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.

Strains (47) of 14 genera isolated from soil and woody chips were tested for their ability to oxidize dibenzofuran, a model compound for highly chlorinated dibenzofuran pollutants. Thirty strains formed one or more isomers of monohydroxylated dibenzofurans identified by chemical structure analysis with hplc and GC-MS, indicating an active monooxygenase system widely distributed in filamentous fungi. Dihydroxylated derivatives were detected in only very low amounts and some degradation products were observed. A few fungi metabolized dibenzofuran only to intermediates with hydrophilic characteristics (eight strains) and nine strains showed no transformation capability. The transformation reactions were not inducible and seemed to be strain-specific.

Following the Chernobyl accident in 1986, sporocarps of Suillus variegatus in Sweden showed a large amount of individual variation in concentration of 137Cs activity. Our aim was to determine the degrees to which this variability in sporocarp 137Cs levels could be explained by differences between (i) local populations, (ii) fungal genets and (iii) locations within genets. Five populations in a 100-yr-old Scots pine forest, located within a 1 km2 area, and two populations in Scots pine/Norway spruce forest, located 40 km north-west of Uppsala, were investigated. In total, 154 sporocarps were analysed to determine their 137Cs content. Of these, the genetic affiliations of 86 were successfully characterized using somatic incompatibility reactions. Twenty-six genets were found which, on average, consisted of 6·5 sporocarps. The genets averaged 7·5 m in size, measured as the length between the most distant sporocarps. The mean sporocarp 137Cs level was 67·1±2·8 kBq kg−1 D.W. (range between 13·6 and 182). According to analyses of variance, within-population variation accounted for 60% of the total variation in 137Cs levels, while 40% was ascribed to variation among populations. Within a population, 137Cs levels did not generally differ significantly between genets. Plausible reasons for intraspecific variation in radiocaesium content in sporocarps are discussed.

Sclerotinia minor accumulates β-carotene at levels dependent upon oxidative growth conditions and differentiation. β-carotene accumulation is 2.5-fold higher in differentiated mycelia at high than at low oxidative stress, and approx. 3-fold higher in differentiated than in undifferentiated mycelia. It is proposed that β-carotene may be produced by the fungus to counteract oxidative stress that develops during growth. This is shown by the finding that exogenous β-carotene at growth non-inhibiting concentrations causes a concentration-dependent reduction of oxidative stress (lipid and protein peroxidation) and sclerotial differentiation in this fungus. The data of this study support our hypothesis that sclerotial differentiation in phytopathogenic fungi may be induced by oxidative stress.

A PCR-based technique based on the ITS1-5.8s-ITS2 domain of the rRNA gene for identifying five species associated with Mycosphaerella leaf disease (MLD) of eucalypts was developed. Primer pairs MC2F and MC2R; ML1F and ML1R; MM1F and MM1R; MN1F and MN1R; and MP1F and MP1R amplified a product for DNA extracted from their single target species, those being M. cryptica, M. lateralis, M. marksii, M. nubilosa and M. parva, respectively. The possibility of false positive amplification by each primer pair was tested in reactions with DNA extracts from 16 other Mycosphaerella species associated with eucalypts and against non-infected Eucalyptus globulus leaves. Under the PCR conditions used, there were no false positive amplifications of the 16 non-target Mycosphaerella species, or from non-symptomatic E. globulus leaves for the primer pairs ML1F and ML1R; MM1F and MM1R; MN1F and MN1R; and MP1F and MP1R. The primer pair MC2F and MC2R amplified a 402 nt product from both the target M. cryptica and non-target M. nubilosa. However, these two species were differentiated by digesting the product with the restriction enzyme Sacc II which resulted in a single 402 nt product for M. cryptica, and two products of 78 and 324 nt for M. nubilosa. All of the primers were able to detect their target Mycosphaerella species from Eucalyptus globulus lesions. PCR reactions with these primers on DNA extracted from Mycosphaerella lesions confirmed the presence of all five species from leaf material collected from three plantations in Western Australia.

The first action spectrum for a photo-induced response of an arbuscular mycorrhizal fungus is reported. At low light intensity, the responsive wavelengths for light-induced hyphal branching of the primary germ tube of Gigaspora gigantea were determined to be in the blue to UV-A range. The action spectrum showed the greatest stimulation of branching occurred around 390 nm although a shoulder was observed between 360–370 nm. A second major peak of light-induced branching occurred at 430 nm. The exposure of specific areas of the germ tube to high intensity blue light for a short period led to several interesting observations. By exposing 2 mm segments (0–2, 2–4, 4–6, etc.) or 3 mm segments away from the tip, it was determined that photoinduction of hyphal branches could occur anywhere along the axis of a growing germ tube except in the apical 2 mm. When 3 mm segments were exposed at greater distances from the tip (6–9, 9–12, and up to 33–36 mm), branches frequently formed in areas not directly exposed to light. The branches were usually in clusters which were spaced approximately 3 or 6 mm apart. Since light scattering could be ruled out, these results indicated that the exposure sites and sites of hyphal branching did not necessarily coincide and suggested the probable involvement of a second messenger during this blue light-induced event.

The genetic variation of Armillaria mellea sensu stricto was studied within and among non-heterothallic populations from Japan and Africa, and heterothallic populations from Europe and North America, using somatic incompatibility tests and RAPD analysis. Non-heterothallic isolates from Japan and Africa were divided into four somatic compatibility (SI) groups (A, B, C and D). SI group A contained half of all Japanese isolates and all African isolates. SI groups B and C each contained four Japanese isolates and D contained one isolate. All European and North American isolates were clearly separated from each other by somatic incompatibility tests. From the RAPD analysis, three distinct groups were separated (non-heterothallic, European and North American groups). The non-heterothallic group was divided into three subgroups (Ia, Ib and Ic). Subgroup Ia and Ib corresponded to SI groups A and B, however, Ic contained SI groups C and D. Subgroup Ia, in which 12 of 14 isolates had the same haplotype, showed a little variation. Non-heterothallic populations were less variable than heterothallic populations. The distribution of the isolates belonging to each SI group overlapped within Japan.

Non-pathogenic binucleate Rhizoctonia species (BNR) belonging to the anastomosis group AG-G are commonly associated with members of the Rhizoctonia solani complex. They provide effective protection to young bean seedlings against root rot caused by R. solani AG-4. Both fungi are morphologically similar and it is difficult to differentiate between them without using laborious conventional techniques. RAPD assays were carried out on a large range of isolates of binucleate Rhizoctonia species to identify markers common to all AG-G isolates. Two fragments of 1368 bp and 882 bp were isolated, cloned and used to probe Southern blots of DNA from: AG-G isolates; isolates from other AGs of binucleate and multinucleate Rhizoctonia species; various heterogeneous pathogens known to infect bean plants; and co-inoculated bean plants with BNR AG-G and R. solani AG-4. The fragments hybridized only to DNA from AG-G isolates. Both fragments were nucleotide sequenced and two pairs of SCAR (sequence characterized amplified region) primers (BR1a F/R and BR1b F/R) were generated for use in PCR. Two fragments of anticipated size were generated following PCR of all isolates of AG-G and not from any range of other fungal species associated with root and leaf diseases of beans. The SCAR primers were also used to detect AG-G isolates in DNA extracted from bean and soil samples co-inoculated with binucleate and multinucleate Rhizoctonia species. The assays were capable of detecting as little as 2·6 pg of fungal DNA in extracts of soil samples. This system offers the potential to determine the presence of AG-G isolates in infected soil and plant samples.

Colonisation of Pinus radiata sapwood by sapstain fungi results in a permanent discoloration of the sap and is one of the major problems associated with P. radiata timber production in New Zealand. No fungicides are available that can provide a reliable level of control of sapstain for the extended time period required to export timber. A 4-year survey, commencing in 1996 revealed that the most common species which cause sapstain on radiata wood are Sphaeropsis sapinea (syn. Diplodia pinea), and two species of Ophiostoma (O. floccosum and O. ips). A total of 21 different species that cause sapstain have been identified to date. Two approaches for the control of sapstain are presented in this paper. The first relies on the ability of microorganisms to inhibit the growth of sapstain species. Such an ability has been demonstrated in laboratory trials on wood chips or wood blocks for 116 isolates of the 848 fungal and bacterial isolates initially considered. Six of the most effective isolates were further tested on sawn timber or debarked logs in field trials. Isolates of Trichoderma spp. and Trichothecium roseum were found to control sapstain as well as the standard fungicide treatments. T. harzianum was significantly better in controlling sapstain in the internal tissues of debarked logs than the fungicide. The second approach is based on inhibition of the sapstain causing fungi by secondary metabolites produced by plants or microorganisms. Massoialactone, produced by various fungi including Trichoderma spp., showed good antisapstain activity in laboratory and field trials. Twenty-nine essential oils from different plant species inhibited O. piceae in the laboratory. The most efficient oils were found to contain high levels of oxygenated monoterpenes. Oxygenated alcohol or phenolic monoterpenes proved to be extremely active against sapstain fungi preventing discoloration of sapwood for up to 9 months. A method of control for sapstain based on pine oil derivatives containing some of these compounds is now being developed for commercial use.

Sclerotinia nivalis causing lettuce drop was found in central China. It was identified on the basis of comparisons of morphological features, cultural characteristics and sclerotial proteins with those of S. sclerotiorum, S. trifoliorum, S. minor and S. nivalis. This is the first report of S. nivalis in China and lettuce is a new host for this pathogen.

From 1991 to 1996, Phellinus noxius was collected on 60 host plant species at 136 different sites in Taiwan, and two host plant species at two different sites on Kinmen Island. It was collected mostly on hosts growing in the low elevation plains and hills of western, eastern and southern Taiwan, while it was found on only a few hosts in northern Taiwan and was absent from the high mountain areas. P. noxius was observed on and isolated from 57 woody species, and three annual herbaceous plants. In the field, basidiomes of P. noxius have only been observed on Casuarina equisetifolia, Delonix regia and Ficus microcarpa. A dark brown mycelial mat on the surface of the roots and up the base of stems was used reliably for the field identification of P. noxius. Although P. noxius did not favour a particular soil pH, it was not found in extreme pH conditions. It was found in soils from pH 4 to 9 and most frequently in soil from pH 5 to 8. P. noxius occurred mostly in soils with sand, loamy sand and sandy loam textures.

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 relative abilities of the multilayer perceptron, radial basis function, asymmetric radial basis function and learning vector quantization artificial neural networks (ANNs) and two non-neural methods to identify fungal spores were compared. ANNs were trained on morphometric data from spores of Pestalotiopsis spp. and a few species in the related Truncatella and Monochaetia. The optimized neural and statistical classifiers had similar identification success on an unseen data set – between 76·0 and 78·8% of a 16-species group and between 63·0 and 67·7% of a 19-species group. The relative merits of each classifier are discussed, as is the potential of ANNs in mycology.

The molecular diversity of Diaporthe helianthi (anamorph Phomopsis helianthi), the causal agent of sunflower stem canker, was studied in 16 isolates of different geographic origin using nuclear and mitochondrial markers. PCR products corresponding to the internal transcribed spacers (ITS1 and ITS2) of the nuclear ribosomal RNA gene, and to the mitochondrial atp6 gene were sequenced. The ITS1 and ITS2 sequences were compared with those of Phomopsis spp. and Diaporthe spp. obtained from databases. The diversity in the region surrounding the atp6 gene was also studied by restriction analysis using four enzymes. The analyses revealed a marked diversity within the sunflower-isolated strains, which appear to belong to phylogenetically unrelated groups. Noticeably, all the isolates collected in France and in the former Yugoslavia, where severe epiphytotics of sunflower stem canker are frequently reported, showed high similarity to each other forming a clade which clearly differentiated from all other ones within the genus Phomopsis. Conversely, all the isolates collected in Italy, where, despite favourable environmental conditions, the incidence of the disease is low, were only distantly related to the former group and showed sequence similarity with other previously established phylogenetic clades within the Phomopsis/Diaporthe complex.

To imbibe and germinate urediniospores require free water or near saturated atmospheres in which both adsorption of water is maximal and capillary condensation pads form. The rate of spore germination is influenced by the amount of free water available. During imbibition, spores swell and capillary pads form beneath spores in contact with the substratum. These pads greatly increase the area of contact with the substratum. Pad area fluctuates and may depend on the balance between the rate of capillary condensation and the rate of uptake of fluid by spores. When spores, on leaves or cellulose acetate, are misted with water they imbibe rapidly and germinate. Adhesion pads which form under fully imbibed, germinating spores are morphologically similar to capillary pads but they differ in composition. On synthetic surfaces, during imbibition of spores and under microscopic glass beads, pads are composed principally of volatile capillary condensation and are removed when samples are freeze-dried. On host surfaces, when spores are fully imbibed and germinating, pads contain non-volatile soluble materials derived from both pathogen and host. These substances are not removed by extended freeze-drying.

Ophiostoma europhioides and O. huntii are two very similar fungi known to cause blue-stain of timber. Both species have been isolated from pine and spruce in Canada and are characterized by Leptographium anamorphs and hat-shaped ascospores. The aim of this study was to compare isolates of O. huntii and O. europhioides from various parts of the world. These isolates were compared morphologically using light and scanning electron microscopy. Sexual compatibility was determined using mating studies. O. huntii isolates from the different geographical areas were similar to each other but distinct from O. europhioides. A new Ophiostoma species, O. aenigmaticum, is described for the Japanese isolates; Leptographium aenigmaticum, its anamorph, is described as a new species.

Orphella catalaunica and O. helicospora spp. nov. both from the hindgut of stonefly (Leuctra) nymphs from Spain, are described and illustrated. They are compared with the other species of the genus. Orphella haysii is reported for the first time in Europe. The generic description of Orphella is emended to accommodate the new characters described for the new species. A dichotomous key for separating the species is provided.

The effects of varying carbon (glucose), nitrogen ((NH4)2SO4, KNO3) and phosphate (KH2PO4) source on solubilization of insoluble Co3(PO4)2.8H2O, Zn3(PO4)2.2H2O and ZnO by the soil fungus Aspergillus niger were assessed. Solubilization activity was quantified by measuring the clear zones produced around colonies of A. niger growing on solidified mineral salts medium amended with the insoluble metal compounds. Effects of nutrient variation on solubilizing properties were compared using ratios of colony growth rate on the metal compounds (Rm) to control growth rate (Rc) and the rate of extension of the zone of solubilization (Rs) compared to the colony growth rate on the metal compound (Rm), i.e. Rm[ratio ]Rc and Rs[ratio ]Rm. Ratios of solubilization rate to growth rate (Rs[ratio ]Rm) on all the compounds decreased with decreasing glucose concentration; there was no solubilization of ZnO below 60 mm glucose and no solubilization of the metal phosphates below 6 mm glucose. Reducing the concentration of ammonium sulphate in the growth medium decreased Rs[ratio ]Rm but these values were increased when the nitrogen source was nitrate. Reducing the phosphate concentration increased solubilization of Co3(PO4)2 but reduced solubilization of Zn3(PO4)2. These findings demonstrate that manipulation of carbon, nitrogen and phosphate sources in the growth medium, and variation of the form of the nutrient source, can be used to alter the solubilizing ability of A. niger. Whilst, in the natural environment, this response to different nutrient sources allows optimal exploitation of resources, the potential to manipulate nutrients for maximum solubilizing ability may prove beneficial for the optimization of the solubilization of metal compounds with respect to the bioremediation of metal-contaminated wastes and polluted ecosystems. It could also prove useful in other biotechnological applications such as metal recycling and extraction of metals from low-grade ores.

After purification by thin-layer chromatography (tlc) several fatty acids stimulated oospore formation in Phytophthora cactorum but not in Phytophthora parasitica. Palmitoleic acid was the most effective and was the only fatty acid tested that promoted oospore formation in P. parasitica. Purification of palmitoleic acid by Florisil column chromatography resulted in a two-fold increase in activity over that purified by tlc. When 0·01 to 100 ng of cholesterol was added to basal medium containing palmitoleic acid, the added cholesterol did not significantly change oospore production by P. cactorum. Oospore formation in P. cactorum was slightly stimulated by tlc-treated aliphatic hydrocarbons, or derivatives of hydrocarbons, but was strongly stimulated by geraniol and squalene. Vitamin A and vitamin A esters stimulated oospore formation in both P. cactorum and P. parasitica. tlc treatment also significantly increased the activity of cholesterol and β-sitosterol on oospore formation by P. cactorum. Both compounds did not stimulate oospore formation by P. parasitica even after tlc treatment.

Anamika gen. nov. is described from southern India with one species, A. indica sp. nov. The genus is characterized by spores with a strongly cavernous ornamentation due to cavernae in the epitunica (perispore), and the possession of cheilo-, pleuro-, and caulocystidia. It seems to be associated with Hopea species (Dipterocarpaceae). Molecular data suggest a close relationship to Hebeloma and Naucoria, but indicate that it represents an independent line of evolution.