Forty-seven isolates of Pythium irregulare from different hosts and geographic origins were compared from molecular, morphological and physiological viewpoints. They were divided into four groups (I–IV) based on ITS-RFLP analysis and RAPD analysis. Groups I and II included 32 and eight isolates, respectively, collected from diverse hosts and geographic origins, and groups III and IV comprised seven isolates derived from sugar beet and sugar beet field soil. Group I had smaller oogonia and oospores than did the other three groups. In groups I and II, a significantly higher percentage of the oogonia produced multiple projections compared to groups III and IV which occasionally produced one projection. The growth rate of the four groups was similar at 5–30 °C. At 33°, many isolates of group I grew rapidly but most of the isolates of other groups grew slowly, and at 35°, the former grew but the latter did not. In phylogenetic analysis based on sequences of the ITS region, four groups of P. irregulare were included in one cluster with P. sylvaticum. Groups I–II and III–IV clustered more tightly in the same branch, respectively. The genetic divergence between I–II and III–IV was higher than between each group (I–II and III–IV) and P. sylvaticum, indicating that groups I–II and III–IV may represent two different species.

The influence of neighbours on individual performance in natural populations of the lichenized ascomycete Umbilicaria spodochroa was investigated using three different neighbourhood models; the polygon model, the fixed radius model and the nearest neighbour model. The data set consisted of the exact position of the holdfast points of the peltate lichens within 29 sample squares in crowded populations as well as the mass, diameter, and no. of apothecia of all thalli. A total of 11246 individual thalli were sampled and measured. The predictive power of all three neighbourhood models was moderate, but highly significant for the whole data as well as within most individual sample quadrats. The nearest neighbour model had the best predictive success, closely followed by the polygon model. The fixed radius model had approximately half the power of the two other models. We suggest that the difference is due to different degrees of realism in the models. Thallus mass was commonly the performance parameter best predicted, followed by thallus diameter and number of apothecia. The predictive power of the models for these natural populations was comparable to values obtained in several laboratory studies with vascular plants. The predictive success of the three different models was strongly correlated for single populations, indicating different levels of interference in different populations.

The formation of sclerotia is inhibited by certain chemicals. These resting fungal structures are also parasitized by mycoparasites. This study reports results of experiments on the effect of four sclerotial inhibitors on the sclerotial mycoparasite Coniothyrium minitans and was carried out in an attempt to determine possible compatibilities between sclerotial inhibitors and mycoparasites. Thioglycolic acid was the most toxic to mycelial growth while its sodium salt was totally non-toxic. Mercaptoethanol and mercaptoethylamine were intermediate. At low concentrations, pycnidial formation by C. minitans was not hindered by any of the compounds tested. All four compounds inhibited the formation of sclerotia in Sclerotinia sclerotiorum. Sclerotia are also parasitized by C. minitans. Na-thioglycolate should be tested further as it had no adverse effect on the mycelial growth and pycnidium formation in C. minitans, while it inhibited extensively the formation of sclerotia in S. sclerotiorum. These data suggest that Na-thioglycolate and C. minitans should be considered for use in integrated control.

In order to integrate ustilaginomycetous anamorphs into the general phylogenetic system of Ustilaginomycetes, partial nuclear large subunit ribosomal DNA sequences of 56 teleomorphic and 19 anamorphic species of the Ustilaginomycetes were analysed. Maximum parsimony and neighbour joining confirm the new suprageneric system of Ustilaginomycetes and indicate that (i) the species of Pseudozyma represent anamorphs of Ustilaginales parasitizing grasses, (ii) Pseudozyma prolifica, the type of Pseudozyma, is very closely related to Ustilago maydis, (iii) Pseudozyma tsukubaënsis is probably synonymous with Ustilago spermophora, (iv) the species of Malassezia represent a group of its own within the Exobasidiomycetidae, (v) Tilletiopsis cremea, T. lilacina and T. washingtonensis belong to the Entylomatales and (vi) T. flava, T. fulvescens and T. minor are members of the Georgefischeriales. Like all Tilletiopsis species tested, T. albescens and T. pallescens are members of the Exobasidiomycetidae, but they cannot be ascribed to any of the known orders of this subclass. The description of the Malasseziales is emended.

Amplified fragment length polymorphism (AFLP) was used to examine genetic variation in two forms of Melampsora rust on Salix viminalis, the ‘stem-infecting form’ (SIF) and the f. sp. larici-epitea typica (LET) of M. epitea. A simple two-tube method was used to obtain genomic DNA suitable for AFLP. Eleven SIF and 26 LET isolates from the UK were tested using two primer combinations. Of the 215 AFLP markers scored, 93% were polymorphic. AFLP profiles were distinct between SIF and LET (Nei & Li's similarity coefficients between SIF and LET isolates = 22–35%). Within SIF, AFLP patterns were very similar (similarity > 98–9%), indicating that SIF is an asexual population and may have a clonal lineage. Within LET, similarities were > 69%. LET isolates collected from a site at Long Ashton in 1991–1993 were closely related and, therefore, may have come from the same local source. Similarity data from AFLP were in good agreement (Spearman's rank correlation = 0.85) with that of RAPD when both SIF and LET isolates were included, but the correlation was less obvious (= 0.49) when only LET isolates were included. Identical banding patterns were obtained when AFLP was performed using either a Perkin–Elmer 480 or a Perkin–Elmer 9700 Thermocyclers, each programmed with a different PCR profile.

Pycnial nectar of one mating type is known to induce cap formation on pycniospores of opposite mating type within several species of Puccinia and Uromyces. To learn if caps are induced by nectar transfers between species, we used interspecific pairings involving six species of Puccinia and three of Uromyces. Overall, caps were induced in 14 pairings between different species involving all tested species, except Puccinia helianthi which has no intraspecific cap induction. Nectar (with pycniospores) exchanged in reciprocal transfers between individual pycnial clusters of two different species gave pycniospore caps in nine of 16 cluster pairings, comparable to rates within species. Spore-free nectar combined from five or more pycnial clusters of one species (to ensure that nectar of two mating types was present) usually induced caps in pycniospores from single pycnial clusters of a second species. This occurred in all tested pairings of species except pairings involving P. helianthi. In experiments with pycniospore-free nectar of one capping type specificity from P. recondita, caps were induced in about 50% of pycnial clusters of unknown capping type from P. triticina or P. hordei and only in pycnial clusters of one capping type from P. triticina or P. reichertii in experiments in which type within species was determined. Coupled with the fact that capping type specificity and mating types are coincident within species, the results indicate that mating type-specific induction of pycniospore caps by nectar extends across species boundaries. Although aecia were never produced in interspecific pairings, cap induction occurred as it does in intraspecific pairings where it precedes aecium formation in species exhibiting the capping phenomenon.

Interactions between springtails (Onychiurus armatus, O. tuberculatus, Folsomia candida) and plant pathogenic fungi (Gaeumannomyces graminis var. tritici, Fusarium culmorum, Bipolaris sorokiniana and Rhizoctonia cerealis) living in the same soil layer were investigated under laboratory conditions. The fungi are responsible for the foot and root disease complex of winter cereals and can cause serious reduction in yield. Since these species coexist in agricultural soils, feeding preference tests were performed in such a way that the springtails were allowed to interact simultaneously with all the tested fungi. O. armatus, O. tuberculatus and F. candida fed on the mycelia of G. graminis var. tritici, F. culmorum and R. cerealis: in the first hours of the trials individuals of all springtail species distributed themselves among the colonies, though moving from one to the other. Subsequently F. culmorum mycelium became the preferred food of all species tested; however, the other two fungi continued to be consumed. Mycelia of G. graminis var. tritici, F. culmorum and R. cerealis were shown to be an adequate food source for reproduction of Folsomia candida. Bipolaris sorokiniana mycelium had both repellent and lethal effects on F. candida and O. armatus, whereas this fungus was lethal, although not repellent, for O. tuberculatus. Long-term experiments on F. candida indicate that conidia of B. sorokiniana were eaten and proved to be a sufficient diet for reproduction.

Arbuscular mycorrhizal fungi (AMF) show significant potential for biocontrol of Phytophthora spp., but there is little evidence for the mechanisms involved in the process. This study establishes that microorganism free exudates from roots colonised by AMF result in significantly less sporulation of P. fragariae than those from uncolonised plants. Experiments in vitro showed that after 48 h in the presence of exudates from strawberry roots colonised by Glomus etunicatum and G. monosporum, sporulation of P. fragariae was reduced by ca 67% and 64% relative to sporulation in the presence of uncolonised roots. After 72 h sporulation was reduced by 83% and 89% respectively. These data were then confirmed in an in vivo system in which Phytophthora fragariae was inoculated into the mycorrhizosphere of either uncolonised strawberry plants or those colonised by G. etunicatum. A similar trend was observed, with a 69% reduction in sporulation of P. fragariae after 72 h in the mycorrhizosphere of colonised plants relative to sporulation in the mycorrhizosphere of uncolonised plants.

Mycelial preparations of Erynia neoaphidis were tested under different drying and storage conditions. For unformulated mycelial discs and formulated alginate granules, sporulation was best maintained if drying at 20–22 °C was performed at 60 or 90% r.h. rather than an ambient humidity of 30%. Storage experiments were performed on preparations dried at 90% r.h. for 72 h. Estimates for a 50% decline in sporulation with storage time (ST50) were computed if there were statistically significant fits using exponential or non-parametric linear regression. For mycelial discs, values of ST50 were between 36–39 d when maintained at 10° with silica gel or 20% r.h., and 14–26 d when kept at 10° and 35% r.h. or with silica gel and 15 or 20°. For alginate granules, ST50 values of 6–9 d were obtained at 10° and 20–55% r.h. A 5- to 9-fold increase in sporulation was produced with granules containing 2% w/v sucrose and 5% w/v starch compared to granules without additives. Elevated humidities are recommended for drying E. neoaphidis mycelia and viability of dried preparations is best maintained if they are stored at 10° compared with 15 or 20°.

Endophytic fungi were isolated from three unidentified Licuala sp. palms in Brunei Darussalam and from three L. ramsayi palms in Australia. Endophytes were very common in both species, with overall colonisation rates of 81–89%. Taking into account a lower sampling frequency in Australia, endophyte diversity was similar in the two Licuala species. The endophyte assemblages examined were very diverse, consisting of 75 fertile species and 60 sterile morphospecies. The endophyte communities of both palms were composed of a single, dominant xylariaceous species, approximately ten less common but equally ubiquitous species and a large number of species occurring at very low frequencies. Differences were observed between the endophytic mycotas of different palm tissues and of tissues of different ages. The results presented suggest that most of the endophytes entered the petiole via the leaf and that transmission of palm endophytes is likely to be horizontal (via airborne propagules) rather than vertical (via seed). Seasonal differences were not observed in Brunei. Increased sampling effort could be expected to yield more endophyte taxa in both species investigated.

Duddingtonia flagrans was grown in shake flask culture on Sabouraud's dextrose medium with and without the addition of agar (to form a slightly more viscous medium). The addition of agar increased the number of chlamydospores produced in late stationary phase, with 8.6×105 chlamydospores ml−1 being obtained on a medium containing 5 g agar l−1. The pH optimum for growth was between 5.5–7.5 but colonies formed on plate cultures buffered at pH 10.5. When grown in shake flask culture at 25 °C and pH 7 on malt extract–yeast extract–peptone–glucose medium (MYPG), D. flagrans had a specific growth rate of 0.21 h−1 (doubling time 3.3 h) and produced 5.1±0.07 mg biomass ml−1. To increase chlamydospore production in a liquid medium, D. flagrans was also grown in a two phase culture system in which late exponential phase biomass produced in MYPG medium was transferred to Vogel's mineral salts medium containing various nitrogen (mycological peptone, casein) and carbon (sodium acetate, starch and glycerol) sources. The highest chlamydospore concentrations (6.2×105 and 5.6×105 ml−1) were observed when the biomass was transferred to Vogel's medium containing 10 g starch or glycerol l−1, respectively.

We have investigated the wheat infection process of Mycosphaerella graminicola (teleomorph of Septoria tritici) through the combined application of differential interference contrast light, confocal laser scanning, and cryo-scanning electron microscopies. Several aspects of fungal development have been documented, including the presence of extracellular cirrus and germling matrices, as well as nutrient-sensitive morphogenesis. The use of confocal laser scanning microscopy was invaluable in documenting the time course of pathogen invasion and symptom development. These data were used to generate summary diagrams of the asexual infection cycle of M. graminicola, to benchmark the efficacy of various crop protection strategies.

Polygalacturonase (PG) synthetized by Fusarium spp. is a polymorphic enzyme with complex isoform patterns influenced by culture conditions and which are variable at the intra- and inter-specific levels. The partial sequence of an endopolygalacturonase coding gene (endopg) has been analyzed in isolates of seven species of Fusarium, most of them associated with Pinus pinea. The genomic fragment analyzed, 740 bp long, included two introns and the exon 4, which contained most of the amino acid motifs conserved in PGs from different origins. The high similarity of the amino acid sequences found among the isolates would indicate that differences in amino acid composition are not probably the main reason of the variability of this enzyme. Therefore, differences in the gene expression and regulation patterns of endopg gene among the isolates should be considered. Both types of sequences, the coding and the two intron sequences contained in the endopg fragment, were compared among the isolates to evaluate their potential use for phylogenetic studies. The different levels of variability of these sequences and the similar results obtained from the phylogenetic analyses when the three sequences (coding, intron and amino acid sequences) were used indicate that this endopg region would be very useful for phylogenetic analysis in the genus Fusarium.

Urediospore-derived infection structures of Phakopsora apoda, a rust fungus on kikuyu grass (Pennisetum clandestinum), penetrate the host leaf directly through the cuticle and not through the stomata. A urediospore germinates on the leaf to form a short germ tube which is delimited from a terminal appressorium by a septum. Most appressoria form at the junctions between epidermal cells. Appressoria are often sessile to the urediospores. From the base of the appressorium, a penetration peg develops, which penetrates through the host cuticle and epidermal cell wall. Penetration of the epidermal cell wall occurs approx. 6 h post inoculation. Once inside the epidermal cell, the penetration peg expands to form a penetration hypha, which traverses the epidermal cell and emerges into the intercellular space of the mesophyll tissue. A septum is formed in the intercellular portion of the penetration hypha, delimiting a primary hypha which extends further into the mesophyll, before branching to form two secondary hyphae. This penetration process appears to be very similar to that of Phakopsora pachyrhizi on soybean.

The recently reported epidemic of rust in Britain on wild and cultivated varieties of the daisy (Bellis perennis), caused by Puccinia distincta, was preceded by records on cultivated plants at Bristol in 1972 and Bognor Regis in 1973 and by sporadic observations of rust on cultivated daisies thereafter in the period from 1978–1996. The first verifiable report of the pathogen on wild B. perennis was from Leeds in 1988. In the spring of 1997, a rust epidemic broke out on wild as well as cultivated daisies, as indicated by numerous reports mainly from the south of Britain. The current paper charts the distribution of P. distincta in Britain from 1972 onwards and speculates about its likely origin.

Ericoid mycorrhizal fungi increase the ability of their host plants to colonise soils polluted with heavy metal ions, although the mechanisms are not clearly understood. Two mycorrhizal mycelia of Oidiodendron maius isolated from contaminated soil were previously shown to tolerate high concentrations of heavy metal ions in the growth medium. The influence of zinc ions on the secretion and activity of polygalacturonase (PG), an extracellular enzyme that hydrolyses the pectin component of the plant cell walls, was investigated because of their significance during saprotrophic growth. Two major PG isoforms expressed both in the absence and in the presence of increasing concentrations of zinc ions were identified. The PG isoforms were purified from the tolerant Oidiodendron strains as well as from ericoid fungal isolates from non-polluted soils. Addition of increasing concentrations of Zn and Cd ions to the purified enzymes resulted in an increase of PG activity of both tolerant and non tolerant O. maius isolates at doses below 1 mM. By contrast, at the same metal ion concentrations PG activity of a sterile isolate from non-polluted soil was unaffected or slightly inhibited. We speculate that the response of PG to heavy metal ions may have been a pre-adaptive factor for the colonisation of polluted soils by O. maius.

Nine isolates of Peronosclerospora sorghi from maize, sorghum and wild sorghum were sampled from Zimbabwe, Zambia, Rwanda, Mozambique and Kenya. They were compared for variation in conidium and conidiophore morphology, temperature requirements for sporulation, germination and germ-tube growth and for pathogenicity on different sorghum and maize cultivars. Although there were significant differences in isolate morphology, all conformed to the known range for P. sorghi. Mean conidial length×width ranged from 21–23 μm×16·9–19·2 μm, and mean conidiophore length (basal cell-branching) ranged from 116·3–135·6 μm. All isolates sporulated in the range 14–26 °C (optimal at 16–23°), although one isolate from maize from Umbeluzi in Mozambique had a broader optimal range for sporulation (12–25°). Conidia of all isolates germinated between 10° and 34°. Germ-tube response to temperature was similar for all isolates (10–34°). The isolates varied in their pathogenicity towards sorghum cultivars, with an isolate from Rwanda being pathogenic to more sorghum differentials than any other. Cluster analysis of isolates based on host reaction indicated five groups at the 85% similarity level. The existence of pathogenic variability has ramifications for the breeding of sorghum for resistance to downy mildew in Africa.

Aseptic root exudates were collected from the liquid culture of roots of two host (Daucus carota and Lycopersicum esculentum) and one non-host plant (Beta vulgaris) of arbuscular mycorrhizal (AM) fungi. Exudate was also collected from maize (Zea mays FRB6) seedlings which were grown hydroponically under aseptic conditions. Exudate fractions of host roots stimulated hyphal branching behind any actively growing hyphal tip of three AM fungi tested (Gigaspora gigantea, G. rosea, and Glomus intraradices). Fractionation patterns obtained from C18 Sepak cartridges loaded with carrot root exudates isolated from roots grown under various phosphorus regimes, TLC analyses, and solubility properties of fractionated components, indicated a range of hydrophilic to hydrophobic hyphal branching stimulators. The 50/70% methanol fraction from a C18 cartridge induced hyphal branching patterns of G. gigantea that were dose dependent and were identical to those observed when germinated G. gigantea spores were grown with host roots in dual culture. Exudate fractions from B. vulgaris inhibited hyphal tip growth, but inhibited hyphal tips formed recovery branches which would allow continued fungal growth. These recovery hyphae were also formed when germinated G. gigantea spores were grown in dual culture with sugar beet roots. The recovery branches induced by non-host roots and the prolific branching induced by host roots have ecological implications.

In an in vitro study, interactions between ectomycorrhizal fungi, saprotrophic basidiomycetes and soil microfungi known from pine forests were examined in relation to different ammonium concentrations. The saprotrophic basidiomycetes Clitocybe marginella and C. vibecina and the soil microfungi Penicillium pinetorum, Oidiodendron flavum and Torulomyces lagena were grown against the ectomycorrhizal Cenococcum geophilum, Laccaria bicolor and Rhizopogon luteolus. Interactions were species specific and overgrowth was the most common (43%), followed by inhibition at distance (26%) and contact inhibition (16%). Ammonium concentrations affected the type and strength of the interactions. The competitive strength of the ectomycorrhizal fungi was relatively high and only the growth of the mycelia of L. bicolor was clearly suppressed by the Clitocybe spp. The interactions are discussed in relation to the ecology of the fungi and potential future studies.

Phylogeny inferred from ITS DNA sequence resolved isolates of Australian Ganoderma into five terminal clades. The phylogenetic analysis was considered superior to sequence variation statistics for delineating species as intra and inter-specific variation were dissimilar across the taxa studied. The analysis also revealed that a number of isolates had been misnamed. Phylogeny inferred from the sequence data supported the retention of Elfvingia and Ganoderma as subgenera of Ganoderma, and the placement of the G. chalceum complex within subgenus Ganoderma. These findings were, however, poorly supported by decay analysis. G. adspersum, a European species considered to be a synonym of G. australe (a species which is in need of neotypification) by some authors, was not synonymous with G. australe from Australia. G. incrassatum from Northern Australia formed a clade with isolates named G. gibbosum from China and an isolate named G. australe from Taiwan. G. weberianum from Australia, originally identified by R. L. Steyaert, formed a terminal clade that was closely related to a second terminal clade comprised of two G. weberianum isolates and an isolate of G. microsporum from Asia. It was concluded that the clades represented two allopatric populations of G. weberianum and that G. microsporum was a synonym of G. weberianum. Isolates determined as G. chalceum by R. L. Steyaert and referred to here as G. cupreum formed a distinct terminal clade most closely related to material identified as G. sinense. A species mistaken for G. lucidum from Australia and Indonesia, a species from temperate and South East Asia containing commercially cultivated strains, and an Argentinean species showed evidence of allopatric speciation. Nomenclatural problems and the implications of our study on the pharmaceutical and commercial exploitation of Ganoderma in Australia are discussed.