Phomopsis cucurbitae is a latent infection fungus which causes muskmelon fruit decay only after harvest. It can cause severe losses during fruit storage and marketing in the U.S.A., Japan and some Central American countries. Previous studies showed that P. cucurbitae produced polygalacturonase (PG) in both culture and muskmelon fruit tissue. In this study, a prominent PG isozyme (PG1) produced by P. cucurbitae in decayed fruit was purified to homogeneity by a procedure of extraction, ultrafiltration, preparative isoelectric focusing, anion exchange, and gel filtration chromatography. The isozyme had a primary endo-activity, a relative molecular weight of 54 kD according to SDS-PAGE, and a pI of 4·2 based on IEF-PAGE. The isozyme was active in a low pH range from 2 to 6, and was optimum at pH 5. Optimum temperature for the activity of PG1 was 40–45°C. The Km and Vmax on polygalacturonic acid were 44·7 μg ml−1 and 0·14 U μg−1 enzyme, respectively. The purified PG1 effectively macerated mature fruit tissue, suggesting that the isozyme may be involved in the pathogenesis of Phomopsis fruit rot of muskmelon.

The ability of the maize pathogen Fusarium subglutinans to metabolize benzoxazolin-2(3H)-one (BOA) and 6-methoxybenzoxazolin- 2(3H)-one (MBOA), important allelochemicals of Zea mays, was studied. Growth of mycelium was completely inhibited by 10 mM BOA and reduced by lower concentrations. In vitro the fungus completely degraded 1 mM concentrations of BOA and MBOA within 2 d. N-(2-hydroxyphenyl)-malonamic acid and N-(2-hydroxy-4-methoxyphenyl)-malonamic acid were identified as the main degradation products of these allelochemicals.

Cladistic analysis of nucleotide characters derived from partial 18S rDNA sequences has been used to infer phylogenetic relationships among five Candida species that exist in nature strictly as intracellular gut endocytobionts of anobiid or cerambycid beetles. Concordant with their assumed taxonomic status, all five species resolve within Saccharomycetales. For both the anobiid-derived taxa, C. ernobii, C. karawaeiwii and C. xestobii, and the cerambycid-derived taxa, C. tenuis and C. rhagii, this phylogenetic position clearly discriminates Candida yeasts from the anobiid yeast-like endocytobionts in Symbiotaphrina which resolve within filamentous ascomycetes. The analyses provide no evidence for a discrete lineage of Candida endocytobionts within Saccharomycetales. Rather, each of the anobiid symbionts and the cerambycid-derived species resolve in separate clades. These data confirm the polyphyletic origins of intracellular symbioses between ascomycetes and Coleoptera and provide another example of convergent evolution in fungal-arthropod associations. The implications of the phylogenetic data for theories on the origins of endocytobiosis are discussed.

The diversity of Eutypa lata was studied in 56 isolates collected from Languedoc-Roussillon, France. The pathogenicity of isolates varied within a very broad range and was not influenced by the cultivar from which they originated. Using 27 RAPD markers, each isolate was identified as an unique genotype. Gene diversity averaged 0·292 for the regional population. Lack of gametic disequilibrium between RAPD loci supported the hypothesis of random mating. The RAPD analysis did not allow subdivision of the population according to geographic location, vine cv. or pathogenicity of E. lata. The composition of the community of fungi was studied in 116 vines showing eutypa dieback symptoms collected at several localities in the region. E. lata was recovered from 80% of the samples, from the sectorial brown lesion characteristic of the disease. This lesion was associated in half of the vines with a central zone of discoloured hard wood and/or a light-coloured lesion of soft consistency. E. lata was isolated alone from 124% of the vines and was associated in 67% of the vines with one, two or three of the following fungi: Sphaeropsis malorum, Phomopsis viticola, Gliocladium roseum, Phaeoacremonium chlamydosporum, P. aleophilum and Phellinus igniarius. The variation in symptoms observed in the vineyard may be partly explained by the wide genetic diversity in E. lata and differences in the composition and functioning of the fungal community.

Ceriporiopsis microporus sp. nov. and Tyromyces formosanus sp. nov., found growing saprotrophically on the decayed stems of Chamaecyparis formosensis and unidentified hardwood, respectively, in Taiwan are described and illustrated. C. microporus is distinguished by small hymenial pores and broadly ellipsoid to subglobose basidiospores. T. formosanus is characterized by large, broadly ellipsoid to subglobose basidiospores. Cultural characteristics are described for the two species.

The genetic relationships between several morphological groups recognized within Colletotrichum acutatum sensu lato were investigated using RAPD analysis and vegetative compatibility analysis. Isolates were examined from fruit rots originating in New Zealand and Australia, from Lupinus spp. in New Zealand, Canada, France and the U.K., and from Pinus radiata in New Zealand and Australia. The genetic distinctness of the groups recognized morphologically is confirmed. Two genetically distinct groups of C. acutatum-like pathogens are recognized from lupin, one comprising isolates from New Zealand and the U.K., the other isolates from Canada and France. C. acutatum f. sp. pineum isolates from New Zealand and Australia form two genetically distinct groups.

During growth of Agaricus bisporus fruit bodies the amount of active tyrosinase increased. The amount of active tyrosinase can be related to the degree of browning, as opposed to the fully activated tyrosinase level. Isoelectric focusing revealed that active and latent tyrosinase isoforms having different isoelectric points could be distinguished. The isoform composition was dependent on the tissue and developmental stage. In the later developmental stages new active isoforms appeared.

Laetiporus sulphureus causes heart-rot in deciduous trees and conifers. European isolates were examined using nuclear DNA markers as well as somatic and sexual compatibility. Pairing tests for somatic compatibility with isolates from 20 different host individuals revealed that each tree is normally colonized by a different genet. The hyphae are multinucleate, basidiospores are binucleate, and conidia contain 2–6 nuclei. Basidiospore germination was erratic, and no clear mating pattern was observed. In one case all single spore isolates from the same basidioma were compatible with each other. Single spore isolates from coniferous and from broadleaf trees were incompatible. The nuclear ribosomal DNA ITS regions from six isolates of different origin revealed nucleotide distances of up to 14·6%. Phylogenetic analysis resulted in a single clade for all isolates. Within this clade, a subclade including only the isolates from gymnosperm hosts was present, indicating that these isolates were derived from ancestral lines from broadleaf hosts. While there is evidence that more than one species or ecotype is represented within the current definition of L. sulphureus, circumscription of additional taxa, and separations within this taxon, remain unclear.

The teleomorphic state of the ericoid mycorrhizal Hymenoscyphus ericae is known only from the type deposition. The production of both the teleomorph and anamorph by an isolate recovered from Ledum groenlandicum collected in an acidic peatland in Alberta, Canada, provided an opportunity to describe and illustrate the holomorph for a North American collection as a new record and as a supplement to the original diagnosis. It also provided further evidence that Hymenoscyphus ericae and Scytalidium vaccinii represent states of a single species, a hypothesis that previously had been tested using nuclear ribosomal DNA analysis. Appropriate cultural conditions and the use of molecular markers are advocated in order to facilitate the identification of mycorrhizal isolates which often remain sterile in pure culture.

Fungi isolated from the leafy liverwort Cephaloziella exiliflora collected in Australia and continental Antarctica were compared with Hymenoscyphus ericae using internal transcribed spacer (ITS) region DNA sequences. The isolates displayed <2·1% sequence divergence within the ITS region, indicating that the endophytes from C. exiliflora are probably H. ericae. The data significantly extend the known host range and geographical distribution of H. ericae and indicate that the fungus has a global distribution.

A new species of Crocicreas is reported on overwintered stems of Epifagus virginianus in New York State in apparently non-organic association with sclerotia of Sclerotium orobanches, itself a rarely reported fungus. The changing concepts of the generic names Crocicreas and Cyathicula are discussed in regard to placement of the new taxon.

Arbuscular (AM) mycorrhizal fungi form symbiotic associations with the roots of plants that lead to increased growth and health of many plants. The agricultural application of mycorrhizas has remained difficult since AM fungi are obligate biotrophs that show only very limited growth in the absence of a host. As a first step in the molecular and genetic characterization of these fungi we have constructed genomic libraries of Glomus versiforme and Gigaspora margarita. We demonstrated that in addition to fungal genes these libraries contain clones derived from the genome of endosymbiotic bacteria that are present in fungal spores. A genomic clone encoding elongation factor 1 alpha (EF-1) was isolated from G. versiforme and to our knowledge this is the first time a low copy number gene was cloned from an AM fungus. The EF-1 promoter is highly active in mycorrhizal roots and will be an important tool for the expression of foreign genes in the fungus.

The time course of release of an extracellular matrix (ECM) from conidia of the barley powdery mildew pathogen Blumeria graminis was investigated by scanning electron and light microscopy. Conidia released the ECM material preferentially onto a hydrophobic surface and release was detected within 20 s of contact of a conidium with the substratum. No such rapid release of an ECM could be detected when conidia were deposited onto the hydrophilic surface of clean glass. A limited amount of ECM was, however, released from conidia onto the hydrophilic surface of a hydrated cellulose membrane. A time study on hydrophobic plastic revealed that although the ECM was clearly present within the first hour after contact of the conidium with the substratum, it was much reduced in quantity after 12 h incubation. The ECM was demonstrated by micromanipulation and light microscopy to be present as a liquid at the contact interface of the conidium and the substratum. The ECM could not be detected by SEM beneath conidia on leaves, but light microscopy and micromanipulation demonstrated that the ECM could be detected beneath some conidia on the waxy surface of an epidermal strip taken from the abaxial surface of a barley leaf. The ECM material stained positively for protein and could not be removed from the conidium interface by vacuum desiccation in the scanning electron microscope indicating that the ECM is not simply water.

The avidity of conidia and 48-h-old germlings of Coniothyrium minitans for FITC-conjugated lectins was characterised by flow cytometry and digital microscopy. Six isolates of C. minitans representing three morphological types were compared. Binding of Con A, SBA and WGA by conidial populations varied markedly in extent and pattern between isolates, however, with increasing culture age, conidia from all isolates demonstrated a significant reduction in lectin avidity. Germling isolates bound significantly different amounts of lectins and lectin binding differed significantly with locality. Spore walls of all germlings from all isolates bound more Con A compared with hyphal apices and mature hyphal walls. In contrast, hyphal apices of the majority of germling isolates, readily bound SBA and mature hyphal walls of germling isolates bound more WGA than other regions of the germlings. Such differential lectin binding by conidia and germlings may influence their specific surface interactions and adherence characteristics.

A preliminary physiological characterization of osmoregulation in an Aspergillus nidulans salt sensitive mutant carrying cotransformed DNA sequences from the marine hyphomycete Dendryphiella salina is described. A genomic DNA library made in lambda EMBL3 was cotransformed with the plasmid pDJB3 into an A. nidulans host carrying a selectable marker for transformation (pyrG89) and a salt sensitivity mutation (sltA1). In some cases D. salina clones appeared to directly complement the salt sensitivity mutation by restoring salt and arginine insensitivity. Other clones gave marked increases in salt tolerance and yet the hosts remained arginine sensitive. Improvements in salt tolerance correlated with an enhanced ability to induce polyol biosynthesis during salt challenge.

Leaves of members of the Cruciferae influence the germination of the entomogenous fungus Metarhizium anisopliae. The percentage germination of conidia on reconstituted epicuticular waxes of oilseed rape, Chinese cabbage, and turnip was influenced by the solvent used, the plant species, and the age of the leaf. The epicuticular waxes contain a mixture of stimulatory and inhibitory compounds. Germination was more rapid and greater on the surfaces of dewaxed than intact leaves suggesting that epicuticular waxes contain fungistatic compounds and/or act as a barrier to the leaching of nutrients. Surface leachates and soluble extracts of leaves increased percentage germination of conidia and the virulence of M. anisopliae to the mustard beetle, Phaedon cochleariae. Plant extracts stimulated germination more than yeast or starch extract. Formulation of conidia in leachates or leaf extracts increased the virulence of M. anisopliae. Germination increased on insect cuticle that were pretreated with leaf extracts/leachates, suggesting that the insect cuticle will adsorb or sequester nutrients.

The 18S rDNA data base for mainstream Peronosporomycetes has been substantially increased. The sub-class divide between the Peronosporomycetidae and the Saprolegniomycetidae is supported. The deep clade separation of the Leptomitales within the Peronosporomycetidae is reinforced and support is provided for divergences within the Phytophthora and Pythium lines. A new family for the Leptolegnia lineage is proposed from the Saprolegniaceae sensu lato.

Somatic compatibility is used to identify clones or vegetative compatibility groups (VCG) in fungal populations. For basidiomycetes, VCGs have normally been associated with either homothallic, non-outcrossing fungi or root decay fungi spreading by vegetative growth. A special instance is provided by the symbiotic relationships between woodwasps and the fungi Amylostereum areolatum and A. chailletii. This association results in clonal propagation, as the wasps (Sirex sp. and Urocerus sp.) transfer arthrospores of A. areolatum or A. chailletii during ovipositing in conifers. Identical isolates of the symbiont are normally carried by all the female offspring of one wasp. The presence of clones of A. areolatum and A. chailletii was tested through somatic compatibility shown in pairings of heterokaryons obtained from wasps, basidiocarps and wood. Isolates found more than 100 km apart within Denmark belonged to the same vegetative compatibility groups. In addition, A. areolatum isolates from Sweden and Lithuania were compatible with a Danish clone, in spite of the barrier of the Baltic Sea. The association between woodwasps and fungi thus creates dispersive clones or VCGs which are stable across time and space. The dispersal through basidiospores may be considered of less importance for A. areolatum, but common in A. chailletii.

Phylogenetic analyses of partial sequences (1002 basepairs) from the nuclear encoded small subunit ribosomal RNA (18S rRNA) were performed to determine the phylogenetic relationships of the ascostromatic fungi, Botryosphaeria, Guignardia, Leptosphaerulina, Didymella, Venturia, Sporormia, and Sporormiella. Our studies confirm the concept that the subclass Loculoascomycetidae is paraphyletic if Chaetothyriales is included, as this order and the plectomycetes constitute a monophyletic clade that is highly supported in our and some previous phylogenetic analyses. In general, taxa that lack pseudoparaphyses (Dothideales) or have reduced hamathecial tissue, such as Botryosphaeria and Guignardia (sensu Sivanesan), are a sister group to the Pleosporales, the most derived group, whose members have pseudoparaphyses. The two species of Leptosphaerulina, which also lack pseudoparaphyses, clustered within the Pleosporales, rather than within the Dothideales, with high confidence from bootstrap values. Didymella nested within the Pleosporales with a high degree of confidence, and is the sister group to Leptosphaerulina. The taxonomic placement of Venturia and Sporormiella corresponds to the Pleosporales.

Morphological variation of germ tubes originating from aeciospores of Peridermium pini and Cronartium flaccidum populations on Pinus sylvestris was investigated in rust populations from Finland, the United Kingdom and Italy. The observed morphological variation was generally higher among than between these rust populations. The variation in germ tube length of the rust samples was high over the incubation period. Peridermium pini could not be distinguished from C. flaccidum based on its germ tube morphology.