The effect of water activity (aw, 0·995–0·85) and temperature (15, 25°C) on the in vitro inter- and intra-specific interactions between thirteen fungi commonly isolated from maize grain were investigated. The fungi were paired and their interactions given a numerical score to obtain an Index of Dominance (ID) for each species. Aspergillus niger had the highest overall ID in most of the conditions tested, while the Aspergillus species tested were also quite dominant. Fusarium species appeared to be dominant only at high water availability (0·995 aw), while Eurotium species dominated at the lower aws (0·85–0·90). The relative growth rates of each fungus were also calculated under the same range of environmental conditions. In general, Aspergillus, Fusarium and Trichoderma species grew most rapidly under the combination of aw and temperature conditions in which they were able to grow, while Penicillium species had the slowest growth rates. There was a positive correlation between growth rate and ID for Trichoderma viride and three Fusarium spp. but not for Aspergillus and Penicillium and Eurotium spp. The different possible strategies in fungal competition for grain are discussed in relation to these in vitro findings.

Geosmithia putterillii is an anamorphic fungus with connections to bark beetles. Genetic variability of 89 isolates traditionally grouped in G. putterillii and G. lavendula isolated from different geographical regions from subcorticolous insects and from other unspecific substrata was assessed using RAPD, sequencing of the ITS region (ITS1-5.8SrDNA-ITS2) and morphological characters. RAPD analysis revealed eight distinct groups. One group was represented by G. lavendula type strain and showed no relations to any other isolate. Five RAPD-types with similar ITS sequences and phenotype were related to the ex-type strain of Penicillium pallidum (generally given as a synonym of G. putterillii). Because of unique phylogenetic position and a phenotype markedly different from G. putterillii, the new combination G. pallida is made here. For another group of isolates formerly identified as G. putterillii the new species G. flava is described based on a characteristic RAPD-type, a unique ITS sequences and a different phenotype. These newly recognized species are stable in culture and with worldwide distribution.

Mycosphaerella punctiformis, the type species of the genus Mycosphaerella, is epitypified by material collected on Quercus robur in The Netherlands. The teleomorph is described in planta, and the Ramularia anamorph, for which the new name R. endophylla is proposed, and the Asteromella spermatial state are characterized in vitro. Sequence data of the nuclear ribosomal DNA are presented and analyzed together with other Mycosphaerella spp. with Ramularia and several other anamorphs. Several strains originating from Quercus, Acer and Tilia showed diverging ITS sequences, indicating that the M. punctiformis complex may comprise more than a single phylogenetic species, but this could not be confirmed by the analysis of our dataset. An endophytic phase is established for the first time in the life-cycle of M. punctiformis, as the species was repeatedly isolated from surface sterilized green healthy leaves of Quercus robur in summer at the epitype locality.

14 different yeasts were isolated from the gut of a variety of insects, including beetles, lacewings, fishflies, craneflies, and a cockroach. One of the yeasts was found both in the gut and on the body surface of a beetle larva. Based on ribosomal DNA sequence comparisons and phenotypic characters, the yeasts were identified as Candida membranifaciens, C. tenuis, Pichia nakazawae, and nine undescribed taxa in Saccharomycotina. All the undescribed taxa reproduced only asexually, and they fit within the limits of the polyphyletic genus Candida. The new species and their type strains are Candida blattariae NRRL Y-27703T, C. amphixiae NRRL Y-27704T, C. michaelii NRRL Y-27705T, C. cerambycidarum NRRL Y-27706T, C. gorgasii NRRL Y-27707T, C. endomychidarum NRRL Y-27708T, C. temnochilae NRRL Y-27763T, C. sinolaborantium NRRL Y-27765T, and C. lessepsii NRRL Y-27766T spp. nov. Phylogenetic analysis of combined small and large subunit ribosomal DNA sequences placed C. amphixiae, C. michaelii, C. cerambycidarum, C. gorgasii, C. endomychidarum, and C. lessepsii in a statistically well supported clade with C. blattariae, C. membranifaciens, C. friedrichii, and C. buinensis as sisters to the clade. The other two new taxa, C. temnochilae and C. sinolaborantium, formed an independent clade basal to the major clade containing C. membranifaciens and closely related taxa. C. sinolaborantium occurred in both Panama and the USA, but there were genetic differences between the isolates from the two places.

In experimental microcosms, three Glomus spp. were subjected to heating to over 200°C at the soil surface and 70° at 5 cm to determine the effect of fire on survival of arbuscular mycorrhizal fungi. Heating reduced the quantity of propagules surviving at the soil surface and the effect declined with depth. While all propagules are likely to be affected by heat, we argue that the hyphal network is most severely disturbed and probably responsible for declines in density of fungi observed in the field following fire.

The morphology of infection structure development of Puccinia recondita f. sp. tritici on and in susceptible and resistant wheat lines inoculated with urediospores was examined by SEM. The germ-tube extends over the leaf surface and elongates perpendicularly to the long axis of the leaf. When the germ-tube encounters the stomatal lip, an appressorium forms over the stoma and the pore is entered by an infection peg produced on the surface of the appressorium in contact with the host leaf. At 6 h post-inoculation (hpi), infection pegs develop terminally substomatal vesicles (SSVs) in the substomatal chambers of all wheat lines. A septum separates each SSV from its interconnective tube. A primary infection hypha forms terminally from the elongated SSV either parallel to the long axis of the stomatal slit or perpendicular to the leaf surface. When a primary infection hypha attaches to a host cell, a septum forms cutting off the tip of the hypha, delimiting a terminal haustorium mother cell (HMC) by 12 hpi. Secondary infection hyphae arise from a position proximal to, and in the proximity of, the HMC septum. Additional HMCs are formed when a secondary hypha or a tertiary hypha adheres to a plant cell. Infection sites with HMCs were observed at 24 hpi and at subsequent sampling stages. There were no significant differences between the infection processes on the three wheat lines examined in this study.

Fungal cultures isolated from oil-polluted sea water near Mumbai, India have been studied for their capability to degrade crude oil. A yeast isolate identified as Yarrowia lipolytica was further investigated with respect to its dimorphic behaviour and alkane degradation. Y. lipolytica NCIM 3589 in the yeast form degraded the aliphatic fraction of crude oil and also pure alkanes (20–60% within 48 h) under aerobic conditions. Unlike most Y. lipolytica strains, our isolate required partial anaerobiosis for mycelium formation. Studies with two isolates suggested that mycelium to yeast transition may be the prerequisite for effective alkane degradation.

An evaluation was made of the genotypic diversity (DNA fingerprinting) of 269 A. flavus strains, including subpopulations isolated from grain sampled at harvest (91 unique ‘fingerprints’ or genotypes/128 strains), field soil (26 genotypes/31 strains), maize insects (49 genotypes/52 strains) and air-spora (56 genotypes/58 strains), from a maize field near Kilbourne, Illinois. Eight A. flavus genotypes were isolated from grain samples harvested in different years (1988–1991). Genotype 36, isolated from three maize samples, matched the DNA fingerprint of a K. E. Papa strain NRRL 19997, isolated from maize grown in Georgia. Ninety-eight percent of the A. flavus genotypes produced sclerotia and 53% produced aflatoxin. Contrasts of DNA fingerprints revealed two matches involving subpopulations from grain and soil, one match for grain and maize insects, and no matches for grain and air-spora. The high genotypic diversity recorded for each subpopulation, in addition to a limited sample size, precluded any assessment of the relative importance of these subpopulations as sources of A. flavus infective inoculum. Aspergillus parasiticus was routinely isolated from soil samples.

Amplified Fragment Length Polymorphism (AFLP) analysis has been used to analyse 100 Australian, European and North American isolates of Leptosphaeria maculans. All isolates had distinct AFLP profiles. They could be classified into five types, which had very few AFLP bands in common and corresponded to classifications made previously on the basis of ability to cause stem cankers on Brassica napus (A group), or inability to do so (B group), and on host range. Four isolates had AFLP profiles completely dissimilar to these groups and to each other. Genetic diversity and geographic differentiation were analysed separately within AFLP types 1 and 2. UPGMA analysis of the 66 AFLP type 1 (A group) isolates using 50 polymorphic bands did not provide evidence for clustering according to geographic origin. Non-metric multidimensional scaling (NMDS) analysis suggested that the Australian and European populations were separate adjacent clusters, while the North American population partially overlapped both the others. This geographic differentiation was supported by Wright's fixation index (Fst) analysis. Three measures of genetic variability between isolates within regions (effective number of alleles, gene diversity, and Shannon index) showed that the North American A group isolates were less diverse than those from Australia and Europe. The 21 AFLP type 2 (B group; NA1 sub-group) isolates did not cluster based on geographic region, which was confirmed by NMDS and Fst analysis. There was a similar degree of genetic diversity within A group and the NA1 sub-group of B group isolates. Unlike other techniques, AFLP analysis can readily discriminate between group B isolates of the L. maculans complex that were previously difficult to classify and also provides individual fingerprints for isolates. Isolates of the A group and of the NA1 sub-group of B group could be also distinguished readily by electrophoretic karyotyping, as the latter isolates had more bands smaller than 1.4 Mb than the A group isolates.

Twenty-four isolates of Aspergillus sojae, A. parasiticus, A. oryzae and A. flavus, including a number that have the capacity to produce aflatoxin, have been compared using amplified fragment length polymorphisms (AFLPs). Based on analysis of 12 different primer combinations, 500 potentially polymorphic fragments have been identified. Analysis of the AFLP data consistently and clearly separates the A. sojae/A. parasiticus isolates from the A. oryzae/A. flavus isolates. Furthermore, there are markers that can be used to distinguish the A. sojae isolates from those of A. parasiticus, which form the basis for species-specific markers. However, whilst there were many polymorphisms between isolates within the A. oryzae/A. flavus subgroup, no markers could be identified that distinguish between the two species. Sequencing of the ribosomal DNA ITS (internal transcribed spacers) from selected isolates also separated the A. sojae/A. parasiticus subgroup from the A. oryzae/A. flavus subgroup, but was unable to distinguish between the A. sojae and A. parasiticus isolates. Some ITS variation was found between isolates within the A. oryzae/A. flavus subgroup, but did not correlate with the species classification, indicating that it is difficult to use molecular data to separate the two species. In addition, sequencing of ribosomal ITS regions and AFLP analysis suggested that some species annotations in public culture collections may be inaccurate.

Species within the genus Botryosphaeria include some of the most widespread and important pathogens of woody plants, and have been the focus of numerous taxonomic studies in recent years. It is currently accepted that anamorphs of Botryosphaeria belong to two distinct genera, Fusicoccum and Diplodia. Species within the genus Fusicoccum commonly produce aseptate, hyaline conidia. In the present study, fungi were isolated from foliage and wood of Eucalyptus in native forests and plantations in Australia. Although these fungi produced Dichomera anamorphs in culture, they clustered within the Fusicoccum clade of Botryosphaeria based on their ITS sequence data. Four species, Botryosphaeria dothidea, B. parva, B. ribis and B. australis produced Dichomera conidia in culture. The Dichomera synanamorphs are described for these four species of Botryosphaeria. In addition, falling within the Fusicoccum clade of Botryosphaeria, two species were found to be distinct from previously described Botryosphaeria spp. based on their ITS sequences, but synonymous with D. versiformis and D. eucalypti. These observations are currently unique to isolates from host trees within the genus Eucalyptus in Australia, and the pleoanamorphic nature of these species is discussed.

The phylogeny of the Dothideomycetes was investigated using nucleotide sequences of SSU and LSU rDNA. 32 new sequences of these regions from 18 species were aligned with five sequences obtained from GenBank, including two representatives of Pezizomycetes used as outgroup. A combined data set of SSU and LSU rDNA was analysed phylogenetically using neighbour-joining and maximum likelihood. The pseudoparaphysate taxa (Pleosporales incl. Melanommatales) form a monophyletic group. A separation of Melanommatales can be rejected using parametric bootstrapping, and this supports previous results obtained from SSU rDNA studies. The aparaphysate Dothideomycetes form a sister-group to the Pleosporales, but with low bootstrap support. Within these species, two well-supported groups can be distinguished, the Dothideales s. str. and the Capnodiales with Myriangiales as sister-groups. The Myriangiales appear paraphyletic, but this has only poor bootstrap support. A monophyly of Dothideales comprising Capnodiales can be rejected with parametric bootstrapping as well as a subdivision of the loculoascomycetes based on form and opening of the ascomata and ascus. The phylogeny of the aparaphysate taxa requires further studies.

A new ascomycete, Antarctomyces psychrotrophicus gen. et sp. nov., characterised by naked asci, hyaline, thick-walled, ellipsoidal to fusiform, echinulate ascospores, and blastoconidia, isolated from Antarctican soil samples, is described and illustrated. Analysis of the nuclear rDNA ITS region sequences showed that this taxon is related to Thelebolaceae.

All available publications providing descriptions of ectomycorrhizas (ECM) were reviewed in order to build a database containing details on fungus forming the ECM, host tree, country where the material for description was collected, and habitat of the ECM. Other secondary data were also recorded. In all 1244 descriptions of ECM published since 1961 in 479 papers were reviewed. The number of different ECM morphotypes described was 814. Most ECM described were collected in Europe and North America. Gymnosperms were the most common tree associates, and boreal and temperate forests the most studied ecosystems. Fungal symbionts were mostly Basidiomycota, epigeous, and with mushroom-like morphology. The paper also addresses the gaps in ECM knowledge that mycorrhizologists should address in future studies.

Genotypic variation among 62 strains of Aphanomyces euteiches, four of A. cochlioides, and a Saprolegnia sp. was investigated using RAPD analysis. Pathogenicity assays on pea, bean, alfalfa, red clover, and sugarbeet were used to determine host preference among the strains of A. euteiches and A. cochlioides. Pathogenicity tests revealed six pathotypes of A. euteiches with host preferences for bean, alfalfa, pea, pea and alfalfa, red clover and alfalfa, and bean and alfalfa. Another group of strains was non-pathogenic on the five plant species. The host of origin tended to be the host on which each strain incited the highest disease severity. A. euteiches did not incite root rot symptoms on sugarbeet, and A. cochlioides was pathogenic only to sugarbeet. RAPD analyses provided a measure of genetic diversity in Aphanomyces. Fifty random decanucleotide primers were screened with five test strains from four hosts representing different pathotypes, and 32 primers amplified DNA fragments from all five strains. Eight primers were chosen for most of this study based on number and polymorphic nature of the bands generated. RAPD assays of 62 strains of A. euteiches with the eight primers yielded 159 polymorphic and no monomorphic, strongly amplified bands. Cluster analyses of RAPD data revealed genotypic differences among three groups of A. euteiches which corresponded to their host of origin and host preference for bean, alfalfa, and red clover/alfalfa. Strains nonpathogenic on all plants tested formed another genotypic group, corroborating results from the pathogenicity assays that indicated this is a discrete group. The bean and non-pathogenic groups were the most distinct. The A. cochlioides and Saprolegnia strains were genotypically distinct from the pathogenic, but not the non-pathogenic strains of A. euteiches. Reproducibility of RAPD assays was confirmed by replicated amplifications and DNA hybridization analysis. Results indicated that A. euteiches is composed of distinct subspecific groups based on genotype and host preference.

Diversity in trichothecene mycotoxin production by 167 isolates of Fusarium graminearum was examined by chemical and molecular methods. Isolates from barley, corn, and wheat grown in Korea produced either deoxynivalenol (DON) or nivalenol (NIV), whereas isolates from corn grown in the United States produced DON only. Southern blotting of MseI-digested genomic DNA's from these isolates was performed using a 0.6-kb fragment of Tri5, a key enzyme for trichothecene production, as a probe. This technique revealed a single-band polymorphism between these isolates, with 1.8- and 2.2-kb bands arising from DON and NIV producers, respectively. The same set of isolates was subjected to previously developed PCR assays using primers derived from Tri7 or Tri13. These assays also revealed a single-band polymorphism between NIV- and DON-producing chemotypes. The polymorphisms at Tri5, Tri7, or Tri13 in all of the US isolates were consistent with their chemotypes as identified by GC–MS. However, for seven Korean isolates, chemical and molecular analyses yielded seemingly inconsistent results. This issue was resolved by Southern blot analysis with the Tri5 probe using two other restriction enzymes and sequence comparison of a 3.8-kb region spanning Tri5. In addition, one of these exceptional isolates was found to carry both DON and NIV chemotype-specific regions, possibly resulting from recombination between the two chemotypes.

A Phytophthora species was found on blighted foliage of Ipomoea longipedunculata, a morning glory native to the highlands of central Mexico. Based on host range, morphology, allozymes, mitochondrial DNA haplotype and rDNA sequences it is concluded that a new Phytophthora species, P. ipomoeae sp. nov., is the causal agent of leaf blight disease on I. longipedunculata.

Genetic variation within and between eighteen isolates of Alternaria brassicicola, five isolates of A. alternata, and a single isolate of Rhynchosporium secalis was compared using Amplified Fragment Length Polymorphisms (AFLPs). The AFLPs consistently distinguished between the three species. AFLPs thus provide a reliable tool for identifying A. brassicicola. The analysis of eighteen isolates of A. brassicicola from different sites also indicated at least moderate levels of genetic diversity within A. brassicicola along the New South Wales coast. Of 43–66 markers scored per primer combination, 16·7–27·9% were polymorphic. On the basis of an unweighted paired group method of arithmetic averages analysis using data from four primer combinations, most isolates were identified as separate genotypes. However, multiple isolates from particular locations tended to cluster together, implying the potential for population structure, and there was a significant positive correlation between Nei's measure of genetic distance and physical distance (r = 0·5486, P<0·001). Despite the absence of an identified sexual stage, A. brassicicola would appear to have a means for generating and maintaining significant variation.

Variation within the internal transcribed spacer (ITS) and the intergenic spacer (IGS) of the ribosomal RNA gene of isolates representing seven European species of Armillaria was examined by PCR, coupled with RFLP analysis and partial sequencing of the ITS region.

The amplified-ITS region was about 840 bp long and uniform in length among the European isolates, while the amplified-IGS region showed four different lengths which corresponded to A. mellea, A. tabescens, A. ectypa and a group including the four other species. A. borealis, A. ostoyae, A. cepistipes and A. gallica.

Restriction digestions of the ITS and IGS regions by Alu I and Rsa I, respectively, gave rise to the same four polymorphic groups. However, A. borealis and A. ostoyae were easily separated from A. cepistipes and A. gallica by digestion of the two rDNA spacers with Hinf I and Taq I. Nde II digests of the amplified ITS could distinguish A. borealis from A. ostoyae and each of the seven species were separated by Alu I digestion of the IGS region. A North American A. mellea isolate, partly examined in this work, was found to be different from the European A. mellea isolates, while there was a close similarity between the European A. ostoyae and an isolate of the same species isolated from the U.S.A.

Cluster analysis based on the presence or absence of comigrating restriction fragments indicated more than 80% similarity between A. borealis and A. ostoyae and between A. cepistipes and A. gallica, while A. mellea, A. tabescens and A. ectypa were found in separate clusters exhibiting, respectively, about 40, 38 and 32% average similarity with the other species.

Although little intraspecific variation was observed in many species, A. gallica and A. cepistipes were found to be heterogeneous. In view of recent results suggesting several groups in A. borealis and A. cepistipes, the Alu I restriction patterns obtained in this work would identify the former species as type B, characterized by an Alu I pattern different from that of A. ostoyae, and the latter species as composed of one isolate (C4) of type B and three isolates (C1, C2 and C3) of type A.

Nucleotide sequences of the rDNA internally transcribed spacer 1 (ITS1) of one isolate of each species showed that A. mellea and A. ectypa differed from the other species by several insertions and point mutations giving rise to a level of similarity ranging from 66 to 79%. This DNA region was highly conserved within the other species which revealed a similarity of 97 to 100%.

These results demonstrate that analysis of rDNA spacers provides appropriate data to circumscribe taxonomic entities within the Armillaria complex and that the phylogenic relationships among species deduced from the present study are consistent with previous analyses based on pairing tests as well as morphological and physiological characters.

Rhynchosporium secalis causes an economically important foliar disease of barley, rye, and other grasses known as leaf blotch or scald. This species has been difficult to classify due to a paucity of morphological features; the genus Rhynchosporium produces conidia from vegetative hyphae directly, without conidiophores or other structures. Furthermore, no teleomorph has been associated with R. secalis, so essentially nothing is known about its phylogenetic relationships. To identify other fungi that might be related to R. secalis, the 18S ribosomal RNA gene and the internal transcribed spacer (ITS) region (ITS1, 5.8S rRNA gene, and ITS2) were sequenced and compared to those in databases. Among 31 18S sequences downloaded from GenBank, the closest relatives to R. secalis were two species of Graphium (hyphomycetes) and two other accessions that were not identified to genus or species. Therefore, 18S sequences were not useful for elucidating the phylogenetic relationships of R. secalis. However, analyses of 76 ITS sequences revealed very close relationships among R. secalis and species of the discomycete genera Tapesia and Pyrenopeziza, as well as several anamorphic fungi including soybean and Adzuki-bean isolates of Phialophora gregata. These species all clustered together with 100% bootstrap support. On the basis of these results, the teleomorph of R. secalis, if it exists, most likely will be a small apothecium produced directly on dead, infected host tissue. The ITS analysis also indicated that higher-level classifications within the discomycetes need to be revised, and that Tapesia and Pyrenopeziza probably do not belong in the Dermateaceae.