A morphological and molecular analysis was performed on 25 individuals of Phaeoacremonium isolated from diseased European and Californian grapevines (Esca disease). An unexpectedly high intra-generic molecular divergence was evidenced by partial rDNA sequencing between P. chlamydosporum isolates on one hand and an aggregate including P. angustius and P. aleophilum isolates and some undescribed ones on the other. These two groups show 26% nucleotide differences within the 26S rDNA fragment sequenced and were unalignable within the ITS2, suggesting distant phylogenetic relationships. Moreover, P. chlamydosporum appeared more closely related to Phialophora verrucosa (supposed to be an anamorph of the Herpotrichiellacae), than to the type species of the genus, P. parasiticum (more related to Magnaporthaceae).

Experimental systems were established for the molecular analysis of different developmental stages of Glomus mosseae. RNA and DNA were simultaneously extracted from ectocarpic spores, chlamydospores, dormant and germinating sporocarps and extraradical hyphae. A β-tubulin gene fragment was obtained by PCR from spore genomic DNA and further analysed. β-tubulin RNA expression could be monitored during the fungal life cycle with a gene-specific primer by RT–PCR using an internal cRNA standard.

The β-1,3-glucanase system of the mycoparasitic T. harzianum, isolate T-Y, was found to be composed of at least five different enzymes. Their migration distance in acrylamide gels corresponded to peptides with molecular masses of 30–200 kDa, and they were named accordingly. The largest enzyme – Gβ-1,3–200, was the most abundant when T-Y was grown with no carbon source. Its secretion was almost eliminated when T-Y was grown on media containing a high concentration of carbon sources such as N- acetylglucosamine (GlcNAc) or malic acid. Several isolates of T. harzianum were found to have a β-1,3-glucanase secretion system, controlled by catabolite repression. Each isolate exhibited a different β-1,3-glucanase profile. Gβ-1,3–200 was isolated and purified: its molecular mass was approximately 75 kDa, and its activity was of the exo-type, specific to β-1,3-glucan linkages. Four short peptides resulting from proteolysis of this enzyme were sequenced, and their sequences were most homologous to LAM1.3, a previously isolated β-1,3-glucanase.

Ectomycorrhizal and saprobic macrofungi growing in the wild were collected from non-auriferous and unpolluted areas and analyzed for gold. Gold was determined using long-term instrumental neutron activation analysis (INAA). In total, 154 samples, including 67 species of ectomycorrhizal fungi and 22 species of terrestrial saprobes, were examined. Gold contents of the both groups were mostly less than 20 ng g−1 of D.W. The highest concentrations (expressed in D.W.) were found in the ectomycorrhizal species Amanita strobiliformis (136 ng g−1), Russula claroflava (148 ng g−1), Cantharellus lutescens (156 and 210 ng g−1), and Boletus edulis (235 ng g−1). Among the saprobic fungi, the highest values were found in Langermannia gigantea (160 ng g−1) and Morchella esculenta (189 ng g−1). Species of Agaricus commonly had relatively high gold values, 10s of ng g−1. The gold content of macrofungal fruit bodies was considerably higher than that of vascular plants, and parallels concentrations found in plants growing in auriferous areas.

Bark beetles (Coleoptera: Scolytidae) are common vectors of Ophiostoma species. These fungi include primary tree pathogens and important sapstain agents. In Mexico, Ips calligraphus and Dendroctonus mexicanus occur on many species of pine. Pinus maximinoi and P. pseudostrobus are the hosts of both species of insects. Little research has been done on ophiostomatoid fungi associated with pine bark beetles in Mexico. We recently obtained specimens of these bark beetles and their galleries from Mexico. The aim of the study was to isolate and identify Ophiostoma species associated with the two beetle species. In total, six ophiostomatoid species were found to be associated with them. These included Ceratocystiopsis minuta, Ophiostoma pluriannulatum, an O. galeiformis-like species, two unidentified Sporothrix spp., as well as a new species similar to O. adjuncti, O. ips, and O. montium, that we name as O. pulvinisporum sp. nov.

In Fusarium section Liseola, the teleomorph is used to identify mating populations that represent different biological species when distinguishing morphological characters are absent in the anamorph. The Gibberella fujikuroi mating populations to which strains of Fusarium section Liseola belong were determined for isolates from sorghum grown at Ifakara, Ilonga and Kachiri, Tanzania. Representatives of all of the mating populations (A–F) were recovered at Ilonga, but C and E were absent at Ifakara and C was absent from Kachiri. The frequency of the different mating populations was similar at all three sites with A (21%) and F (49%) being the most frequent and C and E the least frequent, if they were recovered at all. The relative proportions of mating populations A and F in the population were significantly different from each other at Ilonga, but were not significantly different at Ifakara or Kachiri. Female fertile strains were more common within mating population A than within mating population F. The inbreeding effective population sizes for the A and F mating populations, respectively, were 69 and 91% of count based on mating type, and 88 and 53% of count based on male/hermaphrodite ratios.

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.

The entomopathogenic fungus Alternaria alternata grew equally well on potato dextrose agar (PDA) and also on potato extract agar (PEA). The latter was excellent for sporulation. The fungus grew at a wide temperature range of 15–35 °C with an optimum at 25 °. On PDA sporulation was much reduced as compared to that on PEA. The spores of the fungus germinated only at 100% relative humidity (rh). Darkness significantly increased the germination percentages in the early stages of germination at all temperatures tested. Differences in germination percentages between light and dark conditions were mostly levelled 24 h post incubation. The germ tubes formed distinct appressoria, both on glass slides and on the aphid host Anuraphis nerii, on which appressoria were formed on all parts of the insect bodies, even on the hardest ones, such as the head and thorax. Most appressoria were single globose and formed terminally on hyphal branches. Few were subapical and still fewer compound and multilobed. Detachment of appressoria from their original position revealed an exceedingly smoothened appression area, around which a mucilagenous material was secreted, apparently cementing them onto the host epicuticle. Optimum temperature for appressorium formation was 20–25 °. At these temperatures more than 80% of the emerging germ tubes formed appressoria. The factors affecting spore germination and appressorium formation are discussed in relation to the prevailing environmental conditions in the mediterranean area as well as their role in influencing the spread and activities of the pathogen and the infection of aphids under field conditions.

The synthesis of plant growth hormone auxin, indole-3-acetic acid (IAA), is not only confined to flowering plants. Yeasts and other fungi are also known to produce this hormone and in many cases at higher levels than plants. The main concern of this study was to determine the physical and chemical conditions necessary for optimal biosynthesis of this hormone by Lentinus sajor-caju. Glucose was determined to be superior to sucrose as carbon and energy source. The synthesis of IAA in a nitrogen-free medium or in a medium with low external phosphate was substantially reduced. Light exposed and non-agitated cultures grown in dark had also reduced levels of IAA compared to agitated cultures grown in dark. The highest (0.18 mg ml−1) IAA level was determined in cultures grown in glucose containing medium (pH 7.5) on a rotary shaker (150 rpm) at 30 °C in dark. The biological activity of IAA obtained from the extra-cellular culture of Lentinus sajor-caju was determined using oat coleptile growth test.

The fungal pathogen Entomophaga maimaiga, infecting gypsy moth larvae (Lymantria dispar), produces two types of spores; relatively short-lived conidia are produced externally on cadavers and are actively ejected to cause infection during the same season, while azygospores, produced within cadavers, are dormant after formation and survive unfavourable conditions. This is the first record providing experimental proof of differential reproduction resulting from infections initiated by these two types of spores. Cadavers of larvae that had died from infections initiated by azygospores produced only conidia, regardless of host instar or relative humidity after host death. This is in stark contrast to infections initiated by conidia, which could yield either conidia only, azygospores only, or both spore types, with reproductive outcome primarily influenced by host age. Production of only conidia from infections initiated by azygospores increases opportunities for secondary transmission during the eight week field season; if infections initiated by azygospores produced azygospores, chances for amplification of infections with subsequent epizootic development would be decreased.

The dimorphic Mucor circinelloides requires an anaerobic atmosphere and the presence of 30% CO2 to grow as a multipolar budding yeast, otherwise hyphal growth predominates. Establishing other means to control the morphology would be a distinct advantage in the development of a fermentation process for this organism for the production of heterologous proteins. Thus, conditions suppressing polarised growth while at the same time abolishing the CO2 requirement were investigated in submerged cultivations. It was found that supplementing cultures with mixtures of ergosterol and Tween 80 resulted in yeast-like growth under 100% N2. Their impact on growth and morphological development was assessed at a range of concentrations. Maximum biomass levels and the specific growth rate decreased at elevated levels of ergosterol and Tween 80. Possible effects of carbon dioxide and the added fatty acid/sterol mixture on supporting yeast growth by influencing the fluidity of the plasma membrane or affecting polarised growth are discussed.

Competitive interactions among bark beetle associated fungi are potentially influenced by abiotic factors. Water potential, in particular, undergoes marked changes over the course of beetle colonization of tree hosts. To investigate the impact of water potential on competition among three southern pine beetle associated fungi, Ophiostoma minus, Entomocorticium sp. A and Ceratocystiopsis ranaculosus, we utilized artificial media with water potentials of 0, −5, −10, and −20 MPa. Growth of all three fungi, when grown alone, decreased on media with lower water potentials. Growth rates of all three fungi were likewise reduced in competition experiments. At −5 to −10 MPa, C. ranaculosus (a fungus with beneficial effects toward southern pine beetle) was nearly equal in competitive ability to O. minus (a fungus with antagonistic effects towards southern pine beetle). This was not true on control media, nor at other water potentials tested. The range of water potentials used in our assays was similar to the range of water potentials we measured in loblolly pines within a southern pine beetle infestation. This study indicates that water potential may alter the outcome of competitive interactions among bark beetle-associated fungi in ways that favour bark beetle success.

Four isolates of the entomopathogenic fungus Erynia neoaphidis, from different hosts and locations in Switzerland, were distinguished by their DNA fragment banding pattern obtained by RAPD–PCR. The isolates differed in sporulation and germination rates, but not in virulence (overall mean LD50 16 conidia mm−2) against the aphid Acyrthosiphon pisum. The sporulation rate was 6 to 24 conidia mm−2 10 min−1. On nutrient agar, 24–73% of the conidia produced secondary conidia and 32–68% produced germ-tubes on polystyrene. Differentiation of primary into secondary conidia or germ-tubes is possibly dependent on the presence of free water on the contact surface; on a dry surface, conidia germinated mostly with a germ-tube, whereas on a wet surface the conidia produced a secondary conidium. Experimental support is provided for the claim that, in addition to LD50 values, features such as sporulation rate, spore germination, capacity to form secondary conidia and intraspecific variation should be considered in selecting isolates of E. neoaphidis for biocontrol agents.

Spores of Tetrachaetum elegans were isolated in early autumn from submerged leaves which were randomly collected at a single site from a small stream in southwestern France. In order to investigate potential substrate preferences, spores were sampled in four leaves from seven different plant genera. A total of 96 monosporic isolates were screened for genetic variation in RAPD patterns using nine different primers. Fifty-two fragments were identified and used for calculation of similarity coefficients. A large number of fragments were shared across all isolates, suggesting that the population was genetically homogeneous. The combination of 11 polymorphic fragments contributed to the delineation of 13 RAPD types. Colonization of a single leaf by multiple genotypes was frequently encountered. Fungal genetic assemblages differed between plant genera. Variations in the frequency of occurrence of the various genotypes are discussed in terms of ecological strategies and in reference to previous work at the community level. We suggested two hypotheses: first, substrate preferences are found among aquatic hyphomycete genotypes, and secondly, sequential occupation by distinctive populations may result in different assortments of genotypes on leaf litters of different plants at any given time of sampling.

The effects of varying carbon, nitrogen, phosphate and sulphate source on solubilization of natural gypsum by Aspergillus niger were assessed. The fungus was grown on Czapek Dox agar amended with 0.5% (w/v) gypsum. Solubilization activity was monitored by measuring the clear zone formed underneath and around the growing colonies. On different concentrations of glucose, nitrate, ammonium, urea, phosphate and sulphate, linear growth rate [Rg] was not significantly correlated with gypsum solubilization rate [Rs], but the solubilization ratio [Rs/Rg] was increased by increasing the concentration of glucose, nitrate, and urea. On ammonium nitrogen, the mycelial dry weight was negatively correlated with linear growth, and gypsum solubilization activity was markedly lower than that on nitrate or urea. Gypsum solubilization was strongly correlated with both biomass dry weight and oxalic acid production. The fungus was unable to grow on carbonate, as a carbon source, but the addition of sucrose alleviated the effect of alkalinity caused by sodium carbonate. The optimum C[ratio ]N ratio for gypsum solubilization was 50[ratio ]1, and the importance of phosphate, rather than sulphate, was also shown. Implication of critic acid in the solubilization process was also suggested. This work emphasizes the importance of organic acids, particularly oxalic acid, production by fungi in gypsum solubilization and revealed the optimum nutritional conditions for the solubilization process.

Conidia of Metarhizium flavoviride were suspended in oil formulations and received fatty and other acids before germination. This was done by the acids being added either to the conidial suspensions before inoculation onto agar plates or directly into the agar before the conidia were applied. Certain acids of chain lengths C10 and below, including lactic, salicylic, caprylic and capric acids produced significant inhibition of germination when added to the oil formulations. When incorporated into the agar, all acids of C10 and below were inhibitory, with the exception of sebacic and succinic acids. Sebacic acid (a C10 saturated dicarboyxlic acid) and all the longer chain fatty acids sampled produced no inhibition of germination, either when added to the formulation or the agar. Tests were carried out on a sample of conidia which showed no germination; a few acids stimulated some germination. These included sebacic acid and longer chain fatty acids such as stearic and (inconsistently) lauric acids. Conidia from a long term storage experiment showed increased germination on the addition of stearic and/or lauric acids. The inhibitory effect of capric acid on germination was overcome by a 4–15 times higher concentration of stearic acid.

The genetic relationships among 132 isolates of Sclerotium rolfsii (teleomorph Athelia rolfsii) collected during 1967–97 from 36 different host species over a wide geographic range representing 13 countries were investigated using mycelial compatibility groupings and RAPD analysis. A smaller group of 15 Sclerotium delphinii isolates from five host species and a limited geographic distribution was also studied. The development of aversion reactions following mycelial pairings of isolates in all possible combinations on potato dextrose agar was used to differentiate 71 mycelial compatibility groups (MCG) in S. rolfsii and five MCG in S. delphinii. Many MCG were unique single-member groups and these generally were found in widely separated geographic regions or countries. There was no clear relationship between host of origin and MCG, except for a majority of isolates of S. rolfsii from turfgrass that belonged to MCG 1. Within a specific geographic region, e.g. California, there usually were several different MCG present, some of which were recovered from the same host species. In addition, specific MCG of S. rolfsii were recovered from widely separated geographic regions as well as different host species, e.g. MCG 1 was recovered from turfgrass, carrot, tobacco, and tomato in California, Georgia, North Carolina, and Mexico, respectively. The extent of genetic diversity within and among MCG of S. rolfsii and S. delphinii was studied using RAPD analysis. Isolates from different MCG could be differentiated by their unique banding patterns using six primers. There were no discernible relationships among the various MCG using UPGMA analysis. Isolates within a particular MCG were also genetically diverse, but shared greater numbers of common bands and clustered together. Only a few members of some MCG in S. rolfsii and S. delphinii that had identical RAPD patterns were considered to be clonally derived. The extent of genetic diversity among isolates of S. delphinii was lower than that observed in S. rolfsii.

Several Trichoderma virens (syn. Gliocladium virens) strains have good biocontrol activity against Rhizoctonia solani on cotton but lack some of the commercially desirable characteristics found in other Trichoderma species. In an attempt to combine these desirable characteristics, we used a highly effective biocontrol strain of T. virens in protoplast fusions with a strain of T. koningii, which had good storage qualities, but little biocontrol efficacy. All fusants were morphologically similar to one of the parental species. However, when compared to the morphologically similar T. koningii parent, two fusants showed significantly better biocontrol activity against R. solani on cotton. In addition, one T. virens-like fusant gave significantly less control than the T. virens parent. Fusants also differed from the morphologically similar parent in the production of secondary metabolites. One fusant was obtained which maintained biocontrol activity during storage for up to a year.

Entomophthorales pathogenic to insects and mites often cause epizootics in their host populations, but some have been difficult to culture in vitro and, therefore, to develop as biopesticides. Grace's insect cell culture medium supplemented with lactalbumin hydrolysate and yeastolate has allowed growth of several species which until recently were referred to as obligate parasites. The research reported here was designed to evaluate the effects of the salts, vitamins and amino acids used to prepare the insect cell culture medium on in vitro growth of Batkoa sp. and Furia sp., pathogens of the spittlebug pests of pasture and sugar-cane in Brazil, and Neozygites floridana, a pathogen of several mite species. Also, several sources of carbon and nitrogen were examined. Batkoa sp., Furia sp. and N. floridana were similar concerning their growth patterns in a basic medium with added salts, vitamins and amino acids, as well as with a combination of all three compoments. The addition of salts to the basic medium of sugars plus lactalbumen hydrolysate and yeastolate caused a significant increase in biomass production of the three fungal species. The addition of vitamins and amino acids had less effect. Batkoa sp., Furia sp. and N. floridana are similar in growth patterns in media with various sources of carbon, but different in media with different sources of nitrogen. The production of the three fungal species is significantly higher in medium containing 2.66% glucose than in medium with 2.66% sucrose. The addition of 0.1% monossacarides to media containing 2.66% sucrose did not significantly increase biomass production.

Genetic relationships were investigated among several populations of Pleurotus tuberregium from Nigeria, Papua New Guinea and New Caledonia. Intrastock mating compatibility studies using progeny from two collections demonstrated a tetrapolar mating system for P. tuberregium. Interstock matings among the geographically distinct populations were compatible. All isolates were found to be intersterile with tester strains of other Pleurotus species, showing that P. tuberregium represents a unique intersterility group in Pleurotus. Nucleotide sequences of the ITS region of the rDNA gene were determined for 30 isolates and used to infer phylogenetic structure of populations. Phylogenetic analysis shows that African and Australasian-Pacific isolates form at least two distinct evolutionary lineages. Higher genetic divergence was observed among ITS sequences from the Australasian-Pacific region than among African isolates, which suggests a possible origin of P. tuberregium in the Australasian-Pacific region.