The effects of liming on the composition of the mycoflora of dead, lying wood in a Scots pine stand on acid, nutrient-poor soil was studied after 5 yr. Liming led to a significant increase in species number. Amphinema byssoides, Hyphoderma puberum, Hyphodontia breviseta, Hypochnicium geogenium, and Sistotrema octosporum significantly increased, whereas Botryobasidium subcoronatum and Trechispora farinacea significantly decreased after liming. The proportion of species that are characteristic for coniferous wood decreased, whereas the proportion of indifferent species and species that are characteristic for deciduous wood increased after liming. Explanations for this species shift are discussed and an increase in nitrogen dynamics in the wood is considered the most plausible explanation. Possible ecological consequences of these changes in species composition are briefly discussed.

Lepteutypa hexagonalis sp. nov. is described from a dead trunk of Pinanga sp. (Palmae) collected in an Ecuadorean rainforest. Ascomata are deeply immersed with a distinct ostiolum, asci are cylindrical with a J+ subapical ring, and ascospores are brown, 4-celled, and hexagonal or heptagonal in transverse section.

As a later homonym of Mycosphaerella aggregata (Schweinitz) Stevenson the name Mycosphaerella aggregata Carnegie & Keane is illegitimate. The name Mycosphaerella gregaria is proposed as a replacement with similar etymology. The original description is revised following further collections and includes new hosts and cultural characteristics. Originally thought to be a saprophyte, this species may be a primary pathogen of leaves of Eucalyptus.

This listing covers the period November 1, 1996 through to November 30, 1996. Citations are arranged in groups which roughly correspond with the British Mycological Society's Special Interest Committees.

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In Melanospora zamiae a total of five nuclear divisions took place during ascosporogenesis. The first and second divisions were meiotic in which the single diploid nucleus divided into four haploid nuclei. The mitosis that followed gave rise to eight nuclei which characteristically assumed a 1[ratio ]4[ratio ]3 (apical[ratio ]middle[ratio ]basal) spacing in the clavate ascus. After ascospore delimitation, each nucleus in the young ascospore underwent two successive mitoses producing four haploid nuclei in each spore. Equatorial arrangement of these nuclei was observed in the mature ascospores.

Linear mycelial aggregates (rhizomorphs) produced by the squamulose lichens Toninia opuntioides, Squamarina cartilaginea, Lecanora rhizinata, and Acarospora scotica were examined by transmission electron microscopy (TEM). Cytological features typical of lichenized mycobionts were present, including concentric bodies and plasmalemma invaginations. Some septa in rhizomorphs of S. cartilaginea and A. scotica appeared to be multipored. Septal pores were usually plugged by an electron-dense structure. Intrahyphal hyphae were common to abundant in the rhizomorphs of all four species examined. The wall of the invasive hypha was continuous with inner wall layers of the cell of origin. Contacts between adjacent hyphae involved wall dissolution and formation of new wall layers, leading to anastomosis and/or possibly to intrahyphal invasion. Differentiation of an outer layer of collapsed cells in rhizomorphs of Squamarina cartilaginea and of extremely thick-walled cells Lecanora rhizinata was evident, but no anatomical specialization comparable to the ‘vessel hyphae’ of non-lichen linear mycelial organs was observed. Enlarged spheroid or ovoid cells with dense cytoplasm, numerous mitochondria and lipid reserves occurred in short chains in rhizomorphs of Acarospora scotica; infrequently, similar cells were observed singly in those of Squamarina cartilaginea. These cells were reminiscent in shape of certain types of oil hyphae found in endolithic lichens, although often the lipid content of the enlarged cells was not particularly pronounced.

The antifungal activity of flavone and flavanone was tested in three different concentrations, 0·5, 2 and 8 × 10−4 M, against 34 fungi. In general, flavone was the substance with the higher activity, and could at 2 × 10−4 M completely inhibit several fungi. No linear relationships between the concentration and the antifungal activity could be observed for some fungi. Chaetomium globosum was the only fungus which was totally inhibited by flavanone at 8 × 10−4 M. Several fungi did, however, show a higher inhibition rate at 2 × 10−4 M.

Of the two potato glycoalkaloids, α-chaconine and α-solanine, α-chaconine was the more inhibitory on spore germination in Alternaria brassicicola and Phoma medicaginis, and on growth in liquid culture of these species and also Ascobolus crenulatus and Rhizoctonia solani. At 50 μM or less, solanine caused little (<20%) or no inhibition but, in combination with comparable concentrations of chaconine (which were sometimes also below the activity threshold), synergistic inhibitory effects (up to 100% inhibition) were apparent. A scanning electron microscopic examination of agar-grown cultures of P. medicaginis revealed that both glycoalkaloids at 100 μM inhibited hyphal extension, but that chaconine particularly increased branch formation (three-fold) as well as hyphal thickness and ‘beading’. Glycoalkaloid-containing liquid medium from R. solani cultures did not contain glycoalkaloid hydrolysis products. There was a 17% reduction in the solanine content of the medium, but the chaconine level was not significantly different from that in uninoculated controls. Neither glycoalkaloids nor their hydrolysis products were detectable in the washed mycelium of such cultures.

A new description and illustration of Polydesmus elegans, the type species of Polydesmus, is given. It was formerly considered as congeneric with Sporidesmium. Two new genera, Imimyces to accommodate I. aquaticus, I. bambusae, I. carrii, I. densus, I. heterocateniformis and I. hollowayensis, and Linkosia to accommodate the single species L. coccothrinacis, are proposed. A key to species of Imimyces is provided, and a new species and six new combinations are proposed.

Helicodendron fuscum is described and compared with the similar species H. cumbriense and H. pinicola. Helicondron websteri, formerly confused with H. fuscum, is described as a new species. The anamorph of Tyrannosorus pinicola, Helicodendron pinicola, which has not been validly published is validated. A key for identification and illustrations are provided for all species treated.

The new ascomycete Chaetosphaeria ampulliformis sp. nov. found on decaying wood of an unidentified angiosperm in Taiwan is described and illustrated. It is closely associated with an Hemicorynespora anamorph which grows mostly on the necks of the flask-shaped ascomata. This anamorph is described as Hemicorynespora multiseptata sp. nov. The relationships of these two species to others in the genera are discussed, and a key to the recognized species of Hemicorynespora is provided.

Four inhibitors of the lysine biosynthetic enzyme dihydrodipicolinate synthase (DHDPS) were examined for their effects on the late blight fungus Phytophthora infestans. One of these compounds, dipicolinic acid, reduced mycelial growth of P. infestans by 61% and completely controlled blight infection of leaf discs when used at 1 mM. The other inhibitors, chelidamic acid, chelidonic acid and dimethyl cis-piperidine-2,6-dicarboxylate, were less effective against P. infestans in vitro and in vivo. The effects of dipicolinic acid and chelidonic acid on mycelial growth were partly overcome by the addition of lysine to the growth medium. Both of these compounds reduced DHDPS activity and lysine concentrations in P. infestans, although they had no effect on activities of aspartate kinase and diaminopimelic acid decarboxylase. Both dipicolinic acid and chelidonic acid reduced in vitro activity of DHDPS from P. infestans.

Alternaria guangxiensis and A. bannaensis on Passiflora spp. collected from China are described and illustrated, and their affinities to closely related species are discussed.

Isolates of Verticillium fungicola, collected over a period of 45 yr from various geographical sites, were analysed for their responses to four fungicides (benomyl, thiabendazole, chlorothalonil and diethofencarb), and for colony morphology, virulence and DNA polymorphisms. Three different colony morphologies were observed for this population of isolates including fluffy, dense and appressed. The majority of isolates had the appressed colony morphology. Most isolates exhibited high levels of virulence. The appearance in this population of both benomyl and thiabendazole resistance was correlated with the introduction of benomyl for use on mushrooms. Eighty-eight percent of the isolates were cross-resistant between benomyl and thiabendazole and 80% exhibited negatively correlated cross-resistance between benomyl and diethofencarb. Seventy percent of the isolates exhibited negatively correlated cross-resistance between thiabendazole and diethofencarb. The level of resistance to chlorothalonil was relatively high even prior to its introduction and overall the response to this fungicide appears to have varied little over the last 45 yr. DNA polymorphisms, as detected by randomly amplified polymorphic DNA (RAPD) analysis, divided the isolates into four groupings. Limited correlations could be drawn between RAPD groupings, fungicide response and geographical origin. All recently collected isolates (1993–5) were extremely similar in their response to the four fungicides and had appressed colony morphology, high virulence and were members of RAPD group four. The lack of variation in the recent isolates as compared to the older isolates indicates that the V. fungicola population may be becoming more homogeneous.

One hundred and sixty isolates of ectomycorrhizal agarics, boletes, and related gasteromycetes were examined for 25 morphological and biochemical characters. A wide range of analytical methods are available with which to obtain efficient summaries of the patterns of variation present in data such as these. Agglomerative clustering of 156 isolates and 18 characters for which no data were missing resulted in partitions of the sample corresponding to recognizable taxonomic and ecological groupings. Key characters useful for delimiting these groups are highlighted by means of divisive clustering and classification trees. For example, boletes (Boletinus, Suillus, Xerocomus) and related gasteromycetous allies (Pisolithus, Rhizopogon, Scleroderma) are distinguished by the production of pigment on media containing high levels of glucose. Numerical taxonomic analyses of cultural characters thus can be useful for examining taxonomic relationships, as in the way in which these characters support not only the close relationship between boletes and some gasteromycetes but also the generic circumscriptions of genera such as Laccaria and Lactarius. However, the taxonomic level at which cultural characters prove most effective must be evaluated carefully, in view of the possibility that, in response to selection, cultural characters have evolved in parallel in separate clades. Thus, ecological as well as taxonomic groups were also recognized. Species of both Hebeloma and Laccaria failed to produce pigment, tolerated low temperatures, and metabolized urea. This suggests that great care must be taken in using cultural characters in phylogenetic studies.

Coccodothis sphaeroidea var. mexicana var. nov., a fungus parasitic on Juniperus flaccida, is described and compared with typical C. sphaeroidea.

Ultrastructural details of sporangial plasmodia and zoosporangia of Spongospora subterranea f. sp. nasturtii infecting the roots of watercress were observed using transmission electron microscopy. The plasmodial envelope, the interface between host and parasite, was found to be convoluted, having a large surface area. Pseudo-food vacuoles, formed by convolutions of the plasmodial envelope, contained portions of host cytoplasm. True-food vacuoles containing the remains of host organelles were seen within plasmodia. Similar remains also were seen in the central vacuole. The flagellar apparatus including the kinetosome, with microtubular rootlets, the transition zone, the flagellum and the tapering end-piece were examined and described. These observations are discussed in terms of the nutrition of S. subterranea f. sp. nasturtii, its original classification within the fungi (latterly Plasmodiophoromycetes) and affinities with the protists.

Double-stranded RNA (dsRNA) elements of 8·3 and 5·5 kbp were detected in three of five geographically distinct isolates of Alternaria solani. Variation with respect to the number of dsRNA segments was detected among isolates of the fungus. No virus-like particles were purified from the mycelium, or observed in ultra-thin sections of hyphae. Utilizing differential centrifugation or density gradient centrifugation for subcellular fractionation, dsRNA was found associated specifically with fractions containing 80–100 nm spherical membrane vesicles. Similar vesicles were observed in cytoplasm of hyphae by electron microscopy. Treatment of dsRNA-containing fractions with ribonuclease A did not degrade the dsRNA, suggesting that it is located inside the vesicles. There was no correlation between the radial growth of the isolates in laboratory media and the presence or absence or dsRNA.

Strains of Trichoderma harzianum with either elevated or reduced production of cellulase-complex enzymes β-glucosidase and endoglucanase were constructed using uv-light mutagenesis. In tests for rhizosphere competence two of the cellulase minus strains were found to have significantly enhanced rhizosphere competence, whilst two cellulase overproducers were found not to colonize either the rhizosphere or rhizoplane of bean plants. These results indicate that rhizosphere competence of Trichoderma strains is not always associated with extracellular enzyme production.

Metarhizium anisopliae produces chitinolytic enzymes which have been implicated in digestion of the cuticles of the host insect during the infection process. In this study, enzymatically produced fungal protoplasts and whole mycelium have been used to study the cellular location and regulation of these enzymes. Intact mycelium was not significantly induced by soluble carboxymethylated (alkaline) chitin in the production of chitinolytic enzymes. In contrast, enzymatically produced protoplasts of M. anisopliae were highly inducible for these enzymes. At 24 h incubation, chitin induced protoplasts secreted into the medium 76% of total N-acetylglucosaminidase activity, whereas less than 10% of chitinase activity was secreted. At 48 h incubation, however, N-acetylglucosaminidase secretion had dropped to 34% of total activity, while the proportion of chitinase activity secreted by protoplasts continued to rise. By 48 h, the majority of chitinolytic enzyme activity had become cell-bound in both protoplast preparations and whole cells, and in protoplasts, this activity was mainly located in the membrane/developing wall fraction. The influence of the cell wall in the regulation and secretion of these enzymes is discussed.