Conserved primers were used in a polymerase chain reaction to amplify the ITS region of the rDNA of 100 Microdochium nivale isolates collected from different turfgrasses in southern Ontario. The profile of the restriction digestion of the amplified ITS region revealed that all the M. nivale isolates analysed belonged to var. nivale. RAPD profiling and RFLP analyses of the IGS regions of rDNA revealed extensive genetic diversity within var. nivale. With RAPD markers, the average similarity coefficient was 66% and the estimate of genotypic diversity was 0·179. Population subdivision analysis showed that 92·2% of the total genetic diversity was found among individuals within populations compared to 7·8% among populations. In dendrograms derived from genetic distances using RAPD and IGS-RFLP markers, there was some evidence for host specialization. Most RAPD markers were shared by individuals from different turfgrasses, and the populations were not highly differentiated. The high level of genotypic diversity detected within populations and the low level of genetic differentiation among populations show that recombination and migration are likely playing important roles in the population biology of M. nivale var. nivale.

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.

The saprotrophic fungus Fusarium culmorum, Penicillium hordei, Rhizoctonia solani and Trichoderma harzianum and the arbuscular mycorrhizal fungus Glomus intraradices were examined for content of phospholipid fatty acids (PLFA) and neutral lipid fatty acids (NLFA). The AM fungus differed from the saprotrophic fungi especially by its content of the fatty acid 16[ratio ]1ω5 which was absent in the saprotrophs. The fatty acid 18[ratio ]2ω6,9 was the dominant fatty acid of the saprotrophic fungi while it was negligible in mycelium of G. intraradices. Specificity in content of fatty acids made it possible to quantify G. intraradices and F. culmorum simultaneously in soil. Furthermore, a compartmented growth system made it possible to study mycelial interactions in the absence of roots. We measured hyphal spread of both fungi, hyphal 33P transport of G. intraradices and sporulation of F. culmorum. The two fungi did not interact according to the parameters used in this study. We conclude that fatty acid signatures may be a valuable tool when studying interactions between AM fungi and other fungi in root-free soil.

Three different proteinase inhibitors purified from crayfish blood, a 23 kDa inhibitor of subtilisin, a 155 kDa trypsin-inhibitor (pacifastin) and an α2-macroglobulin were tested for their inhibitory activities against extracellular proteinases from the specialized crayfish parasite Aphanomyces astaci, the saprotrophic A. laevis and the plant parasitic A. chochlioides and A. euteiches. All three crayfish inhibitors were effective against extracellular proteinases from the different Aphanomyces species when defined peptides were used as substrates for the proteinases. Proteolytic activities from A. astaci against a complex substrate, casein were reduced by any of the three crayfish proteinase inhibitors tested. It is, therefore, possible that these proteinase inhibitors may reduce the proteolytic breakdown exerted by A. astaci proteinases during an infection.

An endo-DNase with single strand nicking activity from the bean pathogen, F. solani f. sp. phaseoli has been previously reported to induce the expression of defence genes in peas. Culture filtrates of the potato pathogen, Colletotrichum coccodes, also contain a single strand nicking endo-DNase (CCN). This nuclease has a molecular weight of ∼27 kDa, an isoelectric point of pH 7·8, optimal catalytic activity at pH 5–6 and is stable at temperatures below 50°C. CCN activity increases are observed with addition of cation cofactors, favouring Mn2+>Co2+>Ca2+> Na+>Zn2+. CCN is inhibited by aurintricarboxylic acid, a nuclease inhibitor. The point of CCN cleavage on the DNA molecule is between the 5′-phosphate and the 3′-hydroxyl. CCN also possesses RNase activity. Although the C. coccodes culture filtrate can induce the expression of disease resistance response genes and phytoalexin production in pea tisue, this inductive activity does not co-purify with the CCN DNase activity through the Sephacel G-75 purification step, and thus CCN applied singly does not serve as a signal for initiating the host defence reponses. Because CCN degrades both DNA and RNA, it is more probably a nutrient scavenging enzyme.

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.

A thermostable extracellular glucoamylase from Thermomyces lanuginosus in static culture was purified to SDS–PAGE homogeneity by fractional ammonium sulphate precipitation, ion-exchange chromatography on DEAE–Toyopearl, Butyl–Toyopearl hydrophobic interaction chromatography, gel filtration on Sephacryl S-300 and ion-exchange chromatography on FPLC MonoQ. The molecular weight of the enzyme, consisting of a single polypeptide, was estimated to be 72000 by SDS–PAGE. The glucoamylase exhibited maximal activities at pH 5·0. The optimum temperature for the activity was 70°C. The enzyme was thermostable at 60° with half-lives at 70° of 20 min and 80° of about 6 min. The glucoamylase was a glycoprotein with 11·4% carbohydrate content. The enzyme hydrolysed soluble starch, amylose, amylopectin, dextrin, glycogen, maltotroise and maltose. Starch was the best substrate.

A field study was conducted to determine the size and spatial distribution of mycelial individuals of Pisolithus tinctorius at a site in NSW, Australia. Following collection and mapping of carpophores and isolation of the fungi into axenic culture, genomic DNA was extracted and combined data from RAPD and microsatellite analyses used to identify and map mycelial individuals. Thirty-three genetically distinct individuals were recognized at the field site and, while one large individual (at least 30 m diam.) was identified, most individuals appeared relatively small (<3 m diam.). The size and distribution of individuals is discussed in relation to growth of P. tinctorius mycelia through soil.

A dikaryotic resting spore or two monokaryotic resting spores of Plasmodiophora brassicae were inoculated onto 1-d-old seedlings of Brassica campestris. The relative DNA content of a nucleus in a dikaryotic resting spore corresponded with that of a haploid nucleus in a monokaryotic resting spore. Plasmodia and zoosporangia were observed within the galls in some root cortical cells approximately 2 mo after inoculation. Resting spores were also formed within the galls in some cortical cells, and root hair infection was observed. The frequency of resting spore formation in B. campestris seedlings inoculated with a dikaryotic resting spore or two monokaryotic resting spores was 26·2 and 3·6%, respectively. The results indicate that the life-cycle of P. brassicae was completed on plants infected with a dikaryotic resting spore or by two monokaryotic resting spores.

The aim of this work was to use sexual reproduction to introduce new genotypes into natural populations of Cryphonectria parasitica, the cause of chestnut blight disease. Mating was initiated by painting conidia (which serve as spermatia) onto stromata in cankers initiated in the early spring. The matings yielded perithecia 161 and 180 d after canker initiation. Single-ascospore isolates from these perithecia included cultures with the phenotypes of conidia which had been painted onto the cankers as early as 17 d after canker initiation.

The new combination Thanatephorus obscurus is proposed, based on a study of the type specimen of Ceratobasidium obscurum. The reports of this species as an orchid associate are based on misdeterminations. The unusual gelatinized basidiome of T. obscurus is discussed and compared with that of a new, unnamed taxon from the Cameroon rain forest.

Descriptions and illustrations are provided of two hyphomycete new species from rain forests in Cuba: Dictyochaeta uncinata anam. sp. nov. with setae and conidiophores arising from the same lobed cell and uncinate, filiform conidia, and Helicoma pulchra anam. sp. nov. with helicoid, multiseptate, darkly pigmented conidia. They are compared and contrasted with similar species.

The natural dihydrate form of calcium sulphate, CaSO4.2H2O (gypsum), particularly found in gypsiferous soils and in certain building constructions, was found to be effectively solubilized by both Aspergillus niger and Serpula himantioides. When the fungi were grown on malt extract agar (MEA) medium amended with up to 1% (w/v) of gypsum, solubilization activity was evident by the appearance of a clear zone (haol) around and/or under the growing colonies. The haloes were found subsequently to enclose concentric rings of newly formed crystalline precipitate. The pH profile of the medium underneath the growing mycelium of A. niger was not affected by the presence of gypsum, while the S. himantioides pH profile displayed a slight reduction in pH values when grown on gypsum-containing media compared with the control. Electron microscopy and X-ray microanalysis of the crystals revealed the formation of calcium-containing crystals with the characteristic morphology typical of different forms of calcium oxalate. The complexing activity of fungal-produced organic acids with calcium was suggested to be the prevalent mechanism of solubilization with the production of oxalic acid resulting in precipitation of oxalate. Such activity resulted in the release of available sulphate which increased over the incubation period. The concentrations of sulphate released from 0·5% (w/v) gypsum after growth of A. niger and S. himantioides for 8 d were 14·7±0·7 and 7·4±0·9 μmol cm−3 respectively. These results are discussed in the light of their relevance to land reclamation and plant nutrition, as well as the weathering of building materials containing gypsum.

Discolouration due to senescence differs from blotch-related discolouration, which might indicate differential mechanisms being operational. In samples infected with bacteria or with a partially purified toxin extract, a higher degradation of total tyrosinase than in senescening mushrooms was found. Simultaneously, the active tyrosinase was increasing resulting in an increase in percentage of active tyrosinase. Phenolic substrates of the active tyrosinase were being oxidized, proportionally to the damage detectable on the mushroom cap. γ-Glutaminyl-3,4-dihydroxybenzene was degraded first, followed by γ-glutaminyl-4-hydroxybenzene and later tyrosine. The amount of melanin that was synthesized was larger than the sum of oxidation of the phenols measured. Principal Component Analysis explained 84% of the variance in symptoms, and it demonstrated the phenol oxidation and active tyrosinase level as the most important parameters for the browning induced by bacteria or a tolaasin preparation treatment.

Sordaria brevicollis is a filamentous ascomycete previously considered to be exclusively heterothallic. Here we show that S. brevicollis can exhibit homothallism, and describe the genetic and environmental factors favouring the process. Both mating types can produce perithecia in unmated cultures, but only in the uncrossed perithecia of mtA are ascospores formed (in <30% of the fruitbodies). In most cases, only one or two asci are produced in any uncrossed mtA perithecium, although as many as 13 have been observed. The ascospores show no segregation for mating type; all are mtA. Heterokaryon analysis established that meiosis and recombination occurred during ascospore production in both homothallic and heterothallic development. Homothallic fruiting is inhibited both by crossing with the opposite mating type, and by light.

Gilmaniella bambusae sp. nov., from senescent culms of Bambusa tuldoides in Hong Kong, is described and illustrated. It differs from other species of Gilmaniella in having small conidia and conidiogenous cells with a verrucose wall. A key to and a synopsis of the known species of Gilmaniella is provided.

Larix kaempferi seedlings, in the process of becoming established during the revegetation process following a volcanic eruption, were assessed for the types, occurrence patterns and diversity of their ectomycorrhizas along an elevation gradient. On the basis of macro- and microscopic characteristics, 12 types of ectomycorrhizas were classified. In general, ectomycorrhizal types differed more by site than by seedling age. The majority of root systems of seedlings with an age ranging from 1 to 5 years were colonized by 1 or 2 types of mycorrhizal fungi at low and intermediate elevations, 2 or 3 types at a higher elevation. Under the more stressed environments of high and intermediate elevations, the mean d.w. of 1 yr old seedlings, 40% of which were colonized by 3 or 4 mycorrhizal fungi, was double the weight of the same aged seedlings at lower elevation sites, only 10% of which were colonized by 3 or 4 mycorrhizal fungi. The correspondence between the type and frequency of mycorrhizas, the elevation gradient and litter accumulation suggests that change in litter accumulation along gradient may influence not only mycorrhizal types and their occurrence, but also the diversity of mycorrhizas on one seedling. Diversity of mycorrhizas on the same seedling is assumed to be critical for the establishment of seedlings from the very beginning on stressed sites, and may also be influenced by the availability of nutrients. The more intensive competition between mycorrhizas that occurs due to a reduction in the food source (tip roots) shared by the mycorrhizal fungi with similar resource requirements, results in frequent co-occurrence of mycorrhizas in the same root system or even the same root tip. As a result, the diversity of mycorrhizal types seems to become simplified as the seedlings age.

Various fungi interact with heavy metals (HM) differently regarding their binding ability and their tolerance. Besides the ability of the fungus to form an extensive extramatrical mycelium, its binding and transport properties are the most important factors in ameliorating the effects of HM toxicity on the mycorrhizal symbiosis. The tolerance of seven ectomycorrhizal fungi to elevated lead concentrations was tested using agar cultures and the results were compared to those from liquid culture. Critical toxic concentrations, where the growth of the mycelium was inhibited to 50%, were lower in liquid cultures (around 0·2 mm) in comparison to agar cultures (0·5–2 mm). The less tolerant fungi in agar culture were Amanita muscaria and Laccaria laccata, the most tolerant Lactarius piperatus, Pisolithus tinctorius and two strains of Suillus bovinus, DB83 from a lead polluted area and DB84 from a non-polluted area. Tolerance indices, based on the dry weight of mycelia from liquid culture, differ from the tolerance indices obtained from solid culture. L. laccata growth was limited to a lesser extent than other fungi and the growth of S. bovinus DB83 was strongly stimulated at a Pb concentration of 30 μm, which could indicate lower susceptibility of this strain to low lead concentrations. The uptake, transport and release of Pb were then studied with 210Pb tracer using Conway cells with the active tracer added to the inoculated medium in the centre compartment. The uptake of Pb by P. tinctorius (1·1% of the added activity) was much lower than the uptake by L. laccata and S. bovinus DB83 (6·2 and 5·4% of the added activity respectively). The same situation was reflected in the activity of the tracer transported in the mycelia. Further, the release of transported Pb from mycelia to the outer medium differs between L. laccata and S. bovinus DB83 mycelia, reaching 45 and 10% of the transported activity, respectively, indicating stronger binding of lead to S. bovinus DB83. The results of the tracer study are discussed with respect to various experiments with ectomycorrhizal seedlings and lead.

Chitin, an insoluble polymer, induces the chitinolytic system of Trichoderma harzianum, which is made up of two N-acetylglucosaminidases and four endochitinases. Only one N-acetylglucosaminidase, CHIT 102, was found to exhibit extracellular basal activity. The initial inducer of the chitinolytic system was found to be the chitin monomer N-acetylglucosamine, which preferentially induces CHIT 102.

Twenty-one isolates of the nematode-vectored plant pathogen, Dilophospora alopecuri, were examined by allozyme electrophoresis. The study focused on isolates from Australia, including those associated with populations of the seed-gall nematode, Anguina funesta, in Western Australia (W.A.), where the fungus apparently provides natural control of the A. funesta–Clavibacter toxicus association responsible for annual ryegrass toxicity, and a range of Anguina populations in south-eastern Australia. Reference strains from international culture collections were included. Variation was found in 26 of 27 presumptive loci and 10 electrophoretic types were identified. All Australian isolates fell into six electrophoretic types that formed two groups of three that differed by less than 13% within each group, but differed by over 70% between the groups. Of the isolates from W.A., six fell into one electrophoretic type and one into a second electrophoretic type that differed at one locus only. Three exotic isolates varied from Australian ones by 27–74%. Dilophospora alopecuri exhibited greater within-species allelic variation than previously reported for asexually-reproducing halophase fungi. The lack of variation within W.A. suggests that (i) a teleomorph does not occur under local conditions, (ii) the W.A. population has arisen from a single introduction and (iii) selection of strains suitable for biocontrol of Anguina funesta and Clavibacter toxicus should include material from eastern Australia.