The introduction of recombinant DNA technology in the field of mushroom research has resulted in the cloning and characterization of a large number of genes. In order to study the genetics of compost colonization of A. bisporus, genes encoding enzymes involved in utilization of this substrate have been isolated. In addition, a number of genes which are induced in fruit bodies during fruit body development have been cloned and they will provide more insight in the genetics of this economically important aspect of the life cycle. Other genes that were cloned encode proteins of basic biochemical routes. They provide knowledge on the importance and regulation of these routes in the life cycle of A. bisporus and add to knowledge on the general architecture of A. bisporus genes. Here we present an overview of the currently available biochemical and molecular data of A. bisporus and we discuss the importance of the available genes as genetic markers for breeding purposes.

A taxonomic review and revision of the dematiaceous hyphomycete genus Acrogenospora is presented. Species in this genus produce acrogenous, solitary, nonseptate conidia from mononematous, simple conidiophores, with multiple percurrent proliferations. Acrogenospora altissima comb. nov. and A. megalospora comb. nov. are proposed for the anamorphic states of two Farlowiella species. A. ovalia and A. subprolata spp. nov. are described from submerged wood in Hong Kong. They differ from other Acrogenospora species in shape, colour, and size of their conidia. A taxonomic key to species in the genus is provided.

The occurrence of Lophodermium on fallen needles and Leptostroma, the mitosporic state of Lophodermium, on living needles of Japanese black pine trees treated with simulated acid rain (SAR, pH 3) or tap water (control, pH 6·3) were studied. The amount of fallen needles was also examined. Significantly more needles fell from SAR-treated trees than from control trees, though there were no visible symptoms in the needles of SAR-treated trees. The detection frequency of Lophodermium on fallen needles, and that of endophytic Leptostroma on 2 year old and 3 year old needles, was lower in SAR-treated than control trees. The reduction in the detection of Lophodermium/Leptostroma on needles implied the reduction in the density of endophytic fungi with air pollution.

Anthostomella petrinensis and A. theobromina are described from endemic Pandanus species in Mauritius. They are compared with other Anthostomella species reported on Pandanaceae and Palmae. A table is included, facilitating comparison between the new species and previously published taxa with similarly sized ascospores.

Astrocystis fimbriata, A. rarissima and A. cepiformis spp. nov. are described and illustrated from dead leaves of Pandanus. Their affinities with related taxa are discussed, especially with Astrocystis species on Palmae and with Rosellinia as interpreted in recent studies. One species has stromata which develop from a mat of superficial hyphae, which has not previously been reported for Astrocystis.

Four species of Linocarpon on Pandanus are described and illustrated. L. spathulatum and L. sulcatum spp. nov. have ascospores with grooved appendages and ascomata with eccentric ostioles. L. fasciatum sp. nov. is similar to L. pandanicola, but its ascospores lack appendages and the ascomata are smaller. A collection of L. elaeidis, not previously reported from Mauritius, has ascomata with distinct black papillate necks, in contrast to the type material which lacks these structures.

Soil samples from six sites in Provence, France, were flooded with water and baited with cellophane, specifically to obtain Rhizophlyctis rosea; all proved positive. By standardizing the cellophane addition and counting the R. rosea thalli that grew on it, derivations of thallus recovery g−1 of soil (TRG) were possible. Where aliquot soil samples for assay were small, sterilized soil leachate was used to chemically reinforce the flood water. Mean TRG was 395 for a grassland soil and 1293 following drying and removal of small stones from it. Separated leaf humus from the same dried soil had a mean TRG of 1105. Thought was given to what these figures might represent, in terms of sporangia of R. rosea present in the soil at the time of its collection. These are the first quantitative results in soil ecology for the Chytridiales.

The widespread occurrence of vegetative incompatibility in fungi and the high level of incompatibility gene polymorphisms in fungal populations means that generally parents in a cross will be vegetatively incompatible. In Neurospora crassa the mating type locus even functions as a vegetative incompatibility locus assuring vegetative incompatibility in a cross. In this paper we have tested the effect of vegetative incompatibility on regulating transmission of mitochondrial plasmids and nuclear genes in sexual interactions of N. crassa. In the absence of mating type vegetative incompatibility between the parents, transmission of plasmids from the conidial paternal parent was found to be approximately ten times higher than in normal crosses. Control experiments in which conidia of a contaminating plasmid bearing strain of similar mating type as (and fully vegetatively compatible with) the established maternal culture were added together with the presumed paternal conidia (opposite mating type) showed plasmid transmission to ascospores. Since trichogynes do not fuse with conidia of the same mating type, it may be concluded that plasmids from the contaminating strain entered the maternal tissue by somatic fusion. The fate of conidial nuclei in such sexual interactions has been investigated as well, both under conditions of vegetative compatibility and incompatibility between the strains. These experiments demonstrated that conidia that are vegetatively compatible to the established protoperithecial strain manage to get access to the resources of the maternal culture and initiate new fruiting bodies. This type of nuclear parasitism was never observed when vegetatively incompatible conidia were used. We propose that vegetative incompatibility may function in sexual crosses to protect unfertilised cultures from looting of maternal resources.

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.

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.

The susceptibility of mustard beetle, Phaedon cochleariae, larvae to the insect pathogenic fungus Metarhizium anisopliae, was influenced by the topography of the host plant, the dosage and the larval instar. At high doses (>109 conidia ml−1) more insects were likely to acquire conidia. Most of the inoculum adhered to the mid-ventral region of the abdomen. Inoculum applied to the leaf became diluted during leaf expansion and this decreased beetle mortality. Leaf expansion was slower at 10°C than at alternating temperatures of 23/10° or when constant at 23°. Slightly more larvae acquired conidia when fed on oilseed rape than Chinese cabbage or turnip. Most conidia adhered to the legs and the mid-ventral region of the abdomen. Mortality was usually less on oilseed rape than Chinese cabbage and turnip. These observations suggest that fungistatic compounds of oilseed rape were interfering with the infection process.

The steroidal glycoalkaloid α-tomatine of tomato plants has been reported to protect Lycopersicon species against fungal attack. Two isolates from Fusarium solani were found to produce an extracellular enzyme inducible by α-tomatine. TLC showed that the enzyme catalyzes the hydrolysis of the glycoalkaloid into β-lycotetraose and tomatidine. The enzymatic activity was concentrated against polyethylene glycol 35000, and the enzyme was partially purified by preparative isoelectric focusing, preparative gel electrophoresis and ion-exchange chromatography. The enzyme was found to be a monomer of about 32 kDa by both SDS-PAGE and gel filtration. This molecular mass differs from that of the tomatinase of Fusarium oxysporum (50 kDa). Moreover, polyclonal antibody anti- tomatinase of F. oxysporum f. sp. lycopersici did not recognize the tomatinase from F. solani, suggesting that this tomatinase may be a novel enzyme.

The cyclic tetrapeptide, HC-toxin, is a host-selective virulence determinant produced by the foliar pathogen of maize, Cochliobolus carbonum race 1. HC-toxin is synthesized by a multifunctional peptide synthetase (HTS) encoded by the HTS1 gene. Analyses of culture filtrates identified low toxin-producing and high toxin-producing strains among field isolates of the pathogen. These strains were analyzed by reverse transcription PCR to determine whether synthesis of the toxin is directly influenced by HTS1 transcript levels. The results indicated that expression of HTS1 was up-regulated and reached maximal levels several days before the toxin was detected in the culture medium and that HTS1 transcript levels were not correlated with toxigenicity. These observations suggest that genes in addition to HTS1 are involved in regulation of HC-toxin biosynthesis. The toxin-producing ability of low toxin-producing isolates was enhanced following inoculation and reisolation from leaves of susceptible maize genotypes, suggesting that additional factors within the host environment influence toxin production during pathogenesis.

Ultrastructural and cytochemical investigations of the interaction between Melampsora euphorbiae and its host Euphorbia peplus are described. Two types of collar around the haustorial neck could be recognized, corresponding to the maturity of the haustorium. Using various lectin-gold complexes as probes, different glycoconjugates were revealed in the fungus and host. Chitin was found in walls of uredinospores and intercellular hyphae but not of haustoria. d-glucose and/or d-mannose were strongly indicated in host starch grains and glycogen particles inside the intercellular hyphae, but only lightly in the fungal cytoplasm. Galactose residues and l-fucose were detected in fungal walls, more strongly in those of intercellular hyphae than haustoria. Galactose was also localized cytochemically in lomasome membranes of the fungus. β-Glucosides were detected in the fibrillar wall material bordering intercellular spaces of host tissue.

Nine species of Trametes and five other wood inhabiting basidiomycetes, were collected from the indigenous forests of Zimbabwe and analysed for cellulases, ligninases, extracellular phenolases and wood degrading ability for the first time. Cellulase enzyme activities varied widely among the species. After 15 d growth exo-glucanase activity had increased in the majority of species whilst filter paper activity showed the opposite trend, being greatly reduced in all species on day 15 compared to day 10. Endo-glucanase activity was relatively uniform at both sampling times. The fungi were more active against water soluble cellulose derivatives than filter paper cellulase. In all the fungi tested, cellulose activity on filter paper was significantly less than endo- and exo-glucanase activities. The highest cellulase activity was expressed by Cerrena meyenii (683 U mg−1) Phaeotrametes decipiens, Trametes modesta, and T. pocas also expressed relatively high cellulase activity on all types of cellulose tested. All Trametes species tested positive for extracellular phenol oxidases whilst Fomotopsis spragueii and Irpex stereoides tested negative. All but one of the Trametes species in the study were able to degrade two different lignin preparations in tests for lignin degradation. T. menziesii was unable to degrade both lignin preparations although it had tested positive for production of extracellular oxidase. The species in this study degraded hardwood to a greater extent than softwood. Eight of them caused more than 80% dry weight loss of wood blocks during 70 d incubation. Those fungi that expressed high cellulase activity also caused high weight loss on wood.

Gelasinospora bonaerensis sp. nov., isolated from a soil sample collected in Argentina, is described and illustrated and the sequences corresponding to the ITS1/ITS2 regions and the 5·8 S ribosomal RNA are provided. Its taxonomic relationships with other species of the genus are discussed.

Candida sake was cultured on nutrient yeast dextrose broth, which was diluted and/or modified by the addition of either glycerol, glucose to 0·96 or trehalose to 0·97 water activity (aw) to modify endogenous sugar alcohol and sugar content. Sugar alcohols (glycerol, erythritol, arabitol and mannitol) and sugars (trehalose and glucose) were extracted from the yeast cells and quantified using HPLC. Total polyol and sugar content varied significantly between treatments. The total intracellular concentrations in NYDB medium were significantly increased in NYDB+glucose media. The major intracellular polyols/sugars in cells grown on unmodified NYDB were arabitol, trehalose and glucose with small amounts of glycerol and erythritol. This was changed by reducing aw of the growth medium, particularly with glucose or glycerol. The major polyols in C. sake cells grown on glucose-modified media were arabitol and the low mol wt polyol glycerol, with smaller amounts of glucose. In glycerol-amended full strength normal and diluted media, glycerol was the major intracellular polyol with lower amounts of the other polyols and sugars. The viability of the yeast cells with modified polyols/sugars was significantly improved at lowered aw level (0·935 and 0·95) when compared to unmodified yeast cells. Improvements in water stress tolerance was better in yeast cells grown for 48 than 24 h, especially in those from NYDB modified with either glucose, glycerol or trehalose. Such modifications of endogenous reserves were also shown to preserve or improve the biocontrol potential of the yeast against Penicillium expansum rot of apples. Thus physiological manipulation of intracellular polyol and sugar content may provide a means for developing biocontrol agents with improved ecological fitness in field environments.

Meliola icacinacearum and M. kerichoensis spp. nov. are described and illustrated from Apodytes dimidiata and Croton alienus, respectively. C. alienus is a new host record for Meliola.

This listing covers the period May 1, 1997 through to June 30, 1997. Citations are arranged in groups which roughly correspond with the British Mycological Society's Special Interest Committees. All correspondence about this item should be addressed to the Executive Editor. Reprints of this feature will not be available.