Isolates of Cylindrocladium floridanum obtained from diseased roots of white and black spruce seedlings and surrounding soil in bareroot nurseries in Ontario, Minnesota and Wisconsin area were compared by mitochondrial DNA (mtDNA) and ribosomal DNA (rDNA) restriction fragment length polymorphisms (RFLPs), human minisatellite DNA fingerprints and polymerase chain reaction. Nucleotide sequences of rDNA ITS regions of selected isolates were also performed. Based on the nuclear DNA fingerprinting patterns, these isolates could be divided into three groups, namely S1, S2 and S3. Isolates of S1 and S2 showed the same mtDNA RFLPs which were slightly different from that of S3. Isolates representing each of the three groups showed an identical nucleotide sequence of rDNA ITS regions. These data suggest that all the isolates tested belong to the same species which may be divided into three biotypes or populations.

The PCR technique based upon randomly amplified polymorphic DNA (RAPD) markers using 10-mer oligonucleotide primers was used to investigate the phylogenetic relationships among 33 isolates of Heterobasidion annosum belonging to the intersterility groups F and S. The F isolates originated from Italy, the S isolates from the Italian Alps, northern Europe and North America. The presence or absence of some bands was shown to be population-specific. The North American S group and the European S group differed significantly from each other, but within the latter group there were no significant differences between the Italian S and the northern European S populations, with as much similarity within these populations as between them. More DNA polymorphisms appeared within European F and S groups than in the North American S group. The North American S group appeared to be more closely related to the European S group than to the F group. The isolates of the Italian F population seemed to be most closely related to the Italian S isolates and then, in decreasing order, to the northern European S and North American S isolates. The order of genetic similarity was inversely correlated with the mating frequency in vitro obtained in an earlier study.

Following the Chernobyl accident in 1986, sporocarps of Suillus variegatus in Sweden showed a large amount of individual variation in concentration of 137Cs activity. Our aim was to determine the degrees to which this variability in sporocarp 137Cs levels could be explained by differences between (i) local populations, (ii) fungal genets and (iii) locations within genets. Five populations in a 100-yr-old Scots pine forest, located within a 1 km2 area, and two populations in Scots pine/Norway spruce forest, located 40 km north-west of Uppsala, were investigated. In total, 154 sporocarps were analysed to determine their 137Cs content. Of these, the genetic affiliations of 86 were successfully characterized using somatic incompatibility reactions. Twenty-six genets were found which, on average, consisted of 6·5 sporocarps. The genets averaged 7·5 m in size, measured as the length between the most distant sporocarps. The mean sporocarp 137Cs level was 67·1±2·8 kBq kg−1D.W. (range between 13·6 and 182). According to analyses of variance, within-population variation accounted for 60% of the total variation in 137Cs levels, while 40% was ascribed to variation among populations. Within a population, 137Cs levels did not generally differ significantly between genets. Plausible reasons for intraspecific variation in radiocaesium content in sporocarps are discussed.

Liquid media with differing carbon concentrations and carbon-to-nitrogen ratios were tested for production of desiccation tolerant blastospores of Paecilomyces fumosoroseus. While all media tested supported sporulation in submerged culture, high blastospore concentrations (5·8 × 108 spores ml−1) were produced in media containing 80 g glucose l−1 and 13·2 g Casamino acids l−1 (MS medium) and a significantly higher percentage (79%) of these blastospores survived air drying. Media containing glucose concentrations greater than 20 g l−1 and Casamino acid concentrations between 13·2 and 40 g l−1 supported maximal production of desiccation tolerant blastospores. All 23 isolates of P. fumosoroseus grown in MS media produced high concentrations of desiccation tolerant blastospores. When stored at 4 °C, more than 60% of the lyophilized blastospores produced in MS medium were still viable after 7 months storage while less than 25% of the air-dried blastospores survived after 90 d storage. Standard whitefly bioassays were performed to compare air-dried blastospores of P. fumosoroseus ARSEF 4491 with solid substrate-produced conidia of Beauveria bassiana ARSEF 252. Air-dried blastospores of P. fumosoroseus gave LD50S of 60 and 113 blastospores mm−3 for the silverleaf whitefly (Bemisia argentifolii) in two separate bioassays with potency ratios (LD50B. bassiana/LD50P. fumosoroseus) of 3·9 and 3·8, respectively. These results have demonstrated that high concentrations of blastospores of P. fumosoroseus can be rapidly produced in liquid culture, remain viable following drying, and infect and kill silverleaf whitefly.

Cytoplasmic extracts of Fusarium moniliforme contained a peptidase activity, able to cleave preferentially L-Leu-7-amino-4-methylcoumarin fluorogenic substrate. No activity towards this substrate was detected in various culture media of F. moniliforme supplemented or not with different substrates (bovine serum albumin, bovine haemoglobin, collagen or gelatin), proving that the peptidase was not secreted in these conditions. The cytoplasmic enzyme was purified by high performance liquid chromatography using a combination of an anionic exchange and gel filtration columns. The purified activity gave a single band on sodium dodecyl sulphate-polyacrylamide gel electrophoresis, estimated at Mr 45000 under reducing conditions. The aminopeptidase showed an optimum activity at pH 7·2, an isoelectric point at 4·1, the Michaelis constant was at 50 μm and the Vmax at 12 mM AMC released min−1 mg−1 of protein for L-Leu-AMC. Since this natural peptidase is sensitive to the protease inhibitors 1,10-phenantroline and ethylenediaminetetraacetic acid, it is considered as a metallopeptidase.

Xylomyces is re-examined, the type specimen X. chlamydosporis redescribed and illustrated, and new distribution records are provided. Four new species, X. elegans sp. nov., X. giganteus sp. nov., X. punctatus sp. nov. and X. pusillus sp. nov. are described from wood submerged in freshwater collected in various countries. The chlamydospores of these species are drawn at the same scale as a composite diagram for comparison and each is illustrated with light micrographs. Xylomyces foliicola is regarded as atypical in the genus. A key to the accepted species in Xylomyces is provided.

Thirty-one isolates of the form genera Acremonium and Cephalosoporium were screened for their ability to excrete enzymes capable of degrading β-glucans. Most produced both (1 → 3)- and (1 → 6)-β-glucanases together, although the yields varied with carbon source used. Surprisingly, higher yields of (1 → 3)-β-glucanases were often seen from isolates grown on pustulan, a (1 → 6)-β-glucan which is not hydrolysed by these enzymes. Lower enzyme yields were generally obtained with glucose than with either laminarin, a (1 → 3)-β-glucan or pustulan as carbon sources, suggesting regulation of synthesis by either catabolite repression and/or induction. However, a few isolates, most notably Cephalosporium sp. OXF C13 and Acremonium strictum appeared to have some constitutive-β-glucanase activity. Most of the isolates screened were only very weakly cellulolytic against carboxymethyl cellulose or filter paper as substrates.

On water agarose conidial germination of Ampelomyces quisqualis was greatly enhanced in the presence of powdery mildew conidia. All seven species of powdery mildews tested, representing five genera, were effective in increasing germination of the mycoparasite. Aqueous extract of conidia of Oidium euonymi-japonicae was also stimulatory to the mycoparasite. Germination of conidia of A. quisqualis on water agarose decreased as conidial concentration increased. Germination of the mycoparasite's conidia at a low concentration on water agarose was greatly decreased when they were separated by a polycarbonate membrane from conidia of the same species at a high concentration and incubated. After being incubated with conidia of the mycoparasite at a high concentration, water agarose became inhibitory to germination of conidia of the same species at a low concentration, suggesting the presence of a diffusible self-inhibitor. Water agarose is essentially free from nutrients which may support growth of contaminants that interfere with the effect of stimulators or inhibitors.

Hirsutella versicolor, H. citriformis and H. nivea sp. nov. are described from Homoptera in Thailand. H. versicolor was usually associated with the ascomycete Torrubiella pruinosa and was isolated from ascospores. H. citriformis could not be linked with a teleomorph but was successfully isolated from conidia. H. nivea was not associated with a teleomorph and could not be isolated in pure culture.

Mycelium grew from a spore-mycelial inoculum of Aspergillus oryzae added to ultra-pure water (upw) containing silicon compounds, but did not grow in upw alone. Growth of other fungi also occurred in upw only when silicon compounds were added. Increased growth of A. oryzae, and other fungi, also followed the addition of silicic acid and other silicon compounds to Czapek Dox. Aspergillus oryzae solubilized silicon compounds in both upw and nutrient-rich media. Although interactions between microorganisms and silicon have been generally neglected, the results show that silicon compounds can increase fungal growth under both oligotrophic and nutrient-rich conditions.

Elicitins, holoproteins which act as inducers of hypersensitivity on tobacco, were considered as a characteristic of Phytophthora. They are also produced, along with glycosylated isoforms, by three species belonging to the related genus Pythium, Py. vexans, Py. oedochilum and Py. marsipium, while other Pythium species do not possess such proteins. Various elicitin-like sequences were determined, bringing novel features to the elicitin family, such as an histidine residue and C-terminal extensions on the deduced peptide sequences. As the unique elicitin content of these species supports a distinct location among Pythiaceae, we suggest the separation of vexans, Py. oedochilum and Py. marsipium from Pythium and consider them as linking species between Phytophthora and Pythium.

The tef1 gene coding for translation elongation factor EF1α was identified by a PCR-based approach using degenerate oligonucleotides derived from conserved regions seen in alignments of other EF1αs. The deduced amino acid sequence was compared to other EF1αs. In Southern blot analyses no evidence for a second gene encoding EF1α in Schizophyllum commune was detected. Abundant transcript levels were detected in Northern blot analyses. The open reading frame is interrupted by seven small introns ; however, the positions of these introns are not conserved between the homobasidiomycete Schizophyllum commune and the heterobasidiomycete Puccinia graminis genes.

Zoospore germination and in vitro growth of Phytophthora palmivora were studied in extracts obtained from healthy, wounded and inoculated cacao stem tissues. Extracts from wounded and inoculated stem tissues of IMC 67 (canker resistant genotype) significantly inhibited (P<0·05) zoospore germination and the growth of P. palmivora compared to healthy tissues and the controls. There was no significant difference in the percentage zoospore germination or the growth of the pathogen in the extracts obtained from P 18, SCA 6 and TSH 1076 (susceptible genotypes) and those of the controls, while extracts from ICS 1 and TSH 1188 (moderately resistant genotypes) gave intermediate effects. Also, germ-tube lengths were significantly shorter in IMC 67 extracts than in the controls, moderate in ICS 1 and TSH 1188 extracts and longest in P 18, SCA 6 and TSH 1076 extracts. Tests for antifungal compounds in extracts indicated the presence of phenols. The variation in inhibitory effects of cacao stem extracts on zoospore germination and in vitro growth of P. palmivora can be used as a criterion for selecting cacao genotypes resistant to canker.

Pycnidial hyperparasites of powdery mildew fungi, often used in biological control experiments, are currently considered as belonging to a single species, Ampelomyces quisqualis. However, RFLP analysis of the nuclear rDNA ITS region in a worldwide collection of Ampelomyces isolates showed the existence of seven RFLP groups. Cultural characters, e.g. growth rate of isolates, correlated with the exhibited restriction patterns. The results suggested that A. quisqualis should be regarded as a problematic species complex. The geographical distribution of genetically distinct isolates showed that (i) isolates belonging to the same RFLP group were present even in different continents in their fungal hosts, and (ii) isolates representing various RFLP groups were found in the same geographical region, in the same species of the Erysiphaceae and on the same host plants. The detected genetic differences could influence the applicability of various isolates in biological control.

The temperature optima for germination, radial hyphal extension rate and sporulation were determined for two isolates of Metarhizium flavoviride from acridoid hosts. I91-609 exhibited lower temperature optima for hyphal extension (25·5 °C) and sporulation (24°) than IMI 330189 (27° and 25°, respectively), although temperature optima for germination were similar (ca 30°). The temperature optimum for sporulation was lower than that for hyphal extension.

Further studies were carried out on I91-609 to investigate the effect of temperature and dose on the infection mortality rate of the grasshopper pest, Zonocerus variegatus. Increasing dose resulted in a decrease in mean survival time regardless of incubation temperature. Dose and temperature were shown to interact, with the effects of dose increasing at temperatures either side of the optimum. Furthermore, for each dose, the optimum temperature for infection was estimated to be ca 5° higher than the optimum for growth, and no significant relationship was identified between hyphal extension rate in vitro and host survival time. The implications of these results are discussed with regard to the selection of isolates for use in biological control.

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 white-rot basidiomycete, Inonotus hispidus, produces a characteristic pattern of decay in naturally infected London plane (Platanus × hispanica) in which zones of severely decayed wood, traversed by relatively undegraded xylem rays, alternate with relatively undegraded, gummous ‘reaction zones’. Microscopic observations of London plane wood both naturally colonized and artificially inoculated with I. hispidus indicated that the resistance of reaction zones and xylem rays to degradation is due respectively to obstruction of cell lumina by tyloses and polyphenols, and infiltration of intercellular spaces by polyphenols. Inonotus hispidus was apparently able to circumvent these impedances by forming soft-rot like tunnels through the wood cell walls.

Thirty-eight strains of the entomopathogenic Beauveria bassiana, isolated from diverse species of Lepidoptera (Pyralidae) or Coleoptera (Curculionidae, Chrysomelidae, and Scolytidae) from various geographical sites, were examined by RFLP and RAPD analyses. Similar groupings were recovered from both approaches and these showed clear relationships between the population structure of B. bassiana and some defined host species. Strains isolated from members of the Pyralidae were recovered as two main groups, one group consisted of all strains isolated from Ostrinia irrespective of their origin. The second group consisted primarily of strains isolated from Diatraea in Cuba. All strains isolated from the curculionid genus Sitona clustered as a single distinct group, separated from strains from other curculionids. In contrast, strains isolated from the pyralid genus Maliarpha, and the coleopteran Chrysomelidae, gave heterogenous patterns and were not recovered as distinct groups. Groups from cluster analysis and non-hierarchic ordination methods were compared and the relative merits of the different grouping strategies are discussed.

Delortia, represented by the type, D. palmicola, is redescribed from fresh decaying palm material collected in north Queensland, Australia. Two new species, D. tumidoapicis and D. aquatica, collected from wood submerged in a freshwater stream, also in north Queensland are described. The three species are illustrated with light micrographs and line diagrams and discussed in relation to each other.

Savoryella is reported from wood submerged in rivers and streams in Australia, Brunei, Hong Kong, Malaysia, Mauritius, the Philippines and South Africa. Six species are reported:– Savoryella aquatica, S. curvispora sp. nov., S. fusiformis sp. nov., S. grandispora, S. lignicola and S. verrucosa. A key to Savoryella species is provided and descriptions and illustrations of selected freshwater Savoryella species are given.