Lichens are typically formed by the association of two partners. The fungus (mycobiont) usually comprises most of the lichen, while the photosynthetic algal or cyanobacterial partner is referred to as the photobiont. Many lichens contain more than one photobiont and other associates, the lichenicolous fungi, may also be involved. The spectrum of interactions is fascinating and ranges from mutualism, through commensalism, to situations where one, or sometimes more, of the associates is doomed by the antagonistic activities of an invading fungus. Furthermore, these interactions are dynamic over time. Many mycologists assume that once a lichen ascospore has contacted a suitable photobiont, or once a dual propagule such as a soredium, isidium or lichen fragment has landed on an appropriate surface, a lichen thallus will develop. Accepted dogma is that the thallus will grow to form a mature lichen surviving for tens, if not hundreds or even thousands of years. These are over-simplifications; in fact there is war in the world of lichens. Following a brief consideration of parasitism and other forms of symbiosis, this war will be illustrated under the headings of algal slaves, exploiters of two kingdoms, alien invaders, cosy niche seekers and take-over specialists. It is hoped that this review will encourage mycologists to study these interactions which, as yet, remain largely unexplored.

Visual markers detectable by histochemical staining have been developed for analysing the time course and tissue specificity of maize infections by Fusarium moniliforme. Three F. moniliforme strains, RRC 374, MRC 826 and RRC PAT, were transformed with a plasmid, pHPG, containing the gusA reporter gene which codes for β-glucuronidase (GUS) and the hph gene for hygromycin resistance as the selectable marker. Introduction of plasmid DNA into germinating conidia yielded 1·2×10−7 transformants per conidium; expression of both gusA and hph was however, transient. Stable transformants were obtained using protoplasts as the recipient, but transformation frequency was reduced. Southern blot and PCR analyses confirmed incorporation of pHPG into the genome of all three F. moniliforme strains with gusA properly inserted in MRC 826 and RRC PAT, but apparently disrupted in RRC 374. The growth pattern for transformed F. moniliforme isolates and the parental wild types followed a sigmoid curve on minimal and enriched media. Hygromycin totally inhibited growth for wild type isolates, but not of transformants. Transformed isolates maintained the ability to infect the maize plant. Thus, this study is the first report of F. moniliforme transformed with a visibly detectable reporter gene to use for analysing this endophyte-host interaction of world-wide importance to animal and human health.

Rhizoctonia solani AG-3 causes considerable yield loss in potato fields in eastern Canada and U.S.A. The accurate identification of AG-3 isolates is strategic prior to planting potatoes. To obtain a fast and reliable identification method, RAPD experiments were carried out to obtain specific genetic markers of AG-3 isolates. DNA from various isolates of R. solani was submitted to RAPD amplification using random 10 mers primers. One of the forty primers used yielded a 2·6 kbp fragment present in all isolates of AG-3. The specificity of this fragment was assessed by Southern blot analysis. It was partly sequenced and DNA primers were designed for PCR amplification experiments. A PCR-based restriction mapping method, using one restriction endonuclease, Xho I, was developed for specific detection of AG-3 isolates. Analysis of data showed that AG-3 isolates were distinct to other AGs R. solani. The detection method described here is very specific and reliable; it can be applied on plant tissue and soil infected with R. solani AG-3.

A DNA fragment apparently unique to Verticillium dahliae was found by comparing RAPD profiles of V. dahliae to those of other closely related fungi. RAPD analyses were performed on eight V. dahliae, six V. albo-atrum and three V. tricorpus isolates to identify DNA sequences specific to V. dahliae. RAPD primer E20 (AACGGTGACC) yielded a 567 bp band shared only by V. dahliae isolates. This band from isolate V14 was cloned and sequenced. No significant sequence similarity was found between this amplicon and any other nucleic acid sequence in the databases. Based on the sequence information, a pair of PCR primers, VDS1 (5′-CACATTCAGTTCAGGAGACGGA-3′) and VDS2 (5′-CCTTCTACTGGAGTATTTCGG-3′) was designed. PCR tests showed that VDS1 and VDS2 amplified the expected fragment of DNA from 62 V. dahliae isolates from diverse hosts and geographical origins, but not from any other sources of DNA tested, including DNA from the most closely related species, V. albo-atrum. Southern blot analysis showed that the PCR product specifically hybridized to V. dahliae genomic DNA. An internal control was constructed for competitive PCR and used to develop a detection and quantification assay for V. dahliae, for which the detection limit was determined.

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.

Strains of Colletotrichum species derived from diseased strawberry plants from a wide geographical range were studied using mitochondrial and ribosomal DNA RFLPs, and acetyl and propionyl esterase isoenzymes. Two major species aggregates were detected, centred on C. acutatum and C. gloeosporioides respectively, with significant further subdivision. There were apparent discrepancies in the hierarchical nesting of some taxon groups based on the different molecular techniques. Strains assigned to C. acutatum fell into several rDNA RFLP groups, but there was less variation in mtDNA RFLP band patterns. There appears to be at least one probably clonal population in the U.S.A. which is also present in Europe, and a less well-defined series of groups which are at least sometimes sexually reproducing. Strains assigned to C. fragariae were found not to have distinct rDNA band patterns from the teleomorph linked strains studied, which had been referred to as C. gloeosporioides. They did vary in this respect from C. gloeosporioides associated with Citrus, its type host. It was, therefore, concluded that all the strains studied with cylindrical conidia should be placed within C. fragariae, which is confirmed as separate from C. gloeosporioides and recognized as a holomorphic taxon. Nevertheless, a separate asexually reproducing infraspecific group was distinguishable using mtDNA information. An epitype is designated for C. fragariae.

Various fungi and myxomycetes have been tested for their synthesis and hydrolytic degradation of β-poly(L-malate) (PMLA), a highly anionic polyester of L-malate-malate. The PMLA content of the culture medium, and also of some cell extracts, has been assayed by L-malate-malate dehydrogenase (EC 1.1.1.83)-catalysed reduction of NAD+ after the alkaline hydrolysis of the polymer. All eight myxomycete isolates were producers. Eight producers were Mitosporic fungi but only one Ascomyete was productive. Aureobasidium pullulans contained PMLA in yeast-like cells but not in hyphae. The polymer was bound to membrane fractions from where it was slowly released during preparation for analysis. Only 12 of the 237 fungi and myxomycetes showed PMLA-hydrolase activity; and two of these were producers of PMLA. Fungi with hydrolase activity were mostly different from those releasing L-malate. The Physarum polycephalum-type unbranched polymer of high molecular mass was not recognized in fungi. Fungi, typically A. pullulans, produced polymer of low molecular mass which seemed to be covalently bound to polysaccharide.

Net blotch caused by Pyrenophora teres is a serious disease of barley in many cereal production areas world-wide, including the Western Cape province of South Africa. The pathogen occurs as two forms, P. teres f. teres, which produces net-blotch symptoms, and P. teres f. maculata which produces leaf spots. Pyrenophora japonica and P. hordei, which have also been reported in South Africa, also produce spots on susceptible barley cultivars. Using RAPD markers, spot-forming isolates from the South African population were found to be relatively uniform. Single ascospores were obtained from pseudothecia after in vitro mating had occurred between a verified P. teres net-blotch isolate from Denmark and a representative Pyrenophora leaf spot isolate from South Africa. Using amplified fragment length polymorphism (AFLP) and RAPD markers, recombination was demonstrated in the progeny which had DNA banding patterns different from the two parental isolates. Pathogenicity trials also confirmed that recombination had taken place during mating. Inoculations were conducted on differential cultivars susceptible to the net-blotch or leaf spot forms. The two parents induced typical net-blotch or leaf spot symptoms whereas the progeny mostly induced a jagged spot symptom on each cultivar. Fungicide sensitivity tests using the ergosterol biosynthesis inhibitors triademinol, bromuconazole and triticonazole showed that, due to recombination, some progeny could have increased resistance to these fungicides. Due to mating and subsequent recombination between a net blotch isolate of P. teres and a representative leaf spot isolate, it was concluded that the latter was P. teres f. maculata. These results contrast with the earlier belief that Pyrenophora leaf spot isolates in the Western Cape are P. japonica and P. hordei.

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.

Puccinia menthae is highly variable, with several varieties and variants within varieties. Two principal groups of races, nominated spearmint rust and peppermint rust, have been recognized according to their host range on commercially-important Mentha species, yet both belong to the same variety, P. menthae var. menthae. Ten collections of P. menthae teliospores from four Mentha species in Victoria, Australia, were examined using light microscopy and SEM. The teliospores from M. spicata, M.×cordifolia and M. suaveolens, all hosts to spearmint rust, were verrucose with two equally-sized cells, whereas those from M.×piperita, host to peppermint rust, were generally smooth-walled, and the apical cell was larger and thicker-walled than the basal cell. Fifteen isolates of P. menthae collected from four Mentha species in Victoria were assessed for genomic variation using RAPD analysis and PCR-generated length polymorphism of the ITS region of rDNA. Six out of 113 RAPD primers amplified reproducible marker profiles, 58 polymorphic bands were scored and simple matching distances were computed between the isolates. UPGMA cluster analysis was used to produce a dendrogram and non-metric multi-dimensional scaling to produce a two-dimensional map of the isolates. The spearmint rust and peppermint rust isolates clustered into two non-overlapping groups, providing good evidence that there is limited gene flow between them. All isolates had the same sized ITS fragments. The taxonomic implications of these results are discussed and it is suggested that the peppermint and spearmint rusts should be accorded separate varietal or specific status.

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.

The purification, production and some properties of the intracellular and cell wall associated (1→3)-β-glucanases, (1→6)-β- glucanases and β-glucosidases of Acremonium persicinum have been examined. Anion exchange chromatography revealed the presence of two (1→3)-β-glucanases, one (1→6)-β-glucanase and two β-glucosidases in intracellular extracts of A. persicinum, with further purification by gel filtration chromatography allowing partial characterization of these enzymes. All three intracellular β-glucanases and one of the β-glucosidases appear to be very similar to enzymes found in the extracellular fluid with regard to their molecular masses, hydrolytic action patterns on their substrates, and apparent regulation of syntheses. In contrast, the remaining β-glucosidase appeared to occur only intracellularly and possessed different properties from its extracellular counterpart, most notably being composed of two subunits of 130 and 138 kDa, and its synthesis relatively insensitive to glucose in the medium. Similar anion exchange chromatographic analysis of the cell wall associated enzyme activities extracted by 4 M LiCl revealed the presence of three (1→3)-β-glucanases, one (1→6)-β-glucanase and one β-glucosidase. Except for one (1→3)-β-glucanase all these enzymes appear to be the same as those enzymes found intra- and extracellularly in terms of their action patterns on substrates and their apparent regulation of syntheses. The other apparent cell wall-specific (1→3)-β-glucanase appears to be constitutively produced and is an endo-hydrolase since it displayed no activity toward periodate oxidised laminarin or barley β-glucan. Possible roles for these enzymes are proposed in light of their location, action patterns and apparent regulation of syntheses.

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 development of the peridioles of a Mycocalia sp., and the primordia of Scleroderma verrucosum and S. areolatum, has been studied, particularly in view of the presence of metamorphosed basidia. In the Mycocalia sp. and S. verrucosum spore-like bodies were formed exclusively by transformation of whole basidia. The ontogeny of S. verrucosum has been compared with that of S. areolatum. The structure of the exoperidium of S. verrucosum is much more complicated: hyphal knots play an important part in its construction. The processes giving rise to the exoperidium may be homologous with those constituting universal veils in Agaricales.

A new ascomycete Ascomauritiana lignicola gen. et sp. nov. is described and illustrated from a specimen collected on submerged wood in Mauritius. The taxon is compared with species of Arnium, Melanospora and Pustulipora, unitunicate ascomycetes having brown ascospores with germ pores and with species of Argynna, Caryospora, Lepidopterella and Zopfia. Ascomauritiana is characterized by large 5-septate, brown ascospores with polar germ pores and clavate, 4-spored asci that lack an apical ring and deliquesce early. Its taxonomic placement in the Ascomycetes incertae sedis is discussed.

The products of teliospore germination in Ustilago triodiae and Sporisorium loudetiae-pedicellatae are illustrated. In U. triodiae the transversely-septate basidium is usually three-spored. The sporidia (basidiospores) either bud or form surface hyphae from which branched systems of aerial sporidia arise. A similar haplophase occurs in some other species.

In S. loudetiae-pedicellatae the basidium is unicellular and produces up to four sporidia in succession. These give rise to colonies composed largely of similar cells. No conjugation was seen in either species.

This study investigated the morphology and infectivity of fine endophyte in a mediterranean environment. Five morphological groups of fine endophyte differing in up to 11 characters were present within two pot cultures of fine endophyte from south- western Australia. Occurrence and abundance of a particular type of fine endophyte were not affected by the application of calcium carbonate. It appeared that there may be more than one fungus included among the two sources of fine endophyte, however it was not possible to separate the fungi. A second experiment demonstrated that infective propagules of fine endophyte can be very small (<38 μm) and fresh roots acted as a potential source of infective propagules. There was no infectivity of fine endophyte in the soil at the end of the growing season but it reoccurred in similar quantity in the next growing season.

Oxine and copper oxinate have a long history of use as fungicides. Ability to chelate and lipophilicity have been regarded as essential to the action of oxine. The most widely held hypothesis on the mechanism of action of oxine holds that oxine is only active when it can form saturated chelates with metals in the medium which enter the cell and dissociate to liberate a toxic half-chelate. Metals, chelating molecules and pH were investigated for their effect on the fungitoxicity of oxine and copper oxinate. Oxine fungitoxicity increased with increase in medium pH, inhibitory activity corresponding most closely with the concentration of the neutral species. Chelation of oxine with metals in the medium was found not to be a requirement for oxine fungitoxicity. Potentiation of the action of oxine by metals is explained by the formation of more fungitoxic and soluble metal oxinates and antagonism by the formation of less soluble or less active metal oxinates. Chelating amino acids, nucleic acid bases and EDTA did not antagonize oxine fungitoxicity. Antagonism by riboflavin and folic acid suggests interaction of oxine with specific cellular functions in fungi. The fungitoxicity of copper oxinate was generally not affected by metals, chelating molecules or changes in medium pH. It is proposed that the data support the inherent fungitoxicity of oxine, the role of metal oxinates as co-toxicants and independent mechanisms of action for oxine and copper oxinate.

In September 1990, 74 sporocarps of Battarrea stevenii were observed on the floodplain of the ephemeral Kuiseb River in western Namibia. Herein we report subsequent studies of the distribution, abundance, nutritional role, phenology, and sporocarp development of this fungus in the hyper-arid Namib Desert. Included are full descriptions of developing and mature sporocarps. B. stevenii is a common associate of riparian forests on silty floodplain terraces, but does not form mycorrhizal associations with the dominant woody species, Faidherbia albida or Tamarix usneoides. Rather, clamped mycelium extends throughout floodplain soils decomposing coarse and fine particulate organic material (4–7% of soil dry weight). Sporocarp production occurs 4·5–12 mo post-flooding in response to soil desiccation at depths of 20–35 cm. The extensive mycelium, duration of vegetative growth post-flooding, and large size and abundance of B. stevenii sporocarps suggest that it is an important component of the subsurface decomposer community in the Namib's ephemeral rivers. Given that the fungus has also been recorded from floodplain soils of Angola, Hungary, and New Mexico (U.S.A.), and is known to have a world-wide distribution, we predict that further biogeographical studies will reveal that B. stevenii is a characteristic element of the riparian biota in dryland rivers, which drain approximately one-third of the earth's land surface.

A field study was carried out in a remote broadleaved Fagus longipetiolata forest in Shaanxi province, China to study the natural local distribution of Lentinula edodes. Following spatial mapping, 24 fruit bodies were collected for tissue isolation into axenic culture. 24 genets distributed on fallen tree trunks within a distance of 120 m were identified and clustered into 7 groups using the unweighted pair-group method algorithm using data based on colony morphologies, abilities to degrade aromatic poly-R478 dye, somatic incompatibility reaction patterns and DNA fingerprints. Among the parameters used, the somatic incompatibility reaction, a polygenic phenotype, was the most differentiating, identifying 22 incompatible classes. Two sets of fruit bodies of different genets were so close together that they would otherwise have been described as aggregate fruits of presumed identical origin. Eighteen genets found on the same 5.6 m long tree trunk divided roughly into two clusters, matching their spatial distribution, and a nearby branch bore another distinct cluster. More heterogeneity was encountered between isolates the greater the distance separating them on the original site. Genets on the same tree trunk showed more compatible somatic reactions among themselves, and their DNA fingerprints showed higher similarity. Nevertheless, considering the totality of phenotypic characters, each fruit body is a genet in L. edodes. Such features are concluded to result from a reproductive strategy which depends on basidiospore dispersal. Within each cluster of isolates from the collection site genets seemed to have arisen from multiple sib-mating events. Thus, a cluster may represent a lineage of L. edodes. Individualism in L. edodes is based on a strong somatic incompatibility system. Strong competition from contaminating individuals arriving as air-borne basidiospores could explain decreased and fluctuating crop yields which are now frequently observed in later flushes from the outdoor wood log cultivation system. Further, it would also explain why multispore spawn is not favoured in artificial cultivation of this economically important edible mushroom.