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Molecular studies examine the relationships of Rhynchosporium secalis, the species concepts in the Fusarium avenaceum/F. arthrosporioides/F. tricinctum species complex, and the intra- and intersporal genetic diversity of Glomus intraradices. The amino acid sequence of the RAD51 protein in Pleurotus ostreatus has been determined and compared to that in other fungi.

The growth of Fusarium sambucinum is shown to be inhibited by several salts. The effects of moisture and oxygen availability on rhizomorph generation in Armillaria tabescens have been compared with that of other species, and the growth, and appressorial formation in Metarhizium anisopliae was found to be affected by artificial media on which it is grown. The possibilities for the biocontrol of Botrytis cinerea using Ulocladium atrum as an antagonist have also been investigated.

Glycoproteins in the extracellular matrix formed around germ-tubes and appressoria in Colletotrichum lindemuthianum have been examined and compared with those in other species.

Sorosporella is found to be a synonym of Syngliocladium, and a new species with two varieties described from grasshoppers and locusts. The causal agent of a twig dieback of lingonberry is found to be a previously unrecognised Phomopsis species.

The following new scientific names are introduced: Phomopsis columnaris, and Syngliocladium acridiorum spp. nov.; and S. acridiorum var. madagascariensis var. nov.

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.

Differences in morphology, ITS, IGS, mtSSU and β-tubulin sequences and UP–PCR hybridization were compared between morphologically identified F. avenaceum, F. arthrosporioides, F. anguioides, F. tricinctum, F. graminum and F. acuminatum strains. According to the combined β-tubulin, IGS and ITS tree, the strains of the Fusarium avenaceum/F. arthrosporioides/F. tricinctum species complex species can be divided into seven clusters supported by bootstrap values higher than 50%. The two main groups of European F. avenaceum, which cannot be distinguished by morphology, were separated in the tree based on β-tubulin sequences and less clearly in trees based on IGS and ITS sequences. MtSSU sequences were identical in all F. avenaceum and F. tricinctum strains studied. The European F. avenaceum strains of main group II had identical β-tubulin sequences with one American F. avenaceum strain and four European F. arthrosporioides strains, while F. avenaceum strains of main group I were closely related to two European F. arthrosporioides strains and to one Japanese F. anguioides strain. According to the combined β-tubulin/IGS/ITS sequence tree, European F. arthrosporioides strains were divided into four groups; F. tricinctum strains formed a well-supported cluster, in which two European clusters were separated from one African isolate. In the IGS sequence tree two European F. acuminatum strains together with one American F. acuminatum strain formed a cluster, which was separate from another American F. acuminatum strain. The F. acuminatum cluster was nested within the large F. tricinctum cluster together with one F. reticulatum strain in the combined IGS/β-tubulin tree. Several strains may be intermediates between the F. avenaceum/F. arthrosporioides/F. anguioides and F. tricinctum clusters and represent their own species. These results are partially supported by the results of UP–PCR hybridization analysis. Thus the molecular results may be helpful in future revision in the taxonomy of these species.

The level of molecular variability in the arbuscular mycorrhizal fungus (AMF) Glomus intraradices was assessed. We established several monoxenically growing single-spore cultures of the G. intraradices collected from a long-term soil tillage experiment in Tänikon (Switzerland). They were grown in symbiosis with Ri T-DNA transformed carrot roots. The ITS region was amplified from genomic DNA of fungal spores using ITS1 and ITS4 primers. The amplified ITS region of three of the fungal isolates was cloned and sequenced. All sequences obtained from our samples closely resembled those previously reported for G. intraradices, and no evidence for genetic exchange was found on the interspecific or intergeneric level. Phylogenetic analysis showed the presence of at least two different sequence families within a single-spore isolate. The single strand conformation polymorphism (SSCP) method detected different sequence types in a single PCR sample. This technique enabled us to detect several distinct ITS sequences within each of the single-spore isolates of the AMF. Estimates of intra- and intersporal sequence diversity were obtained by comparing diversity within and among the single-spore isolates. A higher level of diversity was found among spores than within a single spore.

Using degenerated primers for conserved regions of RecA homologs we have isolated a gene from Pleurotus ostreatus that shows characteristic features of RAD51 homologs. The encoded amino acid sequence of P. ostreatusRAD51 (PoRAD51) shows greatest sequence similarities with RAD51 from Coprinus cinereus (89% identity). Furthermore the genomic organisation of PoRAD51 is almost identical to that of RAD51 from C. cinereus. Northern analysis shows that the expression of PoRAD51 is found in vegetative mycelium, and fruit body tissue, and that it is expressed at elevated levels in lamellae/basidia and following DNA damage. A sporulation deficient mutant strain of P. ostreatus (ATTC 58937) showed expression patterns of the RAD51 gene that are similar those of the normal sporulating strain.

Potato dry rot, caused by Fusarium sambucinum, is a major postharvest disease of economic significance worldwide. Postharvest application of thiabendazole to control dry rot is becoming less effective since many strains of F. sambucinum have become resistant to this fungicide. Thus, alternative control strategies are needed. In vitro studies showed that several salts (0.2 M) inhibited completely mycelial growth and spore germination of F. sambucinum. Among these salts, sodium benzoate, sodium metabisulfite, potassium sorbate, trisodium phosphate and aluminium salts were fungitoxic. In vivo studies showed that aluminium chloride in curative application and sodium metabisulfite, sodium carbonate and sodium bicarbonate in preventive application significantly reduced the development of dry rot in potato tuber. Results from this study demonstrate that selected salts can be used to control potato dry rot.

Compared with other Armillaria species, natural melanized rhizomorphs of A. tabescens are rarely observed. Growing in autoclaved Vitis stem segments, A. tabescens isolates from the Ozark Mountains in the central USA formed fully melanized rhizomorphs, thinner and shorter than those observed for other Armillaria species under field conditions, and only under conditions of both high oxygen availability, [ges ]2 μg cm−2 min−1 and moisture near saturation. Conducive conditions were used to compare the rhizomorph generation capacities of A. tabescens, A. gallica, and A. mellea, which have overlapping host and geographic ranges in central North America. While the rhizomorphs of A. tabescens were significantly shorter than those of the other two species, A. gallica and A. tabescens produced similar numbers of rhizomorph initials. Finally, we demonstrated the ability of melanized A. tabescens rhizomorphs to span woody food bases and thereby establish viable infections by penetration of intact bark of Vitis stem segments. We hypothesize that A. tabescens rhizomorphs form under conditions of periodic saturation which promote rapid water movement through naturally occurring lacunae in the soil. Thus, the role of A. tabescens rhizomorphs in the spread of the fungus should be re-evaluated.

Culture media influenced the germination of conidia, appressorial development and mycelial growth of Metarhizium anisopliae. Although the addition of KCl to Sabouraud dextrose agar (SDAM) significantly reduced germination of the conidia of three isolates in vitro and lowered germination and appressorial development on the cuticles of Myzus persicae and Meligethes aeneus, conidia grown on SDAM and minimal medium (MM) were more aggressive than conidia derived from SDA or yeast extract agar. No relationship was found between either germination or appressorial development and LT50 values, suggesting that virulence depends on the speed of infection. Calcofluor staining and lectin binding showed that culture conditions also influenced the adhesion of Metarhizium anisopliae to insect cuticles through alteration of surface carbohydrates such as 1-4-β-glucans. Dark, pigmented conidia from MM bound less lectins and calcofluor whereas the paler conidia from the other media fluoresced more intensely. Conidia from SDAM fluoresced 20-fold brighter and adhered more readily to insect cuticle compared with conidia derived from MM. Although inocula from both media showed elevated pathogenic activity against aphid and pollen beetle, MM-grown conidia were more aggressive since high mortality was induced by comparatively fewer conidia. When fluorescent intensity of calcofluor-stained conidia was compared to the number of conidia adhering to the insect cuticles, the relationship was significant, indicating that this dye has practical implications for the assessment of fungal strains in screening programmes for commercial development.

The dynamics of competitive colonisation of necrotic cyclamen tissue by the plant pathogenic fungus Botrytis cinerea and the saprophytic fungal antagonist Ulocladium atrum were studied immuno-histologically, while sporulation was studied macroscopically. The effect of different time intervals between inoculation of both fungi on resource capture by each species was explored. Colonisation and sporulation were used as indicators for competitive resource capture and the effectiveness of biological control of B. cinerea, using U. atrum. Mycelial biomass and sporulation showed logistical time courses in both species, in monocultures as well as in mixed cultures. Final colonisation and sporulation levels were lowered by competition, indicating competitive resource capture. Analysis of the extent to which sporulation of either fungus could be reduced by co-inoculation with the other fungus at different times, showed that B. cinerea can be completely excluded by ‘early’ pre-inoculation with U. atrum, but not vice versa, indicating that U. atrum can exploit resources in the leaf that are not accessible to B. cinerea. A model of competitive substrate colonisation and resource capture was developed on the basis of the experimental results. Model results confirm that competition for resources provides a sufficient biological explanation for the dynamic interactions between the fungi. The model provides a tool to optimise dose and timing of U. atrum applications providing effective biological control of B. cinerea.

A monoclonal antibody (MAb), UB31, is described that binds to the extracellular matrix (ECM) surrounding germ-tubes and appressoria, but not conidia, of the bean anthracnose fungus, Colletotrichum lindemuthianum. Comparative localisation studies with MAb UB26, which has the same cell type specificity, suggest that the ECM is heterogeneous in composition. Immunofluorescence showed that UB31 labelled appressoria more intensely than germ-tubes, whereas UB26 labelled these structures to a similar extent. Immunofluorescence and TEM-immunogold labelling showed that UB31 antigens were located close to the appressorial wall, while UB26 antigens extended further away from the wall. MAb UB31 bound to the ECMs of all six Colletotrichum species tested. Western blotting and ELISA indicated that the antibody recognises a high Mr glycoprotein (>200000) that may be linked to melanin. The glycoprotein recognised by UB31 was not removed from substrata by ultrasonication, suggesting it may contribute to germling adhesion.

The occurrence of disease outbreaks associated with the genus Sorosporella on grasshoppers and locusts (Orthoptera: Acridoidea) in Africa is reported. Infected hosts, representing ten genera within five acridoid subfamilies, are characterized by red, thick-walled chlamydospores which completely fill the cadaver. On selective media, the chlamydospores, up to seven-years-old, germinated to produce a Syngliocladium anamorph which is considered to be undescribed. The new species Syngliocladium acridiorum is described and two varieties are delimited: var. acridiorum, on various grasshopper and locust genera from the Sahelian region of West Africa; and, var. madagascariensis, on the Madagascan migratory locust. The ecology of these insect-fungal associations is discussed. Sorosporella is treated as a synonym of Syngliocladium.

A fungus was discovered causing a progressive twig dieback on stems of Vaccinium vitis-idaea (lingonberry) in Oregon. Both morphological and molecular data suggest that the fungus belongs in Diaporthe/Phomopsis but is distinct from P. vaccinii, cause of a dieback and fruit rot of blueberry and cranberry (Vaccinium spp.). This fungus is described and illustrated as a new species, Phomopsis columnaris. It is distinguished from other species of Phomopsis by the distinctive conidiophores that consist of vertically aligned cells lining the base and sides of the conidiomata. Another species of Phomopsis described on Vaccinium, Phomopsis myrtilli, known from V. myrtillus, is redescribed and illustrated based on authentic herbarium material.