The ability of an unidentified mycobiont from Pisonia grandis mycorrhizas to utilize organic nitrogen and phosphorus sources was determined in axenic liquid cultures. The fungus utilized inorganic phosphate and both freely- and poorly-soluble salts of inositol hexaphosphate as sole phosphorus sources. With the exception of uric acid which did not support growth, the yield of the mycobiont on all organic nitrogen sources tested was significantly greater than the yield on either NH4+ or NO3−. It is suggested that the major ecological role of the Pisonia mycobiont in stands of P. grandis on coral cays may be rapid absorption of allantoin and urea produced during degradation of uric acid by the soil microflora. This may be important in retaining nitrogen in the soil[ratio ]plant system prior to loss from the coral cay by further degradation, volatilization and/or leaching.

To understand the nature of recombination processes in Beauveria bassiana, double-auxotrophic complementary mutant strains were used to produce six heterokaryons by three different methods. Conidia from these heterokaryons were plated on selective media and stable haploid (but not diploid) recombinants were isolated. Single colony recombinants were recovered with both parental and non-parental random amplified polymorphic DNA (RAPD) profiles. These results suggest that a range of different recombination mechanisms may be occurring in B. bassiana.

The avidity of conidia and 48-h-old germlings of Coniothyrium minitans for FITC-conjugated lectins was characterised by flow cytometry and digital microscopy. Six isolates of C. minitans representing three morphological types were compared. Binding of Con A, SBA and WGA by conidial populations varied markedly in extent and pattern between isolates, however, with increasing culture age, conidia from all isolates demonstrated a significant reduction in lectin avidity. Germling isolates bound significantly different amounts of lectins and lectin binding differed significantly with locality. Spore walls of all germlings from all isolates bound more Con A compared with hyphal apices and mature hyphal walls. In contrast, hyphal apices of the majority of germling isolates, readily bound SBA and mature hyphal walls of germling isolates bound more WGA than other regions of the germlings. Such differential lectin binding by conidia and germlings may influence their specific surface interactions and adherence characteristics.

The devastating dry rot fungus, Serpula lacrymans, has a worldwide occurrence in buildings. We investigated the genetic variation in European isolates belonging to five vegetative compatibility groups (VCGs) by AFLP analysis. Our results indicate that S. lacrymans in Europe is genetically extremely homogenous; only five out of 308 scored AFLP fragments (1.6%) were polymorphic. In contrast, S. himantioides, the closest relative of S. lacrymans, possessed 31.3% polymorphic fragments (84 out of 268). AFLP polymorphisms observed in S. lacrymans were distributed independently of the VCG boundaries, indicating that the VCGs do not represent clones but that different genets of S. lacrymans frequently share similar vic alleles due to low genetic variation. Thus, although the European S. lacrymans is genetically extremely homogeneous, and our results suggest that the species reproduces and spreads mainly sexually and not by clones.

The diversity of Eutypa lata was studied in 56 isolates collected from Languedoc-Roussillon, France. The pathogenicity of isolates varied within a very broad range and was not influenced by the cultivar from which they originated. Using 27 RAPD markers, each isolate was identified as an unique genotype. Gene diversity averaged 0·292 for the regional population. Lack of gametic disequilibrium between RAPD loci supported the hypothesis of random mating. The RAPD analysis did not allow subdivision of the population according to geographic location, vine cv. or pathogenicity of E. lata. The composition of the community of fungi was studied in 116 vines showing eutypa dieback symptoms collected at several localities in the region. E. lata was recovered from 80% of the samples, from the sectorial brown lesion characteristic of the disease. This lesion was associated in half of the vines with a central zone of discoloured hard wood and/or a light-coloured lesion of soft consistency. E. lata was isolated alone from 124% of the vines and was associated in 67% of the vines with one, two or three of the following fungi: Sphaeropsis malorum, Phomopsis viticola, Gliocladium roseum, Phaeoacremonium chlamydosporum, P. aleophilum and Phellinus igniarius. The variation in symptoms observed in the vineyard may be partly explained by the wide genetic diversity in E. lata and differences in the composition and functioning of the fungal community.

A Coniothyrium minitans strain (T3) co-transformed with the genes for β-glucuronidase (uidA) and hygromycin phosphotransferase (hph), the latter providing resistance to the antibiotic hygromycin B, was used to investigate the survival and infection of sclerotia of Sclerotinia sclerotiorum by C. minitans over time in four different soils. Infection of sclerotia was rapid in all cases, with the behaviour of transformant T3 and wild type parent A69 being similar. Differences were seen between the soils in the rate of infection of sclerotia by C. minitans and in their indigenous fungal populations. Amendment of agar with hygromycin B enabled the quantification of C. minitans in soil by dilution plating where there was a high background of other microorganisms. In Lincoln soil from New Zealand, which had a natural but low population of C. minitans, the hygromycin B resistance marker allowed the umambiguous discrimination of the applied transformed isolate from the indigenous hygromycin B sensitive one. In this soil, although the indigenous C. minitans population was detected from sclerotia, none were recovered on the dilution plates, indicating the increased sensitivity of C. minitans detection from soil using sclerotial baiting. C. minitans was a very efficient parasite, being able to infect a large proportion of sclerotia within a relatively short time from an initially low soil population. The addition of hygromycin B to agar also allowed the detection of C. minitans from decaying sclerotia by inhibiting secondary fungal colonisers. This is the first report to show that fungi colonising sclerotia already infected by C. minitans mask the detection of C. minitans from sclerotia rather than displacing the original parasite.

At a high arctic, polar semi-desert site (79°N) in Svalbard, nitrogen, phosphorus and potassium fertilizers were added to the soil for 5 yr to simulate increases in decomposition and nutrient mineralization which may occur as a result of increases in soil temperature and soil moisture caused by environmental change. Abundance of decomposer fungal species, isolated from standing-dead leaves of Dryas octopetala, varied between fertilized and unfertilized plots. Fungal biodiversity, as indicated by the Brillouin index, was lower in dead Dryas leaves from the fertilized plots, although more colonies were isolated from leaves of plants which had been fertilized. The fungi were cosmopolitan and not restricted to tundra areas. The dead leaves from the fertilized plots contained more nitrogen and phosphorus than those of the unfertilized plants. Leaves in the fertilized plots appeared to have been killed by winter injury resulting from an extended growing season in an atypically mild and wet autumn, which was followed quickly by extreme subzero temperatures.

Growing fruit bodies of Agaricus bisporus and Amanita muscaria responded with regenerating white hyphae to cell and tissue injuries caused by intrapileal needle insertion and leucofuchsin injection. We point out reserve cells as a possible source of regenerating hyphae in the wound repair. Such reserve cells were not found in the partial veil and in the surface covering. Damage of the partial veil remained unrepaired and caused lamellar dysplasia. Hydrophilic, somatic tissues reacted immediately and strongly with leucofuchsin, whereas hyphae of the surface covering and partial veil showed a delayed and weak reaction. We explain this by the presence of an extracellular matrix, which consists of hydrophilic mucilaginous substances around tissue-forming hyphae. Transmission and scanning electron microscopical studies revealed that white hyphae were deprived of such matrix material. We conclude that for fungal tissue formation the hyphae have to be capable of producing a substantial amount of extracellular matrix material beyond the cell wall.

The pathogenicity of two isolates of Verticillium lecanii towards non-target invertebrates and six species of aphid was tested in bioassays. There was no evidence of infection in any of the 20 non-target invertebrates. All target aphid species were susceptible to at least one isolate. The level of susceptibility varied between aphid species, with Myzus persicae and Brachycaudus helichrysi showing the greatest susceptibility.

Studies on initial spore deposition, retention and germination on two susceptible aphid species and four resistant non-target insects revealed differences in the behaviour of the pathogen between the two groups. Spore density mm−2 was greater on susceptible insects both immediately post-inoculation and following 24 h incubation. There was no loss of spores from M. persicae over 24 h. All other species showed more than 50% spore loss in the same period. However, even after 90% spore loss, large numbers of spores remained on the bigger insects such as Agonum dorsale. Germination and germ-tube growth were possible on such resistant non-target insects, indicating that resistance to infection occurs after this stage. There was little difference in rate of germination on the two groups. However, differences in germ-tube growth were evident, with the production of longer and narrower germ-tubes on the resistant insects.

The new generic name Lecanostictopsis is introduced with three species, L. kamatii (type species), L. syzygii and L. noumeaensis sp. nov., all of which are associated with leaf lesions on species of Syzygium. The genus is compared and contrasted with Lecanosticta, Stigmina and similar genera. The position of Cercostigmina is discussed in relation to Pseudocercospora and Cercoseptoria. Cercostigmina syzygii sp. nov. associated with leaf lesions on S. cordatum is described, and compared and contrasted with Stenella marasasii on the same host substratum. Pseudocercospora syzygiicola sp. nov. is described from leaf lesions on S. cordatum from South Africa, while Pseudocercospora syzygiorum sp. nov. from S. cumini and Passalora syzygii from S. cumini and S. jambos are described from India.

The formal taxonomy of the new family Myzocytiopsidaceae, with three new genera Myzocytiopsis, Chlamydomyzium and Syzygangia, is presented. The family also includes Gonimochaete.

Intact ungerminated spores or germinating swollen spores of Mucor circinelloides were biolistically transformed to leucine prototrophy with the autonomous replicating plasmids pLeu4 and pMCL1302. The former developmental stage was efficiently transformed with both plasmids. The existence of pLeu4 sequences, as selfreplicating elements, within Leu+ transformants was established by Southern analysis and by the recovery of plasmid pLeu4 in bacteria transformed with total DNA from M. circinelloides transformants. This is the first report of the transformation of intact cells of a member of the Zygomycetes.

Plant pathogenesis by fungi is known to be dependent on the host genotype, the virulence of the pathogen and certain environmental conditions influencing fungal establishment. Previously, it has been shown that Chaetomium globosum, a fungus well-characterized for its biocontrol potential, causes necrosis on barley roots grown in Murashige and Skoog (MS)-agar. Using MS-agar and aeroponic culture as axenic plant growth systems, C. globosum pathogenesis was analyzed with serological and histological methods. Irrespective of the growth system, C. globosum infected the root epidermis. Roots grown in MS-agar were extensively colonized intercellularly and intracellularly up to the inner cortex and the tissue underwent necrosis. In contrast, roots grown in aeroponic culture were not colonized beyond the epidermis and the roots appeared healthy. Histochemical analyses revealed that hypodermal suberization stopped fungal invasion. In root tips known to lack suberization, epidermal papilla formation reduced overall infection frequency. The results indicate that specific environmental conditions are important for infection and disease expression in barley roots. Infection is restricted by two spatial and temporal distinct defence mechanisms: (1) papillae in root tips retarding fungal invasion; and (2) suberization of hypodermal cells blocking fungal radial growth.

Trichoderma harzianum (CCM F-470) was found to produce large amounts of extracellular mutanase (0·33 U ml−1, 1·85 U mg protein−1) when grown aerobically on the optimized mutan medium in fermenter culture with an automatic pH control. The mutanase from this source was purified to homogeneity by a rapid procedure, using ion-exchange chromatography, hydrophobic interaction chromatography and chromatofocusing. The enzyme was recovered with a 94-fold increase in specific activity and a yield of 73%. The molecular weight of the purified enzyme proved to be 67 kDa, as estimated by SDS–PAGE, and to be 274 kDa, as determined by size-exclusion HPLC. These results indicate that the native mutanase is probably a tetramer protein. The isoelectric point was at 7·11, and the carbohydrate content in the purified enzyme was 4·42%. The pH and temperature optima were 5·5 and 40 °C, respectively. The enzyme remained stable over a pH range of 4·5–6·0 and up to 35 ° for 1 h. The values of Km and Vmax under standard assay conditions were 1·2×10−3 g ml−1 and 8·48×10−2 U mg−1, respectively.

Experimental preparations (alginate granules and mycelial mats) of the entomopathogenic Erynia neoaphidis were assessed for their capacity to cause infections in populations of Macrosiphum euphorbiae on pepper plants, in a greenhouse trial performed over 14 d. The dried preparations contained hyphal cells, which upon rehydration produced conidiophores and ejected ballistospores. Applications of alginate granules and mycelial mats on soil were more rapid in causing infections in the host population compared with foliar applications. On the last sample date, infection rates of 10–14% were obtained with foliar applications of E. neoaphidis as alginate granules and mycelial mats, respectively. With soil applications of E. neoaphidis granules and mats, infections were 23–36% after 14 d. From all sample dates, 183 cadavers were found on pepper plants treated with E. neoaphidis and 37 (= 20%) exhibited external sporulation after overnight incubation.

Comparisons were also made with single foliar sprays of Beauveria bassiana (Mycotrol WP®) and the systemic insecticide pymetrozine (Chess WP®), the latter being the only treatment to significantly reduce aphid numbers during the trial period. Treatment with B. bassiana resulted in good initial infection rates (50–60%) which declined over the period and reached the same infection level as E. neoaphidis treatments at the end of the trial. With B. bassiana, a total of 81 cadavers were found, of which 62 (= 77%) sporulated.

In the coastal cliff landscape of southern Scandinavia dense populations of the saxicolous, lichen-forming fungus Lasallia pustulata are subject to disturbances creating small or larger gaps; one or several thalli are removed by strong winds, icing, rock slides, log-falls, branch sweeping or trampling. New patches for colonization are also created when mats of bryophytes, fruticose lichens or pine needles are removed by the same forces. The disturbance gaps are major sites of recruitment in the populations and the age structure of a population is spatially structured by the pattern of gap formation. The revegetation of experimentally created gaps were monitored over a four year period, at the end of which the gaps were filled with new, 1–9 mm sized thalli, unevenly scattered, on average 6500 individuals m−2, covering less than 1% of the substrate. In addition there were clusters of small thalli sprouting from the former attachment site of some of the large thalli that had been removed. The growth of individual thalli in natural gaps and mature populations was also monitored for four years. The largest annual increment in thallus diameter was 15 mm, the average 5·5 mm. Some thalli did not increase in size at all, some became slightly smaller, and some were completely eliminated, apparently by self-thinning. There was no correlation between initial thallus size and annual growth; and age and size are not correlated. The individual variations in growth rate seem to reflect the degree of initial crowding, subsequent competitive success, and local supply of nutrients. The average growth and initial size of individuals plus their density and dispersion are used to model the speed of gap-closure, estimated to be 10–15 years.

The yeast–mycelial dimorphic Aureobasidium pullulans var. pullulans was grown in chemostat culture under zinc-limitation at pH values in the range 2–7. Steady state was obtained and the growth yield with respect to zinc was independent of pH. The culture grew entirely as yeast, independently of the pH in the pH interval 3–7. The exopolysaccharide (EPS) production from the yeast cells was highest in the pH range 3–6 with a maximum at pH 4·0. Only little EPS was produced at pH 7·0 and no EPS was produced at pH 2·1. At pH 2·1 about 20% of the total biomass was in the filamentous growth form and some chlamydospores were present. A change in the carbon source from glucose to sucrose resulted in a more than doubling of the steady-state EPS concentration from 3·1 to 6·9 g l−1. A simple mass balance on carbon was constructed which could account for more than 95% of the carbon.

Random amplified polymorphic DNA polymerase chain reaction (RAPD–PCR) was used to assess the genetic diversity in twelve populations (a total of 144 isolates) of the Pleurotus eryngii complex, sampled in Israel. Our results show a higher level of diversity of RAPD polymorphism in the populations, especially in the drier, stressful climates. Twelve primers used in this study amplified 164 scorable RAPD loci, of which 163 (99.4%) were polymorphic and only 1 monomorphic. Out of the 164 loci, 123 (75%) varied significantly (P < 0.05) in allele frequencies among populations. This total proportion (75%) of significant polymorphic loci far exceeds the 5% level expected by chance (binomial test, P < 0.000001). The levels of polymorphism and gene diversity appeared to be highly significantly different between the populations. Sixty-eight per cent of the RAPD diversity was within populations and 32% was between populations. Inter-population genetic distances showed positive association with geographic distance, which was confirmed with spatial autocorrelation analysis of RAPD frequencies. Spearman rank correlation revealed a strong positive association between high polymorphism and the aridity index. In multiple regression, the coefficient of determination of polymorphism and gene diversity was explained by climatic variables linked to temperature and humidity. Our findings further demonstrate the validity of the ‘environmental theory of genetic diversity' hypothesis within P. eryngii populations in Israel. We suggest that natural selection develops a high level of RAPD polymorphism as adaptation to cope with stressful and temporally heterogeneous environments.

The saprobic microfungi associated with endemic plants of Mauritius have been studied. Over 200 taxa were identified of which approximately 90% are new records for Mauritius including one genus and 38 new species. The mycobiota encountered on the monocotyledonous genus Pandanus is more distinct than that on three dicotyledonous hosts Sideroxylon, Cordemoya and Olea. Arguments are presented to support the inclusion of microfungi in in situ conservation management policies.

Techniques to rapidly identify the basidiomycete fungal partner of ectomycorrhizal associations would be a major advantage for ecological, fungal population dynamics and life history studies of epigeous and hypogeous forms in plantations, forests, wild lands and other native or natural vegetation. PCR–RFLP (Polymerase Chain Reaction–Restriction Fragment Length Polymorphism) identification of DNA regions is an available technique; however, primers which have a high probability of amplifying only the basidiomycete DNA are needed. Here we have assessed the specificity, sensitivity and discrimination of six different primer pairs, three targeting nuclear and three mitochondrial regions, for use in identification of Australian basidiomycete fungi from Eucalyptus forests by matching PCR–RFLP patterns to morphologically defined species. Two sets of primers, one newly designed and targeting the nuclear ribosomal DNA internal transcribed spacers (ITS) and the other amplifying a fragment of mitochondrial large subunit ribosomal DNA met the requirements of high specificity and sensitivity, amplifying DNA from a broad range of larger basidiomycetes, with no amplification of plant, bacterial or ascomycete DNA. The specificity of the ITS primer pair was compared with that of ITS1-F/ITS4-B. PCR–RFLP of the two regions discriminated fungi to species level for 91 fungal species from 28 families. Hence these two DNA regions and the specific primers are a potential practical PCR–RFLP tool for identifying basidiomycetes associated with plants from field samples.