Chaetopsina hongkongensis sp. nov. from decaying palm rachids, and Kionochaeta australiensis sp. nov. from decaying wood submerged in a freshwater stream, are described and illustrated. Both species produced setose conidiophores and phialidic conidiogenous cells. The former is distinct in having polyblastic conidiogenous cells with multiple denticulate loci, and is compared with C. polyblastia. In Kionochaeta australiensis conidiophores have accessory setiform lateral branches, and it is compared with K. keniensis, K. pughii, and K. ramifera. The delimitation of these two genera is discussed with additional information provided from an SEM study of conidiogenous characters in C. hongkongensis.

The position of several endemic and rare species in Agaricus sect. Duploannulati and the limits of the section were investigated by analysis of sequence data from the ribosomal DNA ITS. The results supported the recognition of two groups, which we treat as subsections Chitonioides and Duploannulati. Most of the species studied proved to belong to subsect. Chitonioides. Species excluded from the section, as well as other potential members of sect. Duploannulati, are considered. Morphological traits deemed important for identification of A. nevoi, A. pequinii, A. gennadii, A. rollanii, and A. padanus are discussed. Taxonomic positions of these species in morphologically-based systems and according to molecular systematics data are compared and analyzed.

Rimularia insularis forms an photosynthetic thallus on lichens of the Lecanora rupicola group. In the thalli of R. insularis, some hyphae of the host are detectable, and they are situated mainly in the basal part of the Rimularia's medulla. No Lecanora hyphae were present in the Rimularia's algal layer and they were indistinct in the upper parts of its medulla, from where we obtained clean ITS-sequences of Rimularia. Direct PCR from various sections of the algal layer detected only one photobiont genotype, although the algal cells could be assigned to two morphologically different types. Calcium deposits were found in the upper parts of the medulla, while abundant rock substrate fragments with different mineral compositions were present in the lower parts. Cavities and fissures in the rock below the infected thalli were filled by fungal cells, PCR analyses of such parts indicated that the Rimularia hyphae extend below the host, and into the rock.

Three new species of Corynespora: C. morindae-tinctoriae, C. nana and C. rosacearum on Morinda tinctoria, Lantana indica and Eriobotrya japonica respectively, are described and illustrated from Gorakhpur (U.P.) India.

The taxonomic status and relationship of Tricholoma sulphureum and the similar T. bufonium were investigated using different sets of characters. These included morphological data on fruit bodies, ecological and chorological data, and analysis of the sequence data obtained for the ITS of basidiomes of different ecological and geographic origin. Moreover, the ectomycorrhizas formed by T. bufonium on Abies alba and Quercus sp. were characterised, and anatomical features compared with those of T. sulphureum mycorrhizas on coniferous and broad-leaved host trees. Our results revealed extensive ITS variation in members of the T. sulphureum group, but this variation was not correlated with morphology, ecology, or geographical distribution. We conclude that T. bufonium cannot be maintained as an autonomous taxon and should be treated as an infraspecific variant of T. sulphureum.

Rhynchosporium secalis isolates E97-2 and H97-2, represented the major pathotypes in populations on barley in Alberta, Canada, but differed widely in their virulence. Following greenhouse co-inoculation with the two pathotypes, E97-2, originally isolated from resistant cv. ‘CDC Earl’, predominated over H97-2, isolated from the susceptible cv. ‘Harrington’, from the first to the last of four infection cycles on both ‘CDC Earl’ and ‘Harrington’. These results indicated that the host can rapidly influence pathotype composition and that pathotype E97-2 may have a competitive advantage over H97-2 on these cultivars. DNA polymorphisms were found between isolates from single or mixed inoculations on cvs ‘CDC Earl’ and ‘Harrington’ for four successive cycles. Co-inoculation with the two isolates resulted in a shift to a molecular phenotype more similar to E97-2 than H97-2. The competitive advantage of E97-2 over H97-2, combined with the selective pressure exerted by the host, would explain the increased susceptibility of cv. ‘CDC Earl’ and other cultivars with similar sources of scald resistance, in fields across Alberta. However, H97-2 will likely remain one of the major pathotypes in Alberta due to the relatively large acreage of cv. ‘Harrington’ in this province.

Isolates of Fusarium oxysporum from different habitats were compared with respect to intra- and extracellular isozymes. Five intracellular enzymes: esterase, superoxide dehydrogenase, malate dehydrogenase, dihydrolipoamide dehydrogenase and succinate dehydrogenase were extracted from the mycelium, and four extracellular enzymes: protease, cellulase (endoglucanase), amylase and lipase were obtained from the culture medium. Proteins were separated either by discontinuous PAGE or by IEF, and isozymes were detected by specific staining. The intracellular enzyme data were analysed by an unweighted paired group method analysis (UPGMA), which separated the isolates into three main clusters. The clusters generated from the intracellular enzymes were weakly correlated with the electrophoretic types based on the extracellular enzymes. These results suggest that extracellular enzymes may be of limited value for classification within F. oxysporum.

A preliminary physiological characterization of osmoregulation in an Aspergillus nidulans salt sensitive mutant carrying cotransformed DNA sequences from the marine hyphomycete Dendryphiella salina is described. A genomic DNA library made in lambda EMBL3 was cotransformed with the plasmid pDJB3 into an A. nidulans host carrying a selectable marker for transformation (pyrG89) and a salt sensitivity mutation (sltA1). In some cases D. salina clones appeared to directly complement the salt sensitivity mutation by restoring salt and arginine insensitivity. Other clones gave marked increases in salt tolerance and yet the hosts remained arginine sensitive. Improvements in salt tolerance correlated with an enhanced ability to induce polyol biosynthesis during salt challenge.

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.

The vascular wilt pathogen currently causing severe die-back and mortality of takamaka in the Seychelles has morphological and physiological characters inconsistent with its placement in Verticillium. Features of the pathogen warrant its transfer to Leptographium and Leptographium calophylli comb. nov. is proposed. L. calophylli is described in detail based on new collections.

Craspedodidymum nigroseptatum sp. nov. is described and illustrated based on specimens collected on decaying rachides of Oncosperma horridum in Brunei Darussalam. It differs from other species of Craspedodidymum in producing dark brown conidia with three to four thick, darkly-pigmented septa, and a paler basal cell. Conidia are broadly ellipsoidal to obovoid and truncate at the base. Craspedodidymum nigroseptatum is compared with other species in the genus and a key to the genus is provided.

Three new antineoplastic natural products, combretastatin A-4, dolastatin 10 and halichondrin B, have been evaluated for their antimicrotubule activity in Uromyces appendiculatus urediniospore germlings using indirect immunofluorescence microscopy. In control germlings microtubules were abundant and mostly oriented parallel to the longitudinal axis of the cell. The microtubule cytoskeleton of germlings treated with 1·3×10−5M (10 μg ml−1) dolastatin 10 and 4·5×10−5M (50 μg ml−1) halichondrin B disrupted the microtubule cytoskeleton resulting in the near elimination of microtubule-associated fluorescence. Combretastatin A-4 was less effective, requiring a concentration of 3·2×10−3M (1·0 mg ml−1) to disrupt the microtubule cytoskeleton. These effective doses are consistent with previously examined antimicrotubule agents (e.g. nocodazole, griseofulvin, vincristine sulphate, demecolcine).

The recently reported epidemic of rust in Britain on wild and cultivated varieties of the daisy (Bellis perennis), caused by Puccinia distincta, was preceded by records on cultivated plants at Bristol in 1972 and Bognor Regis in 1973 and by sporadic observations of rust on cultivated daisies thereafter in the period from 1978–1996. The first verifiable report of the pathogen on wild B. perennis was from Leeds in 1988. In the spring of 1997, a rust epidemic broke out on wild as well as cultivated daisies, as indicated by numerous reports mainly from the south of Britain. The current paper charts the distribution of P. distincta in Britain from 1972 onwards and speculates about its likely origin.

In a soil survey, nematophagous fungi were recovered less from agar plates sprinkled with forest soil (Quercus ilex subsp. rotundifolia) than from those incubated with agricultural (Citrus orchards) soil. Nematodes were present in all soils. The organic matter was higher in forest soils. Water extracts from forest soils with high levels of phenols, leaf litter and Q. rotundifolia fresh leaves affected the development and growth of common species of nematophagous and entomopathogenic fungi. These results show that phenolics from leaf letter could play an important role in the ecology and biology of these invertebrate pathogens in soil.

Penicillin was not detected in Aspergillus nidulans liquid cultures with pelleted morphology (pellets 1–5 mm diam.) but production was observed in cultures with homogeneous filamentous morphologies. Adenylate Energy Charge (AEC) and Oxygen Uptake Rates (OUR) were measured in cultures exhibiting the two morphologies and it was shown that the values of both parameters were lowest in pelleted cultures and highest in cultures with a filamentous morphology. In addition, a third morphological form, ‘micropellets’ with intermediate properties between the other two types was encountered. We propose that oxygen limitation brought about by the mass transfer restrictions of pelleted growth inhibits penicillin production.

This issue of Mycological Research News features: Corticioid basidiomycetes: unravelling the phylogeny of fungal cinderellas; Nomenclatural clarifications and new taxa in the Glomeromycota; and Ascobolus immersus spore-guns develop 3 atm pressure. An obituary of Richard W. G. Dennis is also included.

Ten research papers appear in this part. Molecular studies address basidiomycete phylogeny with new data from corticioid fungi; identify a new order of mycorrhizal heterobasidiomycetes; reassess Plasmopara and similar downy mildews; confirm the placement of a new sequestrate Lactarius; show additional Geosmithia species merit recognition; and identify a method of typing Beauveria bassiana strains. Critical studies reveal additional large-spored Daldinia species.

Root border cells produce stimulators of arbuscular mycorrhizal development, and ionizing radiation is shown to promote growth towards the radiation source.

The following new scientific names are introduced: Diversisporales, Sebacinales ords. nov.; Diversisporaceae, Pacisporaceae fams. nov; Diversispora, Protobremia gens. nov.; Daldinia dennisii, D. novaezelandiae, Geosmithia flava, and Lactarius angiocarpus spp. nov.; D. dennisii var. loculatoides, D. dennisii var. microspora vars. nov.; Diversispora spurcum (syn. Glomus spurcum), G. pallida (syn. Penicillium pallidum), Lactarius dolichocaulis (syn. Arcangeliella dolichocaulis), and P. sphaerosperma (syn. Plasmopara sphaerosperma) combs. nov.

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.

Colletotrichum xanthorrhoeae sp. nov. causes leaf spots on Xanthorrhoea preissii and X. platyphylla in south-western Western Australia.

Microbotryum violaceum (anther-smut) from Silene caroliniana and S. virginica produced promycelia that frequently appeared to contain more than three cells according to the number of septations. This is in contrast to samples from S. latifolia and to previous descriptions of this species. Apparent four-celled promycelia contained three nucleate cells and one anucleate zone. Anucleate zones were usually positioned between the first and third cells of the promycelium. Their presence was negatively correlated with the occurrence of intra-promycelial conjugation. Also, unlike isolates from Silene latifolia, isolates from S. caroliniana and S. virginica produced hyphae in the absence of an inducing agent.

Three new thermotolerant species of Corynascus isolated from Indian and Argentinian soils are described and illustrated: C. sexualis sp. nov. characterised by small ascospores and the absence of a Myceliophthora anamorph (present in all other species of the genus); C. similis sp. nov. characterised by navicular ascospores with two lateral to sub-terminal germ pores; and C. verrucosus sp. nov. distinguished by the ellipsoid ascospores with two oblique to sub-terminal germ pores. A study to compare the ITS-region sequences of all species of the genus with representative species of related genera demonstrated that this region is very conserved in this group of fungi and of low taxonomic value. A key to the eight species of the genus now known is provided. The molecular data suggest the genus is best placed in the Chaetomiaceae rather than the Ceratostomataceae.