The purification, production and some properties of the intracellular and cell wall associated (1→3)-β-glucanases, (1→6)-β- glucanases and β-glucosidases of Acremonium persicinum have been examined. Anion exchange chromatography revealed the presence of two (1→3)-β-glucanases, one (1→6)-β-glucanase and two β-glucosidases in intracellular extracts of A. persicinum, with further purification by gel filtration chromatography allowing partial characterization of these enzymes. All three intracellular β-glucanases and one of the β-glucosidases appear to be very similar to enzymes found in the extracellular fluid with regard to their molecular masses, hydrolytic action patterns on their substrates, and apparent regulation of syntheses. In contrast, the remaining β-glucosidase appeared to occur only intracellularly and possessed different properties from its extracellular counterpart, most notably being composed of two subunits of 130 and 138 kDa, and its synthesis relatively insensitive to glucose in the medium. Similar anion exchange chromatographic analysis of the cell wall associated enzyme activities extracted by 4 M LiCl revealed the presence of three (1→3)-β-glucanases, one (1→6)-β-glucanase and one β-glucosidase. Except for one (1→3)-β-glucanase all these enzymes appear to be the same as those enzymes found intra- and extracellularly in terms of their action patterns on substrates and their apparent regulation of syntheses. The other apparent cell wall-specific (1→3)-β-glucanase appears to be constitutively produced and is an endo-hydrolase since it displayed no activity toward periodate oxidised laminarin or barley β-glucan. Possible roles for these enzymes are proposed in light of their location, action patterns and apparent regulation of syntheses.

Phytophthora megakarya is an important pathogen of cocoa in Africa. We used isozyme and RAPD markers to estimate the genetic diversity and structuring among 161 isolates, from the known distribution area of the fungus which corresponds to the cocoa belt in Ghana, Togo, Nigeria, Cameroon, Gabon and Sao Tome. Thirty six and 44 multilocus patterns were identified with isozymes and RAPDs, respectively. Patterns were separated into two highly differentiated genetic groups with both types of markers, one located in Central Africa and the other in West Africa. This distribution coincides with two major biogeographical domains which may reflect an ancient evolution of P. megakarya in this part of Africa. The genotypic diversity was lower in West Africa as compared to Central Africa. Inside Central Africa, isolates from Gabon and Sao Tome were highly differentiated based on RAPDs. Four intermediate marker patterns corresponding to isolates sampled near the border between Nigeria and Cameroon were putatively derived from genetic exchanges between the two major groups. The mating type determination permitted to confirm the high prevalence of A1 over A2. Although clonal multiplication seems to be the rule, indices of other reproduction means have been detected.

Development of mushrooms is driven by genetic and epigenetic factors in a continuous interaction with the environment. It is assumed that each successive stage of morphogenesis depends on specific sets of signals arising at the appropriate time and place during the growth process. Morphogenetic dynamism proceeds in a time dimension through a cascade of signal-effect associations. Developmental errors may occur when such signals originate in the wrong place and/or at the wrong time. As a result various abnormalities such as ectopic tissues can develop and morphogenesis can be severely disturbed. Both endogenous genetic disturbances and exogenous factors can cause developmental errors. Lamellar dysplasia, which is a pore-like proliferation of the gills, forms an example; it may be induced experimentally. Both lamellar dysplasia and rosecomb disease of Agaricus bisporus result from endogenous genetic instability, whereas the developmental errors observed in wet bubble disease, which is caused by the infection of Mycogone perniciosa, originate from an exogenous factor. Morphogenesis normally leads to a symmetrical form of primordia of A. bisporus. Asymmetry is very frequently associated with an underlying pathological situation. Defining exact criteria of and sharp borderlines between normal and abnormal development seems infeasible. Fungi may readily tolerate morphogenetic imprecision. In this report, various macro- and microscopic features of normal and pathological development are illustrated; the dilemma of normal versus abnormal fruit body development has been discussed.

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 preliminary physiological characterization of osmoregulation in an Aspergillus nidulans salt sensitive mutant carrying cotransformed DNA sequences from the marine hyphomycete Dendryphiella salina is described. A genomic DNA library made in lambda EMBL3 was cotransformed with the plasmid pDJB3 into an A. nidulans host carrying a selectable marker for transformation (pyrG89) and a salt sensitivity mutation (sltA1). In some cases D. salina clones appeared to directly complement the salt sensitivity mutation by restoring salt and arginine insensitivity. Other clones gave marked increases in salt tolerance and yet the hosts remained arginine sensitive. Improvements in salt tolerance correlated with an enhanced ability to induce polyol biosynthesis during salt challenge.

Germination of primary and secondary conidia of 33 strains (12 spp.) of co-occurring Conidiobolus and Basidiobolus from three closely adjacent managed habitats was studied in relation to general nutrient level, water activity of substratrum, light and temperature. A further 26 strains (16 spp.) derived from culture collections, and including insect pathogens and saprotrophs, were also compared. Nutrient levels triggering germ-tube formation differed widely amongst strains ; capilliconidial strains and/or presumptive pathogens usually had a low threshold. Successive generations of globose replicative conidia formed alternative conidial forms in increasing proportions. Water activity (aw) strong influenced development of non-globose conidial forms (microconidia, capilliconidia and actively discharged elongate conidia). Profiles of response to nutrients, aw, temperature and light differed between strains (and species) and the comparison represents a first stage in determining niche differentiation, including the putative interactions of these common fungi with litter invertebrates.

The ITS region of the rRNA genes was amplified using DNA extracted from Terfezia pfeilii fruit-bodies. Two types of restriction fragment profiles were revealed among 11 fruit-bodies by the Hinf I restriction enzyme. An additional four truffles collected from the same field one year later were found to have a mixed profile combining both types. Germinated spores from one of these mixed-profile individuals had a single profile belonging to one or the other of the two types. Roots collected around and underneath one Terfezia fruit-body were traced to different plants. Roots of a watermelon plant (Citrullus vulgaris) showed a non-vesicular-arbuscular endomycorrhizal association. Restricted ITS amplification fragments of mycorrhized roots from C. vulgaris were shown to match T. pfeilii fruit-body ITS-RFLP fragments. The significance of this finding with regard to T. pfeilii potential host range is discussed.

Since secondary metabolites are involved in fungal-host interactions, those of endophytes and their hosts were studied to try to understand why endophytic infections remain symptomless. A screening of fungal isolates for biologically active secondary metabolites (antibacterial, antifungal, herbicidal) showed that the proportion of endophytic isolates that produced herbicidally active substances was three times that of the soil isolates and twice that of the phytopathogenic fungi. As markers for the plant defence reaction, the concentrations of certain phenolic metabolites were chosen. Those that differed in concentration were higher in the roots of plants infected with an endophyte than in those infected with a pathogen. The results presented here were regarded together with previous studies on other aspects of the plant defence response using dual cultures of plant host calli and endophytes, and of cell suspension cultures following endophytic as compared to pathogenic elicitation. The following hypothesis was developed: both the pathogen-host and the endophyte-host interactions involve constant mutual antagonisms at least in part based on the secondary metabolites the partners produce. Whereas the pathogen-host interaction is imbalanced and results in disease, that of the endophyte and its host is a balanced antagonism.

The ultrastructure of the dimorphic ascospores of Mamillisphaeria dimorphospora are illustrated. The small brown ascospores differ from the larger hyaline ascospores in having a thick melanin layer in the ascospore wall. They are also 2–3 times smaller and do not germinate on PDA. The significance of these observations with respect to dispersal of aquatic fungi is discussed. The large hyaline ascospores may be morphologically adapted to dispersal in streams, while the smaller brown ascospores are thought to be adapted to aerial dispersal. The reasons for this are discussed. The method by which two spore types can be produced in separate asci in one ascoma is hypothesised.

Macro- and micromorphology of 124 specimens and 11 holotypes of South American taxa of subgenus Elfvingia (= G. applanatum complex) were examined, and were compared with isoenzymic data previously obtained. Two major dermis types were defined and illustrated. Spore ornamentation was inspected under SEM. Sixty-four per cent of the specimens had an anamixodermis, 80% had spores with longitudinal furrows under SEM and 83% had a context layer without streaks of melanoid deposits. Some of our South American collections could be ascribed to G. lipsiense, G. tornatum, G. testaceum and G. lobatum. Other taxa are critically discussed. The position adopted in this work was to join under synonymy closely related taxa on the grounds of morphology and geographical distribution. In general, correlation between morphological features and isoenzymic patterns could not be established. In this group, phenotypic plasticity appears to be great.

The present study treats several fungi associated with leaf spots of Proteaceae from Africa, Australia and India. Leptosphaeria leucadendri (anamorph: Sclerostagonospora leucadendri) is described from Leucadendron leaves from Australia, while three previously described African taxa from Protea leaves are transferred to Phaeophleospora as P. abyssinicae, P. congestum and P. protearum. Trimmatostroma protearum and a Phyllosticta sp. are described from Protea leaves collected in South Africa and Australia, respectively. Cercospora agharkarii, which occurs on Grevillea, is redisposed to Pseudocercospora, while a new genus Pseudohendersonia, is proposed for P. proteae occurring on Protea leaves in South Africa.

Melanospora pascuensis sp. nov., isolated from soil of Easter Island, is described and illustrated. The ITS1, ITS2 and 5·8 S rRNA gene sequences are also provided. The fungus can be recognized by the setose perithecial ascomata and the peculiar ring-like structure surrounding the ascospore germ pores. It is compared with other species of Melanospora and related genera.

Three isolates each, of nine different Trametes and five other wood inhabiting basidiomycetes, were collected from the indigenous forests of Zimbabwe, and the impact of temperature (20–60 °C), osmotic and matric potential (−0·5 to −8·0 MPa), and their interactions on in vitro growth compared. Generally, there was no significant difference between growth of isolates of the same species in relation to temperature. Temperature relationships of the species studied correlated well with their geographic distributions. Species occurring in hot, dry regions tolerated a wide temperature range, with some showing unusually high thermotolerance (55°, T. socotrana, T. cingulata and T. cervina). There were significant intra-strain differences for individual species in relation to solute potential on glycerol-modified media. Generally, growth of all species was better on glycerol- and KCl-modified osmotic media than on a matrically-modified medium (PEG 8000) at 25, 30 and 37°. The limits for growth on the osmotic media were significantly wider than matric medium, being −4·5 to −5·0 and −2·5 to −4·5 MPa, respectively. An Irpex sp. grew at lower water potentials than all other species, with good growth at −7·0 MPa. This study suggests that the capacity of these fungi for effective growth over a range of temperatures, osmotic and matric potentials contributes to their rapid wood decay capacities in tropical climates.

To test the validity of R. tauricus as a separate species, its carbon source utilization, isoenzyme patterns and PCR-coupled RFLP of the ITS of its rDNA were analysed. Whilst R. tauricus differed considerably from R. pusillus and R. miehei in morphological traits as well as its ability to row on single carbon sources, the results obtained from all other experimental approaches suggest extensive similarity between R. tauricus and R. pusillus. These findings lead us to believe that R. tauricus is a mutant heterothallic strain of R. pusillus.

Field isolates of Rhizoctonia solani are presumed to consist of heterokaryotic cells, but the number of different nuclear types present in each cell is unknown, nor is it known if there is any regulation of the heterokaryotic state. To investigate the nature of heterokaryosis in AG 4, hyphal tip subcultures of two strains were examined using vegetative compatibility as a marker. Upon subculture, each isolate could be placed into one of two VCGs, members of which were compatible within the group but incompatible with those of the other group and the parent strain. No other phenotype could distinguish these groups from each other or the parents. Pairing of hyphal tip isolates never resulted in regeneration of the parental strain. Examination of nuclei in the tip cells of incompatible strains by DAPI staining and fluorescence microscopy showed variation in nuclear numbers in different parts of the fungal colony and a significant tendency for some adjacent branch tips to have a similar number of nuclei. These results suggest a mosaic of nuclear, and perhaps mitochondrial, types within the colony, and that subcultures of components of the mosaic retain their differences. This variation implies that regulation of nuclear number within a colony is loosely controlled.

Isolates of Phytophthora infestans of A1 mating type from central Mexico and Wales, when mated to a range of A2 isolates from Russian and Mexico, produced a proportion of abnormal oogonia with several oospheres. Similar oogonia were observed in self- fertile lines resulting from treatment of a Russian A1 isolate with a chemical mutagen followed by the fungicide, metalaxyl.

The electrophoretic karyotype of the Chinese straw mushroom, Volvariella volvacea, was determined. The haploid strain V34 of V. volvacea has 15 chromosomes ranging in size from 1.4 to 5.1 Mb. No chromosomal polymorphism in terms of size and number was seen in either of two growth stages: vegetative mycelia or fruit-body gill tissues. DNA fingerprints were prepared by the arbitrarily- primed polymerase chain reaction. Those obtained from different stages during fruit-body morphogenesis were identical. However, variation in DNA fingerprints was evident in protoplast regenerants derived from the same vegetative mycelium. Thus the haploid mycelium of strain V34 is heterokaryotic but the bulk genotype is stable during fruit-body development. F1 and F2 progenies germinated from the haploid, uninucleate basidiospores from self-fertilized fruit bodies also regularly segregate a range of mycelial morphological variants as well as phenotypic variation revealed by DNA fingerprints. We overview the known mechanisms to generate genetic variation and propose a novel mechanism that could account for the 1:1 segregation ratio of self-fertile to self-sterile progeny regularly obtained from selfed Volvariella volvacea fruit bodies.

This study examined the occurrence of macrofungi and the decay of roofs thatched with water reed, Phragmites australis. Sampling from 20 north- and 20 south-facing roof sides showed that several ascomycetes usually associated with reed in situ are common on thatch. The only basidiomycetes recorded were Mycena species. There was no significant difference in the representation of macrofungi on north- and south-facing roof sides, but Mycena spp. only produced basidiomes on surfaces facing north, suggesting that the dry environment of the south side prevents fruiting. Eleven species were recorded in total, and the average of 2·4 species per roof did not increase with the age of thatch or degree of decay. The same species were generally present on young and old thatch, and no successional stages of fungal communities could be distinguished with increasing roof age.

Deterioration of thatch occurs at the exposed surface of the roof and progresses inwards. Within the layer of reeds outer, middle, and inner zones develop representing different stages in the decay. The zones move inwards as thatch deteriorates. A comparison of the rate of decay among roofs with pitch 30°, 45° and 60° showed that the innermost zone appeared ca 20 cm from the exposed reed butts in both of the steeper roofs, whereas it was no longer present in the roof with low pitch. This suggests that the depth of the zones depends upon the roof slope, and the outer and middle zones move inwards at a higher rate in roofs with a low pitch, resulting in an increased rate of deterioration.

Phragmites thatch appears to harbour its own characteristic macrofungal community, with certain Mycena species likely to represent the principal decomposers. A common feature of fungi occurring on thatch is that they must endure unfavourable conditions.

The effects of a prescribed fire on the presence of ectomycorrhizal fungi on the root tips of ponderosa pine were investigated one year after a prescribed ground fire. Ectomycorrhizas were sampled within 1 m2 plots before and one year after the fire, and in nearby control plots that were not burned. The cores were divided into litter/organic, upper mineral, and lower mineral layers. The total ectomycorrhizal biomass in the control plots did not differ between year one and year two samples for any core layer, while in the fire plots the destruction of the litter/organic layer resulted in an eight-fold reduction in total ectomycorrhizal biomass. Mycorrhizal biomass in the two mineral layers was not significantly reduced by the fire. We used molecular tools to identify fungi directly from the ectomycorrhizas. In unburned plots members of the Russulaceae and Thelephoraceae were among the most frequent and abundant ectomycorrhizal types; species of most other taxa were rare. In the control plots these two families were among the dominant species in both years, but patchiness on a fine spatio-temporal scale caused some major changes in ranking of individual species between sample years. Rhizopogon subcaerulescens was the most pronounced example; its biomass in the control plot samples was seven times greater in year two than in year one because of an exceptionally large cluster of mycorrhizas encountered in a single core. The effect of fire on individual species was difficult to assess because of this patchiness and because all species were low in abundance after the fire. The most abundant pre-fire species were reduced to undetectable post-fire levels, while several less abundant species, including R. subcaerulescens, Cenococcum geophilum, and several unknown types were not substantially reduced by the fire. We speculate that the more abundant species, Martellia sp., thelephoroid 1, and Tomentella sublilacina, were differentially affected because their dominance was most prominent at the litter and organic layers. In any case, a short-term effect of this fire appears to be increased species evenness.

The hyphal wall protects the pressurized cell against lysis, physical abrasion, chemical damage, and probably from other microorganisms and predatory invertebrates. Against these assets we can hypothesize costs for a cell that are associated with a wall. For example, phagocytosis is impossible, and the release of secreted molecules is complicated by the diffusional challenge presented by the mesh of microfibrils and interleaving wall polymers. A more controversial idea is that once delimited by a tough integument, growth becomes dependent upon the exertion of internal force to cause wall yielding, and most mycologists have posited turgor pressure as the origin of this force. In relation to growth then, it seems logical to suggest that fungal walls evolved to meet a multitude of needs, and that once a cell became walled, osmosis would automatically generate the turgor it required for growth.