Ecologically important ectomycorrhizal (EM) associations are poorly known from equatorial rain forests of South America. Recent field studies in the Pakaraima Mountains of western Guyana revealed previously undocumented forests dominated by EM leguminous trees, with a rich assemblage of EM mycobionts. Along transects, basidiomes from 75 species or morphospecies of putatively EM fungi were spatially associated with leguminous host trees. These fungi belonged to the basidiomycete families Boletaceae, Amanitaceae, Russulaceae, Cortinariaceae, Cantharellaceae, Clavulinaceae, and Entolomataceae, all of which are poorly documented from the lowland neotropics. Ectomycorrhizas were confirmed on D. corymbosa, D. altsonii, and D. jenmanii (Caesalpiniaceae, tribe Amherstieae), and a fourth species, Aldina insignis (Papilionaceae). The tribe Amherstieae contains most of the EM leguminous species forming monodominant forests in Guineo-Congolian Africa. Dicymbe species constituted the first record of EM Amherstieae in the New World. A variety of other co-occurring caesalpiniaceous trees failed to exhibit ectomycorrhizas. Transect surveys indicated that D. corymbosa and D. altsonii were: (1) highly clumped and dominant at specific sites; (2) occurred on soils with widely varying chemical and textural characteristics; and (3) the most important hosts for EM fungi in the local landscape. Dicymbe species have life history attributes, including the ectomycorrhizal habit, which enhance their competitive abilities irrespective of soil conditions. The spatial restriction of EM fungal basidiomes indicated that discrete groves of EM trees harbour an important component of regional macromycete diversity.

The release and survival of ascospores of a UK Sclerotinia sclerotiorum isolate were studied. Apothecia placed in a spore clock apparatus with different lighting regimes at 15 °C released ascospores continuously with an increasing rate for the duration of experiments (72–84 h). Spore release was not confined to light or dark periods in alternating regimes and occurred in continuous dark or light. Ascospores were released in both saturated air (90–95% rh) and at 65–75% rh. High temperature and rh were detrimental to ascospore survival but spore viability was maintained for longer periods than previously reported. The significance of these results in relation to disease control is discussed.

A region of about 800 bp of ribosomal DNA has been sequenced in 10 isolates of Polymyxa and one isolate each of Plasmodiophora brassicae and the chytrid Olpidium brassicae. This region consists of about 330 bp at the 3′ end of the 18S gene, the 5·8S DNA and the two internal transcribed spacers. A shorter region was also sequenced from one isolate each of Spongospora subterranea and a Ligniera sp. The results supported the earlier division of P. graminis into three subgroups and the recognition of P. betae as a distinct species. In phylogenetic analyses, the Ligniera and Spongospora isolates grouped with the other plasmodiophorids and the Olpidium isolate with the Mycota. The plasmodiophorids appeared as a distinct group and were not closely related to any other eukaryotes (including a range of fungi and protozoa). The DNA sequences were used to design primers for specific amplification of either Polymyxa or P. graminis DNA.

The two subpopulations of the Dutch elm disease pathogen Ophiostoma novo-ulmi, previously known as the Eurasian (EAN) and North American (NAN) races, are redesignated as subspecies novo-ulmi and americana. In addition to their partial reproductive isolation, wide range of physiological and molecular differences and different geographic ranges, the two subspecies can be discriminated by their perithecial form and dimensions. These perithecial differences are described, using perithecia produced in multiple intra-subspecies crosses. Perithecia of subsp. novo-ulmi have an average neck length of ca 450 μm, base width of ca 103 μm and neck length:base width ratio ca 4.4. Perithecia of subsp. americana have an average neck length of ca 295 μm, base width ca 116 μm and neck length:base width ratio ca 2.6. The average shape and dimensions of subsp. americana perithecia is similar to that of O. ulmi. The average perithecial form of subsp. novo-ulmi, as well as of O. himal-ulmi, is rather distinctive. The current known geographical distribution of subspecies novo-ulmi and americana, based on > 6500 samples, is presented.

Four halophytes belonging to three dicotyledon families, Acanthaceae, Aizoaceae and Chenopodiaceae, were screened for the presence of fungal endophytes. Thirty-six species of fungi, including some sterile forms, were isolated. Camarosporium species showed some degree of host preference as they were the dominant endophytes of the halophytes of Chenopodiaceae but were absent from the other halophytes. Some genera such as Colletotrichum, Phomopsis, Phyllosticta and Sporormiella were ubiquitous.

Fungi were isolated from the beetles, Ips typographus f. japonicus and Yezo spruce (Picea jezoensis) trees infested with the beetles in Hokkaido, Japan. Nine species of ophiostomatoid fungi including one new species were identified. They were Ceratocystiopsis minuta, Ceratocystis polonica, Ophiostoma ainoae, O. bicolor, O. cucullatum, O. europhioides, O. penicillatum, O. piceae, and a new species described here as O. japonicum. Based on frequencies of occurrence, O. ainoae, O. bicolor, O. penicillatum, and O. piceae were regarded as dominant associates of I. typographus japonicus, and C. minuta, C. polonica, O. europhinoides, and O. japonicum were subdominant. The species of ophiostomatoid fungi associated with I. typographus japonicus in Japan are almost identical to those associated with I. typographus infesting Norway spruce (P. abies) in Europe. This study improves our knowledge of the biogeography of the ophiostomatoid fungi and the insects with which they are associated.

Epichloë species are endophytic symbionts of grasses which may differ in the relative importance of their sexual or asexual life cycles. Sexual reproduction of the fungus by stroma-formation prevents host flowering (choke) and thus is highly antagonistic, whereas asexual reproduction through clonal propagation in host seeds does not affect host fitness. Stroma-forming Epichloë endophytes from Bromus erectus and non-stromal strains from B. benekenii and B. ramosus were recognized as a distinct mating population (MP) based on complete sexual compatibility among strains and intersterility between other MPs established by mating tests. This biological species represents the only documented case of highly antagonistic strains interfertile with highly mutualistic strains. A second distinct MP of Epichloë was evident on Brachypodium sylvaticum including both stroma-forming and non-stromal isolates. These two MPs were further characterized by distinct morphologies of fruiting structures, allozyme divergence, β-tubulin gene phylogeny, and host preferences, and were described as new species: E. bromicola associated with Bromus spp. and E. sylvatica with Bp. sylvaticum. Additional mating tests among Epichloë from several, previously unexamined, hosts including Brachypodium pinnatum, Calamagrostis villosa, Festuca spp., Phleum pratense, and Poa spp., expanded the known host ranges of three other European species, E. typhina, E. festucae and E. baconii. Genetic variability of all five European species and gene diversity of host subpopulations were analysed based on allozyme data from a total of 497 Epichloë isolates. Average gene diversity (Hs) within MPs ranged from 0·09 to 0·36 with E. typhina being the most diverse, and GST values, a measure for between subpopulation differentiation, ranged from 0·73 to 0·90 indicating that genetic isolation of endophytes on many host grasses is likely.

A new species, Trichoderma stromaticum, was isolated from ‘witches' broom’ of cacao (Theobroma cacao) in Brazil caused by Crinipellis perniciosa. The Trichoderma was reported earlier as T. viride and T. polysporum. Trichoderma stromaticum reduced new inoculum through the suppression of basidioma formation. It is characterised by having conidia that slowly become yellow-green in agar culture and by stout, ‘Pachybasium-like’, phialides formed on the surface of stromatic structures. The closest relations of T. stromaticum are T. harzianum and T. virens.

Combined analyses of ITS and LSU rDNA sequences were utilized to resolve the phylogenetic relationships of 98 members of the smut genera Lundquistia, Melanopsichium, Moesziomyces, Macalpinomyces, Sporisorium, and Ustilago (Basidiomycota: Ustilaginales). Minimum Evolution and Bayesian inference of phylogeny resolve three major groups of almost identical composition: Sporisorium, Ustilago, and a basal assemblage of both Ustilago and Sporisorium species. Macalpinomyces deserves generic rank regarding its type species M. eriachnes; all other Macalpinomyces species of our study clearly turn out to be part of Ustilago or Sporisorium. Lundquistia evidently belongs to Sporisorium. Moesziomyces, probably paraphyletic, stands basal to all other genera. Interestingly, Melanopsichium belongs to the Ustilago clade, being the only member of the ingroup not parasitizing on Poaceae. The patchy distribution of commonly used morphological characters along our phylograms points to their variability and dependence on the host's morphological traits instead of being valuable for resolving parasite phylogeny. The new combination: Sporisorium fascicularis comb. nov. (syn. Lundquistia fascicularis) is made.

Fifty-eight fungi from different physio-ecological groups were compared for their capacity to oxidize five polycyclic aromatic hydrocarbons (PAH) with three to five benzene rings (R), and produce the appertaining extracellular oxidoreductases in liquid culture. In 14 d, wood- and straw-associated basidiomycetes converted 19–90% of the original PAH compounds. The groups of wood- and straw-degrading, wood-degrading, terricolous, ectomycorrhizal, and mitosporic fungi converted PAH at a proportion of 100[ratio ]75[ratio ]34[ratio ]19[ratio ]18. All fungi preferred fluoranthene and pyrene (4R). Anthracene (3R) was preferred by wood-associated fungi. Phenanthrene (3R) and perylene (5R) were sufficiently converted by wood-associated and terricolous, but poorly by ectomycorrhizal and mitosporic fungi. Nevertheless, fungi that converted the entire set of PAH satisfactorily were found in all five groups. PAH conversion was correlated with the production of manganese peroxidase (r=0·98), peroxidase (r=0·89), and laccase (r=0·85), but not with monophenol monooxygenase (r=0·07). Mn(III) ions oxidized all PAH with preference to anthracene. Hydrogen peroxide converted PAH possibly by the products of Fenton's reaction. Limiting factors were shortages in peroxidases and H2O2. Gymnopilus sapineus and Agrocybe praecox converted top quantities of PAH in the absence of peroxidases, manganese peroxidases, and lignin peroxidases. The relative contributions of intra- and extracellular enzymes to the conversion of PAH and the possible role of the fungi in the long-term detoxification of soil xenobiotics are discussed.

The phylogeny of the family Bacidiaceae (Lecanorales, Ascomycota) was investigated using 65 nuclear ITS1-5·8S-ITS2 ribosomal DNA sequences, 63 of which were newly determined. After exclusion of ambiguous alignment, the data set contained 285 variable characters, 212 of which were parsimony-informative. Phylogenetic estimations were performed with maximum parsimony (unweighted and weighted) and maximum likelihood optimality criteria. Four different phylogenetic hypotheses were tested using a parametric bootstrap approach to simulate the expected null distribution of the difference between the globally optimal tree and the best (constrained) tree agreeing with the null hypotheses under unweighted and weighted parsimony, and maximum likelihood: (1) the genus Bacidia is monophyletic; (2) the genus Bacidina is monophyletic; (3) the genus Toninia is monophyletic; and (4) the family Ramalinaceae is monophyletic and distinct from a monophyletic Bacidiaceae. The monophyly of Bacidia, Toninia, and the Ramalinaceae was rejected under all circumstances. Hence, Bacidiaceae is likely to be a younger synonym of Ramalinaceae. The monophyly of Bacidina was not rejected under any optimality criterion. Furthermore, the data set suggests that the Bacidia beckhausii and B. sabuletorum groups are unrelated to Bacidia s. str., that Megalaria is monophyletic, and that Lecania auct. is polyphyletic.

The development of 12 litter and seven phylloplane fungal species was examined from spore germination to colony sporulation across a series of environmentally relevant UV-B doses. For the litter fungi all aspects of fungal development and morphology studied were affected. On the basis of the responses of mycelial extension rate and spore germination to increasing UV-B, the 12 litter fungi were divided into two groups. Group A (Aspergillus fumigatus, Penicillium hordei, P. janczewskii, P. spinulosum and P. purpurogenum) were sensitive to UV-B, with the predicted effects of a 15% ozone depletion resulting in 22–44% reductions in spore germination. Mycelial extension rate on the agar surface was similarly affected, with reductions ranging from 15 to 25%. In contrast group B (Mucor hiemalis, Cladosporium cladosporioides, Leptosphaeria coniothyrium, Trichoderma viride, Ulocladium consortiale, the Verticillium state of Nectria inventa and Marasmius androsaceus) were relatively insensitive to UV-B, with significant, but small, reductions in mycelial extension rate (<5%) and spore germination (0–22%). Spore production in response to UV-B in the litter species was very variable, reductions ranging from 5% to complete inhibition. Only P. hordei showed a significant increase in spore production in response to UV-B dose. In contrast, in all seven phylloplane species, spore germination was unaffected by increasing dose. Mycelial extension rate was slightly (2–12%), but significantly, inhibited by UV-B for the four phylloplane fungi tested. The contrasting responses of phylloplane and litter fungi to UV-B are discussed along with the implications for resource capture by competing fungal species and the possible effects of UV-B on decomposition processes.

The effects of two UV irradiances (920 and 1200 mW m−2 weighted irradiance) on the conidia and germlings of the ARSEF 2575 and ARSEF 23 strains of M. anisopliae were studied. Conidia were exposed to the two irradiance levels for 1, 2, 3, 4, 6, or 8 h. The 30% increase (from 920 to 1200 mW m−2) in UV irradiance caused a significant decrease in culturability following all periods of exposure and reduced the 50% lethal time (TL50) 36% for strain 2575 and 48% for strain 23. Exposure to UV radiation of only 1 h caused a delay of several hours in the germination of surviving conidia. Longer periods of exposure delayed germination for days, demonstrating that, depending on the dose, the fungus may require a long period of time to recover and to resume germination. The results demonstrated the inability of the fungus to germinate during direct exposure to the UV-B portion of simulated sunlight. Both strains showed a transitory increase in UV tolerance during germination. The beginning of germination increased UV tolerance. However, starting on the 6th hour of germination, a decrease in tolerance was observed, indicating that UV tolerance varies as a function of physiological state and cell-cycle phase.

The temperature optima for germination, radial hyphal extension rate and sporulation were determined for two isolates of Metarhizium flavoviride from acridoid hosts. I91-609 exhibited lower temperature optima for hyphal extension (25·5 °C) and sporulation (24°) than IMI 330189 (27° and 25°, respectively), although temperature optima for germination were similar (ca 30°). The temperature optimum for sporulation was lower than that for hyphal extension.

Further studies were carried out on I91-609 to investigate the effect of temperature and dose on the infection mortality rate of the grasshopper pest, Zonocerus variegatus. Increasing dose resulted in a decrease in mean survival time regardless of incubation temperature. Dose and temperature were shown to interact, with the effects of dose increasing at temperatures either side of the optimum. Furthermore, for each dose, the optimum temperature for infection was estimated to be ca 5° higher than the optimum for growth, and no significant relationship was identified between hyphal extension rate in vitro and host survival time. The implications of these results are discussed with regard to the selection of isolates for use in biological control.

Nuclear ribosomal DNA sequences characteristic of Sebacinaceae were detected by direct amplification of DNA from field collected ectomycorrhizal samples. A study was undertaken to confirm the formation of ectomycorrhizas by Sebacinaceae and to characterise representative samples genetically, morphologically and ultrastructurally. The investigated sebacinoid mycorrhizas were sufficiently characteristic to be identified morphologically. They are distinguished by a characteristic, clampless, hydrophilic extramatrical mycelium, which is very variable in diameter and in wall thickness, and by the presence of distinctive, y-shaped, inflated multibranchings. Differences in the mantle structure clearly discriminate the two investigated sebacinoid mycorrhizal types. Comparison of the D1/D2 domains of the nuclear large subunit pseudogene and the ITS1 and ITS2 regions identifies the fungal partner of one of the mycorrhizal samples as Sebacina incrustans. Ultrastructural investigations of the ectomycorrhizas show a doliporus/parenthesome architecture consistent with that of the Sebacinaceae. Recently published sequence data obtained from sebacinoid mycorrhizas are compared to our sequences and the complex trophic relationships in the Sebacinaceae are discussed. Observations on ectomycorrhizas and basidiomes suggest that species of Sebacinaceae are fairly common mycobionts in various ectomycorrhizal plant communities.

Information on the genetics and metabolism of 4-aminobutyrate (GABA) in yeasts and fungi is reviewed. In spite of ubiquitous occurrence, there is limited information on its function and biological role. Most fungi utilize GABA both as a carbon and a nitrogen source. Fungal endogenous GABA largely originates from the decarboxylation of L-glutamate and is associated with sporulation/spore metabolism. Whatever its source, GABA is catabolized to succinate via succinicsemialdehyde. Taken together these steps define a potential bypass outside the classical tricarboxylic acid cycle. Evidence for the existence of such a functional bypass in fungi is reviewed. The role of GABA and its metabolism in various facets of fungal biology is gradually emerging.

Dikaryotic and haploid mycelia of more than 150 gilled species of euagarics were studied morphologically and by molecular phylogenetic methods. The morphological investigations revealed anamorphs in more than 90 species that were often specific at the genus or family level. Thallic conidiogenesis dominated and varied from fragmentation of normally branched hyphae to the formation of differentiated sympodially branched conidiophores. Secession modes, coiling of the conidiogenous hyphae or the swelling of the conidia were additional distinguishing features. Phylogenetic analysis of the D1–D3 domains of the nuclear gene for the ribosomal large subunit using a Bayesian Markov chain Monte Carlo approach resulted in several well-supported groups that are consistent with anamorph morphology. These results indicate that the anamorphs provide valuable characters for a natural classification of the Agaricales.

The obligate biotrophic pathogen Plasmodiophora brassicae induces cataplastic galls in the roots of various species of the Brassicaceae. The ecotypes Ze-0, Tsu-0, and Ta-0 of Arabidopsis thaliana carry alleles of a dominant single gene (RPB1) for resistance against this pathogen. The pathotype-specific resistance reactions in the roots were accompanied by a hypersensitive response. Infected cells were surrounded by necrotic boundaries and thereby the pathogen growth was restricted. The pathogen could induce hyperplasia and hypertrophy to a slight extent and develop spores within mini-galls surrounded by the necrotic cells, if it was able to colonise meristematic tissue. Ecotype Ze-0 showed the highest level of resistance to P. brassicae isolate ‘e’ as indicated by the very limited number of infected cells, whereas the resistance of the ecotype Ta-0 was rated lower. The results are discussed in relation to the interaction of the pathogen with Brassica crops.

Acid phosphatase production by 12 Hebeloma strains was usually derepressed when inorganic phosphorus in the growth medium was limited, but appeared to be constitutive in some strains. At low temperatures ([les ]12°) arctic strains produced more extracellular and wall-bound acid phosphatase, yet grew more slowly than the temperate strains. We suggest that low growth rates in arctic strains may be a physiological response to cold whereby resources are diverted into carbohydrate accumulation for cryoprotection. At near freezing temperatures, increased extracellular phosphatase production may compensate for a loss of enzyme activity at low temperature and serve to hydrolyse organic phosphorus in frozen soil over winter.