Genetic variation in the pistachio late blight fungus, Alternaria alternata, was investigated by restriction fragment length polymorphism (RFLP) in the rDNA region. Southern hybridization of EcoRI, HindIII, and XbaI digested fungal DNA with a RNA probe derived from Alt1, an rDNA clone isolated from a genomic library of the Japanese pear pathotype of A. alternata, revealed 34 different rDNA haplotypes among 56 isolates collected from four central valley locations in California. Analysis of molecular variation revealed a significant amount of genetic diversity within populations (85.8%), with only marginal variation accounting for differentiation among populations (14.2%, ϕST =0.142). All isolates examined were highly pathogenic. The identity of the four geographic populations sampled was not evident in both cluster and principal component analyses, probably indicating either the selectively neutral nature of rDNA variation or prevalence of widespread gene flow among populations combined with uniform host-selection.

The effectiveness of surface sterilization methods were compared using root tissue of barley (Hordeum vulgare) colonized by two Chaetomium species in an aseptic plant growth system. The reliability of different sterilants to inhibit ascospore germination was tested. Ascospores on nitrocellulose membranes were either treated directly or ascospores adhering to axenic barley seedlings were treated on plant tissue. Inhibition of ascospore germination on nitrocellulose membranes was achieved with lower concentrations of sterilants than when the spores were on plant surfaces. A 10% peracetic acid treatment was necessary if experiments were conducted ad planta. The sterilants penetrated into epidermal root tissue and caused damage to this area, as shown by the vital dye DiOC7(3). It was concluded that effective surface sterilization techniques for ascospores adhering superficially to plant tissue were not appropriate for the detection of fungi growing within the epidermis.

Sphaeropsis sapinea is an endophyte and latent pathogen of pines, assumedly introduced to the Southern Hemisphere along with its host. There are at least three recognised forms of S. sapinea that differ from each other morphologically and can also be separated based on molecular characteristics. Pinus radiata is a native to California but has been used extensively for afforestation in the Southern Hemisphere. For this study, populations of S. sapinea were collected from exotic P. radiata plantations in South Africa, South and Western Australia, Tasmania and New Zealand and from native P. radiata in California. The genotypic diversity of the populations was assessed and compared using vegetative compatibility tests. SSR markers were used to determine the morphotype of isolates from each vegetative compatibility group. All Californian isolates of S. sapinea were found to be of the ‘B’ morphotype, while all introduced isolates in the Southern Hemisphere were of the ‘A’ morphotype. The genotypic diversities of S. sapinea populations ranged from extremely low in Australia to very high in South Africa with New Zealand having an intermediate genotypic diversity. S. sapinea is an asexual fungus and, therefore, different genotypes in an exotic population represent separate introductions. Our results suggest there have been very few introductions into Australia and multiple introductions into South Africa. In addition, it appears that S. sapinea isolates from P. radiata in the Southern Hemisphere did not originate from native P. radiata, but rather the widely planted exotic P. radiata has acquired this fungal endophyte from other Pinus within the exotic environment.

Isolates of Gaeumannomyces graminis were sampled from 16 cereal crops throughout the cereal belt of southern Australia to determine the extent of genetic diversity and the scale of genetic differentiation among pathogen populations. Data from 13 isozyme and 4 RFLP loci differentiated 79 multilocus genotypes among the 320 isolates analysed. All 17 loci differed significantly in allele frequencies across all populations and significant levels of genetic differentiation were detected between most populations. Genetic differentiation among host groups was high (GST = 0.307) and groups of populations from barley, oats and wheat were significantly different. The average genetic identities among populations were low and populations formed genetically related groups based on similarities in recent cereal cropping histories and not geographical origins. Collectively, these analyses indicate restrictions to inter-population gene flow within G. graminis and imply that population differentiation results from genetic drift and host-mediated selection by different cereal species.

That the symbiotic fungus of leaf-cutting ants only occasionally produces the sexual phase makes their identification confusing. This has occurred so rarely, either in laboratory nests, or in unbalanced field nests, that the possibility of contamination of the fungal garden by other fungi cannot be disregarded. In this paper we describe the formation of several basidiomata in a healthy and free-living nest of the leaf-cutting ant Acromyrmex hispidus fallax, the cultivation in vitro of the sterile mycelia (isolated from the fungal garden) with their typical inflated tips, and the similarity of both forms confirmed by RAPD analysis of their genomic DNA. The fungus was identified as Leucoagaricus gongylophorus.

A Melampsora lini β-tubulin gene and flanking sequence has been isolated and characterised. The gene contains 8 introns, is expressed in germinating urediospores and vegetative mycelia and encodes a 448 amino acid protein that is similar to other fungal β-tubulin genes. Evidence for a second β-tubulin gene within the M. lini genome is also presented. The predicted M. lini β-tubulin protein was compared with 34 other fungal β-tubulin proteins in a phylogenetic analysis and, in general, good agreement was observed between the derived β-tubulin based phylogeny and the current taxonomic status of these species. However, a second β-tubulin protein found in five fungal species is atypical when compared to other fungal β-tubulin proteins. Analysis of intron positions within 33 fungal β-tubulin genes showed that intron location was generally characteristic of the fungal class, with euascomycete fungi showing particularly striking conservation of intron position, although intron number was variable and intron sequences showed little conservation.

Estimates of global fungal numbers rely heavily on the ratios of unique fungi to host plants. Evidence for host-specificity, which is basic to our understanding of host to fungus ratios, is therefore explored in this review. There is considerable evidence that some endophytes, pathogens and mycorrhizal fungi are host-specific. Host-specificity however, may be an unwise term for saprobic fungi, and ‘host-exclusivity’ and ‘host-recurrence’ may be more appropriate terms. Concepts of host-specificity, host-exclusivity and host-recurrence are therefore defined and discussed. Suggestions for future work needed in order to establish host-exclusivity and host-recurrence in saprobic fungi are made.

Reference strains of Rhizoctonia solani from AG-1 1A, -1–1B, 1–1C, 2–1, 2–2, and 3 to 9, isolates of AG-1 1A from various rice growing countries and field isolates from a paddy rice field experiment in Côte d'Ivoire were analysed by pectin enzyme analysis. A subset of these isolates was also analysed by A+T-rich DNA (AT-DNA) RFLPs, both with the objectives to study the diversity at various taxonomic levels and to obtain a clearer picture of the relationships between these isolates. Field isolates were submitted to simple sequence repeat PCR (SSR-PCR). Pectin enzyme analysis as well as AT-DNA RFLP showed that isolates of different anastomosis groups generated very distinct patterns. Isolates of AG-1 1A from various countries had a lower degree of variability in zymogram patterns and AT-DNA RFLPS, while zymograms and AT-DNA RFLPs of field isolates obtained from one field experiment consisted of one identical pattern. However, these isolates showed variation in RFLPs obtained through SSR-PCR, indicating that they were not clones sensu stricto.

Fungal communities on decaying fronds of Livistona australis, Oraniopsis appendiculata (Australia), Arenga engleri, Livistona chinensis (Hong Kong), Arenga undulatifolia, Salacca affinis, and Oncosperma horridum (Brunei) were examined for fungi. In all, 288 different taxa were identified. The fungal communities on different frond parts (i.e. leaves, rachis-tips, mid-rachides and rachis-bases), on different hosts, at different sampling sites, at different stages of decay, and in different seasons were compared.

Fungal species compositions were distinct on different hosts and at different sites. Three-dimensional correspondence analysis resulted in: (a) three clusters corresponding to distinct communities on samples in Australia, Brunei and Hong Kong; (b) fungi on palms of the same genera (Arenga undulatifolia and A. engleri; Livistona australis and L. chinensis) at different sites, being more coherent than on palms of different genera at different sites; (c) fungi on palms of different genera at the same site being more coherent than on palms of the same genera at different sites. Fungal taxa on the same palm genus or species in different sampling sites were significantly different. Evidence for host specificity and fungal recurrence on different hosts and frond parts were found. No evidence of seasonal patterns of fungal communities was found on the palm hosts. Only 10% of the fungi were common to all three palm species studied in Brunei and 17% were common to the two palm species at Victoria Peak, Hong Kong.

Significant differences were found in the fungal communities colonising each of the different frond parts (leaves, rachis-tips, mid-rachides and rachis-bases). The greatest differences in most palms were found between the leaves and rachides.

When investigating fungal diversity it is recommended to examine a combination of naturally occurring fronds and frond baits throughout the decomposition process. Since a large number of forests, plant species and even types of plant tissues have yet to be explored by mycologists, we predict that there are an incredibly large number of fungi on these unexplored substrata.

This study has confirmed that fungi on palms are very diverse and suggests some reasons for this. The data has important implications towards future biodiversity studies and estimates of global fungal numbers. Future studies and estimations must reflect and incorporate these results.

Patterns of protein expression in the monokaryons and the derived dikaryon of the basidiomycete Flammulina velutipes were investigated using two-dimensional polyacrylamide gel electrophoresis and silver staining. Over 300 spots were detected on each gel, and 19 proteins were expressed in the dikaryon before fruiting treatment but not expressed in the monokaryon before fruiting treatment. On the other hand, 9 proteins were expressed in the monokaryon specifically. Newly expressed proteins increased after fruiting treatment (at 7 d and 14 d), but decreased after fruit bodies were formed (at 21 d). The number of newly expressed proteins after the fruiting treatment was similar in the monokaryon. Proteins expressed characteristically were classified into 7 types. The highest number of proteins (13 proteins) were specifically expressed in the dikaryon at 14 d when the fruit-bodies were formed. Twenty-seven proteins were expressed specifically in the fruit body. Fruit body specific proteins Pf1 and Pf3 were sequenced. This revealed Pf1 and Pf3 had amino acid sequences that were similar to each other, as well as a high similarity to the deduced amino acid sequence of the FDS gene isolated from F. velutipes.

The ITS II and the first part of the LSU rDNA were amplified from 26 isolates within the genus Entomophthora. The specificity of the primers allowed the use of both in vivo and in vitro material. Size polymorphism and long amplification of the ITS II regions, ranging from 1200 to 2000 bp, were observed. The PCR-products were cut with eight different restriction endonucleases and analysed by UPGMA, one analysis from each of the two regions. Conidial morphology was of predictive value for the overall taxonomy of the genus Entomophthora, as the genus clustered together in the analysis of the LSU rDNA. In both analyses the E. muscae complex clustered into three different clades, which support the validity of E. schizophorae and E. syrphi as separate species. Considerable variation was detected in the E. muscae clade, but it could not be grouped by host, geographic origin or conidial morphology, though the E. muscae s. str. isolates in both analyses grouped together. One isolate with E. muscae-like conidia found on Hymenoptera clustered out within the E. muscae clade, widening the host range for E. muscae significantly.

The genus Paraphaeosphaeria (Loculoascomycetes) was described as a segregate of Leptosphaeria for species producing brown, usually punctate ascospores with rounded ends, a submedian primary septum, an inflated cell above the primary septum, and a Coniothyrium sensu lato anamorph. This study evaluated the taxonomic value of the morphological characters, host range, ecology, and anamorphs in relation to DNA sequence data in order to determine the relationship between species described in Paraphaeosphaeria. Nine species were characterized morphologically and the ITS and 18S regions of the rDNA were sequenced and a phylogeny was inferred. Morphological studies and results of the sequence analyses provide strong support for polyphyly of this genus. Based on these analyses, the concept of Paraphaeosphaeria should be narrowed to reflect a monophyletic generic concept. Characters such as spore septation and method of conidiogenesis were found to predict relatedness.

Development of the powdery mildew fungus Sphaerotheca fusca on leaves of susceptible, resistant and temperature-sensitive resistant melon cultivars at 21 °C and 26 ° was examined by light and scanning electron microscopy. On the susceptible cv. ‘Rochet’ the time course of the infection process was similar at each temperature. Development of powdery mildew colonies paralleled the progressive branching of mycelia and conidiophore formation. On the resistant cv. PMR-6, however, development was arrested at the primary appressorium stage irrespective of the temperature. When the temperature-sensitive resistant line ANC-57 was infected by a race 1 isolate, incubation temperature had a clear effect on the outcome of the interaction. At 21 °, it took longer for symptoms to appear on cv. ANC-57 than on cv. ‘Rochet’, while colonies were limited and sparse. At 26 ° resistance was complete, there being no development.

The causal agent of tobacco anthracnose was identified as Colletotrichum destructivum based on the morphology of the fungus and a comparison of the sequence of the rDNA ITS with those of other Colletotrichum species. The infection process on tobacco (Nicotiana tabacum and N. benthamiana) was examined by light microscopy, which revealed that the pathogen acted as an intracellular hemibiotroph. Penetration occurred preferentially at the anticlinal walls of epidermal cells by an appressorium and penetration peg. An infection vesicle formed in the penetrated host cell by 48 h after inoculation, and out of this, a multi-lobed infection vesicle grew which remained limited to the initially infected cell. The interaction at this point was biotrophic, which was confirmed by plasmolysis and accumulation of a vital stain by the infected host cells. Thin secondary hyphae arose from multi-lobed infection vesicles at 60 h after inoculation, which then penetrated the host cell wall and began the necrotrophic phase of the infection. Acervuli formed on the plant surface by 96 h after inoculation, typically with a single melanized seta. In addition to tobacco, the fungus could infect alfalfa, cowpea, and Medicago truncatula, but not soybean. The process of infection of C. destructivum in tobacco was very similar to that previously reported in alfalfa and cowpea.

A world-wide study of the Oidium species causing economic damage on tomato has identified two taxa using classical morphological, scanning electron microscope (SEM) and molecular phylogenetic analyses. The material consisted of a total of 25 tomato powdery mildew isolates and 29 herbarium specimens coming from all continents where tomatoes are grown. A taxon with non-catenate conidia widespread in Europe, Africa, North and South America and Asia was identified as an O. subgen. Pseudoidium species (teleomorph: Erysiphe sect. Erysiphe). Formerly mistaken for O. lycopersicum (or O. lycopersici), it is now recognised as a distinct species, O. neolycopersici sp. nov. A phylogenetic analysis of the internal transcribed spacer (ITS) sequences of the ribosomal DNA (rDNA) indicated that O. neolycopersici is closely related to Erysiphe macleayae, E. aquilegiae and other Pseudoidium species. Only a taxon with catenate conidia was found on Australian specimens. This was identified as a species of O. subgen. Reticuloidium (teleomorph: Golovinomyces sp.). Phylogenetic analysis of the rDNA ITS sequences showed that this species is closely related to O. longipes infecting eggplant. Because it is most likely to be the same species as the original O. lycopersicum, which was actually first described in Australia, this is here neotypified as O. lycopersici.

Five murine hybridoma cell lines secreting monoclonal antibodies (MAbs) with similar binding specificities were raised to extracts from cyclamen leaves colonized with Ulocladium atrum, a saprotrophic fungus used for biological control of Botrytis cinerea. One of the cell lines produced a MAb, UA–PC3, which was used to develop a quantitative ELISA to determine the biomass of U. atrum in extracts from colonized leaves. The antigen, which is water soluble, was present on the surface of conidia and hyphae and was secreted into culture fluids. Production of the antigen was much greater in vivo than in vitro. Germination of conidia took place in saline buffers at 4 °C after 6 h. To avoid amplification of the antigen in biomass assays of the fungus in extracts from sporulating tissues, coating of microtitre wells in ELISA was reduced to 1 h.

Aquatic hyphomycete assemblages on different types of plant litter in Belarus rivers and streams were investigated to determine whether any substrate specificity or preferences were apparent. Pooled samples (146) from 92 watercourses were analysed. Colonization coefficients were computed for each fungal taxa and substrate type and the resulting matrix analysed with principal component analysis and cluster analysis. The results demonstrate that some substrates support relatively specific aquatic hyphomycete assemblages and it is possible to ordinate plant litter types by means of their fungal complexes. This suggests selective colonization by fungi, i.e. substrate preferences at least in some species. Wood and grass blades bear fungal assemblages clearly distinct from those supported by tree leaf litter (with higher percentage of scolecosporous and antagonistic species). Ordination of plant litter types could be explained by size of substrate units, their chemical composition (in particular lignin content) and, consequently, breakdown rate that affects fungal colonization.

AFLP (amplified fragments length polymorphism) and ISSR (inter simple sequence repeat) analyses were used to detect genetic diversity among 46 Phialophora gregata isolates including 41 from soybean, four from mung bean, and one from adzuki bean. Five AFLP primers amplified 55 fragments, of which 20 bands were polymorphic. Thirteen ISSR primers amplified 66 fragments, of which 45 bands were polymorphic. The ISSR technique detected more polymorphism than the AFLP technique did. A UPGMA (unweighted pair-group arithmetic mean) dendrogram was constructed based on the 121 amplified fragments with AFLP and ISSR primers to depict genetic diversity and relationships among the 46 isolates. Various levels of DNA polymorphism were detected among P. gregata isolates from soybean and mung bean. The estimated average genetic diversity is 0.079 for the population of 45 isolates from soybean and mung bean. The ISSR technique was shown to be more effective and economic than the AFLP technique in detecting genetic variation in P. gregata.

Cordyceps sinensis, the caterpillar fungus in traditional Chinese medicine, has been intensively collected from nature in recent years. As a result, the establishment of the anamorph of this species has become important for large-scale culture to meet increasing demand for medicinal use and to ease exploitation of natural populations. To establish a reliable connection between the teleomorph and anamorph stages, the ITS nrDNA sequences were sequenced from both the stroma of the telemorph and cultures of the anamorph. Observations of microcyclic conidiation were also made on germinated ascospores and compared with the anamorph in culture. Hirsutella sinensis was confirmed as the anamorph of C. sinensis by both DNA sequences and microcyclic conidiation. Two recently described species, C. multiaxialis and C. nepalensis, were shown to share identical or almost identical ITS sequences with C. sinensis. These minor variations were considered to be within the range of variation exhibited within a species, but representing different populations. Sequences from other Cordyceps species included in this study exhibited considerable differences from each other. Therefore, these three entities are probably conspecific, and the names should be regarded as synonymous. The morphological characters used in the description of the two new species are discussed. It is suggested that ITS sequences provided useful information on establishing the anamorph–telemorph connection and assisting in the delimitation of species within Cordyceps.

Relationships between Serpula lacrymans and S. himantioides isolates of ‘wild’ Himalayan woodland and building (European and Australian) origin were examined using RAPD–PCR and ITS rDNA sequence comparison. GelCompar analysis of the genetic fingerprints of eighteen isolates using four RAPD-primer combinations clearly distinguished S. lacrymans and S. himantioides. Little intraspecific variation was observed in S. lacrymans (including isolates of Himalayan woodland origin), relative to S. himantioides. Despite previously reported differences in growth rates and decay capabilities of ‘wild’ Himalayan woodland S. lacrymans isolates and those from buildings, RAPD fingerprints and ITS sequences indicated they were genetically similar. Interspecific ITS sequence polymorphisms were consistent with other studies and clearly demonstrated S. himantioides and S. lacrymans were distinct taxa. Evolutionary questions regarding the origins of S. lacrymans are discussed.