the fungus occurs only sporadically in alpine regions and Scandinavia. It has been hypothesized that E. mammata was introduced to Europe from North America. In this study, E. mammata isolates collected from Europe and North America were compared by a sequence analysis of two DNA markers derived from DNA fingerprints. The objective of the study was to elucidate the relationship between North American and European E. mammata populations by testing two hypotheses: (1) North American and European isolates are conspecific; and (2) the fungus was introduced between continents causing both a founder effect and a genetic bottleneck. North American populations were found to be more polymorphic, but no major phylogenetic differences between fungal isolates collected from different continents were found. This result combined with the historical observations of the disease in Europe implies that E. mammata was introduced to Europe several centuries ago.

Hebeloma radicosoides sp. nov. is described, illustrated and characterised. It superficially resembles H. radicosum in having a long-rooting stipe with a well-formed, membranous annulus and in having preference for animal wastes as its resources. Its pileus is yellower than that of H. radicosum, and it fruits after addition of urea to soil, whereas H. radicosum does not. It also fruits on various animal wastes whereas H. radicosum specifically fruits on mole or mouse middens. Unlike H. radicosum, H. radicosoides has no distinct odour. Hebeloma radicosoides also resembles Hebeloma luchuense and H. spoliatum in having a long-rooting stipe and in fruiting on urea-treated soil, but differs from them by having a yellowish scaly pileus and distinct, membranous annulus.

The causal agent of a patch disease of buffalo grass (syn. St Augustine grass) is determined and described as a new species, Gaeumannomyces wongoonoo sp. nov. Glasshouse experiments have shown that it is pathogenic to buffalo grass (cultivar ST 1191) but not to maize or wheat. The pathogen is different to the varieties of G. graminis in having shorter ascospores (36–75 μm) and producing numerous perithecia readily on malt extract and potato dextrose agars. The disease is named ‘wongoonoo patch’ to distinguish it from take-all patch of turf grasses caused by G. graminis.

The South African Cape Floral Kingdom is the world’s smallest and most diverse plant Kingdom, but is greatly under threat from urbanisation and agriculture. It covers only 90000 km2 and has a Mediterranean climate. This area has a long history of botanical studies, but little research has been undertaken on the associated fungi. Therefore, a biodiversity study of the fungi has been initiated. The catalyst for this study has been the diversity of unusual fungi encountered whilst studying the fungal pathogens of Proteaceae. These pathogens include species, or entire genera of fungi that are specific to genera of Proteaceae. The diversity and uniqueness of the Proteaceae pathogens may indicate a similar diversity in saprobic fungi in this unusual habitat. Therefore, microfungi associated with genera of Proteaceae in various habitats are being systematically sampled over a two-year period. The initial results of this study are presented.

The vegetative life-cycle of Cymadothea trifolii (anamorph Polythrincium trifolii), causing sooty blotch of clover, is described using chemically as well as cryofixed and freeze-substituted samples. The pathogen enters the leaf through stomata and proliferates intercellularly. Nutrients are assumedly obtained via an interaction apparatus produced within the pathogen's hyphae, opposite to which the host cell is triggered to invaginate its plasmalemma. Rare attempts of ‘self-parasitism’ were also seen. Entering the conidial stage, stromata are laid down under the lower epidermis. The dying tissue above may explain the necrotic spots observed on infected leaflets. Foot cells in the conidial stromata produce thick-walled conidiophores, which grow sympodially. New conidiophores may grow into empty shells of old ones. Conidia are detached after pores between them and conidiophores have become plugged by organelles resembling Woronin bodies. Conidia are usually two-celled and their walls contain chitin and β-1,3-glucans as indicated by labelling with gold-conjugated wheat germ agglutinin and anti-β-1,3-glucan antibodies. Both conidiophores and conidia contain a structure which we regard as a new organelle with as yet unknown function.

Two specimens of a new species of Hypocrella with large stromata were collected in Bolivia and Costa Rica. The morphology of the new species, H. macrostroma sp. nov., was compared with that of other species with large stromata, i.e. H. africana, H. gaertneriana, and H. schizostachyi. In addition, phylogenetic analyses of partial sequences from three genes, large subunit nuclear ribosomal DNA (LSU), translation elongation factor 1-α (EF1-α), and RNA polymerase II subunit 1 (RPB1), were conducted to determine the relationships of the new species to other species of Hypocrella/Aschersonia. Phylogenetic analyses show that H. macrostroma belongs to a strongly supported clade that includes H. africana, H. schizostachyi, and Aschersonia insperata, whereas other Hypocrella species belong to two sister clades. Hypocrella macrostroma is described and illustrated, and a lectotype is designated for H. gaertneriana.