Pathways of genetic transfer outside of the normal sexual cycle were examined in Phytophthora infestans. Transformants expressing genes for resistance to G418 or hygromycin were employed to select hybrids or recombinants on double-drug media after in vitro or in planta mixing of zoospores or mycelia. In experiments using pairs of isolates of the same mating type, zoospores fused to form doubly resistant colonies. These were shown to be heterokaryons containing non-recombinant parental nuclei based on the analysis of DNA markers in the hybrids and their single-nuclear derivatives. Mixtures of vegetative hyphae failed to produce hybrids. The application of the drug selection scheme to mating cultures of A1 and A2 strains generally yielded normal progeny, but atypical progeny were also recovered which appeared to be polyploids since all markers from the parents were present.

Co-inoculation of healthy standing rice plants with compatible isolates of Magnaporthe grisea pathogenic to rice resulted in the production of perithecia on the detached portions of leaf sheaths. The isolates had been obtained from the same lesion on a diseased plant collected in Yunnan Province, China. Perithecia were also produced on dead tissue of leaf sheaths and nodes of standing rice plants in a moist chamber. These results strongly suggest that the teleomorph of M. grisea can occur in the upland rice fields in Yunnan.

Four ericoid mycobionts (two isolates of Hymenoscyphus ericae, and two dark, sterile ericoid mycobionts isolated from metal-contaminated mine sites) were grown on solid agar plates supplemented with zinc phosphate (0.25%) containing different forms of nitrogen (nitrate, ammonium or alanine) and different concentrations of carbon (glucose) and phosphorus (K2HPO4). The influence of nutrient variation on solubilizing ability of the fungi was assessed by measuring the zones of solubilization appearing beneath the growing colonies. All four mycobionts were capable of zinc phosphate solubilization in the presence of all three nitrogen sources and in media containing no nitrogen. No solubilization was observed at 0 mM glucose-C but was observed with increasing glucose concentration from 300 to 600 mM C. Increasing phosphorus concentration (0–5 mM P) had no effect on the solubilizing ability of the isolates. All but one of the mycobionts were capable of solubilizing calcium phosphate (CaHPO4), while no solubilization was observed in media containing aluminium phosphate (AlPO4), iron phosphate (FePO4.4H2O) or copper phosphate (Cu3O8P2.2H2O) under conditions which were found to be optimal for zinc phosphate solubilization. Under conditions of glucose at 300 mM C and alanine as the N source in the zinc phosphate-amended agar medium, one of the mycobionts produced new crystals, which were morphologically distinct from the original zinc phosphate crystals. It is concluded that medium composition influences the metal-phosphate solubilizing ability of ericoid mycobionts. The results are discussed in relation to the possible mechanisms involved in solubilization and the potential benefits of metal-phosphate solubilization to ericoid mycobionts and their host plants.

The influence exerted by the non-pathogenic binucleate Rhizoctonia (np-BNR) isolate 232-CG in stimulating plant defence reactions in young bean plants inoculated with the root rot fungus Rhizoctonia solani (AG-4) was examined using light and electron microscopy and further investigated by gold cytochemistry. Severe necrotic lesions on hypocotyles of diseased beans were observed, and the pathogen invaded the cortical tissue causing extensive damage including cell disorganization and cell wall degradation. In contrast, these host reactions were not seen in bean plants inoculated with the non-pathogenic BNR or in plants that were inoculated with BNR and subsequently challenge-inoculated with R. solani. Microscopic examination of hypocotyls inoculated with the non-pathogenic BNR, showed a different host reaction typical of plant defence reactions. In these samples, epidermal and outer cortical cells were impregnated with an electron-dense material. Histochemical assays of this material confirmed the substantial presence of phenols, pectic substances and suberin. Electron microscope observations clearly showed that in non-pathogenic BNR-inoculated plants, fungal cells were confined to the epidermal layer which was darkly stained. Gold cytochemistry confirmed the presence of pectic substances in the electron dense material. The possibility that pectic oligogalacturonides released after hydrolysis by the non- pathogenic BNR enzymes may act as elicitors of defence responses is discussed. The present ultrastructural observations corroborate that non-pathogenic BNR isolates may function as potential inducers of plant disease resistance.

In experiments where groundnut plants with sporulating late leaf spot lesions were exposed to increasing ‘gusty’ and ‘steady’ wind speeds, conidia were more effectively removed by gusty winds than by steady winds of the same mean wind speed. Rain drops dislodged conidia more efficiently than wind, with large drops dispersing conidia more effectively than small ones. No conidia were caught in still air. After most of the conidia had been removed by exposure to high wind speeds, rain was found to remove additional conidia. When plants were exposed to continuous wind or rain, most of the conidia were dispersed during the first few minutes, and the concentration of conidia then declined exponentially with time. From field observations on rain-free days, airborne concentrations of conidia tended to increase as the wind speed increased during the day and with a further increase in wind speed, concentrations decreased. On rainy days, the onset of the first shower coincided with a phenomenal increase in the airborne concentrations of conidia.

Coniothyrium minitans was successfully co-transformed with the uidA (β-glucuronidase) and the hygromycin-resistance (hph) genes. Both were under the control of the glyceraldehyde-3-phosphate promoter from Aspergillus nidulans. Hygromycin resistance was used as a selectable marker for transformation. In successive transformation experiments, transformation frequencies of up to 1000 transformants μg−1 of plasmid DNA were obtained for isolate A69. Of the ten monospore hygromycin-resistant cultures tested, nine also expressed the uidA gene. Expression of hph and uidA was stable in all transformants after several months of successive subculturing on non-selective medium, and after passage through a sclerotium of Sclerotinia sclerotiorum. Southern hybridization analyses showed all transformants carried multiple copies of each marker gene. When grown on PDA, the culture morphology of three of the transformants of (T×2, T×3 and T×4) was similar to the wild type. Four of the five transformants (T×3, T×4, T×21 and T×24) grew as well as the wild type on different media, and responded to changes in water potential in a similar manner to the wild type. All five transformants were equally parasitic on sclerotia of S. sclerotiorum compared with the wild type. Transformants T×3 and T×4 were the most similar to the wild type in biological characteristics and will be used in future studies. The results indicate that hph- and uidA-transformed strains of C. minitans will be useful for ecological studies on its survival and dissemination.

Isolates of Verticillium nigrescens and V. tricorpus were obtained from potato, cotton, eggplant, weeds and field soil in Israel. Chlorate- resistant nitrate-nonutilizing (nit) mutants were generated from each isolate and used in complementation (heterokaryon) tests. Eleven vegetative-compatibility groups (VCGs) were found among 19 V. nigrescens isolates from nine sites, and nine VCGs among 26 isolates of V. tricorpus from eight sites. Optimal growth temperature was 24–27°C for V. nigrescens and 24° for V. tricorpus. None of the isolates caused leaf symptoms or stunting in inoculated eggplant and cotton seedlings, while severe symptoms were caused by V. dahliae. Colonization of inoculated seedlings by V. nigrescens and V. tricorpus occurred primarily in roots and hypocotyls, while V. dahliae heavily colonized upper stems as well.

The discoloration of A. bisporus after infection by Pseudomonas tolaasii, P. gingeri, P. agarici, P. reactans, Verticillium fungicola and Trichoderma harzianum can be distinguished by chromametric measurements. Infection with P. tolaasii caused a specific colour change, independent of the bacterial concentration applied (ΔL = 54.7, Δa = 16.6, Δb = 28.7%). The colour change provoked by P. gingeri had a characteristic profile different from P. tolaasii (ΔL = 36.3, Δa = 14.1, Δb = 49.5%). P. agarici and P. reactans provoked only a slight increase of red colour. Response to T. harzianum was orange, and to V. fungicola brown, similar to P. tolaasii but paler and more yellowish. All pathogens except P. reactans provoked degradation of total tyrosinase to variable extents. Activation of tyrosinase was only observed after infection with P. tolaasii (to almost 7%) and V. fungicola (to 3%).

Anastomoses between hyphae, leading to both successful cell fusions and death of fused cells (vegetative incompatibility) were observed by video microscopy. Anastomosis was seen only to occur between tip cells from side branches, never main runner hyphae, and tip to side fusion was never observed. Perfect hyphal fusion was only observed following pre-contact tropism between the hyphae involved. The time taken for the process of cell wall dissolution and reformation following contact was 15 min.

Comparisons of the qualitative volatile production patterns between seven species of Agaricus, and between two of Volvariella and Pleurotus and one Coprinus species when grown at 25 °C on agar media for 14 d were made. There was good reproducibility between the volatile production patterns of the same species using an electronic nose unit with a 14 conducting sensor polymer array. Principle Component Analysis (PCA) showed that it was possible to discriminate between five of the seven Agaricus species, but that some overlap occurred between the others. Cluster analysis showed that there was also overlap between some species with the tropical collection of A. bitorquis separating out from the others. The volatile production profile of the commercial A. bisporus was close to that of a wild species, A. campestris. A. bisporus could be readily differentiated from other non-Agaricus species. This study demonstrates the potential for using electronic nose systems to rapidly differentiate mycelial cultures of homobasidiomycete mushrooms.

A study of the lichenicolous fungi occurring on species of the lichenized genus Peltigera has resulted in six new species: Libertiella curvispora, L. didymospora, L. fennica Alstrup, Polycoccum superficiale, Roselliniella peltigericola, and Zwackhiomyces kiszkianus. A key to the five known species of Libertiella is included. This paper brings the number of fungi known on this host to 87, of which 61 are not known from any other host genus, providing additional evidence for the richness of Peltigera thalli as a host for novel fungi. The possible hypotheses to explain the richness of this host genus for lichenicolous fungi are enumerated; these are not mutually exclusive.

Ericoid endomycorrhizal fungi (two isolates of Hymenoscyphus ericae obtained from unpolluted heathlands and two H. ericae-type endophytes isolated from Calluna vulgaris growing on Cu-contaminated mine spoil) were grown for 14 d on 10% Rorison's solution containing sodium phytate as the sole P source and either trace (0.16 μM) or elevated (0.25 mM) concentrations of Cu. The elevated levels of Cu in the medium had no effect on the growth of the two H. ericae-type endophytes from mine spoil sites but caused a significant reduction in growth of the two H. ericae isolates from unpolluted sites. Wall, cytoplasmic and extracellular fractions were assayed for phosphomonoesterase (PMEase) and phosphodiesterase (PDEase) activity. Km and Vmax values varied between the different endophytes and both were highest in the wall fractions. Wall-bound phosphatase activity, excluding PDEase of one H. ericae-type endophyte, was generally unaffected after the isolates had been grown on medium containing 0.25 mM Cu. Extracellular PDEase of the two H. ericae-type endophytes from mine spoil sites was stimulated by 0.25 mM Cu in the growth medium. Cu concentrations up to 5.0 mM in the assay medium did not inhibit wall-bound phosphatase activity whereas three of the isolates showed a stimulation of extracellular activity with increasing Cu. The results are discussed in relation to phosphatase activity of ericoid endophytes on Cu-contaminated substrates.

Protoplasts were produced by treating the yeast-like cells of O. piceae and O. quercus with high concentrations of Novozym 234 (20 mg ml−1). Transformants with resistance to hygromycin B were obtained by transforming the protoplasts with the plasmids pAN7-1 and pCB1004 containing the hygromycin B phosphotransferase (hph) gene. For all isolates tested, transformation efficiencies ranged between 103 and 105 transformants μg−1 vector DNA. High polyethylene glycol concentration (66 %) increased the transformation efficiency. Integration of the hph gene into the transformant genome was verified by a polymerase chain reaction and dot DNA hybridization analysis. There was no evidence of mitotic instability of hygromycin B resistance in the transformants.

The antifungal activity of oxine and copper oxinate was investigated using standardized methods to compare efficacy, discriminate activity patterns, elucidate mechanisms of action and establish attributes of relevance to field use. Both agents were shown to be active against a broad range of physiologically diverse fungi. Species of Aspergillus, Penicillium, Fusarium, Rhizopus, Candida, Rhodotorula and Saccharomyces were significantly more resistant than Pythium, Phytophthora, Sclerotina and Trametes, the difference being greater for oxine than for copper oxinate and in Sabouraud than in Czapek–Dox media. Copper oxinate was generally more active and more broadly and rapidly fungicidal than oxine. Both are fungicidal at low concentrations against significant plant pathogens and relatively active against important spoilage and mycotoxin producing moulds. The MIC (minimum inhibitory concentration) and MFC (minimum fungicidal concentration) for both agents were dependent on method and medium. Neither agent produced changes in morphology, asexual reproduction or differentiation. Oxine and copper oxinate were resistant to inactivation by organic materials, interacted synergistically in vitro and did not elicit resistance on long term exposure. Differences in activity pattern suggest independent modes of action. Oxine is worthy of revisitation as a useful agricultural fungicide and preservative.

Confocal laser scanning microscopy was used for in vivo observations of autofluorescent fungal structures of Glomus mosseae in intact, living rye-grass roots. Clear images of hyphae and collapsed arbuscules could be obtained without staining or sectioning roots. As rye-grass roots are highly transparent, with only a few cell layers above the vascular cylinder, they provide an excellent in vivo system for microscopical confocal laser scanning studies of arbuscular mycorrhizal structures.

Perhaps like many other mycologists, my initial encounters with fungi filled me with a desire to engage with mysteries: mysteries embedded in the diversity of form and function in fungi and how this diversity might be related to the life of the forest in which so many of these organisms appear to find their homes. In all good mysteries, the resolution of underlying causes at one level of comprehension only serves to reveal deeper levels for exploration.This can open the way into a cascade that nourishes a growing empathy with fellow beings and so assuages that most fundamental need to have a sense of belonging – to be as one; to be at peace; secure in the knowledge of idiosyncrasies embraced in the fondness of others. I dreamt that fungi would somehow eventually lead me and my fellow travellers down that cascade. I still do.

After purification by thin-layer chromatography (tlc) several fatty acids stimulated oospore formation in Phytophthora cactorum but not in Phytophthora parasitica. Palmitoleic acid was the most effective and was the only fatty acid tested that promoted oospore formation in P. parasitica. Purification of palmitoleic acid by Florisil column chromatography resulted in a two-fold increase in activity over that purified by tlc. When 0·01 to 100 ng of cholesterol was added to basal medium containing palmitoleic acid, the added cholesterol did not significantly change oospore production by P. cactorum. Oospore formation in P. cactorum was slightly stimulated by tlc-treated aliphatic hydrocarbons, or derivatives of hydrocarbons, but was strongly stimulated by geraniol and squalene. Vitamin A and vitamin A esters stimulated oospore formation in both P. cactorum and P. parasitica. tlc treatment also significantly increased the activity of cholesterol and β-sitosterol on oospore formation by P. cactorum. Both compounds did not stimulate oospore formation by P. parasitica even after tlc treatment.

Annulatascus species are common freshwater ascomycetes in the tropics. In this paper, the type species, Annulatascus velatisporus, and a new species, A. triseptatus, are described and illustrated at light and electron microscope levels. Annulatascus triseptatus differs from A. velatisporus in having three-septate ascospores surrounded by a thin sheath. The asci of both species have bilamellate ascus walls and a bipartite apical ring. The upper part of the apical ring differentiates from the inner ascus wall layer and the lower part elongates downwards during maturation. The mesosporium is the first formed ascospore wall layer followed by the episporium, which is covered with verruculose ornamentations. The mucilaginous sheath of the ascospores is fibrillar or amorphous depending on the fixation methods employed, and appears to be derived from the episporial verruculose ornamentations.

This paper describes the use of a monoclonal antibody-based ELISA for the quantification of the effects of Trichoderma harzianum on the saprotrophic growth dynamics of Rhizoctonia solani in unsterile compost-based microcosms. Quantification of R. solani was based on the immunological detection of a constitutive, extracellular, water soluble glycoprotein antigen (the copper-containing enzyme catechol oxidase) which is secreted by actively growing mycelium of the fungus only. Extracts derived from lyophilized mycelium (FDM) were used as a quantifiable and repeatable source of the antigen in order to prepare calibration curves that accounted for incomplete extraction of the antigen from compost samples. These curves were used to convert the absorbance values of extracts in ELISA to FDM biomass equivalents, which allowed comparisons of the saprotrophic growth dynamics of R. solani to be made in the presence and absence of T. harzianum. The high pH (9·6) of the buffer used to extract the antigen from microcosm samples also resulted in the extraction of humic components of the compost which interfered with the sensitivity of the assay. A protocol, based on the determination of optimal ELISA absorbance[ratio ]extract dilution ratios, was used in order to reduce the interference and improve the sensitivity of the quantitative assay.

Armillaria species are amongst the most important pathogens of trees and have a world-wide distribution. In recent years, the taxonomy of Northern Hemisphere Armillaria spp. has been extensively treated, but those occurring in Africa are poorly known. Previously, isolates of Armillaria from Zimbabwe have been grouped based on morphology and biochemical tests. In this study, six isolates representing the three previously characterized groups of Armillaria spp. occurring in Zimbabwe were analysed using DNA-based techniques. Three distinct clusters emerged from both PCR–RFLP and analysis of sequence data for the IGS-1 rRNA operon. The three groups corresponded to those previously identified based on morphology and biochemical tests. Differences in IGS-1 sequences strongly suggest that the Zimbabwean groups represent three distinct taxa. Isolates belonging to Group I, previously assumed to be to A. heimii, were similar to those identified as A. fuscipes from South Africa and La Reunion. Group II isolates resided in a clade apart from all other isolates and appear to represent A. heimii. The remaining isolates residing in Group III clustered with isolates from Zambia and Cameroon. These are different from A. heimii and A. fuscipes and apparently represent an undescribed taxon.