In a 3 year study of oak decline in Central and Southern Europe, a papillate homothallic Phytophthora species was isolated consistently, with other Phytophthora spp., from necrotic fine roots by direct plating on to selective agar medium and from rhizosphere soil samples by baiting with leaves of Quercus robur. The morphology, physiology, RAPD banding patterns and pathogenicity against apple fruits of this Phytophthora sp. are described and compared with those of other papillate Phytophthora species from Waterhouse's Group I, namely P. cactorum, P. clandestina, P. idaei, P. iranica, P. pseudotsugae and P. tentaculata, and semi-papillate Group III P. citricola. The papillate Phytophthora isolates from oak differed from all other Group I species by their uniform, dome-shaped and cottonwool-like colony growth pattern on V8 juice agar and malt extract agar, the frequent occurrence of sympodially branched primary hyphae, a high proportion of elongated, ellipsoid or ovoid oogonia, the absence of amphigynous antheridia and RAPD banding patterns. Additionally, there was no other species in Group I with as much variation in size and shape of the sporangia or large proportion of sporangia with a curved apex, hyphal projections, lateral displacement of the papilla and lateral attachment to the sporangiophore. In pathogenicity tests with infested soil, the isolates proved to be more pathogenic to Q. robur than any other Phytophthora sp. recovered from declining oaks in Central Europe. Based on their unique combination of cultural, sporangial and gametangial morphology, pathogenicity and close association with Quercus but not other trees, the papillate Phytophthora isolates from oak are described as Phytophthora quercina sp. nov.

Phytophthora quercina, a new species associated with oak decline in Europe, has been assigned to Waterhouse's Group I of Phytophthora. The level of intraspecific variation and evidence of affinities to other Group I species and another, as yet unidentified, species from oak, were examined at the molecular level using four random ten-mer primers to amplify total DNA (RAPDs). Sequences and restriction fragment length polymorphisms of a 900 bp PCR product consisting of the ITS1 and ITS2 regions, and the 5.8S subunit of ribosomal DNA were also examined to estimate relatedness to a broader range of Phytophthora species. The RAPD banding patterns of ten isolates of P. quercina from eight sites in Germany, Hungary and Italy were almost identical and distinct from all the other species tested. Their ITS restriction fragment patterns were also identical, as were the ITS sequences of four selected isolates. Phylogenetic analysis of the ITS sequence data confirmed its unique position in this section of the genus which comprises P. quercina, another five Group I species, P. infestans (Group IV) and P. nicotianae (Group II). Isolates of P. quercina formed a distinct branch at the base of this clade showing no close affinities with any other species. Such data support morphological, physiological and pathological evidence that P. quercina is distinct, although it has some affinity with the other Group I species. The results support earlier reports that Waterhouse's groupings of morphospecies do not fully correspond to phylogenetic relationships indicated by molecular studies. The unidentified Phytophthora sp. 2 from oak was closely related to P. ilicis (Group IV); both were distinct on molecular criteria from all other species in the study.

The ITS2 of rDNA of eight strains representing five controversial species and a variety of Cunninghamella, i.e. C. bertholletiae, C. blakesleeana, C. elegans, C. phaeospora var. phaeospora, C. phaeospora var. multiverticillata, and C. polymorpha, were amplified through PCR. The PCR products were purified and their sequences determined. Sequence variations among the three strains of C. elegans and between the two strains each of C. bertholletiae and C. polymorpha are less than 5%, while those among the other three strains each representing a different taxon as well as among these strains and the above mentioned five strains representing two different species are 14–32%. Sequence variations between each of the eight Cunninghamella strains and Rhizopus stolonifer var. lyococcos, used as outgroup, are more than 70%. These results confirm the value of sequence analyses of ITS2 rDNA in the taxonomy of Cunninghamella. C. polymorpha is proven to be synonymous with C. bertholletiae, while the others are considered to be distinct taxa. Phylogenetic analyses of the sequence data by the neighbour-joining method generally reflect the systematic relationship of different species based on morphologic studies made by our research group. The three strains of C. elegans, and the two strains each of C. bertholletiae and C. polymorpha (a synonym of C. bertholletiae) are respectively clustered in the same clade with high confidence, while the strains representing the two varieties of C. phaeospora are also clustered in the same clade though with relatively low bootstrap value and long distance which supports the establishment of the distinct varieties.

A particular group of saprotrophic and ectomycorrhizal fungi produced reproductive structures successively on the forest floor after treatment with some nitrogenous compounds (N compounds) such as urea and aqua ammonia. These fungi were also observed after the decomposition of dead bodies or faeces of animals. Their growth in pure culture was examined in liquid media containing ten different N sources (four inorganic and six organic). The saprotrophic Amblyosporium botrytis, Tephrocybe tesquorum, Coprinus echinosporus and C. phlyctidosporus grew well on ammonium, some amino acids (asparagine, glycine), urea and bovine serum albumin, although A. botrytis did not grow on bovine serum albumin. Coprinus phlyctidosporus grew on nitrate as well as on the above N compounds. Peziza urinophila and Pseudombrophila deerata did not grow on any of the N compounds examined. The ectomycorrhizal Laccaria bicolor, Hebeloma vinosophyllum and Hebeloma sp. showed different patterns of nitrogen utilization: L. bicolor grew well on ammonium, nitrate and urea; Hebeloma spp. grew well on ammonium, nitrate, amino acids, urea and bovine serum albumin. None of the fungi tested grew on ethylenediamine or putrescine. The patterns of growth in relation to the nature of nitrogen supply were discussed in relation to the conditions of soil where these fungi occur.

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.

Mycelial interactions were studied between 28 isolates of Amylostereum areolatum and 15 of A. chailletii from wounded spruce in 10 sample plots in Sweden and Lithuania. Based on somatic incompatibility, nine vegetative compatibility groups (VCGs) of A. areolatum were detected. Five of these VCGs were isolated from two or more trees and included 24 (86%) of all isolates. In A. chailletii, 12 VCGs were found and three contained two isolates each. Grouping of isolates into VCGs was more pronounced in A. areolatum. Two of the A. areolatum VCGs had wide geographical distribution. VCG A2 was isolated from 14 different trees in two Swedish and four Lithuanian sample plots. VCG A1 was found in one plot in Sweden and in two in Lithuania. VCGs of A. chailletii had a local distribution and were confined to a single sample plot or to a forest stand. In A. areolatum occurrence of compatible pairings between isolates was uniform in all spatial scales of investigation: within a plot, within each country and among both countries. The proportion of somatically compatible A. chailletii isolates was significantly lower and decreased with geographic distance.

Turturconchata reticulata gen. et sp. nov., isolated from the decaying stem of an herbaceous dicotyledon, is described and illustrated. It is characterized by dorsiventrally flattened olive brown conidia composed of 19–58 cells. The conidia are borne horizontally on a cuneiform basal cell originating from flexuous, curved to spiral, septate, simple or branched, indeterminate conidiogenous cells. The differences between T. reticulata and the morphologically or ontogenically somewhat related Canalisporium, Hermatomyces, Mycoenterolobium and Oncopodium are briefly discussed.

Isolates of Verticillium lecanii, from insects and other substrates, were tested for vegetative compatibility by observing heterokaryon formation among complementary nitrate-nonutilizing (nit) mutants, Among 33 V. lecanii isolates, 17 were self-incompatible. The 16 self-compatible isolates were divided into 13 vegetative compatibility groups (VCGs). Eleven VCGs were single-member VCGs, and the remaining two included two or three isolates each. Self-incompatibility occurred more frequently among isolates with abundant aerial mycelium, whereas most of the isolates with short or reduced aerial mycelium were self-compatible. Virulence to larvae of Bemisia tabaci ranged from 0 (four isolates) to 83% mortality 4 d after treatment with conidial suspensions. There was no correlation between the capacity of isolates to anastomose and their virulence to larvae of Bemisia tabaci: highly virulent isolates were found at similar frequencies among self-compatible and self-incompatible isolates. Those with abundant aerial mycelium were collectively more virulent (28·5% mortality) than those with reduced mycelium (10·7% mortality). Three isolates belong to VCG VL-11 were all highly virulent.

Genetic divergence among 57 isolates of Colletotrichum lindemuthianum collected in north, central and south America and The Netherlands was assessed on the basis of PCR-RFLP analysis and sequencing of the nuclear rDNA region of the two internal transcribed spacers (ITS 1 and ITS 2) and the 5·8S rRNA gene. A reproducible 0·58 kb fragment was amplified in all 57 isolates. Races of C. lindemuthianum formed two groups based on the restriction of the PCR-amplified ITS regions. Group I consisted mainly of Middle American races (65%), whereas 85% of Andean races belonged in group II. Genetic distances calculated from the sequence polymorphism in the rDNA region ranged from 0·2 to 1·8% among 14 isolates of C. lindemuthianum. The neighbour-joining and parsimony analyses of the sequence data showed no association of any particular ITS genotype with host gene pool, virulence or geographic origin of races. These data suggest that virulence can arise in different geographic areas at different times, independent of genetic background. Molecular polymorphism among isolates of races 7, 17, 31 and 73 collected in different countries was demonstrated by RFLP analysis of the ITS regions. A similar lack of agreement was observed in the sequence data between isolates of race 73 from Mexico and the United States and the Jukes–Cantor genetic distance between the isolates was large (0·9%). These findings support a level of molecular variability within C. lindemuthianum greater than the variability previously characterized by virulence analysis and suggest independent evolution of specific virulence patterns.

Hyphae of Saprolegnia ferax recovered from intracellular acidification with variable degrees of apical vacuolation and migration of cytoplasm out of the apex, prior to apical refilling and resumption of growth. The response was not due to alkalinization, but was generalized to recovery from diverse growth inhibitors including procaine, latrunculin B and the kinase inhibitor 6-dimethylaminopurine. The vacuoles apparently arise from expansion and fusion of apical tubular vacuoles. This process is mediated by microtubules, since their disruption suppresses apical vacuolation. The shape of the vacuoles appears to be F-actin imposed, because their expansion is enhanced by F-actin disruption. The accompanying, often bidirectional, cytoplasmic migrations are independent of tip growth, require F-actin, and probably represent part of a hypothetical generalized cytoplasmic avoidance response.

The effect of the environment on the germination, survival and infection of sorghum by conidia of Peronosclerospora sorghi is unknown in Africa. Dew point temperature, and the effect of conidium age was characterized for an isolate of P. sorghi from Zimbabwe. Germination and germ tube growth took place in the range 10–34°C (optimal at 10–34 and 20–33°, respectively). Infection was optimal at 14–30°. Incidence of infection at different temperatures was correlated with germ tube growth (r=0·8, P<0·001). Germination and germ tube growth occurred from 5 h after commencing incubation of infected leaf material, although immature conidia harvested at 3 h caused a low incidence of infection. Plant age also affected the incidence of infection. Container grown sorghum plants older than 20 d, and maize plants older than 15 d were resistant to systemic infection by conidia. The results indicate that germination, germ tube growth and infection take place over a wide temperature range, and that some limited biotypic variation may exist when these data are compared to other reports of the environmental requirements of P. sorghi from the U.S.A. and India.

Ultrastructure of the marine, bitunicate, ascomycete Julella avicenniae is presented and compared with the marine Pleospora gaudefroyi. Asci of J. avicenniae possess an ocular chamber, a thick endoascus, and a thinner ectoascus. Pseudoparaphyses are enveloped by mucilage (hyphal sheath) which stains with ruthenium red. The mucilage appears to be an extension of the pseudoparaphysis cell wall and internally these cells contain an array of vesicles. Muriform ascospores are surrounded by an exosporial sheath, an electron-dense episporium and a bilamellate mesosporium. Optimum conditions for growth are 25–30°C in 100% artificial seawater glucose- yeast extract-tryptone media, but the fungus also is able to grow at 35° and at higher salinities. The ability of the fungus to withstand extremes of environmental conditions is discussed.

The genetic variability within 600 bp of DNA sequence from the ribosomal internal transcribed spacers (ITS 1 and ITS 2) and the 5·8 S rRNA gene was examined in 52 strains belonging to 29 terverticillate taxa in Penicillium subg. Penicillium from diverse sources and locations. The sequenced region is extremely conserved within the terverticillate penicillia, with only 29 positions differing in one or more taxa. The highest degree of ITS variability was seen among the species close to Penicillium roqueforti (P. roqueforti, P. carneum and P. paneum) whereas the ITS variability was very low between closely related taxa, e.g. among the taxa near P. aurantiogriseum. The relationships among the terverticillate penicillia, and related teleomorphs in Eupenicillium, were analysed from bootstrapped ITS sequence data sets using the neighbour-joining method. The terverticillate penicillia form a well supported clade with Eupenicillium crustaceum. Sequence analysis generally confirmed the overall taxonomy in Penicillium subg. Penicillium but relationships between all the terverticillate taxa could not be clearly established due to the low degree of ITS variability. Nevertheless, clades of Penicillium species sharing environmental characteristics did emerge, e.g. species growing on protein and lipid rich substrates (e.g. P. crustosum and P. commune), species prevalent in dry habitats (e.g. P. chrysogenum and P. nalgiovense), and those prevalent on carbohydrate rich substrates (e.g. P. aurantiogriseum and P. freii).

The effect of xyloglucan on spore germination, hyphal length and mycorrhizal colonization of alfalfa plants was studied. The presence of high concentrations of xyloglucan in the rooting medium inhibited mycorrhizal colonization in plants inoculated with Glomus mosseae. Intermediate xyloglucan concentrations had no effect on arbuscular mycorrhizal (AM) colonization, but a low concentration increased mycorrhization of host plants. The effects of these doses on spore germination and hyphal length of G. mosseae were similar to those observed for mycorrhizal colonization. Production of xyloglucanase was assayed during colonization by the AM fungus G. mosseae in lettuce and onion. Endoxyloglucanase activity peaked 15 d after inoculation, whereas exoxyloglucanase activity peaked at 30 and 50 d. Extracts from external mycelia of G. mosseae showed endo- and exoxyloglucanase activities. Some of the endoxyloglucanase activities detected in AM colonized plant roots may be derived from the AM fungus, as endoxyloglucanase proteins found in the external mycelia of G. mosseae and in mycorrhizal root extracts showed similar electrophoretic mobility. These results suggest that xyloglucanase is involved in the process of colonization of plants by G. mosseae.

Penicillium verrucosum is one of the main producers of ochratoxin A (OA) in agricultural commodities. To forecast the risk of OA contamination, there is a need to improve our knowledge on the ecology of P. verrucosum in the field. Dilution plating on ‘dichloran yeast extract sucrose 18% glycerol agar’ (DYSG) offers a simple and very sensitive method of detecting P. verrucosum propagules in soil. The properties of DYSG are illustrated in a suspension mixture experiment and confirmed in a soil mixture experiment. In the latter, P. verrucosum could be detected in conidial concentrations below 200 colony forming units (cfu) g−1 soil even when it constituted no more than 0·3% of the cfu. Furthermore, the DYSG method can be used to estimate the abundance of P. verrucosum propagules in soil with good precision. In some of the analysed cases, however, it was necessary to use appropriate mathematical models to treat results with high numbers of cfu on the Petri dishes.

Coemansia aciculifera, C. scorpioidea and C. thaxteri were found in the rhizosphere of wheat and a fungus resembling C. spiralis was found in the rhizosphere of barley from two fields in eastern England when serially washed root pieces were incubated on low nutrient agar (SNA).

Conidia of Metarhizium anisopliae need water activity (Aw)>0·98 for germination irrespective of whether they are formulated in an aqueous or oil carrier. The presence of nutrients in the carriers or culture medium accelerated germination but did not increase the range of Aw (or humidities) over which conidia could germinate. Insect extract stimulated more conidia to germinate than yeast extract. Oils appeared to extract fungistatic and stimulatory compounds from the insect cuticle. The ratio of these compounds depends on both the insect species and the carrier. Conidia of M. anisopliae formulated in oils were observed with SEM to flow over the surface of insect and plant cuticles. The conidia were probably deposited at sites which are conducive for germination and infection and consequently increased the overall mortality of insects. In contrast, aqueous formulations of conidia remain as drops on the leaf surface immediately after application with a pipetteman or sprayer.

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.

Pycnidiospores of Phyllosticta ampelicida germinate only after they become attached to a hydrophobic substratum. They do not readily attach or germinate on hydrophilic surfaces or on nutrient-rich media. The properties of the spore surface that function in attachment and signal mediation for germination were investigated in this study. Pycnidiospores were surrounded by a sheath that bound Concanavalin A (Con A)-TRITC and only weakly bound wheat germ agglutinin (WGA)-FITC. Galanthus nivalis lectin-FITC selectively bound primarily to the apical region of the sheath associated with the appendage. Con A, but not WGA or GNL, disrupted spore attachment. The Con A effect on spore attachment was significantly reduced when the lectin was pre-mixed with methyl-D-α-mannoside. The sheath as well as the associated appendage was removed with either Novozym 234 or crude β-glucuronidase. Such sheathless spores were initially adhesion incompetent but, by 40 min, the spores regained their ability to adhere to hydrophobic surfaces through the secretion of material that had an affinity toward colloidal gold. Non-treated pycnidiospores surrounded by sheath remained spatially separate; however, sheathless spores readily agglutinated. Addition of cations enhanced attachment to both hydrophobic and hydrophilic surfaces presumably through the masking of electronegative groups on the sheath or by reduction of the ordered water-shell surrounding the sheath. In particular, Ca2+ induced both attachment and germination on normally non-inductive hydrophilic surfaces, suggesting an additional role for Ca2+ in signal mediation for germination.

The mode of hyphal interaction and parasitism of Coemansia spp., mainly C. aciculifera and C. thaxteri, by Gliocladium roseum, Fusarium flocciferum and Verticillium psalliotae, species that occurred with the Coemansia spp. in wheat rhizospheres, was observed in mixed cultures on low nutrient medium. Two types of interaction occurred. G. roseum and F. flocciferum coiled round, penetrated and grew within the host's hyphae. V. psalliotae grew parallel to and along the host's hyphae, coiling only rarely, and sometimes formed thick mycelial layers on the host's sporangiophores. After infection by each fungus, the host's hyphae became narrower, collapsed and then disintegrated. The observations suggest parasitism followed by lysis rather than the involvement of antibiotics.