Ultrastructural and cytochemical investigations of the interaction between Melampsora euphorbiae and its host Euphorbia peplus are described. Two types of collar around the haustorial neck could be recognized, corresponding to the maturity of the haustorium. Using various lectin-gold complexes as probes, different glycoconjugates were revealed in the fungus and host. Chitin was found in walls of uredinospores and intercellular hyphae but not of haustoria. d-glucose and/or d-mannose were strongly indicated in host starch grains and glycogen particles inside the intercellular hyphae, but only lightly in the fungal cytoplasm. Galactose residues and l-fucose were detected in fungal walls, more strongly in those of intercellular hyphae than haustoria. Galactose was also localized cytochemically in lomasome membranes of the fungus. β-Glucosides were detected in the fibrillar wall material bordering intercellular spaces of host tissue.

Based upon studies of type specimens six species of Stemonitales are redescribed and illustrated: Comatricha microcarpa, C. laxa, C. nigricapillitium, Stemonitis fusca and S. nigrescens are critically reviewed and illustrated. Comatricha microcarpa is considered to be a nomen ambiguum, and Stemonitis nigrescens is treated as an extreme form of S. fusca. S. virginiensis is recognized as a rare species distinct from the smaller forms of S. fusca. Comatricha nigricapillitium comb. nov. is proposed for Lamproderma nigricapillitium.

The arbuscular mycorrhizal (AM) fungus Glomus intraradices was grown in vitro with RIT-DNA transformed Daucus carota roots on plates divided into two compartments. One side of the plates contained only fungal hyphae and spores while the other contained mycorrhizal roots. Using this technique, the limitations of insufficient biological material available for molecular analysis of this obligate symbiont were overcome. Fungal material from the first compartment was used as a pure source of G. intraradices for genomic DNA extraction. PCR amplification as well as southern hybridization were conducted using this DNA. Sufficient pure genomic DNA and mRNA was obtained to carry out Southern analysis, achieve optimum PCR results with 25–35 cycles and conduct RT-PCR. Differential expression of chitin synthase class I and II was detected in G. intraradices. Using degenerate primers specific to fungal chitin synthase sequences, a single amplification product obtained after 25 cycles of PCR was cloned. Sequencing of this fragment revealed similarity to other fungal chitin synthase genes. PCR with these primers and additional primers allowed the amplification of chitin synthase fragments from spores of different isolates of G. intraradices as well as from G. mosseae, Gigaspora margarita, Acaulaspora scrobiculata, Scutellospora calospora and Entrophosphora colombiana. A total of 21 chitin synthase sequences from different species and isolates of various AM fungi were successfully amplified. Sequencing of these fragments permitted their classification into class I and II of the chitin synthase groups.

Field isolates of Rhizoctonia solani are presumed to consist of heterokaryotic cells, but the number of different nuclear types present in each cell is unknown, nor is it known if there is any regulation of the heterokaryotic state. To investigate the nature of heterokaryosis in AG 4, hyphal tip subcultures of two strains were examined using vegetative compatibility as a marker. Upon subculture, each isolate could be placed into one of two VCGs, members of which were compatible within the group but incompatible with those of the other group and the parent strain. No other phenotype could distinguish these groups from each other or the parents. Pairing of hyphal tip isolates never resulted in regeneration of the parental strain. Examination of nuclei in the tip cells of incompatible strains by DAPI staining and fluorescence microscopy showed variation in nuclear numbers in different parts of the fungal colony and a significant tendency for some adjacent branch tips to have a similar number of nuclei. These results suggest a mosaic of nuclear, and perhaps mitochondrial, types within the colony, and that subcultures of components of the mosaic retain their differences. This variation implies that regulation of nuclear number within a colony is loosely controlled.

The genus Agaricus encompasses the cultivated mushroom A. bisporus, and includes both unifactorial heterothallic and homothallic species. The intractable nature of their life cycles and an absence of diagnostic morphological features, hinder analysis of breeding systems in Agaricus and some other homobasidiomycete species. We utilised RAPD markers to assess genetic variation in single spore progeny from different Agaricus species and to confirm heterokaryon formation in matings. Single spore progeny from heterothallic species should be more heterogeneous than those from homothallics. Homokaryotic progeny from the secondarily homothallic A. bisporus were less variable (12%) with fewer segregating loci than the known heterothallic species, A. bitorquis (50%) and A. nivescens (32 %). Variation in the progeny of A. campestris (36%) was similar to that for the heterothallics. Heterothallism in the field mushroom was confirmed by RAPD analysis of putative matings; the first time A. campestris heterokaryons have been constructed. No variation was observed in progeny from two collections of A. subfloccosus. Homogeneity in RAPD profiles, absence of matings and self-fertility of single spores shows that A. subfloccosus is homothallic. In progeny from A. arvensis very low variation (5%) occurred and proportions of segregating loci were around half of those for A. bisporus. However, matings were observed and RAPD characterised within the A. arvensis progeny. RAPD analysis of genetic variation within spore progeny should have general utility in the characterisation of fungal breeding systems.

This paper describes digital image recording and measurement procedures of Fusarium species macroconidia with reference strains of F. avenaceum, F. culmorum, F. graminearum, F. oxysporum, F. sambucinum and Microdochium nivale. Computerized taxonomic recognition of the most important Fusarium species occuring on cereals was achieved by statistical tests based on morphometric parameters from macroconidia (numerical taxonomy). A first grouping resulted from Brandt-Snedecor contingency tests (χ2) indicating different frequency distributions of macroconidia with various numbers of septa. For discrimination and ranking within these groups by clustering procedures, analysis of variance and multiple comparison of means, deviation from circular (circular form factor) was most suitable out of 12 morphometric parameters tested on macroconidia of the most frequent septation classes.

Colletotrichum gloeosporioides f. sp. malvae (C. g. malvae) is effective in controlling round-leaved mallow (Malva pusilla), a common weed in the Canadian prairies. To confirm host range experiments, the latent period and penetration of C. g. malvae was determined under controlled environmental conditions on field crops (wheat, flax, lentil, mustard, rape seed, sugar beet, sunflower, safflower) and on crops in the Malvaceae (okra and cotton) as well as on round-leaved mallow, from which C. g. malvae was originally isolated. In non-target crop plants, very little germination, appressoria formation, or penetration of C. g. malvae were observed compared with the infection occurring on round-leaved mallow. Of the non-target species tested, most penetration was observed on safflower, with only 5·1% penetration form the total appressoria formed compared with 17% on round-leaved mallow. C. g. malvae was re-isolated from all crop cvs tested, but only from inoculated stems and leaves. The recovery of C. g. malvae significantly decreased with time of isolation of plant material for most cvs. Of the millions of conidia applied to non-target crops, only a few were present after 72 h, few appressoria were produced, and only minimal penetration occurred. The behaviour of C. g. malvae conidia on the surface of leaf material of non-target plants supports the visual disease ratings observed in the experiments of crop tolerance under controlled and field condition and host-range tests.

A comprehensive account of the 18 species of Ravenelia from Argentina is presented. Each species is described and illustrated. A key to the species of Ravenelia from Argentina is provided based on micromorphology. Ravenelia echinata var. ectypa and R. macrocarpa are recorded for the first time from Argentina. The name Ravenelia argentinensis was determined to belong to an anamorph, therefore the teleomorph is described as a new species, R. argentinica sp. nov. Several new anamorph/teleomorph connections were made. Names and synonyms for teleomorphs and anamorphs are listed for all species.

We report the ability of Conidiobolus adiaeretus to form repetitional microconidia and capilliconidia. Detailed descriptions of development and germination are given. This is the first report of any entomophthoralean fungus producing both these alternative conidial types. This cuts across current definitions of subgenera in Conidiobolus which are based on the absence of these conidial types or on the presence of either microconidia or capilliconidia but not both. Co-occurrence of both these spore types, along with the unusual mode of formation of the microconidia, and the ability to derive capilliconidia directly from the latter, reinforce other features which set C. adiaeretus apart. Taxonomic, evolutionary and ecological implications are briefly discussed.

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.

Olpidium paradoxum sp. nov. was found to attack adult loricate rotifers and their eggs in a sample of pond water in Japan. The fungus produced zoosporangia inside the host from which exit tubes of variable length grew to the outside environment. Pyriform zoospores with a single long posterior flagellum were released from the sporangia.

Gelasinospora bonaerensis sp. nov., isolated from a soil sample collected in Argentina, is described and illustrated and the sequences corresponding to the ITS1/ITS2 regions and the 5·8 S ribosomal RNA are provided. Its taxonomic relationships with other species of the genus are discussed.

Double-stranded RNA (dsRNA) elements of 8·3 and 5·5 kbp were detected in three of five geographically distinct isolates of Alternaria solani. Variation with respect to the number of dsRNA segments was detected among isolates of the fungus. No virus-like particles were purified from the mycelium, or observed in ultra-thin sections of hyphae. Utilizing differential centrifugation or density gradient centrifugation for subcellular fractionation, dsRNA was found associated specifically with fractions containing 80–100 nm spherical membrane vesicles. Similar vesicles were observed in cytoplasm of hyphae by electron microscopy. Treatment of dsRNA-containing fractions with ribonuclease A did not degrade the dsRNA, suggesting that it is located inside the vesicles. There was no correlation between the radial growth of the isolates in laboratory media and the presence or absence or dsRNA.

An EcoRI 1428 bp A+T-rich, DNA element (MYCDIRE: MYCorrhizal fungus DIspersed Repetitive Element) has been identified in the genome of Scutellospora castanea, an arbuscular mycorrhizal fungus. After sequencing, primers were designed and used in PCR reactions to amplify portions of this element in five species of arbuscular mycorrhizal fungi belonging to four genera of Glomales. Southern hybridizations and partial analysis of the main PCR products confirmed that this element was highly conserved in all the species. Southern blot analysis of single and double digested DNA from two of the glomalean fungi gave smears suggesting that MYCDIRE is scattered throughout the fungal genome. Sequence analyses revealed three copies of a previously reported autonomously replicating sequence (ARS) from Saccharomyces cerevisiae and comparisons indicated similarities of MYCDIRE with the autonomously replicating, A+T-rich element (ACARS) from Acremonium chrysogenum.

The genetics of somatic incompatibility in tetrapolar Collybia fusipes was studied using eight dikaryotic isolates collected from the wild and their experimentally derived progeny. Monokaryons from each isolate were all paired with the same unrelated monokaryon and also paired together in all combinations. The somatic compatibility of the two resulting sets of dikaryons was studied. Two different types of somatic incompatible interaction were observed, lightly or heavily pigmented lines developing between the two isolates. The dikaryons that had one nuclear type in common and one coming from sibling monokaryons were compatible in 7–27% of the cases, incompatible with a lightly pigmented interaction in 30–93% and incompatible with a heavily pigmented interaction in 0–53%. The results suggest that at least three to four loci control the somatic incompatibility in C. fusipes, one of them alone controlling the heavily pigmented interaction.

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

The coexistence in the same pycnidial conidioma of discrete ampulliform and hyaline conidiogenous cells and integrated conidiogenous cells on filiform, septate conidiophores, is described in Pyrenochaeta dolichi. A new Monodictys-like synanamorph is also reported in this species. Monodictys-like conidia are produced on lateral branches from the vegetative hyphae and germinate through the conidiogenous scar. The taxonomic position of P. dolichi is discussed since there is no suitable place for this fungus in the current systematic schemes for this group of fungi.

Most species in Ceratocystiopsis share many characters with species in Ophiostoma. Unlike other Ceratocystiopsis species, C. falcata appears to have enteroblastic conidium development and what appears to be a Chalara anamorph. Morphologically, Cp. falcata is thus more similar to Ceratocystis (with Chalara anamorphs) than Ophiostoma, although it is very distinct from Ceratocystis in perithecial characteristics. Recent studies using molecular data have shown that, despite its peripheral similarity to Ceratocystis, Cp. falcata is distantly related to either Ceratocystis or Ophiostoma. In view of this molecular evidence a new genus, Cornuvesica, is described for it, characterized by having falcate, sheathed and septate ascospores. The anamorph of Cornuvesica is morphologically similar to Chalara but conidia are obovoid with only one truncate end. Conidia are apparently not produced by ring wall building and Chalara is not an appropriate genus for it. We suggest that the anamorph of Cornuvesica represents a genus distinct from Chalara.

Four species of Biflagellospora are reported from submerged wood samples in Thailand. They are characterized by simple, cylindrical, mostly geniculate, brown conidiophores with one or more sub-hyaline to light-brown conidia bearing long filiform appendages on each of two terminal cells. B. japonica is a new record for Thailand. B. siamensis, B. papillata and B. gracilis are described as new species.